Question

正如Git中心上的Fresco项目所说：“在Android 4.x及更低版本中，Fresco将图像放在Android内存的特殊区域。这样可以让您的应用程序运行得更快 - 并且经常遭受可怕的OutOfMemoryError。”

从this回答，我知道用ashmem放置位图。

我的问题是：为什么壁画剂量不能在Android 5.0或更高版本的ashmem中放置位图？ Android是否会更改某些系统功能并将其禁用？

Answer 1

是的，Google在Android 5.0中禁用了可清除的位图。

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中，他们提到：

Android 5.0及更高版本的内存管理比早期版本有了很大改进，因此将位图缓存保留在Java堆上更加安全。

为什么fresco选择不在android 5.0或更高版本上将位图放在ashmem中

3 个答案: