根据前面文章中ListView拖拽的实现原理，我们也是很容易实现推拽GridView的，下面我就以相同步骤实现基本的GridView拖拽效果。
因为GridView不用做分组处理，代码处理起来更简洁，而且原理前面已经讲解清楚了，代码中只是简单的过下，必要的地方简单的注释一下。
1.主界面DragGridActivity.
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public class DragGridActivity extends Activity { private static List<String> list = null; //自定义适配器 private DragGridAdapter adapter = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.drag_grid_activity); initData(); //后面用到的自定义GridView DragGridView dragGridView = (DragGridView)findViewById(R.id.drag_grid); adapter = new DragGridAdapter(this, list); dragGridView.setAdapter(adapter); } public void initData(){ //数据结果 list = new ArrayList<String>(); for(int i=0; i<12; i++){ list.add("grid_"+i%12); } }} |
2.主界面UI布局drag_grid_activity.xml.
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<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#ffffff" android:padding="10dip" > <com.fengjian.test.DragGridView android:id="@+id/drag_grid" android:layout_width="fill_parent" android:layout_height="wrap_content" android:cacheColorHint="#00000000" android:numColumns="3" android:stretchMode="columnWidth" android:verticalSpacing="5dip" android:horizontalSpacing="20dip" android:background="#ffffff"/></LinearLayout> |
3.列表项布局drag_grid_item.xml.
<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingLeft="5dip" android:paddingRight="5dip"> <ImageView android:id="@+id/drag_grid_item_image" android:src="@drawable/grid_icon" android:layout_margin="5dip" android:layout_alignParentTop="true" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <ImageView android:id="@+id/drag_grid_item_drag" android:src="@drawable/grid_drag" android:layout_alignParentTop="true" android:layout_alignParentRight="true" android:layout_width="wrap_content" android:layout_height="wrap_content"/></RelativeLayout> |
4.自定义适配器DragGridAdapter，继承ArrayAdapter<String>.
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public static class DragGridAdapter extends ArrayAdapter<String>{ public DragGridAdapter(Context context, List<String> objects) { super(context, 0, objects); } public List<String> getList(){ return list; } @Override public View getView(int position, View convertView, ViewGroup parent) { View view = convertView; if(view==null){ view = LayoutInflater.from(getContext()).inflate(R.layout.drag_grid_item, null); } try { //根据文件名获取资源文件夹中的图片资源 Field f= (Field)R.drawable.class.getDeclaredField(getItem(position)); int i=f.getInt(R.drawable.class); ImageView imageview= (ImageView)view.findViewById(R.id.drag_grid_item_image); imageview.setImageResource(i); } catch (SecurityException e) { e.printStackTrace(); } catch (NoSuchFieldException e) { e.printStackTrace(); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } return view; } } |
5.自定义视图类DragGridView，继承GridView.
public class DragGridView extends GridView { //定义基本的成员变量 private ImageView dragImageView; private int dragSrcPosition; private int dragPosition; //x,y坐标的计算 private int dragPointX; private int dragPointY; private int dragOffsetX; private int dragOffsetY; private WindowManager windowManager; private WindowManager.LayoutParams windowParams; private int scaledTouchSlop; private int upScrollBounce; private int downScrollBounce; public DragGridView(Context context, AttributeSet attrs) { super(context, attrs); }} |
6. 重写触控拦截事件方法onInterceptTouchEvent().
