有关硬件加速器的问题hardwareAccelerated

最新推荐文章于 2019-11-13 16:26:01 发布

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本文讨论了Android中硬件加速器hardwareAccelerated可能导致的大图加载问题，包括Bitmap too large to be uploaded into a texture的错误。通过关闭硬件加速或者使用BitmapRegionDecoder分块加载图片来解决此问题。此外，还提到了内存溢出问题的解决策略，如减小图片尺寸、及时释放Bitmap对象和调整程序heap size。

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今天也遇到了这样的问题，在用整张图片当做背景的时候，报错了，还以为内存溢出，但不是，是提示的最大储存位数不够。balabala·····

我就找了找弄了一个最残暴的方法，将硬件加速器hardwareAccelerated设置为false就不报错了，可以正常运行了。不过还有更好的方法，当然从网上借鉴来的方法，来学习应用到我的程序中。http://blog.zfdang.com/2013/03/summary-of-image-processing-in-android/ 总结的比较大神，看懂了也。分享给大家也作为我的学习笔记。以下为其内容：

第一个问题是out of memory

`1`	`java.lang.OutOfMemoryError: bitmap size exceeds VM budget`

这个据说是VM对一个程序申请的所有的bitmap对象会有一个最大值的要求。解决这个问题有几个方法：

1. 从源文件生成图片时，直接将图片缩小，而不是加载原始大小的图片。如下代码：

 
   01Bitmap bitmap = null;
 
   02if  (mUseZoomOut || mUseZoomIn) {
 
   03    // decode image size (decode metadata only, not the whole image)
 
   04    o =  new BitmapFactory.Options();
 
   05    o.inJustDecodeBounds = true;
 
   06    stream = new FileInputStream(filename);
 
   07    BitmapFactory.decodeStream(stream, null, o);
 
   08    stream.close();
 
   09 
 
   10    // get original image size
 
   11    int inWidth =  o.outWidth;
 
   12    int inHeight = o.outHeight;
 
   13    clog(String.format("Original bitmap size: (%dx%d).", inWidth, inHeight));
 
   14 
 
   15    // get size for pre-resized image
 
   16    o =  new Options();
 
   17    o.inSampleSize = Math.max(inWidth/targetWidth, inHeight/targetHeight);
 
   18}
 
   19 
 
   20// decode pre-resized image
 
   21stream = new FileInputStream(filename);
 
   22// o.inPurgeable = true;
 
   23bitmap = BitmapFactory.decodeStream(stream, null, o);
 
   24stream.close();
 
   25clog(String.format("Pre-sized bitmap size: (%dx%d).", bitmap.getWidth(), bitmap.getHeight()));

2. 及时删除不需要使用的bitmap对象，不要将所有的对象都cache住

3. 增加程序的heap size。从某个版本开始，android manifest文件里有一个新的属性了：

`1`	`android:largeHeap="true"`

android:largeHeap

 
   1Whether your application's processes should be created with a large Dalvik heap. This applies to all processes created for the application. It only applies to the first application loaded into a process; if you're using a shared user ID to allow multiple applications to use a process, they all must use this option consistently or they will have unpredictable results.
 
   2Most apps should not need this and should instead focus on reducing their overall memory usage for improved performance. Enabling this also does not guarantee a fixed increase in available memory, because some devices are constrained by their total available memory.
 
   3To query the available memory size at runtime, use the methods getMemoryClass() or getLargeMemoryClass().

第二个问题是

`1`	`Bitmap too large to be uploaded into a texture exception`

这个问题下面链接有详细描述：

http://stackoverflow.com/questions/7428996/hw-accelerated-activity-how-to-get-opengl-texture-size-limit

简单说就是硬件加速的时候，对图片的大小有限制。不同设备可能有不同的最大值。这个问题悲催的地方是，程序貌似没有捕获到这个exception, 结果是程序也不报错，图片也显示不出来。只有看debug log才能发现这个error message.

一个解决的方法是禁止硬件加速，简单粗暴：

 
   1android:hardwareAccelerated="false"
 
   2 
 
   3android:hardwareAccelerated
 
   4Whether or not hardware-accelerated rendering should be enabled for all activities and views in this application — "true" if it should be enabled, and "false" if not. The default value is "true"  if you've set either minSdkVersion or targetSdkVersion to "14" or higher; otherwise, it's "false".
 
   5Starting from Android 3.0 (API level 11), a hardware-accelerated OpenGL renderer is available to applications, to improve performance for many common 2D graphics operations. When the hardware-accelerated renderer is enabled, most operations in Canvas, Paint, Xfermode, ColorFilter, Shader, and Camera are accelerated. This results in smoother animations, smoother scrolling, and improved responsiveness overall, even for applications that do not explicitly make use the framework's OpenGL libraries.
 
   6Note that not all of the OpenGL 2D operations are accelerated. If you enable the hardware-accelerated renderer, test your application to ensure that it can make use of the renderer without errors.
 
   7For more information, read the Hardware Acceleration guide.

比较好的解决方法是类似google map的实现：将图片分成不同的块，每次加载需要的块。android提供了一个方法：

http://developer.android.com/reference/android/graphics/BitmapRegionDecoder.html

 
   1public  void drawBitmap (Bitmap bitmap, Rect src, RectF dst, Paint paint)
 
   2 
 
   3public  Bitmap decodeRegion (Rect rect, BitmapFactory.Options options)