PreferenceFragment.java revision b1ad5977bc8178b6d350ebe9099daded4c1ef603
1/* 2 * Copyright (C) 2010 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 17package android.preference; 18 19import android.app.Activity; 20import android.app.Fragment; 21import android.content.Intent; 22import android.content.SharedPreferences; 23import android.os.Bundle; 24import android.os.Handler; 25import android.os.Message; 26import android.view.LayoutInflater; 27import android.view.View; 28import android.view.ViewGroup; 29import android.widget.ListView; 30 31/** 32 * Shows a hierarchy of {@link Preference} objects as 33 * lists. These preferences will 34 * automatically save to {@link SharedPreferences} as the user interacts with 35 * them. To retrieve an instance of {@link SharedPreferences} that the 36 * preference hierarchy in this fragment will use, call 37 * {@link PreferenceManager#getDefaultSharedPreferences(android.content.Context)} 38 * with a context in the same package as this fragment. 39 * <p> 40 * Furthermore, the preferences shown will follow the visual style of system 41 * preferences. It is easy to create a hierarchy of preferences (that can be 42 * shown on multiple screens) via XML. For these reasons, it is recommended to 43 * use this fragment (as a superclass) to deal with preferences in applications. 44 * <p> 45 * A {@link PreferenceScreen} object should be at the top of the preference 46 * hierarchy. Furthermore, subsequent {@link PreferenceScreen} in the hierarchy 47 * denote a screen break--that is the preferences contained within subsequent 48 * {@link PreferenceScreen} should be shown on another screen. The preference 49 * framework handles showing these other screens from the preference hierarchy. 50 * <p> 51 * The preference hierarchy can be formed in multiple ways: 52 * <li> From an XML file specifying the hierarchy 53 * <li> From different {@link Activity Activities} that each specify its own 54 * preferences in an XML file via {@link Activity} meta-data 55 * <li> From an object hierarchy rooted with {@link PreferenceScreen} 56 * <p> 57 * To inflate from XML, use the {@link #addPreferencesFromResource(int)}. The 58 * root element should be a {@link PreferenceScreen}. Subsequent elements can point 59 * to actual {@link Preference} subclasses. As mentioned above, subsequent 60 * {@link PreferenceScreen} in the hierarchy will result in the screen break. 61 * <p> 62 * To specify an {@link Intent} to query {@link Activity Activities} that each 63 * have preferences, use {@link #addPreferencesFromIntent}. Each 64 * {@link Activity} can specify meta-data in the manifest (via the key 65 * {@link PreferenceManager#METADATA_KEY_PREFERENCES}) that points to an XML 66 * resource. These XML resources will be inflated into a single preference 67 * hierarchy and shown by this fragment. 68 * <p> 69 * To specify an object hierarchy rooted with {@link PreferenceScreen}, use 70 * {@link #setPreferenceScreen(PreferenceScreen)}. 71 * <p> 72 * As a convenience, this fragment implements a click listener for any 73 * preference in the current hierarchy, see 74 * {@link #onPreferenceTreeClick(PreferenceScreen, Preference)}. 75 * 76 * <a name="SampleCode"></a> 77 * <h3>Sample Code</h3> 78 * 79 * <p>The following sample code shows a simple preference fragment that is 80 * populated from a resource. The resource it loads is:</p> 81 * 82 * {@sample development/samples/ApiDemos/res/xml/preferences.xml preferences} 83 * 84 * <p>The fragment implementation itself simply populates the preferences 85 * when created. Note that the preferences framework takes care of loading 86 * the current values out of the app preferences and writing them when changed:</p> 87 * 88 * {@sample development/samples/ApiDemos/src/com/example/android/apis/preference/FragmentPreferences.java 89 * fragment} 90 * 91 * @see Preference 92 * @see PreferenceScreen 93 */ 94public abstract class PreferenceFragment extends Fragment implements 95 PreferenceManager.OnPreferenceTreeClickListener { 96 97 private static final String PREFERENCES_TAG = "android:preferences"; 98 99 private PreferenceManager mPreferenceManager; 100 private ListView mList; 101 private boolean mHavePrefs; 102 private boolean mInitDone; 103 104 /** 105 * The starting request code given out to preference framework. 106 */ 107 private static final int FIRST_REQUEST_CODE = 100; 108 109 private static final int MSG_BIND_PREFERENCES = 0; 110 private Handler mHandler = new Handler() { 111 @Override 112 public void handleMessage(Message msg) { 113 switch (msg.what) { 114 115 case MSG_BIND_PREFERENCES: 116 bindPreferences(); 117 break; 118 } 119 } 120 }; 121 122 final private Runnable mRequestFocus = new Runnable() { 123 public void run() { 124 mList.focusableViewAvailable(mList); 125 } 126 }; 127 128 @Override 129 public void onCreate(Bundle savedInstanceState) { 130 super.onCreate(savedInstanceState); 131 mPreferenceManager = new PreferenceManager(getActivity(), FIRST_REQUEST_CODE); 132 mPreferenceManager.setOnPreferenceTreeClickListener(this); 133 } 134 135 @Override 136 public View onCreateView(LayoutInflater inflater, ViewGroup container, 137 Bundle savedInstanceState) { 138 return