经常使用今日头条、网易新闻的同学们应该都会注意到用于管理多个频道的可拖动排序GridView,下面介绍一下可拖动的DragGridView的实现方法。代码放在GitHub上https://github.com/zhaoyu87/DragGridView,需要的同学可以下载
DragGridView继承自GridView,当长按选中某个item进行拖动,放手更新GridView顺序:
1.重写onTouchEvent响应拖动事件:被按下时记录按下坐标;拖动时更新被拖动视图显示;放开时更新排序
2.设置OnItemLongClickListener:响应长按选取拖动item,获取被选中item bitmap,添加到窗口显示
3.通过view.getDrawingCache()获取被选中item的bitmap,用于绘制拖动的view
4.使用WindowManager来向窗口添加view,更新view显示。
5. MotionEvent中的getX()为相对于容器的坐标,这里就是GridView;getRawX()为相对于整个屏幕的坐标
DragGridView实现如下,注释中有更详细的解释
public class DragGridView extends GridView {
private static final int DRAG_IMG_SHOW = 1;
private static final int DRAG_IMG_NOT_SHOW = 0;
private static final String LOG_TAG = "DragGridView";
private static final float AMP_FACTOR = 1.2f;
/**被拖动的视图*/
private ImageView dragImageView;
private WindowManager.LayoutParams dragImageViewParams;
private WindowManager windowManager;
private boolean isViewOnDrag = false;
/**前一次拖动的位置*/
private int preDraggedOverPositon = AdapterView.INVALID_POSITION;
private int downRawX;
private int downRawY;
/**长按选中拖动item*/
private OnItemLongClickListener onLongClickListener = new OnItemLongClickListener(){
@Override
//长按item开始拖动
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
//记录长按item位置
preDraggedOverPositon = position;
//获取被长按item的drawing cache
view.destroyDrawingCache();
view.setDrawingCacheEnabled(true);
//通过被长按item,获取拖动item的bitmap
Bitmap dragBitmap = Bitmap.createBitmap(view.getDrawingCache());
//设置拖动item的参数
dragImageViewParams.gravity = Gravity.TOP | Gravity.LEFT;
//设置拖动item为原item 1.2倍
dragImageViewParams.width = (int)(AMP_FACTOR*dragBitmap.getWidth());
dragImageViewParams.height = (int)(AMP_FACTOR*dragBitmap.getHeight());
//设置触摸点为绘制拖动item的中心
dragImageViewParams.x = (downRawX - dragImageViewParams.width/2);
dragImageViewParams.y = (downRawY - dragImageViewParams.height/2);
dragImageViewParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
| WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
| WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
| WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
dragImageViewParams.format = PixelFormat.TRANSLUCENT;
dragImageViewParams.windowAnimations = 0;
//dragImageView为被拖动item的容器,清空上一次的显示
if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {
windowManager.removeView(dragImageView);
dragImageView.setTag(DRAG_IMG_NOT_SHOW);
}
//设置本次被长按的item
dragImageView.setImageBitmap(dragBitmap);
//添加拖动item到屏幕
windowManager.addView(dragImageView, dragImageViewParams);
dragImageView.setTag(DRAG_IMG_SHOW);
isViewOnDrag = true;
//设置被长按item不显示
((GridViewAdapter)getAdapter()).hideView(position);
return true;
}
};
public DragGridView(Context context) {
super(context);
initView();
}
public DragGridView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
public DragGridView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initView();
}
public void initView() {
setOnItemLongClickListener(onLongClickListener);
//初始化显示被拖动item的image view
dragImageView = new ImageView(getContext());
dragImageView.setTag(DRAG_IMG_NOT_SHOW);
//初始化用于设置dragImageView的参数对象
dragImageViewParams = new WindowManager.LayoutParams();
//获取窗口管理对象,用于后面向窗口中添加dragImageView
windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
//被按下时记录按下的坐标
if(ev.getAction() == MotionEvent.ACTION_DOWN) {
//获取触摸点相对于屏幕的坐标
downRawX = (int)ev.getRawX();
downRawY = (int)ev.getRawY();
}
//dragImageView处于被拖动时,更新dragImageView位置
else if((ev.getAction() == MotionEvent.ACTION_MOVE) && (isViewOnDrag == true)) {
Log.i(LOG_TAG, "" + ev.getRawX() + " " + ev.getRawY());
//设置触摸点为dragImageView中心
dragImageViewParams.x = (int)(ev.getRawX() - dragImageView.getWidth()/2);
dragImageViewParams.y = (int)(ev.getRawY() - dragImageView.getHeight()/2);
//更新窗口显示
windowManager.updateViewLayout(dragImageView, dragImageViewParams);
//获取当前触摸点的item position
int currDraggedPosition = pointToPosition((int)ev.getX(), (int)ev.getY());
//如果当前停留位置item不等于上次停留位置的item,交换本次和上次停留的item
if((currDraggedPosition != AdapterView.INVALID_POSITION) && (currDraggedPosition != preDraggedOverPositon)) {
((GridViewAdapter)getAdapter()).swapView(preDraggedOverPositon, currDraggedPosition);
preDraggedOverPositon = currDraggedPosition;
}
}
//释放dragImageView
else if((ev.getAction() == MotionEvent.ACTION_UP) && (isViewOnDrag == true)) {
((GridViewAdapter)getAdapter()).showHideView();
if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {
windowManager.removeView(dragImageView);
dragImageView.setTag(DRAG_IMG_NOT_SHOW);
}
isViewOnDrag = false;
}
return super.onTouchEvent(ev);
}
}
GridViewAdapter继承自BaseAdapter:
1.提供showHideView、hideView两个方法用于显示和隐藏选中Item的Text
2.提供swapView方法用于拖动过程中更新GridView中item显示
public class GridViewAdapter extends BaseAdapter {
private Context context;
private List<String> strList;
private int hidePosition = AdapterView.INVALID_POSITION;
public GridViewAdapter(Context context, List<String> strList) {
this.context = context;
this.strList = strList;
}
@Override
public int getCount() {
return strList.size();
}
@Override
public String getItem(int position) {
return strList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
TextView view;
if(convertView == null) {
view = new TextView(context);
}
else {
view = (TextView)convertView;
}
//hide时隐藏Text
if(position != hidePosition) {
view.setText(strList.get(position));
}
else {
view.setText("");
}
view.setId(position);
return view;
}
public void hideView(int pos) {
hidePosition = pos;
notifyDataSetChanged();
}
public void showHideView() {
hidePosition = AdapterView.INVALID_POSITION;
notifyDataSetChanged();
}
public void removeView(int pos) {
strList.remove(pos);
notifyDataSetChanged();
}
//更新拖动时的gridView
public void swapView(int draggedPos, int destPos) {
//从前向后拖动,其他item依次前移
if(draggedPos < destPos) {
strList.add(destPos+1, getItem(draggedPos));
strList.remove(draggedPos);
}
//从后向前拖动,其他item依次后移
else if(draggedPos > destPos) {
strList.add(destPos, getItem(draggedPos));
strList.remove(draggedPos+1);
}
hidePosition = destPos;
notifyDataSetChanged();
}
}
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