Android Api Demos登顶之路（八十六）Graphics-->Regions

/*这个demon演示了Region的不同的组合方式。 组合即当前的Region和另外的一个Region组合，可以用不同的Op方式来进行组合。Op是一个枚举，定义在Region类中。假设用region1  去组合region2   public enum Op {          DIFFERENCE(0), //最终区域为region1 与 region2不同的区域          INTERSECT(1), // 最终区域为region1 与 region2相交的区域          UNION(2),      //最终区域为region1 与 region2组合一起的区域          XOR(3),        //最终区域为region1 与 region2相交之外的区域          REVERSE_DIFFERENCE(4), //最终区域为region2 与 region1不同的区域          REPLACE(5); //最终区域为为region2的区域   }   */public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(new SampleView(this));    }    private class SampleView extends View{        private Paint mPaint=new Paint();        private Rect mRect1=new Rect();        private Rect mRect2=new Rect();        public SampleView(Context context) {            super(context);            setFocusable(true);            mPaint.setAntiAlias(true);            mPaint.setTextSize(16);            mPaint.setTextAlign(Paint.Align.CENTER);            mRect1.set(10, 10, 100, 80);            mRect2.set(50, 50, 130, 110);        }        @Override        protected void onDraw(Canvas canvas) {            canvas.drawColor(Color.GRAY);            canvas.save();            canvas.translate(80, 5);            //绘制原始图形            drawOrginalRects(canvas,0xff);            canvas.restore();            canvas.save();            canvas.translate(0, 120);            //绘制组合在一起的区域            drawRgn(canvas,Color.RED,"union",Region.Op.UNION);            canvas.restore();            canvas.save();            canvas.translate(160, 120);            //绘制组合在一起的区域            drawRgn(canvas,Color.BLUE,"Xor",Region.Op.XOR);            canvas.restore();            canvas.save();            canvas.translate(0, 260);            //绘制组合在一起的区域            drawRgn(canvas,Color.GREEN,"Difference",Region.Op.DIFFERENCE);            canvas.restore();            canvas.save();            canvas.translate(160, 260);            //绘制组合在一起的区域            drawRgn(canvas,Color.WHITE,"union",Region.Op.INTERSECT);            canvas.restore();        }        private void drawRgn(Canvas canvas, int color, String str, Op op) {            if(str!=null){                mPaint.setColor(Color.BLACK);                canvas.drawText(str, 80, 24, mPaint);            }            //定义一个区域            Region rgn=new Region();            rgn.set(mRect1);            rgn.op(mRect2, op);            mPaint.setColor(color);            //定义一个区域迭代器            RegionIterator iter=new RegionIterator(rgn);            Rect r=new Rect();            canvas.translate(0, 30);            while(iter.next(r)){                //迭代所有的rect并绘制                canvas.drawRect(r, mPaint);            }            drawOrginalRects(canvas, 0x88);        }        private void drawOrginalRects(Canvas canvas, int alpha) {            mPaint.setStyle(Paint.Style.STROKE);            mPaint.setColor(Color.RED);            mPaint.setAlpha(alpha);            drawCentered(canvas,mRect1,mPaint);            mPaint.setColor(Color.BLUE);            mPaint.setAlpha(alpha);            drawCentered(canvas,mRect2,mPaint);            //canvas.drawRect(mRect2, mPaint);            mPaint.setStyle(Paint.Style.FILL);        }        //将外边框的宽度设置为0.5个像素        private void drawCentered(Canvas canvas, Rect r, Paint p) {            float inset=p.getStrokeWidth()*0.5f;            if(inset==0){                inset=0.5f;            }            canvas.drawRect(r.left+inset, r.top+inset, r.right-inset, r.bottom-inset, p);        }    }}