有些项目，需要让控件或者布局进行水平和垂直同时能拖拽，当然，ScrollView 和 HorizontalScrollView 的结合写法是一种写法。但是，这么写用户体验效果不佳，会有迟钝感，因此推荐下面的写法。继承之FrameLayout，代码是在网上找的。
package com.test; import java.util.List; import android.content.Context; import android.graphics.Rect; import android.util.AttributeSet; import android.view.FocusFinder; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.ViewParent; import android.view.animation.AnimationUtils; import android.widget.FrameLayout; import android.widget.Scroller; /** * Reference to ScrollView and HorizontalScrollView */ public class Myscroll extends FrameLayout { static final int ANIMATED_SCROLL_GAP = 250; static final float MAX_SCROLL_FACTOR = 0.5f; private long mLastScroll; private final Rect mTempRect = new Rect(); private Scroller mScroller; /** * Flag to indicate that we are moving focus ourselves. This is so the * code that watches for focus changes initiated outside this ScrollView * knows that it does not have to do anything. */ private boolean mScrollViewMovedFocus; /** * Position of the last motion event. */ private float mLastMotionY; private float mLastMotionX; /** * True when the layout has changed but the traversal has not come through yet. * Ideally the view hierarchy would keep track of this for us. */ private boolean mIsLayoutDirty = true; /** * The child to give focus to in the event that a child has requested focus while the * layout is dirty. This prevents the scroll from being wrong if the child has not been * laid out before requesting focus. */ private View mChildToScrollTo = null; /** * True if the user is currently dragging this ScrollView around. This is * not the same as 'is being flinged', which can be checked by * mScroller.isFinished() (flinging begins when the user lifts his finger). */ private boolean mIsBeingDragged = false; /** * Determines speed during touch scrolling */ private VelocityTracker mVelocityTracker; /** * When set to true, the scroll view measure its child to make it fill the currently * visible area. */ private boolean mFillViewport; /** * Whether arrow scrolling is animated. */ private boolean mSmoothScrollingEnabled = true; private int mTouchSlop; private int mMinimumVelocity; private int mMaximumVelocity; /** * ID of the active pointer. This is used to retain consistency during * drags/flings if multiple pointers are used. */ private int mActivePointerId = INVALID_POINTER; /** * Sentinel value for no current active pointer. * Used by {@link #mActivePointerId}. */ private static final int INVALID_POINTER = -1; private boolean mFlingEnabled = true; public Myscroll(Context context) { this(context, null); } public Myscroll(Context context, AttributeSet attrs) { super(context, attrs); initScrollView(); } @Override protected float getTopFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); if (getScrollY() < length) { return getScrollY() / (float) length; } return 1.0f; } @Override protected float getLeftFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getHorizontalFadingEdgeLength(); if (getScrollX() < length) { return getScrollX() / (float) length; } return 1.0f; } @Override protected float getRightFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getHorizontalFadingEdgeLength(); final int rightEdge = getWidth() - getPaddingRight(); final int span = getChildAt(0).getRight() - getScrollX() - rightEdge; if (span < length) { return span / (float) length; } return 1.0f; } @Override protected float getBottomFadingEdgeStrength() { if (getChildCount() == 0) { return 0.0f; } final int length = getVerticalFadingEdgeLength(); final int bottomEdge = getHeight() - getPaddingBottom(); final int span = getChildAt(0).getBottom() - getScrollY() - bottomEdge; if (span < length) { return span / (float) length; } return 1.0f; } /** * @return The maximum amount this scroll view will scroll in response to * an arrow event. */ public int getMaxScrollAmountV() { return (int) (MAX_SCROLL_FACTOR * (getBottom() - getTop())); } public int getMaxScrollAmountH() { return (int) (MAX_SCROLL_FACTOR * (getRight() - getLeft())); } private void initScrollView() { mScroller = new Scroller(getContext()); setFocusable(true); setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); setWillNotDraw(false); final ViewConfiguration configuration = ViewConfiguration.get(getContext()); mTouchSlop = configuration.getScaledTouchSlop(); mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); } @Override public void addView(View child) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child); } @Override public void addView(View child, int index) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, index); } @Override public void addView(View child, ViewGroup.LayoutParams params) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, params); } @Override public void addView(View child, int index, ViewGroup.LayoutParams params) { if (getChildCount() > 0) { throw new IllegalStateException("ScrollView