Environment.getExternalStorageDirectory() on the emulator

问题

I want to read and write images to the external storage in my app. From what I read the following is the correct way to get a handle on the directory.

 File externalStorageDir = Environment.getExternalStorageDirectory();
 File picturesDir = new File(externalStorageDir, "Pictures");

However ...

 picturesDir.exists(); // == null
 picturesDir.mkdir(); // == false

Is this because I'm using the emulator?

回答1:

You might want to make sure you have external storage enabled:

In Eclipse, go to Window > Android SDK and AVD Manager. Select the appropriate AVD and then click Edit.

Make sure you have SD card support enabled. If you do not, click the "New" button and select the "SD Card Support" option.

EDIT: Also need to add

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

to the manifest.

回答2:

By default, the emulator will be launched without a sd card. You should create a sd card image first by using the mksdcard command in console. See SDK document:https://developer.android.com/studio/command-line/mksdcard.html

Hence, in the console, type the command to launch an emulator with that sd card:

    emulator -avd <emulator name> -sdcard <sdcard image name>

For better performance, I strongly suggest you debug your app via a real device.

来源：https://stackoverflow.com/questions/7591531/environment-getexternalstoragedirectory-on-the-emulator