android圓角矩形進度條

最近做項目，有個一個需求，就是圓角進度條。效果圖如下。

當時項目時間很緊，沒多去想怎麼實現最佳，就直接把美工給的圓角進度條裁剪成了四份。來做 Canvas 剪切繪制。這樣雖然也能達到效果，但是服用性很差。最近網上搜索了很長時間，發現Paint畫筆，有遮擋層的功能。android.graphics.Paint.setXfermode(Xfermode xfermode) 。其中一個參數就是

Mode.DST_OUT 顯示底圖與上層圖非交集的底圖圖像。於是就有個思路，先繪制圓角矩形進度條，然後設置畫筆遮擋屬性，再繪制扇形，來遮罩圓角矩形。這樣就可以實現圓角矩形進度條的功能了。

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback{
	
	SurfaceHolder mSurfaceHolder;
	boolean isRun;
	
	/** 進度條背景**/
	Bitmap bmpDes; 
	/** 移動角度**/
	float m = 0;
	/** 包圍進度條背景的圓半徑**/
	float r;
	/** 移動速度**/
	float speed;
	
	public MySurfaceView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
		mSurfaceHolder = this.getHolder();
		mSurfaceHolder.addCallback(this);
		/** 加載進度條**/
		bmpDes = BitmapFactory.decodeResource(getResources(), R.drawable.d1).copy(Bitmap.Config.ARGB_8888, true);
		/** 計算半徑**/
		r = (float) Math.sqrt(Math.pow(bmpDes.getWidth()/2, 2) + Math.pow(bmpDes.getHeight()/2, 2));
		/** 根據25s，計算移動速度**/
		speed = (float) (360 / (25000 / 33.0));
	}

	@Override
	public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
		// TODO Auto-generated method stub
		
	}

	@Override
	public void surfaceCreated(SurfaceHolder arg0) {
		// TODO Auto-generated method stub
		isRun = true;
		new Thread(){
			public void run(){
				while(isRun){
					long start = System.currentTimeMillis();
					Canvas canvas = null;
					synchronized (mSurfaceHolder) {
						canvas = mSurfaceHolder.lockCanvas();
						if(canvas != null ){
							onGameDraw(canvas);
							if(canvas != null && mSurfaceHolder != null){
								mSurfaceHolder.unlockCanvasAndPost(canvas);
							}
							m += speed;
							if(m >= 360)
								m = 0;
						}
					}
					long end = System.currentTimeMillis() - start;
					if(end < 33){
						try {
							Thread.sleep(end);
						} catch (InterruptedException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}
			}
		}.start();
	}

	@Override
	public void surfaceDestroyed(SurfaceHolder arg0) {
		// TODO Auto-generated method stub
		isRun = false;
	}
	
	private void onGameDraw(Canvas canvas){
/*		canvas.drawColor(Color.BLACK);
		c = new Canvas(bmpDes);
		Paint paint = new Paint();
		paint.setAntiAlias(true);
		paint.setXfermode(new PorterDuffXfermode(Mode.DST_OUT));
		int sc = c.saveLayer(0, 0, bmpDes.getWidth(), bmpDes.getHeight(), null, LAYER_FLAGS);
		c.drawArc(new RectF(-(r - bmpDes.getWidth()/2), -(r - bmpDes.getHeight()/2), r*2, r*2), 0, m, true, paint);
		c.restoreToCount(sc);
		canvas.drawBitmap(bmpDes, 0, 0, null);*/
		
	     canvas.drawColor(Color.BLACK);  
	     Paint paint = new Paint();  
	     paint.setFilterBitmap(false);  	  
	     // 繪制第二層
	     int sc = canvas.saveLayer(0, 0, 0 + bmpDes.getWidth(), 0 + bmpDes.getHeight(), null,  
	                Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG  
	                        | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG  
	                        | Canvas.FULL_COLOR_LAYER_SAVE_FLAG  
	                        | Canvas.CLIP_TO_LAYER_SAVE_FLAG);  
	     // 繪制進度條背景
	     canvas.drawBitmap(bmpDes, 0, 0, paint); 
	     // 設置遮擋屬性
	     paint.setXfermode(new PorterDuffXfermode(Mode.DST_OUT)); 
	     // 繪制遮擋扇形
	     canvas.drawArc(new RectF(-(r - bmpDes.getWidth()/2), -(r - bmpDes.getHeight()/2), r*2, r*2), 0, m, true, paint);
	     // 將第二層反饋給畫布
	     canvas.restoreToCount(sc);
	}
}