can host only one direct child"); } super.addView(child, index, params); } /** * @return Returns true this ScrollView can be scrolled */ private boolean canScrollV() { View child = getChildAt(0); if (child != null) { int childHeight = child.getHeight(); return getHeight() < childHeight + getPaddingTop() + getPaddingBottom(); } return false; } private boolean canScrollH() { View child = getChildAt(0); if (child != null) { int childWidth = child.getWidth(); return getWidth() < childWidth + getPaddingLeft() + getPaddingRight() ; } return false; } /** * Indicates whether this ScrollView's content is stretched to fill the viewport. * * @return True if the content fills the viewport, false otherwise. */ public boolean isFillViewport() { return mFillViewport; } /** * Indicates this ScrollView whether it should stretch its content height to fill * the viewport or not. * * @param fillViewport True to stretch the content's height to the viewport's * boundaries, false otherwise. */ public void setFillViewport(boolean fillViewport) { if (fillViewport != mFillViewport) { mFillViewport = fillViewport; requestLayout(); } } /** * @return Whether arrow scrolling will animate its transition. */ public boolean isSmoothScrollingEnabled() { return mSmoothScrollingEnabled; } /** * Set whether arrow scrolling will animate its transition. * @param smoothScrollingEnabled whether arrow scrolling will animate its transition */ public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { mSmoothScrollingEnabled = smoothScrollingEnabled; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); if (!mFillViewport) { return; } final int heightMode = MeasureSpec.getMode(heightMeasureSpec); final int widthMode = MeasureSpec.getMode(widthMeasureSpec); if (heightMode == MeasureSpec.UNSPECIFIED && widthMode == MeasureSpec.UNSPECIFIED) { return; } if (getChildCount() > 0) { final View child = getChildAt(0); int height = getMeasuredHeight(); int width = getMeasuredWidth(); if (child.getMeasuredHeight() < height || child.getMeasuredWidth() < width) { width -= getPaddingLeft(); width -= getPaddingRight(); int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); height -= getPaddingTop(); height -= getPaddingBottom(); int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } } } @Override public boolean dispatchKeyEvent(KeyEvent event) { // Let the focused view and/or our descendants get the key first return super.dispatchKeyEvent(event) || executeKeyEvent(event); } /** * You can call this function yourself to have the scroll view perform * scrolling from a key event, just as if the event had been dispatched to * it by the view hierarchy. * * @param event The key event to execute. * @return Return true if the event was handled, else false. */ public boolean executeKeyEvent(KeyEvent event) { mTempRect.setEmpty(); boolean handled = false; if (event.getAction() == KeyEvent.ACTION_DOWN) { switch (event.getKeyCode()) { case KeyEvent.KEYCODE_DPAD_LEFT: if(canScrollH()){ if (!event.isAltPressed()) { handled = arrowScrollH(View.FOCUS_LEFT); } else { handled = fullScrollH(View.FOCUS_LEFT); } } break; case KeyEvent.KEYCODE_DPAD_RIGHT: if(canScrollH()){ if (!event.isAltPressed()) { handled = arrowScrollH(View.FOCUS_RIGHT); } else { handled = fullScrollH(View.FOCUS_RIGHT); } } break; case KeyEvent.KEYCODE_DPAD_UP: if(canScrollV()){ if (!event.isAltPressed()) { handled = arrowScrollV(View.FOCUS_UP); } else { handled = fullScrollV(View.FOCUS_UP); } } break; case KeyEvent.KEYCODE_DPAD_DOWN: if(canScrollV()){ if (!event.isAltPressed()) { handled = arrowScrollV(View.FOCUS_DOWN); } else { handled = fullScrollV(View.FOCUS_DOWN); } } break; } } return handled; } private boolean inChild(int x, int y) { if (getChildCount() > 0) { final int scrollX = getScrollX(); final int scrollY = getScrollY(); final View child = getChildAt(0); return !(y < child.getTop() - scrollY || y >= child.getBottom() - scrollY || x < child.getLeft() - scrollX || x >= child.getRight() - scrollX); } return false; } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { /* * This method JUST determines whether we want to intercept the motion. * If we return true, onMotionEvent will be called and we do the actual * scrolling there. */ /* * Shortcut the most recurring case: the user is in the dragging * state and he is moving his finger. We want to intercept this * motion. */ final int action = ev.getAction(); if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { return true; } switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_MOVE: { /* * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check * whether the user has moved far enough from his original down touch. */ /* * Locally do absolute value. mLastMotionY is set to the y value * of the down event. */ final int activePointerId = mActivePointerId; if (activePointerId == INVALID_POINTER) { // If we don't have a valid id, the touch down wasn't on