LoaderManager.java revision f73c75ca20fcaaee1b0eeaaf756252c33e3099c6
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 24import java.io.FileDescriptor; 25import java.io.PrintWriter; 26 27/** 28 * Interface associated with an {@link Activity} or {@link Fragment} for managing 29 * one or more {@link android.content.Loader} instances associated with it. This 30 * helps an application manage longer-running operations in conjunction with the 31 * Activity or Fragment lifecycle; the most common use of this is with a 32 * {@link android.content.CursorLoader}, however applications are free to write 33 * their own loaders for loading other types of data. 34 * 35 * <p>As an example, here is the full implementation of a {@link Fragment} 36 * that displays a {@link android.widget.ListView} containing the results of 37 * a query against the contacts content provider. It uses a 38 * {@link android.content.CursorLoader} to manage the query on the provider. 39 * 40 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/FragmentListCursorLoader.java 41 * fragment_cursor} 42 */ 43public abstract class LoaderManager { 44 /** 45 * Callback interface for a client to interact with the manager. 46 */ 47 public interface LoaderCallbacks<D> { 48 /** 49 * Instantiate and return a new Loader for the given ID. 50 * 51 * @param id The ID whose loader is to be created. 52 * @param args Any arguments supplied by the caller. 53 * @return Return a new Loader instance that is ready to start loading. 54 */ 55 public Loader<D> onCreateLoader(int id, Bundle args); 56 57 /** 58 * Called when a previously created loader has finished its load. Note 59 * that normally an application is <em>not</em> allowed to commit fragment 60 * transactions while in this call, since it can happen after an 61 * activity's state is saved. See {@link FragmentManager#openTransaction() 62 * FragmentManager.openTransaction()} for further discussion on this. 63 * 64 * <p>This function is guaranteed to be called prior to the release of 65 * the last data that was supplied for this Loader. At this point 66 * you should remove all use of the old data (since it will be released 67 * soon), but should not do your own release of the data since its Loader 68 * owns it and will take care of that. The Loader will take care of 69 * management of its data so you don't have to. In particular: 70 * 71 * <ul> 72 * <li> <p>The Loader will monitor for changes to the data, and report 73 * them to you through new calls here. You should not monitor the 74 * data yourself. For example, if the data is a {@link android.database.Cursor} 75 * and you place it in a {@link android.widget.CursorAdapter}, use 76 * the {@link android.widget.CursorAdapter#CursorAdapter(android.content.Context, 77 * android.database.Cursor, int)} constructor <em>without</em> passing 78 * in either {@link android.widget.CursorAdapter#FLAG_AUTO_REQUERY} 79 * or {@link android.widget.CursorAdapter#FLAG_REGISTER_CONTENT_OBSERVER} 80 * (that is, use 0 for the flags argument). This prevents the CursorAdapter 81 * from doing its own observing of the Cursor, which is not needed since 82 * when a change happens you will get a new Cursor throw another call 83 * here. 84 * <li> The Loader will release the data once it knows the application 85 * is no longer using it. For example, if the data is 86 * a {@link android.database.Cursor} from a {@link android.content.CursorLoader}, 87 * you should not call close() on it yourself. If the Cursor is being placed in a 88 * {@link android.widget.CursorAdapter}, you should use the 89 * {@link android.widget.CursorAdapter#swapCursor(android.database.Cursor)} 90 * method so that the old Cursor is not closed. 91 * </ul> 92 * 93 * @param loader The Loader that has finished. 94 * @param data The data generated by the Loader. 95 */ 96 public void onLoadFinished(Loader<D> loader, D data); 97 98 /** 99 * Called when a previously created loader is being reset, and thus 100 * making its data unavailable. The application should at this point 101 * remove any references it has to the Loader's data. 102 * 103 * @param loader The Loader that is being reset. 