为什么 fresco 选择不将位图放在 android 5.0 或更高版本的 ashmem 中

Question

正如 git 中心上的 Fresco 项目所说："In Android 4.x and lower, Fresco puts images in a special region of Android memory. This lets your application run faster - and suffer the dreaded OutOfMemoryError much less often."

从 this 的回答中，我知道它使用 ashmem 来放置位图。

我的问题是：为什么 fresco 在 android 5.0 或更高版本上不将位图放入 ashmem 中？ Android 是否更改了某些系统功能并将其禁用？

Answer 1

是的，Google 在 Android 5.0 中禁用了可清除位图。

Answer 2

  you can see here

https://android.googlesource.com/platform/frameworks/base/+/android-cts-7.1_r2/graphics/java/android/graphics/BitmapFactory.java

 /**
     * @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;

Answer 3

在 Fresco documentation 他们提到：

Android 5.0 and newer has much improved memory management than earlier versions, so it is safer to leave the bitmap cache on the Java heap.

为什么 fresco 选择不将位图放在 android 5.0 或更高版本的 ashmem 中

Why fresco chose not put bitmap in ashmem on android 5.0 or higher

android

memory-management

bitmap

fresco