content. break; } final int pointerIndex = ev.findPointerIndex(activePointerId); final float y = ev.getY(pointerIndex); final int yDiff = (int) Math.abs(y - mLastMotionY); if (yDiff > mTouchSlop) { mIsBeingDragged = true; mLastMotionY = y; } final float x = ev.getX(pointerIndex); final int xDiff = (int) Math.abs(x - mLastMotionX); if (xDiff > mTouchSlop) { mIsBeingDragged = true; mLastMotionX = x; } break; } case MotionEvent.ACTION_DOWN: { final float x = ev.getX(); final float y = ev.getY(); if (!inChild((int)x, (int) y)) { mIsBeingDragged = false; break; } /* * Remember location of down touch. * ACTION_DOWN always refers to pointer index 0. */ mLastMotionY = y; mLastMotionX = x; mActivePointerId = ev.getPointerId(0); /* * If being flinged and user touches the screen, initiate drag; * otherwise don't. mScroller.isFinished should be false when * being flinged. */ mIsBeingDragged = !mScroller.isFinished(); break; } case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: /* Release the drag */ mIsBeingDragged = false; mActivePointerId = INVALID_POINTER; break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); break; } /* * The only time we want to intercept motion events is if we are in the * drag mode. */ return mIsBeingDragged; } @Override public boolean onTouchEvent(MotionEvent ev) { if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { // Don't handle edge touches immediately -- they may actually belong to one of our // descendants. return false; } if (mVelocityTracker == null) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(ev); final int action = ev.getAction(); switch (action & MotionEvent.ACTION_MASK) { case MotionEvent.ACTION_DOWN: { final float x = ev.getX(); final float y = ev.getY(); if (!(mIsBeingDragged = inChild((int) x, (int) y))) { return false; } /* * If being flinged and user touches, stop the fling. isFinished * will be false if being flinged. */ if (!mScroller.isFinished()) { mScroller.abortAnimation(); } // Remember where the motion event started mLastMotionY = y; mLastMotionX = x; mActivePointerId = ev.getPointerId(0); break; } case MotionEvent.ACTION_MOVE: if (mIsBeingDragged) { // Scroll to follow the motion event final int activePointerIndex = ev.findPointerIndex(mActivePointerId); final float y = ev.getY(activePointerIndex); final int deltaY = (int) (mLastMotionY - y); mLastMotionY = y; final float x = ev.getX(activePointerIndex); final int deltaX = (int) (mLastMotionX - x); mLastMotionX = x; scrollBy(deltaX, deltaY); } break; case MotionEvent.ACTION_UP: if (mIsBeingDragged) { if(mFlingEnabled){ final VelocityTracker velocityTracker = mVelocityTracker; velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); int initialVelocitx = (int) velocityTracker.getXVelocity(); int initialVelocity = (int) velocityTracker.getYVelocity(); // int initialVelocitx = (int) velocityTracker.getXVelocity(mActivePointerId); // int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); if (getChildCount() > 0) { if(Math.abs(initialVelocitx) > initialVelocitx || Math.abs(initialVelocity) > mMinimumVelocity) { fling(-initialVelocitx, -initialVelocity); } } } mActivePointerId = INVALID_POINTER; mIsBeingDragged = false; if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } break; case MotionEvent.ACTION_CANCEL: if (mIsBeingDragged && getChildCount() > 0) { mActivePointerId = INVALID_POINTER; mIsBeingDragged = false; if (mVelocityTracker != null) { mVelocityTracker.recycle(); mVelocityTracker = null; } } break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); break; } return true; } private void onSecondaryPointerUp(MotionEvent ev) { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_ID_MASK) >> MotionEvent.ACTION_POINTER_ID_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { // This was our active pointer going up. Choose a new // active pointer and adjust accordingly. final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionX = ev.getX(newPointerIndex); mLastMotionY = ev.getY(newPointerIndex); mActivePointerId = ev.getPointerId(newPointerIndex); if (mVelocityTracker != null) { mVelocityTracker.clear(); } } } /** * <p> * Finds the next focusable component that fits in the specified bounds. * </p> * * @param topFocus look for a candidate is the one at the top of the bounds * if topFocus is true, or at the bottom of the bounds if topFocus is * false * @param top the top offset of the bounds in which a focusable must be * found * @param bottom the bottom offset of the bounds in which a focusable must * be found * @return the next focusable component in the bounds or null if none can * be found */ private View findFocusableViewInBoundsV(boolean topFocus, int top, int bottom) { List<View> focusables = getFocusables(View.FOCUS_FORWARD); View focusCandidate = null; /* * A fully contained focusable is one where its top is below the bound's * top, and its bottom is above the bound's bottom. A partially * contained