FileDocCategorySizeDatePackage
SaveRestoreState.javaAPI DocAndroid 1.5 API3865Wed May 06 22:41:08 BST 2009com.example.android.apis.app

SaveRestoreState

public class SaveRestoreState extends android.app.Activity

Demonstrates required behavior of saving and restoring dynamic activity state, so that an activity will restart with the correct state if it is stopped by the system.

In general, any activity that has been paused may be stopped by the system at any time if it needs more resources for the currently running activity. To handle this, before being paused the {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()} method is called before an activity is paused, allowing it to supply its current state. If that activity then needs to be stopped, upon restarting it will receive its last saved state in {@link android.app.Activity#onCreate}.

In this example we are currently saving and restoring the state of the top text editor, but not of the bottom text editor. You can see the difference by editing the two text fields, then going to a couple different applications while the demo is running and then returning back to it. The system takes care of saving a view's state as long as an id has been assigned to the view, so we assign an ID to the view being saved but not one to the view that isn't being saved.

Demo

App/Activity/Save & Restore State

Source files

src/com.example.android.apis/app/SaveRestoreState.java The Save/Restore Screen implementation
/res/any/layout/save_restore_state.xml Defines contents of the screen

Fields Summary
Constructors Summary
Methods Summary
java.lang.CharSequencegetSavedText()
Retrieve the text that is currently in the "saved" editor.

        return ((EditText)findViewById(R.id.saved)).getText();
protected voidonCreate(android.os.Bundle savedInstanceState)
Initialization of the Activity after it is first created. Here we use {@link android.app.Activity#setContentView setContentView()} to set up the Activity's content, and retrieve the EditText widget whose state we will save/restore.

        // Be sure to call the super class.
        super.onCreate(savedInstanceState);

        // See assets/res/any/layout/save_restore_state.xml for this
        // view layout definition, which is being set here as
        // the content of our screen.
        setContentView(R.layout.save_restore_state);

        // Set message to be appropriate for this screen.
        ((TextView)findViewById(R.id.msg)).setText(R.string.save_restore_msg);
voidsetSavedText(java.lang.CharSequence text)
Change the text that is currently in the "saved" editor.

        ((EditText)findViewById(R.id.saved)).setText(text);