android可拖动排序GridView实现
浏览数：20 /
时间：2015年06月11日
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。关于WindowManagerService对窗口的组织方式，博客http://blog.csdn.net/luoshengyang/article/details/8498908有介绍，可以参考。
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
1 public class DragGridView extends GridView {
2 private static final int DRAG_IMG_SHOW = 1;
3 private static final int DRAG_IMG_NOT_SHOW = 0;
4 private static final String LOG_TAG = "DragGridView";
5 private static final float AMP_FACTOR = 1.2f;
6
7 /**被拖动的视图*/
8 private ImageView dragImageView;
9 private WindowManager.LayoutParams dragImageViewParams;
10 private WindowManager windowManager;
11 private boolean isViewOnDrag = false;
12
13 /**前一次拖动的位置*/
14 private int preDraggedOverPositon = AdapterView.INVALID_POSITION;
15 private int downRawX;
16 private int downRawY;
17
18 /**长按选中拖动item*/
19 private OnItemLongClickListener onLongClickListener = new OnItemLongClickListener(){
20
21 @Override
22 //长按item开始拖动
23 public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
24
25 //记录长按item位置
26 preDraggedOverPositon = position;
27
28 //获取被长按item的drawing cache
29 view.destroyDrawingCache();
30 view.setDrawingCacheEnabled(true);
31 //通过被长按item，获取拖动item的bitmap
32 Bitmap dragBitmap = Bitmap.createBitmap(view.getDrawingCache());
33
34 //设置拖动item的参数
35 dragImageViewParams.gravity = Gravity.TOP | Gravity.LEFT;
36 //设置拖动item为原item 1.2倍
37 dragImageViewParams.width = (int)(AMP_FACTOR*dragBitmap.getWidth());
38 dragImageViewParams.height = (int)(AMP_FACTOR*dragBitmap.getHeight());
39 //设置触摸点为绘制拖动item的中心
40 dragImageViewParams.x = (downRawX - dragImageViewParams.width/2);
41 dragImageViewParams.y = (downRawY - dragImageViewParams.height/2);
42 dragImageViewParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
43 | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
44 | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
45 | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN;
46 dragImageViewParams.format = PixelFormat.TRANSLUCENT;
47 dragImageViewParams.windowAnimations = 0;
48
49 //dragImageView为被拖动item的容器，清空上一次的显示
50 if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {
51 windowManager.removeView(dragImageView);
52 dragImageView.setTag(DRAG_IMG_NOT_SHOW);
53 }
54
55 //设置本次被长按的item
56 dragImageView.setImageBitmap(dragBitmap);
57
58 //添加拖动item到屏幕
59 windowManager.addView(dragImageView, dragImageViewParams);
60 dragImageView.setTag(DRAG_IMG_SHOW);
61 isViewOnDrag = true;
62
63 //设置被长按item不显示
64 ((GridViewAdapter)getAdapter()).hideView(position);
65 return true;
66 }
67 };
68
69 public DragGridView(Context context) {
70 super(context);
71 initView();
72 }
73
74 public DragGridView(Context context, AttributeSet attrs) {
75 super(context, attrs);
76 initView();
77 }
78
79 public DragGridView(Context context, AttributeSet attrs, int defStyleAttr) {
80 super(context, attrs, defStyleAttr);
81 initView();
82 }
83
84 public void initView() {
85 setOnItemLongClickListener(onLongClickListener);
86 //初始化显示被拖动item的image view
87 dragImageView = new ImageView(getContext());
88 dragImageView.setTag(DRAG_IMG_NOT_SHOW);
89 //初始化用于设置dragImageView的参数对象
90 dragImageViewParams = new WindowManager.LayoutParams();
91 //获取窗口管理对象，用于后面向窗口中添加dragImageView
92 windowManager = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
