问题
I have an app in which it has a main canvas and i have added another canvas of bitmap on top of it. In the main canvas I have eraser in which it will detect when the user touches the bitmap area. I want to know the x and y inside the bitmap where the eraser touches and so on while moving from main canvas since the bitmap canvas is different from the main canvas. I want the x and y of the main canvas be the same with the bitmap canvas to be move. Thanks
Here's my snippet
public void touch_move(float x, float y) {
float dx = Math.abs(x - mX);
float dy = Math.abs(y - mY);
if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
mX = x;
mY = y;
}
if(istouchingBitmap(x, y) == true){
float xRatio = (float)bitmap.getWidth() / parent.getWidth();
float yRatio = (float)bitmap.getHeight() / parent.getHeight();
float xPos = lastX * xRatio;
float yPos = lastY * yRatio;
eraseBitmap(bitmap, xPos , yPos , 5);
}
}
function to detect the bitmap when touch
/**
*
* @param x The X location of the cursor in main View.
* @param y The Y location of the cursor in main View.
* @return This is only used to detect if the cursor is touching the Bitmap Image.
*/
public boolean istouchingBitmap(float x, float y) {
matrix.invert(inverse);
float[] pts = {x, y};
inverse.mapPoints(pts);
if (!bounds.contains(pts[0], pts[1])) {
return false;
}
// copy the location
lastX = x;
lastY = y;
return Color.alpha(bitmap.getPixel((int) pts[0], (int) pts[1])) != 0;
}
回答1:
You only need to get the X and Y values from the touch event.
Then sustract the top,left margin/offset values respectively.
The result is the X,Y coordinate relative to the start of the bitmap.
PD: When doing this, i was having problems handling the status bar height, since the way of measuring it changes between Android version and device model.
Hope this helps.
回答2:
Finally :). This code will map the screen X and Y to the x and y inside the bitmap. Hope it help others. Good luck
float[] point = new float[] {lastX, lastY};
Matrix inverse = new Matrix();
matrix.invert(inverse);
inverse.mapPoints(point);
bitmapX = point[0];
bitmapY = point[1];
canvas.drawCircle(bitmapX, bitmapY, radius, mPaint); // punch a hole
来源:https://stackoverflow.com/questions/33519081/how-to-get-the-x-and-y-touch-location-inside-the-bitmap