LoaderManager.java revision fb3cffeb35368da22f99b85d45039c4e6e471c06
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.app; 18 19import android.content.Loader; 20import android.os.Bundle; 21import android.util.Log; 22import android.util.SparseArray; 23 24/** 25 * Interface associated with an {@link Activity} or {@link Fragment} for managing 26 * one or more {@link android.content.Loader} instances associated with it. 27 */ 28public interface LoaderManager { 29 /** 30 * Callback interface for a client to interact with the manager. 31 */ 32 public interface LoaderCallbacks<D> { 33 /** 34 * Instantiate and return a new Loader for the given ID. 35 * 36 * @param id The ID whose loader is to be created. 37 * @param args Any arguments supplied by the caller. 38 * @return Return a new Loader instance that is ready to start loading. 39 */ 40 public Loader<D> onCreateLoader(int id, Bundle args); 41 42 /** 43 * Called when a previously created loader has finished its load. Note 44 * that normally an application is <em>not</em> allowed to commit fragment 45 * transactions while in this call, since it can happen after an 46 * activity's state is saved. See {@link FragmentManager#openTransaction() 47 * FragmentManager.openTransaction()} for further discussion on this. 48 * 49 * @param loader The Loader that has finished. 50 * @param data The data generated by the Loader. 51 */ 52 public void onLoadFinished(Loader<D> loader, D data); 53 } 54 55 /** 56 * Ensures a loader is initialized and active. If the loader doesn't 57 * already exist, one is created and (if the activity/fragment is currently 58 * started) starts the loader. Otherwise the last created 59 * loader is re-used. 60 * 61 * <p>In either case, the given callback is associated with the loader, and 62 * will be called as the loader state changes. If at the point of call 63 * the caller is in its started state, and the requested loader 64 * already exists and has generated its data, then 65 * callback. {@link LoaderCallbacks#onLoadFinished} will 66 * be called immediately (inside of this function), so you must be prepared 67 * for this to happen. 68 */ 69 public <D> Loader<D> initLoader(int id, Bundle args, 70 LoaderManager.LoaderCallbacks<D> callback); 71 72 /** 73 * Creates a new loader in this manager, registers the callbacks to it, 74 * and (if the activity/fragment is currently started) starts loading it. 75 * If a loader with the same id has previously been 76 * started it will automatically be destroyed when the new loader completes 77 * its work. The callback will be delivered before the old loader 78 * is destroyed. 79 */ 80 public <D> Loader<D> restartLoader(int id, Bundle args, 81 LoaderManager.LoaderCallbacks<D> callback); 82 83 /** 84 * Stops and removes the loader with the given ID. 85 */ 86 public void stopLoader(int id); 87 88 /** 89 * Return the Loader with the given id or null if no matching Loader 90 * is found. 91 */ 92 public <D> Loader<D> getLoader(int id); 93} 94 95class LoaderManagerImpl implements LoaderManager { 96 static final String TAG = "LoaderManagerImpl"; 97 static final boolean DEBUG = true; 98 99 // These are the currently active loaders. A loader is here 100 // from the time its load is started until it has been explicitly 101 // stopped or restarted by the application. 102 final SparseArray<LoaderInfo> mLoaders = new SparseArray<LoaderInfo>(); 103 104 // These are previously run loaders. This list is maintained internally 105 // to avoid destroying a loader while an application is still using it. 106 // It allows an application to restart a loader, but continue using its 107 // previously run loader until the new loader's data is available. 108 final SparseArray<LoaderInfo> mInactiveLoaders = new SparseArray<LoaderInfo>(); 109 110 Activity mActivity; 111 boolean mStarted; 112 boolean mRetaining; 113 boolean mRetainingStarted; 114 115 final class LoaderInfo implements Loader.OnLoadCompleteListener<Object> { 116 final int mId; 117 final Bundle mArgs; 118 LoaderManager.LoaderCallbacks<Object> mCallbacks; 119 Loader<Object> mLoader; 120 Object mData; 121 boolean mStarted; 122 boolean mRetaining; 123 boolean mRetainingStarted; 124 boolean mDestroyed; 125 boolean mListenerRegistered; 126 127 public LoaderInfo(int id, Bundle args, LoaderManager.LoaderCallbacks<Object> callbacks) { 128 mId = id; 129 mArgs = args; 130 mCallbacks = callbacks; 131 } 132 133 void start() { 134 if (mRetaining && mRetainingStarted) { 135 // Our owner is started, but we were being retained from a 136 // previous instance in the started state... so there is really 137 // nothing to do here, since the loaders are still started. 