彻底解决 Canvas 引起的 java.lang.unsupported operation exception, android.view.GLES20Canvas.clipPath(GLES20

最近在做一个电子书项目，想要把开源的Shelves+iReader的翻页卷曲等弄到一起，在做卷曲效果时遇到以下问题：

 java.lang.unsupported operation exception, android.view.GLES20Canvas.clipPath(GLES20Canvas...

万能的谷哥告诉我，这是硬件加速的问题，可是我从来没开启过硬件加速啊，做了个测试，View层的硬件加速已经干掉了

，那硬件加速肯定来自于Canvas绘制层了，测试了下，果然是绘制层开启了硬件加速。

给一个链接，讲硬件加速讲的很清楚的文章：点击查看

综合看了之后解决了，即在AndroidManifest.xml application下设定：

<application
        android:label="@string/application_name"
        android:hardwareAccelerated="false">

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关于 Hardware Acceleration

　 1、不同层级的加速：

Application

<applicationandroid:hardwareAccelerated="true" ...>

Activity

<application android:hardwareAccelerated="true">
    <activity ... />
    <activity android:hardwareAccelerated="false" />
</application>

Window

    getWindow().setFlags(
    WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED,
    WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED);

View

myView.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

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