public class ShaderActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		ShaderView shaderView = new ShaderView(getApplicationContext());
		this.setContentView(shaderView,new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT));
	}
	static class ShaderView extends View{

		private Bitmap mBitmap;
		private Shader linearGradient ;
		private Shader composeShader;
		private Shader bitmapShader;
		private Shader radialGradient;
		private Shader sweepGradient;
		private Rect rect;
		private Paint paint;
		public ShaderView(Context context) {
		super(context);
		InputStream is = context.getResources().openRawResource(R.drawable.ic_launcher);
		mBitmap = BitmapFactory.decodeStream(is);
		/**
		 * 注意1:中心坐标是相对canvas的坐标系设置的。下边SweepGradient类似
		 * 注意2:positions 坐标最小为0，最大为1，只是一个比例，不是具体值
		 */
		radialGradient = new RadialGradient(140, 100, 50, new int[]{Color.RED,Color.GREEN,Color.BLUE}, new float[]{0f,0.5f,1f}, TileMode.MIRROR);
		/**
		 * 注意3：postion参数，0指的是正常坐标系的0度角方向，顺时针增加. 0.3则为正常坐标系的-360*0.3
  而下边中0.3对应的Color.RED指的是从0.3开始有颜色渐变。而在0～0.3之间没有颜色渐变的
  同理，0.6指的是从0.3~0.6 Color.RED变为Color.GREEN 0.6时候，颜色为Color.GREEN  再从0.6～0.8 由Color.GREEN变为 Color.BLUE。 0.8的时候为Color.BLUE 0.8～1 依    然为纯Color.BLUE
		 */
		sweepGradient = new SweepGradient(100, 340, new int[]{Color.RED, Color.GREEN,Color.BLUE},new float[]{0.3f,0.6f,0.8f});
		bitmapShader = new BitmapShader(mBitmap, TileMode.REPEAT, TileMode.REPEAT);
		/**
		 *注意4：如果前四个参数设置为 0，0，0，5 这是纵方向重复，反之设为0，0，5，0单横方向重复
		 */
		linearGradient = new LinearGradient(0, 0, 5, 5, 0x00ffffff, 0xff000000, TileMode.REPEAT);
		/**
		 * 注意5：new PorterDuffXfermode(PorterDuff.Mode.SRC_OVER)  参数和下边的效果是一样的
		 */
		composeShader = new ComposeShader(bitmapShader, linearGradient, PorterDuff.Mode.SRC_OVER);
		rect = new Rect();
		paint = new Paint();
	}
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		rect.set(0, 0, 200, 200);
		paint.setShader(radialGradient);
		canvas.drawRect(rect, paint);
		
		rect.set(240, 0, 480, 200);
		/**
		 * 注意6：TileMode.REPEAT 和 TileMode.MIRROR 都是重复叠。但是TileMode.CLAMP指的是如果shader不注意画满区间，以边缘颜色填充
		 */
		paint.setShader(new RadialGradient(340, 100, 50, new int[]{Color.RED,Color.GREEN,Color.BLUE}, new float[]{0f,0.5f,1f}, TileMode.CLAMP));

                /**
		 * 注意7：如果设置了Shader 再设置color是没有效果的
		 */
                paint.setColor(Color.RED);
		canvas.drawRect(rect, paint);
		
		rect.set(0, 240, 200, 480);
		paint.setShader(sweepGradient);
		canvas.drawRect(rect, paint);
		
		
		rect.set(240,240,480,480);
		paint.setShader(bitmapShader);
		canvas.drawRect(rect, paint);
		
		rect.set(0,500,200,700);
		paint.setShader(linearGradient);
		canvas.drawRect(rect, paint);
		
		rect.set(220,500,480,700);
		paint.setShader(composeShader);
		canvas.drawRect(rect, paint);
		
	}
	
}
}