1 /* 2 * Copyright (C) 2006 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 android.content; 18 19 import java.util.Map; 20 21 /** 22 * Interface for accessing and modifying preference data returned by {@link 23 * Context#getSharedPreferences}. For any particular set of preferences, 24 * there is a single instance of this class that all clients share. 25 * Modifications to the preferences must go through an {@link Editor} object 26 * to ensure the preference values remain in a consistent state and control 27 * when they are committed to storage. 28 * 29 * <p><em>Note: currently this class does not support use across multiple 30 * processes. This will be added later.</em> 31 * 32 * @see Context#getSharedPreferences 33 */ 34 public interface SharedPreferences { 35 /** 36 * Interface definition for a callback to be invoked when a shared 37 * preference is changed. 38 */ 39 public interface OnSharedPreferenceChangeListener { 40 /** 41 * Called when a shared preference is changed, added, or removed. This 42 * may be called even if a preference is set to its existing value. 43 * 44 * <p>This callback will be run on your main thread. 45 * 46 * @param sharedPreferences The {@link SharedPreferences} that received 47 * the change. 48 * @param key The key of the preference that was changed, added, or 49 * removed. 50 */ onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key)51 void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key); 52 } 53 54 /** 55 * Interface used for modifying values in a {@link SharedPreferences} 56 * object. All changes you make in an editor are batched, and not copied 57 * back to the original {@link SharedPreferences} until you call {@link #commit} 58 * or {@link #apply} 59 */ 60 public interface Editor { 61 /** 62 * Set a String value in the preferences editor, to be written back once 63 * {@link #commit} or {@link #apply} are called. 64 * 65 * @param key The name of the preference to modify. 66 * @param value The new value for the preference. 67 * 68 * @return Returns a reference to the same Editor object, so you can 69 * chain put calls together. 70 */ putString(String key, String value)71 Editor putString(String key, String value); 72 73 /** 74 * Set an int value in the preferences editor, to be written back once 75 * {@link #commit} or {@link #apply} are called. 76 * 77 * @param key The name of the preference to modify. 78 * @param value The new value for the preference. 79 * 80 * @return Returns a reference to the same Editor object, so you can 81 * chain put calls together. 82 */ putInt(String key, int value)83 Editor putInt(String key, int value); 84 85 /** 86 * Set a long value in the preferences editor, to be written back once 87 * {@link #commit} or {@link #apply} are called. 88 * 89 * @param key The name of the preference to modify. 90 * @param value The new value for the preference. 91 * 92 * @return Returns a reference to the same Editor object, so you can 93 * chain put calls together. 94 */ putLong(String key, long value)95 Editor putLong(String key, long value); 96 97 /** 98 * Set a float value in the preferences editor, to be written back once 99 * {@link #commit} or {@link #apply} are called. 100 * 101 * @param key The name of the preference to modify. 102 * @param value The new value for the preference. 103 * 104 * @return Returns a reference to the same Editor object, so you can 105 * chain put calls together. 106 */ putFloat(String key, float value)107 Editor putFloat(String key, float value); 108 109 /** 110 * Set a boolean value in the preferences editor, to be written back 111 * once {@link #commit} or {@link #apply} are called. 112 * 113 * @param key The name of the preference to modify. 114 * @param value The new value for the preference. 115 * 116 * @return Returns a reference to the same Editor object, so you can 117 * chain put calls together. 118 */ putBoolean(String key, boolean value)119 Editor putBoolean(String key, boolean value); 120 121 /** 122 * Mark in the editor that a preference value should be removed, which 123 * will be done in the actual preferences once {@link #commit} is 124 * called. 125 * 126 * <p>Note that when committing back to the preferences, all removals 127 * are done first, regardless of whether you called remove before 128 * or after put methods on this editor. 129 * 130 * @param key The name of the preference to remove. 131 * 132 * @return Returns a reference to the same Editor object, so you can 133 * chain put calls together. 134 */ remove(String key)135 Editor remove(String key); 136 137 /** 138 * Mark in the editor to remove <em>all</em> values from the 139 * preferences. Once commit is called, the only remaining preferences 140 * will be any that you have defined in this editor. 141 * 142 * <p>Note that when committing back to the preferences, the clear 143 * is done first, regardless of whether you called clear before 144 * or after put methods on this editor. 145 * 146 * @return Returns a reference to the same Editor object, so you can 147 * chain put calls together. 148 */ clear()149 Editor clear(); 150 151 /** 152 * Commit your preferences changes back from this Editor to the 153 * {@link SharedPreferences} object it is editing. This atomically 154 * performs the requested modifications, replacing whatever is currently 155 * in the SharedPreferences. 156 * 157 * <p>Note that when two editors are modifying preferences at the same 158 * time, the last one to call commit wins. 159 * 160 * <p>If you don't care about the return value and you're 161 * using this from your application's main thread, consider 162 * using {@link #apply} instead. 163 * 164 * @return Returns true if the new values were successfully written 165 * to persistent storage. 166 */ commit()167 boolean commit(); 168 169 /** 170 * Commit your preferences changes back from this Editor to the 171 * {@link SharedPreferences} object it is editing. This atomically 172 * performs the requested modifications, replacing whatever is currently 173 * in the SharedPreferences. 