[java] view plain

Note that unlike

clipRect() and clipPath() which transform their arguments by the

current matrix, clipRegion() assumes its argument is already in the

coordinate system of the current layer's bitmap, and so not

transformation is performed.

Note that unlike clipRect() and clipPath() which transform their arguments by the current matrix, clipRegion() assumes its argument is already in the coordinate system of the current layer's bitmap, and so not transformation is performed. 与clipRect和clipPath要使用当前的matrix进行变换不同。clipRegion不会进行转换。也就是说canvas的matrix对clipRegion没有影响。

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), paint);//矩形实际大小为50*50

canvas.drawColor(Color.BLACK);

Paint paint=new Paint(); canvas.scale(0.5f, 0.5f); canvas.save(); canvas.clipRect(new Rect(100,100,200,200));//裁剪区域实际大小为50*50 canvas.drawColor(Color.RED); canvas.restore(); canvas.drawRect(new Rect(0,0,100,100), paint);//矩形实际大小为50*50 canvas.clipRegion(new Region(new Rect(300,300,400,400)));//裁剪区域实际大小为100*100 canvas.drawColor(Color.BLACK);

可以看到，Canvas的变换 对clipRegion没有作用。

ApiDemo中关于组合的例子：

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Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

}

View {

private Paint mPaint;

private Path mPath;

public SampleView(Context context) {

super(context);

private void drawScene(Canvas canvas) {

, mPaint);

mPaint.setColor(Color.BLUE);

, mPaint);

}

@Override

protected void onDraw(Canvas canvas) {

canvas.clipPath(mPath); // makes the clip empty

, Path.Direction.CCW);

public class Clipping extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new SampleView(this)); } private static class SampleView extends View { private Paint mPaint; private Path mPath; public SampleView(Context context) { super(context); setFocusable(true); mPaint = new Paint(); mPaint.setAntiAlias(true); mPaint.setStrokeWidth(6); mPaint.setTextSize(16); mPaint.setTextAlign(Paint.Align.RIGHT); mPath = new Path(); } private void drawScene(Canvas canvas) { canvas.clipRect(0, 0, 100, 100); canvas.drawColor(Color.WHITE); mPaint.setColor(Color.RED); canvas.drawLine(0, 0, 100, 100, mPaint); mPaint.setColor(Color.GREEN); canvas.drawCircle(30, 70, 30, mPaint); mPaint.setColor(Color.BLUE); canvas.drawText("Clipping", 100, 30, mPaint); } @Override protected void onDraw(Canvas canvas) { canvas.drawColor(Color.GRAY); canvas.save(); canvas.translate(10, 10); drawScene(canvas); canvas.restore(); canvas.save(); canvas.translate(160, 10); canvas.clipRect(10, 10, 90, 90); canvas.clipRect(30, 30, 70, 70, Region.Op.DIFFERENCE); drawScene(canvas); canvas.restore(); canvas.save(); canvas.translate(10, 160); mPath.reset(); canvas.clipPath(mPath); // makes the clip empty mPath.addCircle(50, 50, 50, Path.Direction.CCW); canvas.clipPath(mPath, Region.Op.REPLACE); drawScene(canvas); canvas.restore(); canvas.save(); canvas.translate(160, 160); canvas.clipRect(0, 0, 60, 60); canvas.clipRect(40, 40, 100, 100, Region.Op.UNION); drawScene(canvas); canvas.restore(); canvas.save(); canvas.translate(10, 310); canvas.clipRect(0, 0, 60, 60); canvas.clipRect(40, 40, 100, 100, Region.Op.XOR); drawScene(canvas); canvas.restore(); canvas.save(); canvas.translate(160, 310); canvas.clipRect(0, 0, 60, 60); canvas.clipRect(40, 40, 100, 100, Region.Op.REVERSE_DIFFERENCE); drawScene(canvas); canvas.restore(); } } }
效果图：