138 mStarted = true; 139 return; 140 } 141 142 if (mStarted) { 143 // If loader already started, don't restart. 144 return; 145 } 146 147 if (DEBUG) Log.v(TAG, " Starting: " + this); 148 if (mLoader == null && mCallbacks != null) { 149 mLoader = mCallbacks.onCreateLoader(mId, mArgs); 150 } 151 if (mLoader != null) { 152 if (!mListenerRegistered) { 153 mLoader.registerListener(mId, this); 154 mListenerRegistered = true; 155 } 156 mLoader.startLoading(); 157 mStarted = true; 158 } 159 } 160 161 void retain() { 162 if (DEBUG) Log.v(TAG, " Retaining: " + this); 163 mRetaining = true; 164 mRetainingStarted = mStarted; 165 mStarted = false; 166 mCallbacks = null; 167 } 168 169 void finishRetain() { 170 if (mRetaining) { 171 if (DEBUG) Log.v(TAG, " Finished Retaining: " + this); 172 mRetaining = false; 173 if (mStarted != mRetainingStarted) { 174 if (!mStarted) { 175 // This loader was retained in a started state, but 176 // at the end of retaining everything our owner is 177 // no longer started... so make it stop. 178 stop(); 179 } 180 } 181 if (mStarted && mData != null) { 182 // This loader was retained, and now at the point of 183 // finishing the retain we find we remain started, have 184 // our data, and the owner has a new callback... so 185 // let's deliver the data now. 186 callOnLoadFinished(mLoader, mData); 187 } 188 } 189 } 190 191 void stop() { 192 if (DEBUG) Log.v(TAG, " Stopping: " + this); 193 mStarted = false; 194 if (!mRetaining) { 195 if (mLoader != null && mListenerRegistered) { 196 // Let the loader know we're done with it 197 mListenerRegistered = false; 198 mLoader.unregisterListener(this); 199 mLoader.stopLoading(); 200 } 201 mData = null; 202 } 203 } 204 205 void destroy() { 206 if (DEBUG) Log.v(TAG, " Destroying: " + this); 207 mDestroyed = true; 208 mCallbacks = null; 209 if (mLoader != null) { 210 if (mListenerRegistered) { 211 mListenerRegistered = false; 212 mLoader.unregisterListener(this); 213 } 214 mLoader.destroy(); 215 } 216 } 217 218 @Override public void onLoadComplete(Loader<Object> loader, Object data) { 219 if (DEBUG) Log.v(TAG, "onLoadComplete: " + this + " mDestroyed=" + mDestroyed); 220 221 if (mDestroyed) { 222 return; 223 } 224 225 // Notify of the new data so the app can switch out the old data before 226 // we try to destroy it. 227 mData = data; 228 callOnLoadFinished(loader, data); 229 230 if (DEBUG) Log.v(TAG, "onLoadFinished returned: " + this); 231 232 // We have now given the application the new loader with its 233 // loaded data, so it should have stopped using the previous 234 // loader. If there is a previous loader on the inactive list, 235 // clean it up. 236 LoaderInfo info = mInactiveLoaders.get(mId); 237 if (info != null && info != this) { 238 info.destroy(); 239 mInactiveLoaders.remove(mId); 240 } 241 } 242 243 void callOnLoadFinished(Loader<Object> loader, Object data) { 244 if (mCallbacks != null) { 245 String lastBecause = null; 246 if (mActivity != null) { 247 lastBecause = mActivity.mFragments.mNoTransactionsBecause; 248 mActivity.mFragments.mNoTransactionsBecause = "onLoadFinished"; 249 } 250 try { 251 mCallbacks.onLoadFinished(loader, data); 252 } finally { 253 if (mActivity != null) { 254 mActivity.mFragments.mNoTransactionsBecause = lastBecause; 255 } 256 } 257 } 258 } 259 260 @Override 261 public String toString() { 262 StringBuilder sb = new StringBuilder(64); 263 sb.append("LoaderInfo{"); 264 sb.append(Integer.toHexString(System.identityHashCode(this))); 265 sb.append(" #"); 266 sb.append(mId); 267 if (mArgs != null) { 268 sb.append(" "); 269 sb.append(mArgs.toString()); 270 } 271 sb.append("}"); 272 return sb.toString(); 273 } 274 } 275 276 LoaderManagerImpl(Activity activity, boolean started) { 277 mActivity = activity; 278 mStarted = started; 279 } 280 281 void updateActivity(Activity activity) { 282 mActivity = activity; 283 } 284 285 private LoaderInfo createLoader(int id, Bundle args, 286 LoaderManager.LoaderCallbacks<Object> callback) { 287 LoaderInfo info = new LoaderInfo(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 288 mLoaders.put(id, info); 289 Loader<Object> loader = callback.onCreateLoader(id, args); 290 info.mLoader = (Loader<Object>)loader; 291 if (mStarted) { 292 // The activity will start all existing loaders in it's onStart(), 293 // so only start them here if we're past that point of the activitiy's 294 // life cycle 295 info.start(); 296 } 297 return info; 298 } 299 300 @SuppressWarnings("unchecked") 301 public <D> Loader<D> initLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 302 LoaderInfo info = mLoaders.get(id); 303 304 if (DEBUG) Log.v(TAG, "initLoader in " + this + ": cur=" + info); 305 306 if (info == null) { 307 // Loader doesn't already exist; create. 