focusable is one where some part of it is within the * bounds, but it also has some part that is not within bounds. A fully contained * focusable is preferred to a partially contained focusable. */ boolean foundFullyContainedFocusable = false; int count = focusables.size(); for (int i = 0; i < count; i++) { View view = focusables.get(i); int viewTop = view.getTop(); int viewBottom = view.getBottom(); if (top < viewBottom && viewTop < bottom) { /* * the focusable is in the target area, it is a candidate for * focusing */ final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom); if (focusCandidate == null) { /* No candidate, take this one */ focusCandidate = view; foundFullyContainedFocusable = viewIsFullyContained; } else { final boolean viewIsCloserToBoundary = (topFocus && viewTop < focusCandidate.getTop()) || (!topFocus && viewBottom > focusCandidate .getBottom()); if (foundFullyContainedFocusable) { if (viewIsFullyContained && viewIsCloserToBoundary) { /* * We're dealing with only fully contained views, so * it has to be closer to the boundary to beat our * candidate */ focusCandidate = view; } } else { if (viewIsFullyContained) { /* Any fully contained view beats a partially contained view */ focusCandidate = view; foundFullyContainedFocusable = true; } else if (viewIsCloserToBoundary) { /* * Partially contained view beats another partially * contained view if it's closer */ focusCandidate = view; } } } } } return focusCandidate; } private View findFocusableViewInBoundsH(boolean leftFocus, int left, int right) { List<View> focusables = getFocusables(View.FOCUS_FORWARD); View focusCandidate = null; /* * A fully contained focusable is one where its left is below the bound's * left, and its right is above the bound's right. A partially * contained focusable is one where some part of it is within the * bounds, but it also has some part that is not within bounds. A fully contained * focusable is preferred to a partially contained focusable. */ boolean foundFullyContainedFocusable = false; int count = focusables.size(); for (int i = 0; i < count; i++) { View view = focusables.get(i); int viewLeft = view.getLeft(); int viewRight = view.getRight(); if (left < viewRight && viewLeft < right) { /* * the focusable is in the target area, it is a candidate for * focusing */ final boolean viewIsFullyContained = (left < viewLeft) && (viewRight < right); if (focusCandidate == null) { /* No candidate, take this one */ focusCandidate = view; foundFullyContainedFocusable = viewIsFullyContained; } else { final boolean viewIsCloserToBoundary = (leftFocus && viewLeft < focusCandidate.getLeft()) || (!leftFocus && viewRight > focusCandidate.getRight()); if (foundFullyContainedFocusable) { if (viewIsFullyContained && viewIsCloserToBoundary) { /* * We're dealing with only fully contained views, so * it has to be closer to the boundary to beat our * candidate */ focusCandidate = view; } } else { if (viewIsFullyContained) { /* Any fully contained view beats a partially contained view */ focusCandidate = view; foundFullyContainedFocusable = true; } else if (viewIsCloserToBoundary) { /* * Partially contained view beats another partially * contained view if it's closer */ focusCandidate = view; } } } } } return focusCandidate; } /** * <p>Handles scrolling in response to a "home/end" shortcut press. This * method will scroll the view to the top or bottom and give the focus * to the topmost/bottommost component in the new visible area. If no * component is a good candidate for focus, this scrollview reclaims the * focus.</p> * * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go the top of the view or * {@link android.view.View#FOCUS_DOWN} to go the bottom * @return true if the key event is consumed by this method, false otherwise */ public boolean fullScrollV(int direction) { boolean down = direction == View.FOCUS_DOWN; int height = getHeight(); mTempRect.top = 0; mTempRect.bottom = height; if (down) { int count = getChildCount(); if (count > 0) { View view = getChildAt(count - 1); mTempRect.bottom = view.getBottom(); mTempRect.top = mTempRect.bottom - height; } } return scrollAndFocusV(direction, mTempRect.top, mTempRect.bottom); } public boolean fullScrollH(int direction) { boolean right = direction == View.FOCUS_RIGHT; int width = getWidth(); mTempRect.left = 0; mTempRect.right = width; if (right) { int count = getChildCount(); if (count > 0) { View view = getChildAt(0); mTempRect.right = view.getRight(); mTempRect.left = mTempRect.right - width; } } return scrollAndFocusH(direction, mTempRect.left, mTempRect.right); } /** * <p>Scrolls the view to make the area defined by <code>top</code> and * <code>bottom</code> visible. This method attempts to give the focus * to a component visible in this area. If no component can be focused in * the new visible area, the focus is reclaimed by this scrollview.