104 */ 105 public void onLoaderReset(Loader<D> loader); 106 } 107 108 /** 109 * Ensures a loader is initialized and active. If the loader doesn't 110 * already exist, one is created and (if the activity/fragment is currently 111 * started) starts the loader. Otherwise the last created 112 * loader is re-used. 113 * 114 * <p>In either case, the given callback is associated with the loader, and 115 * will be called as the loader state changes. If at the point of call 116 * the caller is in its started state, and the requested loader 117 * already exists and has generated its data, then 118 * callback {@link LoaderCallbacks#onLoadFinished} will 119 * be called immediately (inside of this function), so you must be prepared 120 * for this to happen. 121 * 122 * @param id A unique identifier for this loader. Can be whatever you want. 123 * Identifiers are scoped to a particular LoaderManager instance. 124 * @param args Optional arguments to supply to the loader at construction. 125 * @param callback Interface the LoaderManager will call to report about 126 * changes in the state of the loader. Required. 127 */ 128 public abstract <D> Loader<D> initLoader(int id, Bundle args, 129 LoaderManager.LoaderCallbacks<D> callback); 130 131 /** 132 * Starts a new or restarts an existing {@link android.content.Loader} in 133 * this manager, registers the callbacks to it, 134 * and (if the activity/fragment is currently started) starts loading it. 135 * If a loader with the same id has previously been 136 * started it will automatically be destroyed when the new loader completes 137 * its work. The callback will be delivered before the old loader 138 * is destroyed. 139 * 140 * @param id A unique identifier for this loader. Can be whatever you want. 141 * Identifiers are scoped to a particular LoaderManager instance. 142 * @param args Optional arguments to supply to the loader at construction. 143 * @param callback Interface the LoaderManager will call to report about 144 * changes in the state of the loader. Required. 145 */ 146 public abstract <D> Loader<D> restartLoader(int id, Bundle args, 147 LoaderManager.LoaderCallbacks<D> callback); 148 149 /** 150 * Stops and removes the loader with the given ID. If this loader 151 * had previously reported data to the client through 152 * {@link LoaderCallbacks#onLoadFinished(Loader, Object)}, a call 153 * will be made to {@link LoaderCallbacks#onLoaderReset(Loader)}. 154 */ 155 public abstract void destroyLoader(int id); 156 157 /** 158 * @deprecated Renamed to {@link #destroyLoader}. 159 */ 160 @Deprecated 161 public void stopLoader(int id) { 162 destroyLoader(id); 163 } 164 165 /** 166 * Return the Loader with the given id or null if no matching Loader 167 * is found. 168 */ 169 public abstract <D> Loader<D> getLoader(int id); 170 171 /** 172 * Print the LoaderManager's state into the given stream. 173 * 174 * @param prefix Text to print at the front of each line. 175 * @param fd The raw file descriptor that the dump is being sent to. 176 * @param writer A PrintWriter to which the dump is to be set. 177 * @param args Additional arguments to the dump request. 178 */ 179 public abstract void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args); 180} 181 182class LoaderManagerImpl extends LoaderManager { 183 static final String TAG = "LoaderManagerImpl"; 184 static final boolean DEBUG = true; 185 186 // These are the currently active loaders. A loader is here 187 // from the time its load is started until it has been explicitly 188 // stopped or restarted by the application. 189 final SparseArray<LoaderInfo> mLoaders = new SparseArray<LoaderInfo>(); 190 191 // These are previously run loaders. This list is maintained internally 192 // to avoid destroying a loader while an application is still using it. 193 // It allows an application to restart a loader, but continue using its 194 // previously run loader until the new loader's data is available. 