LoaderManager.java revision 0e3b8f421dfcc5363f234eb1b76479cb2fb2e8ee
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.DebugUtils; 22import android.util.Log; 23import android.util.SparseArray; 24 25import java.io.FileDescriptor; 26import java.io.PrintWriter; 27import java.lang.reflect.Modifier; 28 29/** 30 * Interface associated with an {@link Activity} or {@link Fragment} for managing 31 * one or more {@link android.content.Loader} instances associated with it. This 32 * helps an application manage longer-running operations in conjunction with the 33 * Activity or Fragment lifecycle; the most common use of this is with a 34 * {@link android.content.CursorLoader}, however applications are free to write 35 * their own loaders for loading other types of data. 36 * 37 * <p>As an example, here is the full implementation of a {@link Fragment} 38 * that displays a {@link android.widget.ListView} containing the results of 39 * a query against the contacts content provider. It uses a 40 * {@link android.content.CursorLoader} to manage the query on the provider. 41 * 42 * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/FragmentListCursorLoader.java 43 * fragment_cursor} 44 */ 45public abstract class LoaderManager { 46 /** 47 * Callback interface for a client to interact with the manager. 48 */ 49 public interface LoaderCallbacks<D> { 50 /** 51 * Instantiate and return a new Loader for the given ID. 52 * 53 * @param id The ID whose loader is to be created. 54 * @param args Any arguments supplied by the caller. 55 * @return Return a new Loader instance that is ready to start loading. 56 */ 57 public Loader<D> onCreateLoader(int id, Bundle args); 58 59 /** 60 * Called when a previously created loader has finished its load. Note 61 * that normally an application is <em>not</em> allowed to commit fragment 62 * transactions while in this call, since it can happen after an 63 * activity's state is saved. See {@link FragmentManager#openTransaction() 64 * FragmentManager.openTransaction()} for further discussion on this. 65 * 66 * <p>This function is guaranteed to be called prior to the release of 67 * the last data that was supplied for this Loader. At this point 68 * you should remove all use of the old data (since it will be released 69 * soon), but should not do your own release of the data since its Loader 70 * owns it and will take care of that. The Loader will take care of 71 * management of its data so you don't have to. In particular: 72 * 73 * <ul> 74 * <li> <p>The Loader will monitor for changes to the data, and report 75 * them to you through new calls here. You should not monitor the 76 * data yourself. For example, if the data is a {@link android.database.Cursor} 77 * and you place it in a {@link android.widget.CursorAdapter}, use 78 * the {@link android.widget.CursorAdapter#CursorAdapter(android.content.Context, 79 * android.database.Cursor, int)} constructor <em>without</em> passing 80 * in either {@link android.widget.CursorAdapter#FLAG_AUTO_REQUERY} 81 * or {@link android.widget.CursorAdapter#FLAG_REGISTER_CONTENT_OBSERVER} 82 * (that is, use 0 for the flags argument). This prevents the CursorAdapter 83 * from doing its own observing of the Cursor, which is not needed since 84 * when a change happens you will get a new Cursor throw another call 85 * here. 86 * <li> The Loader will release the data once it knows the application 87 * is no longer using it. For example, if the data is 88 * a {@link android.database.Cursor} from a {@link android.content.CursorLoader}, 89 * you should not call close() on it yourself. If the Cursor is being placed in a 90 * {@link android.widget.CursorAdapter}, you should use the 91 * {@link android.widget.CursorAdapter#swapCursor(android.database.Cursor)} 92 * method so that the old Cursor is not closed. 93 * </ul> 94 * 95 * @param loader The Loader that has finished. 96 * @param data The data generated by the Loader. 97 */ 98 public void onLoadFinished(Loader<D> loader, D data); 99 100 /** 101 * Called when a previously created loader is being reset, and thus 102 * making its data unavailable. The application should at this point 103 * remove any references it has to the Loader's data. 104 * 105 * @param loader The Loader that is being reset. 106 */ 107 public void onLoaderReset(Loader<D> loader); 108 } 109 110 /** 111 * Ensures a loader is initialized and active. If the loader doesn't 112 * already exist, one is created and (if the activity/fragment is currently 113 * started) starts the loader. Otherwise the last created 114 * loader is re-used. 115 * 116 * <p>In either case, the given callback is associated with the loader, and 117 * will be called as the loader state changes. If at the point of call 118 * the caller is in its started state, and the requested loader 119 * already exists and has generated its data, then 120 * callback {@link LoaderCallbacks#onLoadFinished} will 121 * be called immediately (inside of this function), so you must be prepared 122 * for this to happen. 123 * 124 * @param id A unique identifier for this loader. Can be whatever you want. 125 * Identifiers are scoped to a particular LoaderManager instance. 126 * @param args Optional arguments to supply to the loader at construction. 127 * If a loader already exists (a new one does not need to be created), this 128 * parameter will be ignored and the last arguments continue to be used. 129 * @param callback Interface the LoaderManager will call to report about 130 * changes in the state of the loader. Required. 