基于SurfaceView实现可拖动视频控件

public class DragSurfaceView extends SurfaceView implements View.OnTouchListener {
  protected int screenWidth;
  protected int screenHeight;
  protected int lastX;
  protected int lastY;
  private int oriLeft;
  private int oriRight;
  private int oriTop;
  private int oriBottom;
  private int dragDirection;
  private static final int TOP = 0x15;
  private static final int LEFT = 0x16;
  private static final int BOTTOM = 0x17;
  private static final int RIGHT = 0x18;
  private static final int LEFT_TOP = 0x11;
  private static final int RIGHT_TOP = 0x12;
  private static final int LEFT_BOTTOM = 0x13;
  private static final int RIGHT_BOTTOM = 0x14;
  private static final int CENTER = 0x19;
  private int offset = 20;

  /**
   * 初始化获取屏幕宽高
   */
  protected void initScreenW_H() {
    screenHeight = getResources().getDisplayMetrics().heightPixels - 40;
    screenWidth = getResources().getDisplayMetrics().widthPixels;
    Log.i("DragViewTAG", "DragSurfaceView.initScreenW_H: screenWidth="+screenWidth+", screenHeight="+screenHeight);
  }
  public DragSurfaceView(Context context) {
    super(context);
    setOnTouchListener(this);
    initScreenW_H();
  }

  public DragSurfaceView(Context context, AttributeSet attrs) {
    super(context, attrs);
    setOnTouchListener(this);
    initScreenW_H();
  }

  public DragSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    setOnTouchListener(this);
    initScreenW_H();
  }


  @Override
  public boolean onTouch(View v, MotionEvent event) {
    int action = event.getAction();
    if (action == MotionEvent.ACTION_DOWN) {
      oriLeft = v.getLeft();
      oriRight = v.getRight();
      oriTop = v.getTop();
      oriBottom = v.getBottom();
      lastY = (int) event.getRawY();
      lastX = (int) event.getRawX();
      dragDirection = getDirection(v, (int) event.getX(),
          (int) event.getY());
    }
    // 处理拖动事件
    delDrag(v, event, action);
    if(action==MotionEvent.ACTION_UP){
      dragDirection=0;
    }
    invalidate();
    return true;
  }


  /**
   * 获取触摸点flag
   *
   * @param v
   * @param x
   * @param y
   * @return
   */
  protected int getDirection(View v, int x, int y) {
    int left = v.getLeft();
    int right = v.getRight();
    int bottom = v.getBottom();
    int top = v.getTop();
    if (x < 40 && y < 40) {
      return LEFT_TOP;
    }
    if (y < 40 && right - left - x < 40) {
      return RIGHT_TOP;
    }
    if (x < 40 && bottom - top - y < 40) {
      return LEFT_BOTTOM;
    }
    if (right - left - x < 40 && bottom - top - y < 40) {
      return RIGHT_BOTTOM;
    }
    if (x < 40) {
      return LEFT;
    }
    if (y < 40) {
      return TOP;
    }
    if (right - left - x < 40) {
      return RIGHT;
    }
    if (bottom - top - y < 40) {
      return BOTTOM;
    }
    return CENTER;
  }

  /**
   * 处理拖动事件
   *
   * @param v
   * @param event
   * @param action
   */
  protected void delDrag(View v, MotionEvent event, int action) {
    switch (action) {
      case MotionEvent.ACTION_MOVE:
        int dx = (int) event.getRawX() - lastX;
        int dy = (int) event.getRawY() - lastY;
        switch (dragDirection) {
          case LEFT: // 左边缘
            left(v, dx);
            break;
          case RIGHT: // 右边缘
            right(v, dx);
            break;
          case BOTTOM: // 下边缘
            bottom(v, dy);
            break;
          case TOP: // 上边缘
            top(v, dy);
            break;
          case CENTER: // 点击中心-->>移动
            center(v, dx, dy);
            break;
          case LEFT_BOTTOM: // 左下
            left(v, dx);
            bottom(v, dy);
            break;
          case LEFT_TOP: // 左上
            left(v, dx);
            top(v, dy);
            break;
          case RIGHT_BOTTOM: // 右下
            right(v, dx);
            bottom(v, dy);
            break;
          case RIGHT_TOP: // 右上
            right(v, dx);
            top(v, dy);
            break;
          default:
            break;
        }
        v.layout(oriLeft, oriTop, oriRight, oriBottom);
//        if (dragDirection != CENTER) {
//          v.layout(oriLeft, oriTop, oriRight, oriBottom);
//        }
        lastX = (int) event.getRawX();
        lastY = (int) event.getRawY();
        Log.i("DragViewTAG", "DragSurfaceView.delDrag:ACTION_MOVE direction="+dragDirection+", left="+oriLeft+", top="+oriTop+", right="+oriRight+", bottom="+oriBottom);
        break;
      case MotionEvent.ACTION_UP:
        ViewGroup.LayoutParams newLayoutParams = getNewLayoutParams();
        if(newLayoutParams!=null){
          Log.i("DragViewTAG", "DragSurfaceView.delDrag:ACTION_UP width="+newLayoutParams.width+", height="+newLayoutParams.height);
          setLayoutParams(newLayoutParams);
        }else {
          Log.e("DragViewTAG", "DragSurfaceView.delDrag: 父组件类型？");
          v.layout(oriLeft, oriTop, oriRight, oriBottom);
        }
        break;
      default:
        break;
    }
  }

  private ViewGroup.LayoutParams getNewLayoutParams(){
    if(getLayoutParams() instanceof RelativeLayout.LayoutParams){
      RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams)getLayoutParams( );
      lp.leftMargin = oriLeft;
      lp.topMargin = oriTop;
      lp.width = oriRight-oriLeft;
      lp.height = oriBottom-oriTop;
      return lp;
    }else if(getLayoutParams() instanceof FrameLayout.LayoutParams) {
      FrameLayout.LayoutParams lp = (FrameLayout.LayoutParams) getLayoutParams();
      lp.leftMargin = oriLeft;
      lp.topMargin = oriTop;
      lp.width = oriRight - oriLeft;
      lp.height = oriBottom - oriTop;
      return lp;
    }
    return null;
  }

  /**
   * 触摸点为中心->>移动
   *
   * @param v
   * @param dx
   * @param dy
   */
  private void center(View v, int dx, int dy) {
    oriLeft += dx;
    oriTop += dy;
    oriRight += dx;
    oriBottom += dy;
    Log.i("DragViewTAG", "DragSurfaceView.center: v.left="+v.getLeft()+", v.top="+v.getTop());
    if (oriLeft < -offset) {
      Log.e("DragViewTAG", "DragSurfaceView.center: 左侧越界, left="+oriLeft+", offset="+offset);
      oriLeft = -offset;
      oriRight = oriLeft + v.getWidth();
    }
    if (oriRight > screenWidth + offset) {
      Log.e("DragViewTAG", "DragSurfaceView.center: 右侧越界, right="+oriRight+", screenWidth="+screenWidth+", offset="+offset);
      oriRight = screenWidth + offset;
      oriLeft = oriRight - v.getWidth();
    }
    if (oriTop < -offset) {
      Log.e("DragViewTAG", "DragSurfaceView.center: 顶部越界, top="+oriTop+", offset="+offset);
      oriTop = -offset;
      oriBottom = oriTop + v.getHeight();
    }
    if (oriBottom > screenHeight + offset) {
      Log.e("DragViewTAG", "DragSurfaceView.center: 底部越界, bottom="+oriBottom+", screenHeight="+screenHeight+", offset="+offset);
      oriBottom = screenHeight + offset;
      oriTop = oriBottom - v.getHeight();
    }
//    v.layout(left, top, right, bottom);

  }

  /**
   * 触摸点为上边缘
   *
   * @param v
   * @param dy
   */
  private void top(View v, int dy) {
    oriTop += dy;
    if (oriTop < -offset) {
      oriTop = -offset;
    }
    if (oriBottom - oriTop - 2 * offset < 200) {
      oriTop = oriBottom - 2 * offset - 200;
    }
  }

  /**
   * 触摸点为下边缘
   *
   * @param v
   * @param dy
   */
  private void bottom(View v, int dy) {
    oriBottom += dy;
    if (oriBottom > screenHeight + offset) {
      oriBottom = screenHeight + offset;
    }
    if (oriBottom - oriTop - 2 * offset < 200) {
      oriBottom = 200 + oriTop + 2 * offset;
    }
  }

  /**
   * 触摸点为右边缘
   *
   * @param v
   * @param dx
   */
  private void right(View v, int dx) {
    oriRight += dx;
    if (oriRight > screenWidth + offset) {
      oriRight = screenWidth + offset;
    }
    if (oriRight - oriLeft - 2 * offset < 200) {
      oriRight = oriLeft + 2 * offset + 200;
    }
  }

  /**
   * 触摸点为左边缘
   *
   * @param v
   * @param dx
   */
  private void left(View v, int dx) {
    oriLeft += dx;
    if (oriLeft < -offset) {
      oriLeft = -offset;
    }
    if (oriRight - oriLeft - 2 * offset < 200) {
      oriLeft = oriRight - 2 * offset - 200;
    }
  }

  /**
   * 获取截取宽度
   *
   * @return
   */
  public int getCutWidth() {
    return getWidth() - 2 * offset;
  }

  /**
   * 获取截取高度
   *
   * @return
   */
  public int getCutHeight() {
    return getHeight() - 2 * offset;
  }
}