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구글.안드로이드.Google.Android.소스. PersistentState.java

원본 : http://code.google.com/android/samples/ApiDemos/src/com/google/android/samples/app/PersistentState.html * Copyright (C) 2007 Google Inc.
 /*
 * 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.google.android.samples.app;

// Need the following import to get access to the app resources, since this
// class is in a sub-package.

import com.google.android.samples.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>onFreeze()</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 &amp; Restore State
 *
 * <h4>Source files</h4>
 * <table class="LinkTable">
 *         <tr>
 *             <td class="LinkColumn">src/com/google/android/samples/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 icicle) {
       
// Be sure to call the super class.
       
super.onCreate(icicle);

       
// 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;
}