首先Listview继承关系：
ListView --extends--> AbsListview --extends--> AdapterView --extends--> ViewGroup --extends--> View
ListView的构造方法：
此时初始化listview的风格，间距
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public ListView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);//TypedArray实例是个属性的容器，context.obtainStyledAttributes()方法返回得到final TypedArray a = context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ListView, defStyleAttr, defStyleRes);//从属性处初始化值CharSequence[] entries = a.getTextArray(com.android.internal.R.styleable.ListView_entries);//如果值不为null,shezhi moren de buju fangshiif (entries != null) {setAdapter(new ArrayAdapter<CharSequence>(context,com.android.internal.R.layout.simple_list_item_1, entries));}//系统自带的风格线final Drawable d = a.getDrawable(com.android.internal.R.styleable.ListView_divider);if (d != null) {// If a divider is specified use its intrinsic height for divider heightsetDivider(d);}//设置listview头部final Drawable osHeader = a.getDrawable(com.android.internal.R.styleable.ListView_overScrollHeader);if (osHeader != null) {setOverscrollHeader(osHeader);}//设置listview底部final Drawable osFooter = a.getDrawable(com.android.internal.R.styleable.ListView_overScrollFooter);if (osFooter != null) {setOverscrollFooter(osFooter);}//设置listview Item的间距final int dividerHeight = a.getDimensionPixelSize(com.android.internal.R.styleable.ListView_dividerHeight, 0);if (dividerHeight != 0) {setDividerHeight(dividerHeight);}mHeaderDividersEnabled = a.getBoolean(R.styleable.ListView_headerDividersEnabled, true);mFooterDividersEnabled = a.getBoolean(R.styleable.ListView_footerDividersEnabled, true);a.recycle();}
在往下看：
响应箭头事件时，列表视图可以滚动的最大值.
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public int getMaxScrollAmount() {return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop));}
在往下看：
确保Listview触及顶部或底部边缘 调整在ListView顶部或底部的view以适应我们的视觉感应;
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private void adjustViewsUpOrDown() {final int childCount = getChildCount();int delta;if (childCount > 0) {View child;if (!mStackFromBottom) {// Uh-oh -- we came up short. Slide all views up to make them// align with the topchild = getChildAt(0);delta = child.getTop() - mListPadding.top;if (mFirstPosition != 0) {// It's OK to have some space above the first item if it is// part of the vertical spacingdelta -= mDividerHeight;}if (delta < 0) {// We only are looking to see if we are too low, not too highdelta = 0;}} else {// we are too high, slide all views down to align with bottomchild = getChildAt(childCount - 1);delta = child.getBottom() - (getHeight() - mListPadding.bottom);if (mFirstPosition + childCount < mItemCount) {// It's OK to have some space below the last item if it is// part of the vertical spacingdelta += mDividerHeight;}if (delta > 0) {delta = 0;}}if (delta != 0) {offsetChildrenTopAndBottom(-delta);}}}接下来是添加头部的方法；为ListView顶部添加一个固定的View，如果HeaderView多于一个，会按照添加的顺序进行排列：public void addHeaderView(View v, Object data, boolean isSelectable) {final FixedViewInfo info = new FixedViewInfo();info.view = v;info.data = data;info.isSelectable = isSelectable;mHeaderViewInfos.add(info);mAreAllItemsSelectable &= isSelectable;// Wrap the adapter if it wasn't already wrapped.if (mAdapter != null) {if (!(mAdapter instanceof HeaderViewListAdapter)) {mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, mAdapter);}// In the case of re-adding a header view, or adding one later on,// we need to notify the observer.if (mDataSetObserver != null) {mDataSetObserver.onChanged();}}}
接下来 添加 头部view的方法和获取头部view的数目：
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public void addHeaderView(View v) {addHeaderView(v, null, true);}@Overridepublic int getHeaderViewsCount() {return mHeaderViewInfos.size();}
删除头部的方法；如果头部信息的list>0,并且Adapter不为null，删除头部信息，并进行回调：
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public boolean removeHeaderView(View v) {//如果头部信息的list>0,并且Adapter不为null，删除头部信息，并进行回调if (mHeaderViewInfos.size() > 0) {boolean result = false;if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeHeader(v)) {if (mDataSetObserver != null) {mDataSetObserver.onChanged();}result = true;}//调用下面删除指定view的操作removeFixedViewInfo(v, mHeaderViewInfos);return result;}return false;}这是找到对应的view进行删除操作：
private void removeFixedViewInfo(View v, ArrayList<FixedViewInfo> where) { int len = where.size(); for (int i = 0; i < len; ++i) { FixedViewInfo info = where.get(i); if (info.view == v) { where.remove(i); break; } } }添加Listview底部布局：