174 * 175 * <p>Note that when two editors are modifying preferences at the same 176 * time, the last one to call apply wins. 177 * 178 * <p>Unlike {@link #commit}, which writes its preferences out 179 * to persistent storage synchronously, {@link #apply} 180 * commits its changes to the in-memory 181 * {@link SharedPreferences} immediately but starts an 182 * asynchronous commit to disk and you won't be notified of 183 * any failures. If another editor on this 184 * {@link SharedPreferences} does a regular {@link #commit} 185 * while a {@link #apply} is still outstanding, the 186 * {@link #commit} will block until all async commits are 187 * completed as well as the commit itself. 188 * 189 * <p>As {@link SharedPreferences} instances are singletons within 190 * a process, it's safe to replace any instance of {@link #commit} with 191 * {@link #apply} if you were already ignoring the return value. 192 * 193 * <p>You don't need to worry about Android component 194 * lifecycles and their interaction with <code>apply()</code> 195 * writing to disk. The framework makes sure in-flight disk 196 * writes from <code>apply()</code> complete before switching 197 * states. 198 * 199 * <p class='note'>The SharedPreferences.Editor interface 200 * isn't expected to be implemented directly. However, if you 201 * previously did implement it and are now getting errors 202 * about missing <code>apply()</code>, you can simply call 203 * {@link #commit} from <code>apply()</code>. 204 */ apply()205 void apply(); 206 } 207 208 /** 209 * Retrieve all values from the preferences. 210 * 211 * @return Returns a map containing a list of pairs key/value representing 212 * the preferences. 213 * 214 * @throws NullPointerException 215 */ getAll()216 Map<String, ?> getAll(); 217 218 /** 219 * Retrieve a String value from the preferences. 220 * 221 * @param key The name of the preference to retrieve. 222 * @param defValue Value to return if this preference does not exist. 223 * 224 * @return Returns the preference value if it exists, or defValue. Throws 225 * ClassCastException if there is a preference with this name that is not 226 * a String. 227 * 228 * @throws ClassCastException 229 */ getString(String key, String defValue)230 String getString(String key, String defValue); 231 232 /** 233 * Retrieve an int value from the preferences. 234 * 235 * @param key The name of the preference to retrieve. 236 * @param defValue Value to return if this preference does not exist. 237 * 238 * @return Returns the preference value if it exists, or defValue. Throws 239 * ClassCastException if there is a preference with this name that is not 240 * an int. 241 * 242 * @throws ClassCastException 243 */ getInt(String key, int defValue)244 int getInt(String key, int defValue); 245 246 /** 247 * Retrieve a long value from the preferences. 248 * 249 * @param key The name of the preference to retrieve. 250 * @param defValue Value to return if this preference does not exist. 251 * 252 * @return Returns the preference value if it exists, or defValue. Throws 253 * ClassCastException if there is a preference with this name that is not 254 * a long. 255 * 256 * @throws ClassCastException 257 */ getLong(String key, long defValue)258 long getLong(String key, long defValue); 259 260 /** 261 * Retrieve a float value from the preferences. 262 * 263 * @param key The name of the preference to retrieve. 264 * @param defValue Value to return if this preference does not exist. 265 * 266 * @return Returns the preference value if it exists, or defValue. Throws 267 * ClassCastException if there is a preference with this name that is not 268 * a float. 269 * 270 * @throws ClassCastException 271 */ getFloat(String key, float defValue)272 float getFloat(String key, float defValue); 273 274 /** 275 * Retrieve a boolean value from the preferences. 276 * 277 * @param key The name of the preference to retrieve. 278 * @param defValue Value to return if this preference does not exist. 279 * 280 * @return Returns the preference value if it exists, or defValue. Throws 281 * ClassCastException if there is a preference with this name that is not 282 * a boolean. 283 * 284 * @throws ClassCastException 285 */ getBoolean(String key, boolean defValue)286 boolean getBoolean(String key, boolean defValue); 287 288 /** 289 * Checks whether the preferences contains a preference. 290 * 291 * @param key The name of the preference to check. 292 * @return Returns true if the preference exists in the preferences, 293 * otherwise false. 294 */ contains(String key)295 boolean contains(String key); 296 297 /** 298 * Create a new Editor for these preferences, through which you can make 299 * modifications to the data in the preferences and atomically commit those 300 * changes back to the SharedPreferences object. 301 * 302 * <p>Note that you <em>must</em> call {@link Editor#commit} to have any 303 * changes you perform in the Editor actually show up in the 304 * SharedPreferences. 305 * 306 * @return Returns a new instance of the {@link Editor} interface, allowing 307 * you to modify the values in this SharedPreferences object. 308 */ edit()309 Editor edit(); 310 311 /** 312 * Registers a callback to be invoked when a change happens to a preference. 313 * 314 * @param listener The callback that will run. 315 * @see #unregisterOnSharedPreferenceChangeListener 316 */ registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener)317 void registerOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener); 318 319 /** 320 * Unregisters a previous callback. 321 * 322 * @param listener The callback that should be unregistered. 323 * @see #registerOnSharedPreferenceChangeListener 324 */ unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener)325 void unregisterOnSharedPreferenceChangeListener(OnSharedPreferenceChangeListener listener); 326 } 327