android SurfaceView绘制 重新学习--切图clipRect详解
解释都在代码注释中：
1 public class SampleView extends View { 2 private Paint mPaint; 3 private Path mPath; 4 5 public SampleView(Context context) { 6 super(context); 7 setFocusable(true); 8 9 mPaint = new Paint(); 10 mPaint.setAntiAlias(true); 11 mPaint.setStrokeWidth(6); 12 mPaint.setTextSize(16); 13 mPaint.setTextAlign(Paint.Align.RIGHT); 14 15 mPath = new Path(); 16 } 17 18 private void drawScene(Canvas canvas) { 19 canvas.clipRect(0, 0, 100, 100); 20 21 canvas.drawColor(Color.WHITE); 22 23 mPaint.setColor(Color.RED); 24 canvas.drawLine(0, 0, 100, 100, mPaint); 25 26 mPaint.setColor(Color.GREEN); 27 canvas.drawCircle(30, 70, 30, mPaint); 28 29 mPaint.setColor(Color.BLUE); 30 canvas.drawText("Clipping", 100, 30, mPaint); 31 } 32 33 @Override 34 protected void onDraw(Canvas canvas) { 35 canvas.drawColor(Color.GRAY); 36 canvas.save(); 37 canvas.translate(10, 10); 38 drawScene(canvas); 39 canvas.restore(); 40 41 // Region.Op.DIFFERENCE B-A 42 canvas.save(); 43 canvas.translate(160, 10); 44 canvas.clipRect(10, 10, 90, 90); // B 45 canvas.clipRect(30, 30, 70, 70, Region.Op.DIFFERENCE); // A 46 drawScene(canvas); 47 canvas.restore(); 48 49 // 这里因为在3.0以上的硬件上开启了硬件加速,会有问题. 50 // Region.Op.REPLACE 不论A和B的集合状况，B的范围将全部进行显示，如果和A有交集，则将覆盖A的交集范围 51 // canvas.save(); 52 // canvas.translate(10, 160); 53 // mPath.reset(); 54 // canvas.clipPath(mPath); // B 55 // mPath.addCircle(50, 50, 50, Path.Direction.CCW); 56 // canvas.clipPath(mPath, Region.Op.REPLACE);// A 57 // drawScene(canvas); 58 // canvas.restore(); 59 60 // Region.Op.UNION AB并集范围 61 canvas.save(); 62 canvas.translate(160, 160); 63 canvas.clipRect(0, 0, 60, 60);// B 64 canvas.clipRect(40, 40, 100, 100, Region.Op.UNION);// A 65 drawScene(canvas); 66 canvas.restore(); 67 68 // Region.Op.XOR 异或，去掉AB相交的部分 69 canvas.save(); 70 canvas.translate(10, 310); 71 canvas.clipRect(40, 40, 100, 100); // B 72 canvas.clipRect(0, 0, 60, 60, Region.Op.XOR); // A 73 drawScene(canvas); 74 canvas.restore(); 75 76 // Region.Op.REVERSE_DIFFERENCE A-B 77 canvas.save(); 78 canvas.translate(160, 310); 79 canvas.clipRect(0, 0, 60, 60); // B 80 canvas.clipRect(40, 40, 100, 100, Region.Op.REVERSE_DIFFERENCE);// A 81 drawScene(canvas); 82 canvas.restore(); 83 } 84 }
这个在游戏中还是很常用的。
关于硬件加速的问题，http://developer.android.com/guide/topics/graphics/hardware-accel.html#controlling
谷歌文档说的很清楚。
