1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.example.android.apis.app; 18 19 // Need the following import to get access to the app resources, since this 20 // class is in a sub-package. 21 import com.example.android.apis.R; 22 23 import android.app.Activity; 24 import android.os.Bundle; 25 import android.widget.EditText; 26 import android.widget.TextView; 27 28 /** 29 * <p>Demonstrates required behavior of saving and restoring dynamic activity 30 * state, so that an activity will restart with the correct state if it is 31 * stopped by the system.</p> 32 * 33 * <p>In general, any activity that has been paused may be stopped by the system 34 * at any time if it needs more resources for the currently running activity. 35 * To handle this, before being paused the 36 * {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()} method is called before 37 * an activity is paused, allowing it to supply its current state. If that 38 * activity then needs to be stopped, upon restarting it will receive its 39 * last saved state in 40 * {@link android.app.Activity#onCreate}.</p> 41 * <p>In this example we are currently saving and restoring the state of the 42 * top text editor, but not of the bottom text editor. You can see the difference 43 * by editing the two text fields, then going to a couple different 44 * applications while the demo is running and then returning back to it. The 45 * system takes care of saving a view's state as long as an id has been 46 * assigned to the view, so we assign an ID to the view being saved but not 47 * one to the view that isn't being saved.</p> 48 * <h4>Demo</h4> 49 * App/Activity/Save & Restore State 50 * <h4>Source files</h4> 51 * <table class="LinkTable"> 52 <tr> 53 <td class="LinkColumn">src/com.example.android.apis/app/SaveRestoreState.java</td> 54 <td class="DescrColumn">The Save/Restore Screen implementation</td> 55 </tr> 56 <tr> 57 <td class="LinkColumn">/res/any/layout/save_restore_state.xml</td> 58 <td class="DescrColumn">Defines contents of the screen</td> 59 </tr> 60 </table> 61 */ 62 public class SaveRestoreState extends Activity 63 { 64 /** 65 * Initialization of the Activity after it is first created. Here we use 66 * {@link android.app.Activity#setContentView setContentView()} to set up 67 * the Activity's content, and retrieve the EditText widget whose state we 68 * will save/restore. 69 */ 70 @Override 71 protected void onCreate(Bundle savedInstanceState) { 72 // Be sure to call the super class. 73 super.onCreate(savedInstanceState); 74 75 // See assets/res/any/layout/save_restore_state.xml for this 76 // view layout definition, which is being set here as 77 // the content of our screen. 78 setContentView(R.layout.save_restore_state); 79 80 // Set message to be appropriate for this screen. 81 ((TextView)findViewById(R.id.msg)).setText(R.string.save_restore_msg); 82 } 83 84 /** 85 * Retrieve the text that is currently in the "saved" editor. 86 */ 87 CharSequence getSavedText() { 88 return ((EditText)findViewById(R.id.saved)).getText(); 89 } 90 91 /** 92 * Change the text that is currently in the "saved" editor. 93 */ 94 void setSavedText(CharSequence text) { 95 ((EditText)findViewById(R.id.saved)).setText(text); 96 } 97 } 98 99