</p> * * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} * to go upward * {@link android.view.View#FOCUS_DOWN} to downward * @param top the top offset of the new area to be made visible * @param bottom the bottom offset of the new area to be made visible * @return true if the key event is consumed by this method, false otherwise */ private boolean scrollAndFocusV(int direction, int top, int bottom) { boolean handled = true; int height = getHeight(); int containerTop = getScrollY(); int containerBottom = containerTop + height; boolean up = direction == View.FOCUS_UP; View newFocused = findFocusableViewInBoundsV(up, top, bottom); if (newFocused == null) { newFocused = this; } if (top >= containerTop && bottom <= containerBottom) { handled = false; } else { int delta = up ? (top - containerTop) : (bottom - containerBottom); doScrollY(delta); } if (newFocused != findFocus() && newFocused.requestFocus(direction)) { mScrollViewMovedFocus = true; mScrollViewMovedFocus = false; } return handled; } private boolean scrollAndFocusH(int direction, int left, int right) { boolean handled = true; int width = getWidth(); int containerLeft = getScrollX(); int containerRight = containerLeft + width; boolean goLeft = direction == View.FOCUS_LEFT; View newFocused = findFocusableViewInBoundsH(goLeft, left, right); if (newFocused == null) { newFocused = this; } if (left >= containerLeft && right <= containerRight) { handled = false; } else { int delta = goLeft ? (left - containerLeft) : (right - containerRight); doScrollX(delta); } if (newFocused != findFocus() && newFocused.requestFocus(direction)) { mScrollViewMovedFocus = true; mScrollViewMovedFocus = false; } return handled; } /** * Handle scrolling in response to an up or down arrow click. * * @param direction The direction corresponding to the arrow key that was * pressed * @return True if we consumed the event, false otherwise */ public boolean arrowScrollV(int direction) { View currentFocused = findFocus(); if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); final int maxJump = getMaxScrollAmountV(); if (nextFocused != null && isWithinDeltaOfScreenV(nextFocused, maxJump, getHeight())) { nextFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(nextFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect); doScrollY(scrollDelta); nextFocused.requestFocus(direction); } else { // no new focus int scrollDelta = maxJump; if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { scrollDelta = getScrollY(); } else if (direction == View.FOCUS_DOWN) { if (getChildCount() > 0) { int daBottom = getChildAt(0).getBottom(); int screenBottom = getScrollY() + getHeight(); if (daBottom - screenBottom < maxJump) { scrollDelta = daBottom - screenBottom; } } } if (scrollDelta == 0) { return false; } doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); } if (currentFocused != null && currentFocused.isFocused() && isOffScreenV(currentFocused)) { // previously focused item still has focus and is off screen, give // it up (take it back to ourselves) // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are // sure to // get it) final int descendantFocusability = getDescendantFocusability(); // save setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); requestFocus(); setDescendantFocusability(descendantFocusability); // restore } return true; } public boolean arrowScrollH(int direction) { View currentFocused = findFocus(); if (currentFocused == this) currentFocused = null; View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); final int maxJump = getMaxScrollAmountH(); if (nextFocused != null && isWithinDeltaOfScreenH(nextFocused, maxJump)) { nextFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(nextFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect); doScrollX(scrollDelta); nextFocused.requestFocus(direction); } else { // no new focus int scrollDelta = maxJump; if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { scrollDelta = getScrollX(); } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { int daRight = getChildAt(0).getRight(); int screenRight = getScrollX() + getWidth(); if (daRight - screenRight < maxJump) { scrollDelta = daRight - screenRight; } } if (scrollDelta == 0) { return false; } doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); } if (currentFocused != null && currentFocused.isFocused() && isOffScreenH(currentFocused)) { // previously focused item still has focus and is off screen, give // it up (take it back to ourselves) // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are // sure to // get it) final int descendantFocusability = getDescendantFocusability(); // save setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); requestFocus(); setDescendantFocusability(descendantFocusability); // restore } return true; } /** * @return whether the descendant of this scroll view is scrolled off * screen. */ private boolean isOffScreenV(View descendant) { return !isWithinDeltaOfScreenV(descendant, 0, getHeight()); } private boolean isOffScreenH(View descendant) { return !isWithinDeltaOfScreenH(descendant, 0); } /** * @return whether the descendant of this scroll view is within delta * pixels of being on the screen. */ private boolean isWithinDeltaOfScreenV(View descendant, int delta, int height) { descendant.