Android编程之控件可拖动的实现方法

private static final String TAG = "DragViewActivity";
private ImageView iv_dv_view;
private TextView tv_drag_view;
private int startx;
private int starty;
private SharedPreferences sp;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.dragview);
//   Drawable drawable = new ColorDrawable(color.transparent);
//   getWindow().setBackgroundDrawable(drawable);
    iv_dv_view = (ImageView) this.findViewById(R.id.iv_dv_view);
    tv_drag_view = (TextView) this.findViewById(R.id.tv_drag_view);
    sp = this.getSharedPreferences("config", Context.MODE_PRIVATE);
    iv_dv_view.setOnTouchListener(this);
  }
  @Override
  protected void onResume() {
    super.onResume();
    int x = sp.getInt("lastx", 0);
    int y = sp.getInt("lasty", 0);
//   iv_dv_view.layout(iv_dv_view.getLeft() + x, iv_dv_view.getTop() + y,
//       iv_dv_view.getRight() + x, iv_dv_view.getBottom() + y);
//   iv_dv_view.invalidate();//界面重新渲染
    LayoutParams params = (LayoutParams) iv_dv_view.getLayoutParams();
    params.leftMargin = x;
    params.topMargin = y;
    iv_dv_view.setLayoutParams(params);
  }
  @Override
  public boolean onTouch(View v, MotionEvent event) {
    switch (v.getId()) {
    // 如果手指放在imageView上拖动
    case R.id.iv_dv_view:
      // event.getRawX(); //获取手指第一次接触屏幕在x方向的坐标
      switch (event.getAction()) {
      case MotionEvent.ACTION_DOWN:// 获取手指第一次接触屏幕
        startx = (int) event.getRawX();
        starty = (int) event.getRawY();
        break;
      case MotionEvent.ACTION_MOVE:// 手指在屏幕上移动对应的事件
        int x = (int) event.getRawX();
        int y = (int) event.getRawY();
        if (y <400) {
          // 设置TextView在窗体的下面
          tv_drag_view.layout(tv_drag_view.getLeft(), 420,
              tv_drag_view.getRight(), 440);
        } else {
          tv_drag_view.layout(tv_drag_view.getLeft(), 60,
              tv_drag_view.getRight(), 80);
        }
        // 获取手指移动的距离
        int dx = x - startx;
        int dy = y - starty;
        // 得到imageView最开始的各顶点的坐标
        int l = iv_dv_view.getLeft();
        int r = iv_dv_view.getRight();
        int t = iv_dv_view.getTop();
        int b = iv_dv_view.getBottom();
        // 更改imageView在窗体的位置
        iv_dv_view.layout(l + dx, t + dy, r + dx, b + dy);
        // 获取移动后的位置
        startx = (int) event.getRawX();
        starty = (int) event.getRawY();
        break;
      case MotionEvent.ACTION_UP:// 手指离开屏幕对应事件
        Log.i(TAG, "手指离开屏幕");
        // 记录最后图片在窗体的位置
        int lasty = iv_dv_view.getTop();
        int lastx = iv_dv_view.getLeft();
        Editor editor = sp.edit();
        editor.putInt("lasty", lasty);
        editor.putInt("lastx", lastx);
        editor.commit();
        break;
      }
      break;
    }
    return true;// 不会中断触摸事件的返回
}

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