android sharepreferencess

!!readme.md

SharedPreferences

01_getSharedPreferences.java

private String sharedPrefFile = "com.example.android.hellosharedprefs";
mPreferences = getSharedPreferences(sharedPrefFile,MODE_PRIVATE);

02_save_retore.java

   @Override
   protected void onPause() {
      super.onPause();
      SharedPreferences.Editor preferencesEditor =  mPreferences.edit();
      preferencesEditor.clear();
      preferencesEditor.putInt("count", mCount);
      preferencesEditor.putInt("color", mCurrentColor);
      preferencesEditor.apply();
   }

   @Override
   protected void onCreate(Bundle savedState) {
      //...
      mPreferences = getSharedPreferences(sharedPrefFile, MODE_PRIVATE);
      if (savedInstanceState != null) {
          mCount = mPreferences.getInt("count", 1);
          mShowCount.setText(String.format("%s", mCount));

          mCurrentColor = mPreferences.getInt("color", mCurrentColor);
          mShowCount.setBackgroundColor(mCurrentColor);

          mNewText = mPreferences.getString("text", "");
      } else {
         // … 
      }
}

    

03_listen_to_changes.java

//interface and callback
public class SettingsActivity extends AppCompatActivity
    implements OnSharedPreferenceChangeListener { ...
    
    public void onSharedPreferenceChanged(
        SharedPreferences sharedPreferences, String key) {
        if (key.equals(MY_KEY)) {
            // Do something
        }
    }
}


//Creating and registering listener
SharedPreferences.OnSharedPreferenceChangeListener listener =
    new SharedPreferences.OnSharedPreferenceChangeListener() {
  public void onSharedPreferenceChanged(
     SharedPreferences prefs, String key) {
        // Implement listener here
  }
};
prefs.registerOnSharedPreferenceChangeListener(listener);