Android 2D Graphics学习（二）、Canvas篇2、Canvas裁剪和Region、RegionIter(2)_H5之家

ApiDemo中关于组合的例子：

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：

5、裁剪的一个小用处
public class ClippingRegion extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(new SampleView(this)); } private class SampleView extends View { private Bitmap mBitmap; private int limitLength = 0; private int width; private int heigth; private static final int CLIP_HEIGHT = 30; private boolean status = HIDE;//显示还是隐藏的状态，最开始为HIDE private static final boolean SHOW = true;//显示图片 private static final boolean HIDE = false;//隐藏图片 public SampleView(Context context) { super(context); mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image1); limitLength = width = mBitmap.getWidth(); heigth = mBitmap.getHeight(); } @Override protected void onDraw(Canvas canvas) { Region region = new Region(); int i = 0; while (i * CLIP_HEIGHT <= heigth) {//计算clip的区域 if (i % 2 == 0) { region.union(new Rect(0, i * CLIP_HEIGHT, limitLength, (i + 1) * CLIP_HEIGHT)); } else { region.union(new Rect(width - limitLength, i * CLIP_HEIGHT, width, (i + 1) * CLIP_HEIGHT)); } i++; } canvas.clipRegion(region); canvas.drawBitmap(mBitmap, 0, 0, new Paint()); if (status == HIDE) {//如果此时是隐藏 limitLength -= 5; if(limitLength<=0) status=SHOW; } else {//如果此时是显示 limitLength += 5; if(limitLength>=width) status=HIDE; } invalidate(); } } }
效果就是一直这样交叉的隐藏和显示图片

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