Android4.0 开启硬件加速后部分应用运行出错。

出现异常：

12-20 15:18:19.543: E/AndroidRuntime(26301): FATAL EXCEPTION: main
12-20 15:18:19.543: E/AndroidRuntime(26301): java.lang.UnsupportedOperationException
12-20 15:18:19.543: E/AndroidRuntime(26301): at android.view.GLES20Canvas.clipPath(GLES20Canvas.java:429)
12-20 15:18:19.543: E/AndroidRuntime(26301): at cn.hpc.ui.MyView.drawArea(MyView.java:66)

关闭硬件加速则运行正常。

原因在这里

http://developer.android.com/guide/topics/graphics/hardware-accel.html

Hardware Acceleration

Beginning in Android 3.0 (API level 11), the Android 2D rendering pipeline is designed to better support hardware acceleration.

从Android 3.0（API Level 11）开始，Android的2D渲染管线可以更好的支持硬件加速。硬件加速使用GPU进行View上的绘制操作。

... ...

Unsupported Drawing Operations

不支持的绘图方法：

Canvas
- clipPath()
- clipRegion()
- drawPicture()
- drawTextOnPath()
- drawVertices()
Paint
- setLinearText()
- setMaskFilter()
- setRasterizer()
Xfermodes
- AvoidXfermode
- PixelXorXfermode

我的应用中，正好用到第一种 clipPath.所以运行出错。

问题找到，

解决方法：

有4种控件硬件加速的方法。

1 Application level

In your Android manifest file, add the following attribute to the<application>tag to enable hardware acceleration for your entire application:

在应用程序AndroidManifest.xml文件中，为application标签添加如下的属性即可为整个应用程序true开启、false关闭硬件加速

<application android:hardwareAccelerated="false" ...>

2 Activity level

在应用程序AndroidManifest.xml文件中，只需在activity元素中添加 android:hardwareAccelerated 属性即可。例：在application级别开启硬件加速，但在activity上关闭硬件加速。

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

3 Window level

If you need even more fine-grained control, you can enable hardware acceleration for a given window with the following code:

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

Note: You currently cannot disable hardware acceleration at the window level.

4 View level

You can disable hardware acceleration for an individual view at runtime with the following code:

myView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);

测试中第1, 2 中都无效，第3种只能开启硬件加速,而不能关闭硬件加速。
只有第4种适合。只对当前View关闭硬件加速。 优点：View中使用到上述硬件加速不支持的方法时，强制关闭硬件加速。其它地方，由系统决定是否硬件加速。

android4.0 开启硬件加速后应用运行出错

Hardware Acceleration

Unsupported Drawing Operations

2 Activity level

3 Window level

4 View level

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