android的拖拽问题--onTouchEvent事件
要实现图片的拖拽 主要是通过onTouchEven计算好坐标事件 然后进行重绘。下面的程序是别人的，重新加载 了一次
?img = BitmapFactory.decodeResource(context.getResources(), drawable); 加载一个图片在案例中专门做了一个类 进行设置。
加载图片之后 就可以进行实践判断和重绘
@Override protected void onDraw(Canvas canvas) { //canvas.drawColor(0xFFCCCCCC); //if you want another background color //draw the balls on the canvas for (ColorBall ball : colorballs) { canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null); } }?
public boolean onTouchEvent(MotionEvent event) { int eventaction = event.getAction(); int X = (int)event.getX(); int Y = (int)event.getY(); switch (eventaction ) { case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball balID = 0; for (ColorBall ball : colorballs) { // check if inside the bounds of the ball (circle) // get the center for the ball int centerX = ball.getX() + 25; int centerY = ball.getY() + 25; // calculate the radius from the touch to the center of the ball double radCircle = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y))); // if the radius is smaller then 23 (radius of a ball is 22), then it must be on the ball if (radCircle < 23){ balID = ball.getID(); break; } // check all the bounds of the ball (square) //if (X > ball.getX() && X < ball.getX()+50 && Y > ball.getY() && Y < ball.getY()+50){ //balID = ball.getID(); //break; //} } break; case MotionEvent.ACTION_MOVE: // touch drag with the ball // move the balls the same as the finger if (balID > 0) { colorballs[balID-1].setX(X-25); colorballs[balID-1].setY(Y-25); } break; case MotionEvent.ACTION_UP: // touch drop - just do things here after dropping break; } // redraw the canvas invalidate(); return true; }?