保存首选项在 Android 中引发异常

Question

I am trying to save user preferences in Android with the following code:

import java.util.prefs.Preferences;

class MyClass {
    void save() throws Exception {
        _prefs.put("NAME","VALUE");
        _prefs.flush(); // Throws exception
    }
    private final Preferences _prefs = Preferences.userNodeForPackage(MyClass.class);
}

... but the "flush" call generates the following exception:

W/java.util.prefs: Could not lock User prefs.  Unix error code 2.
W/System.err: java.util.prefs.BackingStoreException: Couldn't get file lock.

I guessed it was a problem with permissions. So I added the following to AndroidManifest.xml

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

But I still get the exception.

How can I save user preferences in Android with the java.util.prefs.Preferences class?

Answer 1

read some doc , especially WARNING section

On Android, the Preference nodes corresponding to the "system" and "user" preferences are stored in sections of the file system that are inaccessible to apps. Further, allowing apps to set "system wide" preferences is contrary to android's security model.

instead of Preferences use SharedPreferences , some doc about in HERE