我想在 View 上的点之间画线，然后将这些点拉到所需的位置，即使形状会发生变化。
我知道如何通过使用此方法在两点之间绘制线条canvas.drawLine(10, 10, 90, 10, paint);我可以在两点之间绘制线条。
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最佳答案
这是完成的过程。假设您有自己的观点，请将其全局化:
PointF topLeft = new PointF(10,10);
PointF topRight = new PointF(90,10);
PointF bottomLeft = new PointF(10,90);
PointF bottomRight = new PointF(90,90);
您需要做的是围绕每个点创建一个RectF。 RectF越大，该点的触摸区域越大。
float sizeOfRect = 5f;
RectF topLeftTouchArea = new RectF(topLeft.x - sizeOfRect, topLeft.y - sizeOfRect, topLeft.x + sizeOfRect, topLeft.y + sizeOfRect);
//Do this for the other points too
定义一些全局变量以跟踪用户在onTouch中的操作。一个int是要触摸的角，其他四个是角的标识符。
private final int NONE = -1, TOUCH_TOP_LEFT = 0, TOUCH_TOP_RIGHT = 1, TOUCH_BOT_LEFT = 2, TOUCH_BOT_RIGHT = 3;
int currentTouch = NONE;
现在，在您的onTouch事件中，您可以像这样检查用户的接触点:
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
//The user just put their finger down.
//We check to see which corner the user is touching
//And set our global, currentTouch, to the appropriate constant.
case MotionEvent.ACTION_DOWN:
if (topLeftTouchArea.contains(event.getX(), event.getY()) {
currentTouch = TOUCH_TOP_LEFT;
} else if (topRightTouchArea.contains(event.getX(),event.getY()) {
currentTouch = TOUCH_TOP_RIGHT;
} else if (botLeftTouchArea.contains(event.getX(),event.getY()) {
currentTouch = TOUCH_BOT_LEFT;
} else if (botRightTouchArea.contains(event.getX(), event.getY()) {
currentTouch = TOUCH_BOT_RIGHT;
} else {
return false; //Return false if user touches none of the corners
}
return true; //Return true if the user touches one of the corners
//Now we know which corner the user is touching.
//When the user moves their finger, we update the point to the user position and invalidate.
case MotionEvent.ACTION_MOVE:
switch (currentTouch) {
case TOUCH_TOP_LEFT:
topLeft.x = event.getX();
topLeft.y = event.getY();
//The bottom left x position has to move with the top left corner
bottomLeft.x = topLeft.x;
//The top right y position has to move with the top left corner
topRight.y = topLeft.y;
invalidate();
return true;
case TOUCH_TOP_RIGHT:
topRight.x = event.getX();
topRight.y = event.getY();
//The top left y position has to move with the top right corner
topLeft.y = topRight.y;
//The bottom right x position has to move with the top right corner
bottomRight.x = topRight.x;
invalidate();
return true;
case TOUCH_BOT_LEFT:
bottomLeft.x = event.getX();
bottomLeft.y = event.getY();
bottomRight.y = bottomLeft.y;
topLeft.x = bottomLeft.x;
invalidate();
return true;
case TOUCH_BOT_RIGHT:
bottomRight.x = event.getX();
bottomRight.y = event.getY();
topRight.x = bottomRight.x;
bottomLeft.y = bottomRight.y;
invalidate();
return true;
}
//We returned true for all of the above cases, because we used the event
return false; //If currentTouch is none of the above cases, return false
//Here the user lifts up their finger.
//We update the points one last time, and set currentTouch to NONE.
case MotionEvent.ACTION_UP:
switch (currentTouch) {
case TOUCH_TOP_LEFT:
topLeft.x = event.getX();
topLeft.y = event.getY();
//The bottom left x position has to move with the top left corner
bottomLeft.x = topLeft.x;
//The top right y position has to move with the top left corner
topRight.y = topLeft.y;
invalidate();
currentTouch = NONE;
return true;
case TOUCH_TOP_RIGHT:
topRight.x = event.getX();
topRight.y = event.getY();
//The top left y position has to move with the top right corner
topLeft.y = topRight.y;
//The bottom right x position has to move with the top right corner
bottomRight.x = topRight.x;
invalidate();
currentTouch = NONE;
return true;
case TOUCH_BOT_LEFT:
bottomLeft.x = event.getX();
bottomLeft.y = event.getY();
bottomRight.y = bottomLeft.y;
topLeft.x = bottomLeft.x;
invalidate();
currentTouch = NONE;
return true;
case TOUCH_BOT_RIGHT:
bottomRight.x = event.getX();
bottomRight.y = event.getY();
topRight.x = bottomRight.x;
bottomLeft.y = bottomRight.y;
invalidate();
currentTouch = NONE;
return true;
}
return false;
}
}
这是在您的点周围制作一个矩形。想象一下在图片中围绕您的点绘制的框。这些是由Rect对象创建的“触摸板”。矩形的大小由sizeOfRect设置。在onTouchEvent中，它检查每个矩形对象，以查看用户的触摸是否在矩形内，这表明用户试图触摸该点。