徹底解決 Canvas 引起的 java.lang.unsupported operation exception, android.view.GLES20Canvas.clipPath(GLES20Canvas異常

最近在做一個電子書項目，想要把開源的Shelves+iReader的翻頁卷曲等弄到一起，在做卷曲效果時遇到以下問題：

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

萬能的谷哥告訴我，這是硬件加速的問題，可是我從來沒開啟過硬件加速啊，做了個測試，View層的硬件加速已經干掉了

，那硬件加速肯定來自於Canvas繪制層了，測試了下，果然是繪制層開啟了硬件加速。

給一個鏈接，講硬件加速講的很清楚的文章：點擊查看

綜合看了之后解決了，即在AndroidManifest.xml application下設定：

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

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關於 Hardware Acceleration

　 1、不同層級的加速：

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、如何判斷是否開啟了硬件加速

在繪制之前，你必須做該測試 Canvas.isHardwareAccelerated() 替代View.isHardwareAccelerated() 在必要時。

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、開啟硬件加速之后，許多2D的繪制方法會拋出異常：

• 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