inflater.inflate(com.android.internal.R.layout.preference_list_content, 139 container, false); 140 } 141 142 @Override 143 public void onActivityCreated(Bundle savedInstanceState) { 144 super.onActivityCreated(savedInstanceState); 145 getListView().setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY); 146 147 if (mHavePrefs) { 148 bindPreferences(); 149 } 150 151 mInitDone = true; 152 153 if (savedInstanceState != null) { 154 Bundle container = savedInstanceState.getBundle(PREFERENCES_TAG); 155 if (container != null) { 156 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 157 if (preferenceScreen != null) { 158 preferenceScreen.restoreHierarchyState(container); 159 } 160 } 161 } 162 } 163 164 @Override 165 public void onStop() { 166 super.onStop(); 167 mPreferenceManager.dispatchActivityStop(); 168 } 169 170 @Override 171 public void onDestroy() { 172 super.onDestroy(); 173 mPreferenceManager.dispatchActivityDestroy(); 174 } 175 176 @Override 177 public void onSaveInstanceState(Bundle outState) { 178 super.onSaveInstanceState(outState); 179 180 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 181 if (preferenceScreen != null) { 182 Bundle container = new Bundle(); 183 preferenceScreen.saveHierarchyState(container); 184 outState.putBundle(PREFERENCES_TAG, container); 185 } 186 } 187 188 @Override 189 public void onActivityResult(int requestCode, int resultCode, Intent data) { 190 super.onActivityResult(requestCode, resultCode, data); 191 192 mPreferenceManager.dispatchActivityResult(requestCode, resultCode, data); 193 } 194 195 /** 196 * Returns the {@link PreferenceManager} used by this fragment. 197 * @return The {@link PreferenceManager}. 198 */ 199 public PreferenceManager getPreferenceManager() { 200 return mPreferenceManager; 201 } 202 203 /** 204 * Sets the root of the preference hierarchy that this fragment is showing. 205 * 206 * @param preferenceScreen The root {@link PreferenceScreen} of the preference hierarchy. 207 */ 208 public void setPreferenceScreen(PreferenceScreen preferenceScreen) { 209 if (mPreferenceManager.setPreferences(preferenceScreen) && preferenceScreen != null) { 210 mHavePrefs = true; 211 if (mInitDone) { 212 postBindPreferences(); 213 } 214 } 215 } 216 217 /** 218 * Gets the root of the preference hierarchy that this fragment is showing. 219 * 220 * @return The {@link PreferenceScreen} that is the root of the preference 221 * hierarchy. 222 */ 223 public PreferenceScreen getPreferenceScreen() { 224 return mPreferenceManager.getPreferenceScreen(); 225 } 226 227 /** 228 * Adds preferences from activities that match the given {@link Intent}. 229 * 230 * @param intent The {@link Intent} to query activities. 231 */ 232 public void addPreferencesFromIntent(Intent intent) { 233 requirePreferenceManager(); 234 235 setPreferenceScreen(mPreferenceManager.inflateFromIntent(intent, getPreferenceScreen())); 236 } 237 238 /** 239 * Inflates the given XML resource and adds the preference hierarchy to the current 240 * preference hierarchy. 241 * 242 * @param preferencesResId The XML resource ID to inflate. 243 */ 244 public void addPreferencesFromResource(int preferencesResId) { 245 requirePreferenceManager(); 246 247 setPreferenceScreen(mPreferenceManager.inflateFromResource(getActivity(), 248 preferencesResId, getPreferenceScreen())); 249 } 250 251 /** 252 * {@inheritDoc} 253 */ 254 public boolean onPreferenceTreeClick(PreferenceScreen preferenceScreen, Preference preference) { 255 return false; 256 } 257 258 /** 259 * Finds a {@link Preference} based on its key. 260 * 261 * @param key The key of the preference to retrieve. 262 * @return The {@link Preference} with the key, or null. 263 * @see PreferenceGroup#findPreference(CharSequence) 264 */ 265 public Preference findPreference(CharSequence key) { 266 if (mPreferenceManager == null) { 267 return null; 268 } 269 return mPreferenceManager.findPreference(key); 270 } 271 272 private void requirePreferenceManager() { 273 if (mPreferenceManager == null) { 274 throw new RuntimeException("This should be called after super.onCreate."); 275 } 276 } 277 278 private void postBindPreferences() { 279 if (mHandler.hasMessages(MSG_BIND_PREFERENCES)) return; 280 mHandler.obtainMessage(MSG_BIND_PREFERENCES).sendToTarget(); 281 } 282 283 private void bindPreferences() { 284 final PreferenceScreen preferenceScreen = getPreferenceScreen(); 285 if (preferenceScreen != null) { 286 preferenceScreen.bind(getListView()); 287 } 288 } 289 290 private ListView getListView() { 291 ensureList(); 292 return mList; 293 } 294 295 private void ensureList() { 296 if (mList != null) { 297 return; 298 } 299 View root = getView(); 300 if (root == null) { 301 throw new IllegalStateException("Content view not yet created"); 302 } 303 View rawListView = root.findViewById(android.R.id.list); 304 if (!(rawListView instanceof ListView)) { 305 throw new RuntimeException( 306 "Content has view with id attribute 'android.R.id.list' " 307 + "that is not a ListView class"); 308 } 309 mList = (ListView)rawListView; 310 if (mList == null) { 311 throw new RuntimeException( 312 "Your content must have a ListView whose id attribute is " + 313 "'android.R.id.list'"); 314 } 315 mHandler.post(mRequestFocus); 316 } 317} 318