195 final SparseArray<LoaderInfo> mInactiveLoaders = new SparseArray<LoaderInfo>(); 196 197 Activity mActivity; 198 boolean mStarted; 199 boolean mRetaining; 200 boolean mRetainingStarted; 201 202 final class LoaderInfo implements Loader.OnLoadCompleteListener<Object> { 203 final int mId; 204 final Bundle mArgs; 205 LoaderManager.LoaderCallbacks<Object> mCallbacks; 206 Loader<Object> mLoader; 207 Object mData; 208 boolean mStarted; 209 boolean mNeedReset; 210 boolean mRetaining; 211 boolean mRetainingStarted; 212 boolean mDestroyed; 213 boolean mListenerRegistered; 214 215 public LoaderInfo(int id, Bundle args, LoaderManager.LoaderCallbacks<Object> callbacks) { 216 mId = id; 217 mArgs = args; 218 mCallbacks = callbacks; 219 } 220 221 void start() { 222 if (mRetaining && mRetainingStarted) { 223 // Our owner is started, but we were being retained from a 224 // previous instance in the started state... so there is really 225 // nothing to do here, since the loaders are still started. 226 mStarted = true; 227 return; 228 } 229 230 if (mStarted) { 231 // If loader already started, don't restart. 232 return; 233 } 234 235 if (DEBUG) Log.v(TAG, " Starting: " + this); 236 if (mLoader == null && mCallbacks != null) { 237 mLoader = mCallbacks.onCreateLoader(mId, mArgs); 238 } 239 if (mLoader != null) { 240 if (!mListenerRegistered) { 241 mLoader.registerListener(mId, this); 242 mListenerRegistered = true; 243 } 244 mLoader.startLoading(); 245 mStarted = true; 246 } 247 } 248 249 void retain() { 250 if (DEBUG) Log.v(TAG, " Retaining: " + this); 251 mRetaining = true; 252 mRetainingStarted = mStarted; 253 mStarted = false; 254 mCallbacks = null; 255 } 256 257 void finishRetain() { 258 if (mRetaining) { 259 if (DEBUG) Log.v(TAG, " Finished Retaining: " + this); 260 mRetaining = false; 261 if (mStarted != mRetainingStarted) { 262 if (!mStarted) { 263 // This loader was retained in a started state, but 264 // at the end of retaining everything our owner is 265 // no longer started... so make it stop. 266 stop(); 267 } 268 } 269 } 270 271 if (mStarted && mData != null) { 272 // This loader has retained its data, either completely across 273 // a configuration change or just whatever the last data set 274 // was after being restarted from a stop, and now at the point of 275 // finishing the retain we find we remain started, have 276 // our data, and the owner has a new callback... so 277 // let's deliver the data now. 278 callOnLoadFinished(mLoader, mData); 279 } 280 } 281 282 void stop() { 283 if (DEBUG) Log.v(TAG, " Stopping: " + this); 284 mStarted = false; 285 if (!mRetaining) { 286 if (mLoader != null && mListenerRegistered) { 287 // Let the loader know we're done with it 288 mListenerRegistered = false; 289 mLoader.unregisterListener(this); 290 mLoader.stopLoading(); 291 } 292 } 293 } 294 295 void destroy() { 296 if (DEBUG) Log.v(TAG, " Destroying: " + this); 297 mDestroyed = true; 298 if (mCallbacks != null && mLoader != null && mData != null && mNeedReset) { 299 String lastBecause = null; 300 if (mActivity != null) { 301 lastBecause = mActivity.mFragments.mNoTransactionsBecause; 302 mActivity.mFragments.mNoTransactionsBecause = "onLoaderReset"; 303 } 304 try { 305 mCallbacks.onLoaderReset(mLoader); 306 } finally { 307 if (mActivity != null) { 308 mActivity.mFragments.mNoTransactionsBecause = lastBecause; 309 } 310 } 311 } 312 mNeedReset = false; 313 mCallbacks = null; 314 mData = null; 315 if (mLoader != null) { 316 if (mListenerRegistered) { 317 mListenerRegistered = false; 318 mLoader.unregisterListener(this); 319 } 320 mLoader.reset(); 321 } 322 } 323 324 @Override public void onLoadComplete(Loader<Object> loader, Object data) { 325 if (DEBUG) Log.v(TAG, "onLoadComplete: " + this + " mDestroyed=" + mDestroyed); 326 327 if (mDestroyed) { 328 return; 329 } 330 331 // Notify of the new data so the app can switch out the old data before 332 // we try to destroy it. 333 mData = data; 334 if (mStarted) { 335 callOnLoadFinished(loader, data); 336 } 337 338 if (DEBUG) Log.v(TAG, "onLoadFinished returned: " + this); 339 340 // We have now given the application the new loader with its 341 // loaded data, so it should have stopped using the previous 342 // loader. If there is a previous loader on the inactive list, 343 // clean it up. 344 LoaderInfo info = mInactiveLoaders.get(mId); 345 if (info != null && info != this) { 346 info.mNeedReset = false; 347 info.destroy(); 348 mInactiveLoaders.remove(mId); 349 } 350 } 351 352 void