如何在android中使Canvas绘制区域透明? [英] How to make Canvas draw area transparent in android?
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问题描述
我想让 Canvas 区域透明,因为我想在它后面添加一个 Image,以便 Canvas 操作发生在图像上方.我的画布代码在这里
I would like to make Canvas area transparent because I would like to add an Image behind it so that Canvas actions happen above the image.My code for the canvas is here
public class Panel extends SurfaceView implements SurfaceHolder.Callback {
private ViewThread mThread;
private ArrayList<Element> mElements = new ArrayList<Element>();
public Panel(Context context, AttributeSet attrs) {
super(context, attrs);
getHolder().addCallback(this);
mThread = new ViewThread(this);
}
public void doDraw(Canvas canvas) {
canvas.drawColor(Color.TRANSPARENT);
synchronized (mElements) {
for (Element element : mElements) {
element.doDraw(canvas);
}
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// TODO Auto-generated method stub
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
if (!mThread.isAlive()) {
mThread = new ViewThread(this);
mThread.setRunning(true);
mThread.start();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
if (mThread.isAlive()) {
mThread.setRunning(false);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
synchronized (mElements) {
mElements.add(new Element(getResources(), (int) event.getX(), (int) event.getY()));
}
return super.onTouchEvent(event);
}
}
如何实现它,任何关于它的片段都会非常有帮助.谢谢
How to achieve it, any snippets on it will be very much helpful.Thanks
推荐答案
我得到了这个输出
public Panel(Context context, AttributeSet attrs) {
super(context, attrs);
this.setBackgroundColor(Color.TRANSPARENT);
this.setZOrderOnTop(true); //necessary
getHolder().setFormat(PixelFormat.TRANSPARENT);
getHolder().addCallback(this);
mThread = new ViewThread(this);
}
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