为什么 getExternalFilesDirs() 在某些设备上不起作用? [英] Why getExternalFilesDirs() doesn't work on some devices?

问题描述

我的应用在 Android 5.0 上运行.我使用方法 getExternalFilesDirs() 来检查外部 SD 卡是否可用.如果返回超过 1 个 File，则表示存在外部 SD 卡.

My app runs on Android 5.0. I use method getExternalFilesDirs() to check if external SD card is available. If it returns more than 1 File, that means external SD card exists.

但在某些设备上(例如 Elephone G2)，方法 getExternalFilesDirs() 仅返回主存储的一个目录.我确定该设备具有外部 SD 卡 (/storage/sdcard1/).

But on some devices (for example Elephone G2), method getExternalFilesDirs() returns only one directory of primary storage. I'm sure that device has external SD card (/storage/sdcard1/).

谁能给我答案?

推荐答案

为了让 getExternalFilesDirs 返回 SD 卡的路径，OEM 必须在设备特定的 init.rc 中设置 SECONDARY_STORAGE 环境变量此处提到的文件:https://source.android.com/devices/storage/config-example.html

For getExternalFilesDirs to return the path of the sdcard, the OEM must have set the SECONDARY_STORAGE environment variable in the device specific init.rc file as mentioned here: https://source.android.com/devices/storage/config-example.html

在此处查看 getExternalFilesDirs 的来源:http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/app/ContextImpl.java#1039

Look at the source of getExternalFilesDirs here: http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/app/ContextImpl.java#1039

该值是从 Environment.buildExternalStorageAppFilesDirs 获得的.看看这里的来源:http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/os/Environment.java#206

The value is obtained from Environment.buildExternalStorageAppFilesDirs. Look at that source here: http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/os/Environment.java#206

该值取决于 mExternalDirsForApp，后者又通过读取 SECONDARY_STORAGE 变量的内容来填充:http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/os/Environment.java#136

The value is dependent on mExternalDirsForApp, which in turn is populated by reading the contents of SECONDARY_STORAGE variable: http://androidxref.com/5.1.1_r6/xref/frameworks/base/core/java/android/os/Environment.java#136

如您所见，如果未设置 SECONDARY_STORAGE 变量，则不会返回 sdcard 路径.您可以通过转到 adb shell 并查看 echo $SECONDARY_STORAGE

As you can see, if the SECONDARY_STORAGE variable is not set, the sdcard path will not be returned. You can cross-check this by going to adb shell and looking at the output of echo $SECONDARY_STORAGE

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