308 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 309 } else { 310 info.mCallbacks = (LoaderManager.LoaderCallbacks<Object>)callback; 311 } 312 313 if (info.mData != null && mStarted) { 314 // If the loader has already generated its data, report it now. 315 info.callOnLoadFinished(info.mLoader, info.mData); 316 } 317 318 return (Loader<D>)info.mLoader; 319 } 320 321 @SuppressWarnings("unchecked") 322 public <D> Loader<D> restartLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 323 LoaderInfo info = mLoaders.get(id); 324 if (DEBUG) Log.v(TAG, "restartLoader in " + this + ": cur=" + info); 325 if (info != null) { 326 LoaderInfo inactive = mInactiveLoaders.get(id); 327 if (inactive != null) { 328 if (info.mData != null) { 329 // This loader now has data... we are probably being 330 // called from within onLoadComplete, where we haven't 331 // yet destroyed the last inactive loader. So just do 332 // that now. 333 if (DEBUG) Log.v(TAG, " Removing last inactive loader in " + this); 334 inactive.destroy(); 335 mInactiveLoaders.put(id, info); 336 } else { 337 // We already have an inactive loader for this ID that we are 338 // waiting for! Now we have three active loaders... let's just 339 // drop the one in the middle, since we are still waiting for 340 // its result but that result is already out of date. 341 if (DEBUG) Log.v(TAG, " Removing intermediate loader in " + this); 342 info.destroy(); 343 } 344 } else { 345 // Keep track of the previous instance of this loader so we can destroy 346 // it when the new one completes. 347 if (DEBUG) Log.v(TAG, " Making inactive: " + info); 348 mInactiveLoaders.put(id, info); 349 } 350 } 351 352 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 353 return (Loader<D>)info.mLoader; 354 } 355 356 public void stopLoader(int id) { 357 if (DEBUG) Log.v(TAG, "stopLoader in " + this + " of " + id); 358 int idx = mLoaders.indexOfKey(id); 359 if (idx >= 0) { 360 LoaderInfo info = mLoaders.valueAt(idx); 361 mLoaders.removeAt(idx); 362 info.destroy(); 363 } 364 } 365 366 @SuppressWarnings("unchecked") 367 public <D> Loader<D> getLoader(int id) { 368 LoaderInfo loaderInfo = mLoaders.get(id); 369 if (loaderInfo != null) { 370 return (Loader<D>)mLoaders.get(id).mLoader; 371 } 372 return null; 373 } 374 375 void doStart() { 376 if (DEBUG) Log.v(TAG, "Starting: " + this); 377 if (mStarted) { 378 RuntimeException e = new RuntimeException("here"); 379 e.fillInStackTrace(); 380 Log.w(TAG, "Called doStart when already started: " + this, e); 381 return; 382 } 383 384 // Call out to sub classes so they can start their loaders 385 // Let the existing loaders know that we want to be notified when a load is complete 386 for (int i = mLoaders.size()-1; i >= 0; i--) { 387 mLoaders.valueAt(i).start(); 388 } 389 mStarted = true; 390 } 391 392 void doStop() { 393 if (DEBUG) Log.v(TAG, "Stopping: " + this); 394 if (!mStarted) { 395 RuntimeException e = new RuntimeException("here"); 396 e.fillInStackTrace(); 397 Log.w(TAG, "Called doStop when not started: " + this, e); 398 return; 399 } 400 401 for (int i = mLoaders.size()-1; i >= 0; i--) { 402 mLoaders.valueAt(i).stop(); 403 } 404 mStarted = false; 405 } 406 407 void doRetain() { 408 if (DEBUG) Log.v(TAG, "Retaining: " + this); 409 if (!mStarted) { 410 RuntimeException e = new RuntimeException("here"); 411 e.fillInStackTrace(); 412 Log.w(TAG, "Called doRetain when not started: " + this, e); 413 return; 414 } 415 416 mRetaining = true; 417 mStarted = false; 418 for (int i = mLoaders.size()-1; i >= 0; i--) { 419 mLoaders.valueAt(i).retain(); 420 } 421 } 422 423 void finishRetain() { 424 if (DEBUG) Log.v(TAG, "Finished Retaining: " + this); 425 426 mRetaining = false; 427 for (int i = mLoaders.size()-1; i >= 0; i--) { 428 mLoaders.valueAt(i).finishRetain(); 429 } 430 } 431 432 void doDestroy() { 433 if (!mRetaining) { 434 if (DEBUG) Log.v(TAG, "Destroying Active: " + this); 435 for (int i = mLoaders.size()-1; i >= 0; i--) { 436 mLoaders.valueAt(i).destroy(); 437 } 438 } 439 440 if (DEBUG) Log.v(TAG, "Destroying Inactive: " + this); 441 for (int i = mInactiveLoaders.size()-1; i >= 0; i--) { 442 mInactiveLoaders.valueAt(i).destroy(); 443 } 444 mInactiveLoaders.clear(); 445 } 446} 447