Android : Save application state on screen orientation change

Question

I have seen the following links before posting this question

http://www.devx.com/wireless/Article/40792/1954

Saving Android Activity state using Save Instan

Answer 1

There is another possibility using which you can keep the state as it is even on Orientation change using the onConfigurationChanged(Configuration newConfig).

Called by the system when the device configuration changes while your activity is running. Note that this will only be called if you have selected configurations you would like to handle with the configChanges attribute in your manifest. If any configuration change occurs that is not selected to be reported by that attribute, then instead of reporting it the system will stop and restart the activity (to have it launched with the new configuration).

At the time that this function has been called, your Resources object will have been updated to return resource values matching the new configuration.

Answer 2

Well if you have the same layout for both screens then there is no need to do so just add below line in your manifest in Activity node

android:configChanges="keyboardHidden|orientation"

for Android 3.2 (API level 13) and newer:

android:configChanges="keyboardHidden|orientation|screenSize"

because the "screen size" also changes when the device switches between portrait and landscape orientation. Documentation here: http://developer.android.com/guide/topics/manifest/activity-element.html

Answer 3

There are 2 ways of doing this, the first one is in the AndroidManifest.xml file. You can add this to your activity's tag. This documentation will give you an in depth explanation, but put simply it uses these values and tells the activity not to restart when one of these values changes.

android:configChanges="keyboardHidden|orientation|screenSize|screenLayout"

And the second one is: overriding onSaveInstanceState and onRestoreInstanceState. This method requires some more effort, but arguably is better. onSaveInstanceState saves the values set (manually by the developer) from the activity before it's killed, and onRestoreInstanceState restores that information after onStart() Refer to the official documentation for a more in depth look. You don't have to implement onRestoreInstanceState, but that would involve sticking that code in onCreate().

In my sample code below, I am saving 2 int values, the current position of the spinner as well as a radio button.

 @Override
    public void onSaveInstanceState(@NonNull Bundle savedInstanceState) {
        spinPosition = options.getSelectedItemPosition();
        savedInstanceState.putInt(Constants.KEY, spinPosition);
        savedInstanceState.putInt(Constants.KEY_RADIO, radioPosition);
        super.onSaveInstanceState(savedInstanceState);

    }

    // And we restore those values with `getInt`, then we can pass those stored values into the spinner and radio button group, for example, to select the same values that we saved earlier. 

    @Override
    public void onRestoreInstanceState(@NotNull Bundle savedInstanceState) {
        spinPosition = savedInstanceState.getInt(Constants.KEY);
        radioPosition = savedInstanceState.getInt(Constants.KEY_RADIO);
        options.setSelection(spinPosition, true);
        type.check(radioPosition);
        super.onRestoreInstanceState(savedInstanceState);
    }