93 }
94
95
96 @Override
97 public boolean onTouchEvent(MotionEvent ev) {
98
99 //被按下时记录按下的坐标
100 if(ev.getAction() == MotionEvent.ACTION_DOWN) {
101 //获取触摸点相对于屏幕的坐标
102 downRawX = (int)ev.getRawX();
103 downRawY = (int)ev.getRawY();
104 }
105 //dragImageView处于被拖动时，更新dragImageView位置
106 else if((ev.getAction() == MotionEvent.ACTION_MOVE) && (isViewOnDrag == true)) {
107 Log.i(LOG_TAG, "" + ev.getRawX() + " " + ev.getRawY());
108 //设置触摸点为dragImageView中心
109 dragImageViewParams.x = (int)(ev.getRawX() - dragImageView.getWidth()/2);
110 dragImageViewParams.y = (int)(ev.getRawY() - dragImageView.getHeight()/2);
111 //更新窗口显示
112 windowManager.updateViewLayout(dragImageView, dragImageViewParams);
113 //获取当前触摸点的item position
114 int currDraggedPosition = pointToPosition((int)ev.getX(), (int)ev.getY());
115 //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
116 if((currDraggedPosition != AdapterView.INVALID_POSITION) && (currDraggedPosition != preDraggedOverPositon)) {
117 ((GridViewAdapter)getAdapter()).swapView(preDraggedOverPositon, currDraggedPosition);
118 preDraggedOverPositon = currDraggedPosition;
119 }
120 }
121 //释放dragImageView
122 else if((ev.getAction() == MotionEvent.ACTION_UP) && (isViewOnDrag == true)) {
123 ((GridViewAdapter)getAdapter()).showHideView();
124 if((int)dragImageView.getTag() == DRAG_IMG_SHOW) {
125 windowManager.removeView(dragImageView);
126 dragImageView.setTag(DRAG_IMG_NOT_SHOW);
127 }
128 isViewOnDrag = false;
129 }
130 return super.onTouchEvent(ev);
131 }
132 }
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
1 public class GridViewAdapter extends BaseAdapter {
2 private Context context;
3 private List<String> strList;
4 private int hidePosition = AdapterView.INVALID_POSITION;
5
6 public GridViewAdapter(Context context, List<String> strList) {
7 this.context = context;
8 this.strList = strList;
9 }
10
11 @Override
12 public int getCount() {
13 return strList.size();
14 }
15
16 @Override
17 public String getItem(int position) {
18 return strList.get(position);
19 }
20
21 @Override
22 public long getItemId(int position) {
23 return position;
24 }
25
26 @Override
27 public View getView(int position, View convertView, ViewGroup parent) {
28 TextView view;
29 if(convertView == null) {
30 view = new TextView(context);
31 }
32 else {
33 view = (TextView)convertView;
34 }
35
36 //hide时隐藏Text
37 if(position != hidePosition) {
38 view.setText(strList.get(position));
39 }
40 else {
41 view.setText("");
42 }
43 view.setId(position);
44
45 return view;
46 }
47
48 public void hideView(int pos) {
49 hidePosition = pos;
50 notifyDataSetChanged();
51 }
52
53 public void showHideView() {
54 hidePosition = AdapterView.INVALID_POSITION;
55 notifyDataSetChanged();
56 }
57
58 public void removeView(int pos) {
59 strList.remove(pos);
60 notifyDataSetChanged();
61 }
62
63 //更新拖动时的gridView
64 public void swapView(int draggedPos, int destPos) {
65 //从前向后拖动，其他item依次前移
66 if(draggedPos < destPos) {
67 strList.add(destPos+1, getItem(draggedPos));
68 strList.remove(draggedPos);
69 }
70 //从后向前拖动，其他item依次后移
71 else if(draggedPos > destPos) {
72 strList.add(destPos, getItem(draggedPos));
73 strList.remove(draggedPos+1);
74 }
75 hidePosition = destPos;
76 notifyDataSetChanged();
77 }
78 }
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