/** * Add a fixed view to appear at the bottom of the list. If addFooterView is * called more than once, the views will appear in the order they were * added. Views added using this call can take focus if they want. * <p> * NOTE: Call this before calling setAdapter. This is so ListView can wrap * the supplied cursor with one that will also account for header and footer * views. * * @param v The view to add. * @param data Data to associate with this view * @param isSelectable true if the footer view can be selected */ public void addFooterView(View v, Object data, boolean isSelectable) { // NOTE: do not enforce the adapter being null here, since unlike in // addHeaderView, it was never enforced here, and so existing apps are // relying on being able to add a footer and then calling setAdapter to // force creation of the HeaderViewListAdapter wrapper FixedViewInfo info = new FixedViewInfo(); info.view = v; info.data = data; info.isSelectable = isSelectable; mFooterViewInfos.add(info); // in the case of re-adding a footer view, or adding one later on, // we need to notify the observer if (mAdapter != null && mDataSetObserver != null) { mDataSetObserver.onChanged(); } } /** * Add a fixed view to appear at the bottom of the list. If addFooterView is called more * than once, the views will appear in the order they were added. Views added using * this call can take focus if they want. * <p>NOTE: Call this before calling setAdapter. This is so ListView can wrap the supplied * cursor with one that will also account for header and footer views. * * * @param v The view to add. */ public void addFooterView(View v) { addFooterView(v, null, true); }获取添加的底部布局的个数：
@Override public int getFooterViewsCount() { return mFooterViewInfos.size(); }删除指定的底部布局，并通知其他相关：
/** * Removes a previously-added footer view. * * @param v The view to remove * @return * true if the view was removed, false if the view was not a footer view */ public boolean removeFooterView(View v) { if (mFooterViewInfos.size() > 0) { boolean result = false; if (mAdapter != null && ((HeaderViewListAdapter) mAdapter).removeFooter(v)) { if (mDataSetObserver != null) { mDataSetObserver.onChanged(); } result = true; } removeFixedViewInfo(v, mFooterViewInfos); return result; } return false; }获取listview使用的Adapter:
/** * Returns the adapter currently in use in this ListView. The returned adapter * might not be the same adapter passed to {@link #setAdapter(ListAdapter)} but * might be a {@link WrapperListAdapter}. *返回listview当前正在使用的Adapter，adapter不一定是通过setAdapter方法传入的adapter，有可能是一个WrapperListAdapter * @return The adapter currently used to display data in this ListView. * * @see #setAdapter(ListAdapter) */ @Override public ListAdapter getAdapter() { return mAdapter; }为listview添加数据setAdapter 实现原理：
/** * Sets the data behind this ListView. * * The adapter passed to this method may be wrapped by a {@link WrapperListAdapter}, * depending on the ListView features currently in use. For instance, adding * headers and/or footers will cause the adapter to be wrapped. * 通过setAdapter方法添加的adapter根据当前ListView的使用情况可能被装饰为一个WrapperListAdapter，比如说添加一个HeaderView或者FooterView。
在该方法中，先把以前的数据和观察者去掉，然后再重新设置各种参数
* @param adapter The ListAdapter which is responsible for maintaining the * data backing this list and for producing a view to represent an * item in that data set. * * @see #getAdapter() */ @Override public void setAdapter(ListAdapter adapter) { if (mAdapter != null && mDataSetObserver != null) { mAdapter.unregisterDataSetObserver(mDataSetObserver); }//重置list
resetList(); mRecycler.clear(); if (mHeaderViewInfos.size() > 0|| mFooterViewInfos.size() > 0) { mAdapter = new HeaderViewListAdapter(mHeaderViewInfos, mFooterViewInfos, adapter); } else { mAdapter = adapter; } mOldSelectedPosition = INVALID_POSITION; mOldSelectedRowId = INVALID_ROW_ID; // AbsListView#setAdapter will update choice mode states. super.setAdapter(adapter); if (mAdapter != null) { mAreAllItemsSelectable = mAdapter.areAllItemsEnabled(); mOldItemCount = mItemCount; mItemCount = mAdapter.getCount(); checkFocus(); mDataSetObserver = new AdapterDataSetObserver(); mAdapter.registerDataSetObserver(mDataSetObserver); mRecycler.setViewTypeCount(mAdapter.getViewTypeCount()); int position; if (mStackFromBottom) { position = lookForSelectablePosition(mItemCount - 1, false); } else { position = lookForSelectablePosition(0, true); } setSelectedPositionInt(position); setNextSelectedPositionInt(position); if (mItemCount == 0) { // Nothing selected checkSelectionChanged(); } } else { mAreAllItemsSelectable = true; checkFocus(); // Nothing selected checkSelectionChanged(); } requestLayout(); }在20行调用了 ，清空listview的头部，也清空底部，删除layout中所有的view：
/** * The list is empty. Clear everything out. * */ @Override void resetList() { // The parent's resetList() will remove all views from the layout so we need to // cleanup the state of our footers and headers clearRecycledState(mHeaderViewInfos); clearRecycledState(mFooterViewInfos); super.resetList(); mLayoutMode = LAYOUT_NORMAL; }8,9行调用clearRecycledState
private void clearRecycledState(ArrayList<FixedViewInfo> infos) { if (infos != null) { final int count = infos.size(); for (int i = 0; i < count; i++) { final View child = infos.get(i).view; final LayoutParams p = (LayoutParams) child.getLayoutParams(); if (p != null) { p.recycledHeaderFooter = false; } } } }