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@Overridepublic boolean onInterceptTouchEvent(MotionEvent ev) { if(ev.getAction()==MotionEvent.ACTION_DOWN){ int x = (int)ev.getX(); int y = (int)ev.getY(); dragSrcPosition = dragPosition = pointToPosition(x, y); if(dragPosition==AdapterView.INVALID_POSITION){ return super.onInterceptTouchEvent(ev); } ViewGroup itemView = (ViewGroup) getChildAt(dragPosition-getFirstVisiblePosition()); dragPointX = x - itemView.getLeft(); dragPointY = y - itemView.getTop(); dragOffsetX = (int) (ev.getRawX() - x); dragOffsetY = (int) (ev.getRawY() - y); View dragger = itemView.findViewById(R.id.drag_grid_item_drag); //如果选中拖动图标 if(dragger!=null&&dragPointX>dragger.getLeft()&&dragPointX<dragger.getRight()&&dragPointY>dragger.getTop()&&dragPointY<dragger.getBottom()+20){ upScrollBounce = Math.min(y-scaledTouchSlop, getHeight()/4); downScrollBounce = Math.max(y+scaledTouchSlop, getHeight()*3/4); itemView.setDrawingCacheEnabled(true); Bitmap bm = Bitmap.createBitmap(itemView.getDrawingCache()); startDrag(bm, x, y); } return false; } return super.onInterceptTouchEvent(ev);} |
startDrag和stopDrag方法如下：
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public void startDrag(Bitmap bm, int x, int y){ stopDrag(); windowParams = new WindowManager.LayoutParams(); windowParams.gravity = Gravity.TOP|Gravity.LEFT; windowParams.x = x - dragPointX + dragOffsetX; windowParams.y = y - dragPointY + dragOffsetY; windowParams.width = WindowManager.LayoutParams.WRAP_CONTENT; windowParams.height = WindowManager.LayoutParams.WRAP_CONTENT; windowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN; windowParams.format = PixelFormat.TRANSLUCENT; windowParams.windowAnimations = 0; ImageView imageView = new ImageView(getContext()); imageView.setImageBitmap(bm); windowManager = (WindowManager)getContext().getSystemService("window"); windowManager.addView(imageView, windowParams); dragImageView = imageView;}public void onDrag(int x, int y){ if(dragImageView!=null){ windowParams.alpha = 0.8f; windowParams.x = x - dragPointX + dragOffsetX; windowParams.y = y - dragPointY + dragOffsetY; windowManager.updateViewLayout(dragImageView, windowParams); } int tempPosition = pointToPosition(x, y); if(tempPosition!=INVALID_POSITION){ dragPosition = tempPosition; } //滚动 if(y<upScrollBounce||y>downScrollBounce){ //使用setSelection来实现滚动 setSelection(dragPosition); } } |
7.重写onTouchEvent()方法.
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@Overridepublic boolean onTouchEvent(MotionEvent ev) { if(dragImageView!=null&&dragPosition!=INVALID_POSITION){ int action = ev.getAction(); switch(action){ case MotionEvent.ACTION_UP: int upX = (int)ev.getX(); int upY = (int)ev.getY(); stopDrag(); onDrop(upX,upY); break; case MotionEvent.ACTION_MOVE: int moveX = (int)ev.getX(); int moveY = (int)ev.getY(); onDrag(moveX,moveY); break; default:break; } return true; } return super.onTouchEvent(ev);} |
其中onDrag方法如下：
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public void onDrag(int x, int y){ if(dragImageView!=null){ windowParams.alpha = 0.8f; windowParams.x = x - dragPointX + dragOffsetX; windowParams.y = y - dragPointY + dragOffsetY; windowManager.updateViewLayout(dragImageView, windowParams); } int tempPosition = pointToPosition(x, y); if(tempPosition!=INVALID_POSITION){ dragPosition = tempPosition; } //滚动 if(y<upScrollBounce||y>downScrollBounce){ //使用setSelection来实现滚动 setSelection(dragPosition); } } |
8.放下影像，数据更新。
在onDrop方法中实现：
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public void onDrop(int x, int y){ //为了避免滑动到分割线的时候，返回-1的问题 int tempPosition = pointToPosition(x, y); if(tempPosition!=INVALID_POSITION){ dragPosition = tempPosition; } //超出边界处理 if(y<getChildAt(0).getTop()){ //超出上边界 dragPosition = 0; }else if(y>getChildAt(getChildCount()-1).getBottom()||(y>getChildAt(getChildCount()-1).getTop()&&x>getChildAt(getChildCount()-1).getRight())){ //超出下边界 dragPosition = getAdapter().getCount()-1; } //数据交换 if(dragPosition!=dragSrcPosition&&dragPosition>-1&&dragPosition<getAdapter().getCount()){ DragGridAdapter adapter = (DragGridAdapter)getAdapter(); String dragItem = adapter.getItem(dragSrcPosition); adapter.remove(dragItem); adapter.insert(dragItem, dragPosition); Toast.makeText(getContext(), adapter.getList().toString(), Toast.LENGTH_SHORT).show(); } } |
10.最终效果图如下：
图1
图2
这篇文章也算是前面文章的一个补充和扩展。