正如 git hub 上的 Fresco 项目所说:“在 Android 4.x 及更低版本中,Fresco 将图像放在 Android 内存的一个特殊区域中。这可以让您的应用程序运行得更快 - 并且更少地遭受可怕的 OutOfMemoryError。”
从这个答案中,我知道它使用 ashmem 来放置位图。
我的问题是:为什么 fresco 不将位图放在 android 5.0 或更高版本的 ashmem 中?Android 是否会更改某些系统功能并将其禁用?
正如 git hub 上的 Fresco 项目所说:“在 Android 4.x 及更低版本中,Fresco 将图像放在 Android 内存的一个特殊区域中。这可以让您的应用程序运行得更快 - 并且更少地遭受可怕的 OutOfMemoryError。”
从这个答案中,我知道它使用 ashmem 来放置位图。
我的问题是:为什么 fresco 不将位图放在 android 5.0 或更高版本的 ashmem 中?Android 是否会更改某些系统功能并将其禁用?
是的,Google 在 Android 5.0 中禁用了可清除位图。
you can see here
/**
* @deprecated As of {@link android.os.Build.VERSION_CODES#LOLLIPOP}, this is
* ignored.
*
* In {@link android.os.Build.VERSION_CODES#KITKAT} and below, if this
* is set to true, then the resulting bitmap will allocate its
* pixels such that they can be purged if the system needs to reclaim
* memory. In that instance, when the pixels need to be accessed again
* (e.g. the bitmap is drawn, getPixels() is called), they will be
* automatically re-decoded.
*
* <p>For the re-decode to happen, the bitmap must have access to the
* encoded data, either by sharing a reference to the input
* or by making a copy of it. This distinction is controlled by
* inInputShareable. If this is true, then the bitmap may keep a shallow
* reference to the input. If this is false, then the bitmap will
* explicitly make a copy of the input data, and keep that. Even if
* sharing is allowed, the implementation may still decide to make a
* deep copy of the input data.</p>
*
* <p>While inPurgeable can help avoid big Dalvik heap allocations (from
* API level 11 onward), it sacrifices performance predictability since any
* image that the view system tries to draw may incur a decode delay which
* can lead to dropped frames. Therefore, most apps should avoid using
* inPurgeable to allow for a fast and fluid UI. To minimize Dalvik heap
* allocations use the {@link #inBitmap} flag instead.</p>
*
* <p class="note"><strong>Note:</strong> This flag is ignored when used
* with {@link #decodeResource(Resources, int,
* android.graphics.BitmapFactory.Options)} or {@link #decodeFile(String,
* android.graphics.BitmapFactory.Options)}.</p>
*/
@Deprecated
public boolean inPurgeable;
在Fresco 文档中,他们提到:
与早期版本相比,Android 5.0 和更高版本的内存管理有了很大改进,因此将位图缓存留在 Java 堆上更安全。