| /* |
| * Copyright (C) 2007 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package com.example.android.apis.app; |
| |
| // Need the following import to get access to the app resources, since this |
| // class is in a sub-package. |
| |
| import com.example.android.apis.R; |
| |
| import android.app.Activity; |
| import android.content.SharedPreferences; |
| import android.os.Bundle; |
| import android.widget.EditText; |
| import android.widget.TextView; |
| |
| /** |
| * Simple example of using persistent preferences to retain a screen's state. |
| * <p>This can be used as an alternative to the normal |
| * <code>onSaveInstanceState()</code> mechanism, if you |
| * wish the state to persist even after an activity is finished.</p> |
| * |
| * <p>Note that using this approach requires more care, since you are sharing |
| * the persistent state potentially across multiple instances of the activity. |
| * In particular, if you allow a new instance of the activity to be launched |
| * directly on top of the existing instance, the state can get out of sync |
| * because the new instance is resumed before the old one is paused.</p> |
| * |
| * <p>For any persistent state that is not simplistic, a content |
| * provider is often a better choice.</p> |
| * |
| * <p>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 back from the activity and |
| * starting it again.</p> |
| * |
| * <h4>Demo</h4> |
| * App/Activity/Save & Restore State |
| * |
| * <h4>Source files</h4> |
| * <table class="LinkTable"> |
| * <tr> |
| * <td class="LinkColumn">src/com.example.android.apis/app/PersistentState.java</td> |
| * <td class="DescrColumn">The Save/Restore Screen implementation</td> |
| * </tr> |
| * <tr> |
| * <td class="LinkColumn">/res/any/layout/save_restore_state.xml</td> |
| * <td class="DescrColumn">Defines contents of the screen</td> |
| * </tr> |
| * </table> |
| * |
| */ |
| public class PersistentState extends Activity |
| { |
| /** |
| * 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 persistent. |
| */ |
| @Override |
| protected void onCreate(Bundle savedInstanceState) { |
| // 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.persistent_msg); |
| |
| // Retrieve the EditText widget whose state we will save. |
| mSaved = (EditText)findViewById(R.id.saved); |
| } |
| |
| /** |
| * Upon being resumed we can retrieve the current state. This allows us |
| * to update the state if it was changed at any time while paused. |
| */ |
| @Override |
| protected void onResume() { |
| super.onResume(); |
| |
| SharedPreferences prefs = getPreferences(0); |
| String restoredText = prefs.getString("text", null); |
| if (restoredText != null) { |
| mSaved.setText(restoredText, TextView.BufferType.EDITABLE); |
| |
| int selectionStart = prefs.getInt("selection-start", -1); |
| int selectionEnd = prefs.getInt("selection-end", -1); |
| if (selectionStart != -1 && selectionEnd != -1) { |
| mSaved.setSelection(selectionStart, selectionEnd); |
| } |
| } |
| } |
| |
| /** |
| * Any time we are paused we need to save away the current state, so it |
| * will be restored correctly when we are resumed. |
| */ |
| @Override |
| protected void onPause() { |
| super.onPause(); |
| |
| SharedPreferences.Editor editor = getPreferences(0).edit(); |
| editor.putString("text", mSaved.getText().toString()); |
| editor.putInt("selection-start", mSaved.getSelectionStart()); |
| editor.putInt("selection-end", mSaved.getSelectionEnd()); |
| editor.commit(); |
| } |
| |
| private EditText mSaved; |
| } |