callOnLoadFinished(Loader<Object> loader, Object data) { 353 if (mCallbacks != null) { 354 String lastBecause = null; 355 if (mActivity != null) { 356 lastBecause = mActivity.mFragments.mNoTransactionsBecause; 357 mActivity.mFragments.mNoTransactionsBecause = "onLoadFinished"; 358 } 359 try { 360 mCallbacks.onLoadFinished(loader, data); 361 } finally { 362 if (mActivity != null) { 363 mActivity.mFragments.mNoTransactionsBecause = lastBecause; 364 } 365 } 366 mNeedReset = true; 367 } 368 } 369 370 @Override 371 public String toString() { 372 StringBuilder sb = new StringBuilder(64); 373 sb.append("LoaderInfo{"); 374 sb.append(Integer.toHexString(System.identityHashCode(this))); 375 sb.append(" #"); 376 sb.append(mId); 377 if (mArgs != null) { 378 sb.append(" "); 379 sb.append(mArgs.toString()); 380 } 381 sb.append("}"); 382 return sb.toString(); 383 } 384 385 public String toBasicString() { 386 StringBuilder sb = new StringBuilder(64); 387 sb.append("LoaderInfo{"); 388 sb.append(Integer.toHexString(System.identityHashCode(this))); 389 sb.append(" #"); 390 sb.append(mId); 391 sb.append("}"); 392 return sb.toString(); 393 } 394 395 public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { 396 writer.print(prefix); writer.print("mId="); writer.print(mId); 397 writer.print(" mArgs="); writer.println(mArgs); 398 writer.print(prefix); writer.print("mCallbacks="); writer.println(mCallbacks); 399 writer.print(prefix); writer.print("mLoader="); writer.println(mLoader); 400 writer.print(prefix); writer.print("mData="); writer.println(mData); 401 writer.print(prefix); writer.print("mStarted="); writer.print(mStarted); 402 writer.print(" mRetaining="); writer.print(mRetaining); 403 writer.print(" mDestroyed="); writer.println(mDestroyed); 404 writer.print(prefix); writer.print("mNeedReset="); writer.print(mNeedReset); 405 writer.print(" mListenerRegistered="); writer.println(mListenerRegistered); 406 } 407 } 408 409 LoaderManagerImpl(Activity activity, boolean started) { 410 mActivity = activity; 411 mStarted = started; 412 } 413 414 void updateActivity(Activity activity) { 415 mActivity = activity; 416 } 417 418 private LoaderInfo createLoader(int id, Bundle args, 419 LoaderManager.LoaderCallbacks<Object> callback) { 420 LoaderInfo info = new LoaderInfo(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 421 mLoaders.put(id, info); 422 Loader<Object> loader = callback.onCreateLoader(id, args); 423 info.mLoader = (Loader<Object>)loader; 424 if (mStarted) { 425 // The activity will start all existing loaders in it's onStart(), 426 // so only start them here if we're past that point of the activitiy's 427 // life cycle 428 info.start(); 429 } 430 return info; 431 } 432 433 @SuppressWarnings("unchecked") 434 public <D> Loader<D> initLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 435 LoaderInfo info = mLoaders.get(id); 436 437 if (DEBUG) Log.v(TAG, "initLoader in " + this + ": cur=" + info); 438 439 if (info == null) { 440 // Loader doesn't already exist; create. 441 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 442 } else { 443 info.mCallbacks = (LoaderManager.LoaderCallbacks<Object>)callback; 444 } 445 446 if (info.mData != null && mStarted) { 447 // If the loader has already generated its data, report it now. 448 info.callOnLoadFinished(info.mLoader, info.mData); 449 } 450 451 return (Loader<D>)info.mLoader; 452 } 453 454 @SuppressWarnings("unchecked") 455 public <D> Loader<D> restartLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 456 LoaderInfo info = mLoaders.get(id); 457 if (DEBUG) Log.v(TAG, "restartLoader in " + this + ": cur=" + info); 458 if (info != null) { 459 LoaderInfo inactive = mInactiveLoaders.get(id); 460 if (inactive != null) { 461 if (info.mData != null) { 462 // This loader now has data... we are probably being 463 // called from within onLoadComplete, where we haven't 464 // yet destroyed the last inactive loader. So just do 465 // that now. 466 if (DEBUG) Log.v(TAG, " Removing last inactive loader in " + this); 467 inactive.mNeedReset = false; 468 inactive.destroy(); 469 mInactiveLoaders.put(id, info); 470 } else { 471 // We already have an inactive loader for this ID that we are 472 // waiting for! Now we have three active loaders... let's just 473 // drop the one in the middle, since we are still waiting for 474 // its result but that result is already out of date. 475 if (DEBUG) Log.v(TAG, " Removing intermediate loader in " + this); 476 info.destroy(); 477 } 478 } else { 479 // Keep track of the previous instance of this loader so we can destroy 480 // it when the new one completes. 