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(descendant, mTempRect); return (mTempRect.bottom + delta) >= getScrollY() && (mTempRect.top - delta) <= (getScrollY() + height); } private boolean isWithinDeltaOfScreenH(View descendant, int delta) { descendant.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(descendant, mTempRect); return (mTempRect.right + delta) >= getScrollX() && (mTempRect.left - delta) <= (getScrollX() + getWidth()); } /** * Smooth scroll by a Y delta * * @param delta the number of pixels to scroll by on the Y axis */ private void doScrollY(int delta) { if (delta != 0) { if (mSmoothScrollingEnabled) { smoothScrollBy(0, delta); } else { scrollBy(0, delta); } } } private void doScrollX(int delta) { if (delta != 0) { if (mSmoothScrollingEnabled) { smoothScrollBy(delta, 0); } else { scrollBy(delta, 0); } } } /** * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. * * @param dx the number of pixels to scroll by on the X axis * @param dy the number of pixels to scroll by on the Y axis */ public void smoothScrollBy(int dx, int dy) { if (getChildCount() == 0) { // Nothing to do. return; } long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; if (duration > ANIMATED_SCROLL_GAP) { final int height = getHeight() - getPaddingBottom() - getPaddingTop(); final int bottom = getChildAt(0).getHeight(); final int maxY = Math.max(0, bottom - height); final int scrollY = getScrollY(); dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; final int width = getWidth() - getPaddingRight() - getPaddingLeft(); final int right = getChildAt(0).getWidth(); final int maxX = Math.max(0, right - width); final int scrollX = getScrollX(); dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; mScroller.startScroll(scrollX, scrollY, dx, dy); invalidate(); } else { if (!mScroller.isFinished()) { mScroller.abortAnimation(); } scrollBy(dx, dy); } mLastScroll = AnimationUtils.currentAnimationTimeMillis(); } /** * Like {@link #scrollTo}, but scroll smoothly instead of immediately. * * @param x the position where to scroll on the X axis * @param y the position where to scroll on the Y axis */ public final void smoothScrollTo(int x, int y) { smoothScrollBy(x - getScrollX(), y - getScrollY()); } /** * <p>The scroll range of a scroll view is the overall height of all of its * children.</p> */ @Override protected int computeVerticalScrollRange() { final int count = getChildCount(); final int contentHeight = getHeight() - getPaddingBottom() - getPaddingTop(); if (count == 0) { return contentHeight; } return getChildAt(0).getBottom(); } @Override protected int computeHorizontalScrollRange() { final int count = getChildCount(); final int contentWidth = getWidth() - getPaddingLeft() - getPaddingRight(); if (count == 0) { return contentWidth; } return getChildAt(0).getRight(); } @Override protected int computeVerticalScrollOffset() { return Math.max(0, super.computeVerticalScrollOffset()); } @Override protected int computeHorizontalScrollOffset() { return Math.max(0, super.computeHorizontalScrollOffset()); } @Override protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { int childWidthMeasureSpec; int childHeightMeasureSpec; childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) { final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { // This is called at drawing time by ViewGroup. We don't want to // re-show the scrollbars at this point, which scrollTo will do, // so we replicate most of scrollTo here. // // It's a little odd to call onScrollChanged from inside the drawing. // // It is, except when you remember that computeScroll() is used to // animate scrolling. So unless we want to defer the onScrollChanged() // until the end of the animated scrolling, we don't really have a // choice here. // // I agree. The alternative, which I think would be worse, is to post // something and tell the subclasses later. This is bad because there // will be a window where mScrollX/Y is different from what the app // thinks it is. // int x = mScroller.getCurrX(); int y = mScroller.getCurrY(); if (getChildCount() > 0) { View child = getChildAt(0); x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()); y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight()); super.scrollTo(x, y); } awakenScrollBars(); // Keep on drawing until the animation has finished. postInvalidate(); } } /** * Scrolls the view to the given child. * * @param child the View to scroll to */ private void scrollToChild(View child) { child.getDrawingRect(mTempRect); /* Offset from child's local coordinates to ScrollView coordinates */ offsetDescendantRectToMyCoords(child, mTempRect); int scrollDeltaV = computeScrollDeltaToGetChildRectOnScreenV(mTempRect); int scrollDeltaH = computeScrollDeltaToGetChildRectOnScreenH(mTempRect); if (scrollDeltaH != 0 || scrollDeltaV != 0) { scrollBy(scrollDeltaH, scrollDeltaV); } } /** * If rect is off screen, scroll just enough to get it (or at least the * first screen size chunk of it) on screen. * * @param rect The rectangle. * @param immediate True to scroll immediately without animation * @return true if scrolling was performed */ private boolean scrollToChildRect(Rect rect, boolean immediate) { final int deltaV = computeScrollDeltaToGetChildRectOnScreenV(rect); final int deltaH = computeScrollDeltaToGetChildRectOnScreenH(rect); final boolean scroll = deltaH != 0 || deltaV != 0; if (scroll) { if (immediate) { scrollBy(deltaH, deltaV); } else { smoothScrollBy(deltaH, deltaV); } } return scroll; } /** * Compute the amount to scroll in the Y direction in order to get * a rectangle completely on the screen (or, if taller than the screen, * at least the first screen size chunk of it). * * @param rect The rect. * @return The scroll delta. */ protected int computeScrollDeltaToGetChildRectOnScreenV(Rect rect) { if (getChildCount() == 0) return 0; int height = getHeight(); int screenTop = getScrollY(); int screenBottom = screenTop + height; int fadingEdge = getVerticalFadingEdgeLength(); // leave room for top fading edge as long as rect isn't at very top if (rect.top > 0) { screenTop += fadingEdge; } // leave room for bottom fading edge as long as rect isn't at very bottom if (rect.bottom < getChildAt(0).getHeight()) { screenBottom -= fadingEdge; } int scrollYDelta = 0; if (rect.bottom > screenBottom && rect.top > screenTop) { // need to move down to get it in view: move down just enough so // that the entire rectangle is in view (or at least the first // screen size chunk). if (rect.height() > height) { // just enough to get screen size chunk on scrollYDelta += (rect.top - screenTop); } else { // get entire rect at bottom of screen scrollYDelta += (rect.bottom - screenBottom); } // make sure we aren't scrolling beyond the end of our content int bottom = getChildAt(0).getBottom(); int distanceToBottom = bottom - screenBottom; scrollYDelta = Math.min(scrollYDelta, distanceToBottom); } else if (rect.top < screenTop && rect.bottom < screenBottom) { // need to move up to get it in view: move up just enough so that // entire rectangle is in view (or at least the first screen // size chunk of it). if (rect.height() > height) { // screen size chunk scrollYDelta -= (screenBottom - rect.bottom); } else { // entire rect at top scrollYDelta -= (screenTop - rect.top); } // make sure we aren't scrolling any further than the top our content scrollYDelta = Math.max(scrollYDelta, -getScrollY()); } return scrollYDelta; } protected int computeScrollDeltaToGetChildRectOnScreenH(Rect rect) { if (getChildCount() == 0) return 0; int width = getWidth(); int screenLeft = getScrollX(); int screenRight = screenLeft + width; int fadingEdge = getHorizontalFadingEdgeLength(); // leave room for left fading edge as long as rect isn't at very left if (rect.left > 0) { screenLeft += fadingEdge; } // leave room for right fading edge as long as rect isn't at very right if (rect.right < getChildAt(0).getWidth()) { screenRight -= fadingEdge; } int scrollXDelta = 0; if (rect.right > screenRight && rect.left > screenLeft) { // need to move right to get it in view: move right just enough so // that the entire rectangle is in view (or at least the first // screen size chunk). if (rect.width() > width) { // just enough to get screen size chunk on scrollXDelta += (rect.left - screenLeft); } else { // get entire rect at right of screen scrollXDelta += (rect.right - screenRight); } // make sure we aren't scrolling beyond the end of our content int right = getChildAt(0).getRight(); int distanceToRight = right - screenRight; scrollXDelta = Math.min(scrollXDelta, distanceToRight); } else if (rect.left < screenLeft && rect.right < screenRight) { // need to move right to get it in view: move right just enough so that // entire rectangle is in view (or at least the first screen // size chunk of it). if (rect.width() > width) { // screen size chunk scrollXDelta -= (screenRight - rect.right); } else { // entire rect at left scrollXDelta -= (screenLeft - rect.left); } // make sure we aren't scrolling any further than the left our content scrollXDelta = Math.max(scrollXDelta, -getScrollX()); } return scrollXDelta; } @Override public void requestChildFocus(View child, View focused) { if (!mScrollViewMovedFocus) { if (!mIsLayoutDirty) { scrollToChild(focused); } else { // The child may not be laid out yet, we can't compute the scroll yet mChildToScrollTo = focused; } } super.requestChildFocus(child, focused); } /** * When looking for focus in children of a scroll view, need to be a little * more careful not to give focus to something that is scrolled off screen. * * This is more expensive than the default {@link android.view.ViewGroup} * implementation, otherwise this behavior might have been made the default. */ @Override protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) { // convert from forward / backward notation to up / down / left / right // (ugh). // TODO: // if (direction == View.FOCUS_FORWARD) { // direction = View.FOCUS_RIGHT; // } else if (direction == View.FOCUS_BACKWARD) { // direction = View.FOCUS_LEFT; // } final View nextFocus = previouslyFocusedRect == null ? FocusFinder.getInstance().findNextFocus(this, null, direction) : FocusFinder.getInstance().findNextFocusFromRect(this, previouslyFocusedRect, direction); if (nextFocus == null) { return false; } // if (isOffScreenH(nextFocus)) { // return false; // } return nextFocus.requestFocus(direction, previouslyFocusedRect); } @Override public boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate) { // offset into coordinate space of this scroll view rectangle.offset(child.getLeft() - child.getScrollX(), child.getTop() - child.getScrollY()); return scrollToChildRect(rectangle, immediate); } @Override public void requestLayout() { mIsLayoutDirty = true; super.requestLayout(); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { super.onLayout(changed, l, t, r, b); mIsLayoutDirty = false; // Give a child focus if it needs it if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { scrollToChild(mChildToScrollTo); } mChildToScrollTo = null; // Calling this with the present values causes it to re-clam them scrollTo(getScrollX(), getScrollY()); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); View currentFocused = findFocus(); if (null == currentFocused || this == currentFocused) return; // If the currently-focused view was visible on the screen when the // screen was at the old height, then scroll the screen to make that // view visible with the new screen height. if (isWithinDeltaOfScreenV(currentFocused, 0, oldh)) { currentFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(currentFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreenV(mTempRect); doScrollY(scrollDelta); } final int maxJump = getRight() - getLeft(); if (isWithinDeltaOfScreenH(currentFocused, maxJump)) { currentFocused.getDrawingRect(mTempRect); offsetDescendantRectToMyCoords(currentFocused, mTempRect); int scrollDelta = computeScrollDeltaToGetChildRectOnScreenH(mTempRect); doScrollX(scrollDelta); } } /** * Return true if child is an descendant of parent, (or equal to the parent). */ private boolean isViewDescendantOf(View child, View parent) { if (child == parent) { return true; } final ViewParent theParent = child.getParent(); return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); } /** * Fling the scroll view * * @param velocityY The initial velocity in the Y direction. Positive * numbers mean that the finger/cursor is moving down the screen, * which means we want to scroll towards the top. */ public void fling(int velocityX, int velocityY) { if (getChildCount() > 0) { int width = getWidth() - getPaddingRight() - getPaddingLeft(); int right = getChildAt(0).getWidth(); int height = getHeight() - getPaddingBottom() - getPaddingTop(); int bottom = getChildAt(0).getHeight(); mScroller.fling(getScrollX(), getScrollY(), velocityX, velocityY, 0, Math.max(0, right - width), 0, Math.max(0, bottom - height)); // final boolean movingDown = velocityX > 0 || velocityY > 0; // // View newFocused = // findFocusableViewInMyBoundsV(movingDown, mScroller.getFinalY(), findFocus()); // if (newFocused == null) { // newFocused = this; // } // // if (newFocused != findFocus() // && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { // mScrollViewMovedFocus = true; // mScrollViewMovedFocus = false; // } invalidate(); } } /** * {@inheritDoc} * * <p>This version also clamps the scrolling to the bounds of our child. */ @Override public void scrollTo(int x, int y) { // we rely on the fact the View.scrollBy calls scrollTo. if (getChildCount() > 0) { View child = getChildAt(0); x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()); y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight()); if (x != getScrollX() || y != getScrollY()) { super.scrollTo(x, y); } } } private int clamp(int n, int my, int child) { if (my >= child || n < 0) { /* my >= child is this case: * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * or * |--------------- me ---------------| * |------ child ------| * * n < 0 is this case: * |------ me ------| * |-------- child --------| * |-- mScrollX --| */ return 0; } if ((my+n) > child) { /* this case: * |------ me ------| * |------ child ------| * |-- mScrollX --| */ return child-my; } return n; } public boolean isFlingEnabled() { return mFlingEnabled; } public void setFlingEnabled(boolean flingEnabled) { this.mFlingEnabled = flingEnabled; } }