使用canvas.clipPath来裁剪时部分机型出现问题

使用canvas.clipPath来裁剪时部分机型出现问题

	项目中用canvas.clipPath来进行裁剪画布，出现在部分机型裁剪出来的效果一直是矩形的bug。

	出现的原因：默认开启硬件加速导致的bug。

	解决方案：关闭硬件加速。在配置文件该activity的声明中添加android:hardwareAccelerated="false"即可解决问题

参考链接：http://stackoverflow.com/questions/16889815/canvas-clippath-only-works-on-android-emulator

	  http://www.cnblogs.com/lonelyDog/archive/2012/07/12/2588477.html

关于 Hardware Acceleration

1、不同层级的加速：

Application;
Activity


;
Window getWindow().setFlags(
WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED,
WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED);;
ViewmyView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);;

2、如何判断是否开启了硬件加速

在绘制之前，你必须做该测试 Canvas.isHardwareAccelerated() 替代View.isHardwareAccelerated() 在必要时。

View.isHardwareAccelerated() ;//returns true if the View is attached to a hardware accelerated window.
Canvas.isHardwareAccelerated();// returns true if the Canvas is hardware accelerated;

3、开启硬件加速之后，许多2D的绘制方法会抛出异常：

Canvas

clipPath()
clipRegion()
drawPicture()
drawTextOnPath()
drawVertices()
Paint
setLinearText()
setMaskFilter()
setRasterizer()
Xfermodes
AvoidXfermode
PixelXorXfermode
In addition, some operations behave differently with hardware acceleration enabled:
Canvas
clipRect(): XOR, Difference and ReverseDifference clip modes are ignored. 3D transforms do not apply to the clip rectangle
drawBitmapMesh(): colors array is ignored
Paint
setDither(): ignored
setFilterBitmap(): filtering is always on
setShadowLayer(): works with text only
PorterDuffXfermode
PorterDuff.Mode.DARKEN will be equivalent to SRC_OVER when blending against the framebuffer.
PorterDuff.Mode.LIGHTEN will be equivalent to SRC_OVER when blending against the framebuffer.
PorterDuff.Mode.OVERLAY will be equivalent to SRC_OVER when blending against the framebuffer.
ComposeShader
ComposeShader can only contain shaders of different types (a BitmapShader and a LinearGradient for instance, but not two instances of BitmapShader )
ComposeShader cannot contain a ComposeShader