481 if (DEBUG) Log.v(TAG, " Making inactive: " + info); 482 mInactiveLoaders.put(id, info); 483 } 484 } 485 486 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 487 return (Loader<D>)info.mLoader; 488 } 489 490 public void destroyLoader(int id) { 491 if (DEBUG) Log.v(TAG, "stopLoader in " + this + " of " + id); 492 int idx = mLoaders.indexOfKey(id); 493 if (idx >= 0) { 494 LoaderInfo info = mLoaders.valueAt(idx); 495 mLoaders.removeAt(idx); 496 info.destroy(); 497 } 498 idx = mInactiveLoaders.indexOfKey(id); 499 if (idx >= 0) { 500 LoaderInfo info = mInactiveLoaders.valueAt(idx); 501 mInactiveLoaders.removeAt(idx); 502 info.destroy(); 503 } 504 } 505 506 @SuppressWarnings("unchecked") 507 public <D> Loader<D> getLoader(int id) { 508 LoaderInfo loaderInfo = mLoaders.get(id); 509 if (loaderInfo != null) { 510 return (Loader<D>)mLoaders.get(id).mLoader; 511 } 512 return null; 513 } 514 515 void doStart() { 516 if (DEBUG) Log.v(TAG, "Starting: " + this); 517 if (mStarted) { 518 RuntimeException e = new RuntimeException("here"); 519 e.fillInStackTrace(); 520 Log.w(TAG, "Called doStart when already started: " + this, e); 521 return; 522 } 523 524 mStarted = true; 525 526 // Call out to sub classes so they can start their loaders 527 // Let the existing loaders know that we want to be notified when a load is complete 528 for (int i = mLoaders.size()-1; i >= 0; i--) { 529 mLoaders.valueAt(i).start(); 530 } 531 } 532 533 void doStop() { 534 if (DEBUG) Log.v(TAG, "Stopping: " + this); 535 if (!mStarted) { 536 RuntimeException e = new RuntimeException("here"); 537 e.fillInStackTrace(); 538 Log.w(TAG, "Called doStop when not started: " + this, e); 539 return; 540 } 541 542 for (int i = mLoaders.size()-1; i >= 0; i--) { 543 mLoaders.valueAt(i).stop(); 544 } 545 mStarted = false; 546 } 547 548 void doRetain() { 549 if (DEBUG) Log.v(TAG, "Retaining: " + this); 550 if (!mStarted) { 551 RuntimeException e = new RuntimeException("here"); 552 e.fillInStackTrace(); 553 Log.w(TAG, "Called doRetain when not started: " + this, e); 554 return; 555 } 556 557 mRetaining = true; 558 mStarted = false; 559 for (int i = mLoaders.size()-1; i >= 0; i--) { 560 mLoaders.valueAt(i).retain(); 561 } 562 } 563 564 void finishRetain() { 565 if (DEBUG) Log.v(TAG, "Finished Retaining: " + this); 566 567 mRetaining = false; 568 for (int i = mLoaders.size()-1; i >= 0; i--) { 569 mLoaders.valueAt(i).finishRetain(); 570 } 571 } 572 573 void doDestroy() { 574 if (!mRetaining) { 575 if (DEBUG) Log.v(TAG, "Destroying Active: " + this); 576 for (int i = mLoaders.size()-1; i >= 0; i--) { 577 mLoaders.valueAt(i).destroy(); 578 } 579 } 580 581 if (DEBUG) Log.v(TAG, "Destroying Inactive: " + this); 582 for (int i = mInactiveLoaders.size()-1; i >= 0; i--) { 583 mInactiveLoaders.valueAt(i).destroy(); 584 } 585 mInactiveLoaders.clear(); 586 } 587 588 @Override 589 public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { 590 if (mLoaders.size() > 0) { 591 writer.print(prefix); writer.println("Active Loaders:"); 592 String innerPrefix = prefix + " "; 593 for (int i=0; i < mLoaders.size(); i++) { 594 LoaderInfo li = mLoaders.valueAt(i); 595 writer.print(prefix); writer.print(" #"); writer.print(mLoaders.keyAt(i)); 596 writer.print(": "); writer.println(li.toBasicString()); 597 li.dump(innerPrefix, fd, writer, args); 598 } 599 } 600 if (mInactiveLoaders.size() > 0) { 601 writer.print(prefix); writer.println("Inactive Loaders:"); 602 String innerPrefix = prefix + " "; 603 for (int i=0; i < mInactiveLoaders.size(); i++) { 604 LoaderInfo li = mInactiveLoaders.valueAt(i); 605 writer.print(prefix); writer.print(" #"); writer.print(mInactiveLoaders.keyAt(i)); 606 writer.print(": "); writer.println(li.toBasicString()); 607 li.dump(innerPrefix, fd, writer, args); 608 } 609 } 610 } 611} 612