131 */ 132 public abstract <D> Loader<D> initLoader(int id, Bundle args, 133 LoaderManager.LoaderCallbacks<D> callback); 134 135 /** 136 * Starts a new or restarts an existing {@link android.content.Loader} in 137 * this manager, registers the callbacks to it, 138 * and (if the activity/fragment is currently started) starts loading it. 139 * If a loader with the same id has previously been 140 * started it will automatically be destroyed when the new loader completes 141 * its work. The callback will be delivered before the old loader 142 * is destroyed. 143 * 144 * @param id A unique identifier for this loader. Can be whatever you want. 145 * Identifiers are scoped to a particular LoaderManager instance. 146 * @param args Optional arguments to supply to the loader at construction. 147 * @param callback Interface the LoaderManager will call to report about 148 * changes in the state of the loader. Required. 149 */ 150 public abstract <D> Loader<D> restartLoader(int id, Bundle args, 151 LoaderManager.LoaderCallbacks<D> callback); 152 153 /** 154 * Stops and removes the loader with the given ID. If this loader 155 * had previously reported data to the client through 156 * {@link LoaderCallbacks#onLoadFinished(Loader, Object)}, a call 157 * will be made to {@link LoaderCallbacks#onLoaderReset(Loader)}. 158 */ 159 public abstract void destroyLoader(int id); 160 161 /** 162 * @deprecated Renamed to {@link #destroyLoader}. 163 */ 164 @Deprecated 165 public void stopLoader(int id) { 166 destroyLoader(id); 167 } 168 169 /** 170 * Return the Loader with the given id or null if no matching Loader 171 * is found. 172 */ 173 public abstract <D> Loader<D> getLoader(int id); 174 175 /** 176 * Print the LoaderManager's state into the given stream. 177 * 178 * @param prefix Text to print at the front of each line. 179 * @param fd The raw file descriptor that the dump is being sent to. 180 * @param writer A PrintWriter to which the dump is to be set. 181 * @param args Additional arguments to the dump request. 182 */ 183 public abstract void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args); 184 185 /** 186 * Control whether the framework's internal loader manager debugging 187 * logs are turned on. If enabled, you will see output in logcat as 188 * the framework performs loader operations. 189 */ 190 public static void enableDebugLogging(boolean enabled) { 191 LoaderManagerImpl.DEBUG = enabled; 192 } 193} 194 195class LoaderManagerImpl extends LoaderManager { 196 static final String TAG = "LoaderManager"; 197 static boolean DEBUG = true; 198 199 // These are the currently active loaders. A loader is here 200 // from the time its load is started until it has been explicitly 201 // stopped or restarted by the application. 202 final SparseArray<LoaderInfo> mLoaders = new SparseArray<LoaderInfo>(); 203 204 // These are previously run loaders. This list is maintained internally 205 // to avoid destroying a loader while an application is still using it. 206 // It allows an application to restart a loader, but continue using its 207 // previously run loader until the new loader's data is available. 208 final SparseArray<LoaderInfo> mInactiveLoaders = new SparseArray<LoaderInfo>(); 209 210 Activity mActivity; 211 boolean mStarted; 212 boolean mRetaining; 213 boolean mRetainingStarted; 214 215 final class LoaderInfo implements Loader.OnLoadCompleteListener<Object> { 216 final int mId; 217 final Bundle mArgs; 218 LoaderManager.LoaderCallbacks<Object> mCallbacks; 219 Loader<Object> mLoader; 220 Object mData; 221 Object mDeliveredData; 222 boolean mStarted; 223 boolean mRetaining; 224 boolean mRetainingStarted; 225 boolean mDestroyed; 226 boolean mListenerRegistered; 227 228 public LoaderInfo(int id, Bundle args, LoaderManager.LoaderCallbacks<Object> callbacks) { 229 mId = id; 230 mArgs = args; 231 mCallbacks = callbacks; 232 } 233 234 void start() { 235 if (mRetaining && mRetainingStarted) { 236 // Our owner is started, but we were being retained from a 237 // previous instance in the started state... so there is really 238 // nothing to do here, since the loaders are still started. 239 mStarted = true; 240 return; 241 } 242 243 if (mStarted) { 244 // If loader already started, don't restart. 245 return; 246 } 247 248 mStarted = true; 249 250 if (DEBUG) Log.v(TAG, " Starting: " + this); 251 if (mLoader == null && mCallbacks != null) { 252 mLoader = mCallbacks.onCreateLoader(mId, mArgs); 253 } 254 if (mLoader != null) { 255 if (mLoader.getClass().isMemberClass() 256 && !Modifier.isStatic(mLoader.getClass().getModifiers())) { 257 throw new IllegalArgumentException( 258 "Object returned from onCreateLoader must not be a non-static inner member class: " 259 + mLoader); 260 } 261 if (!mListenerRegistered) { 262 mLoader.registerListener(mId, this); 263 mListenerRegistered = true; 264 } 265 mLoader.startLoading(); 266 } 267 } 268 269 void retain() { 270 if (DEBUG) Log.v(TAG, " Retaining: " + this); 271 mRetaining = true; 272 mRetainingStarted = mStarted; 273 mStarted = false; 274 mCallbacks = null; 275 } 276 277 void finishRetain() { 278 if (mRetaining) { 279 if (DEBUG) Log.v(TAG, " Finished Retaining: " + this); 280 mRetaining = false; 281 if (mStarted != mRetainingStarted) { 282 if (!mStarted) { 283 // This loader was retained in a started state, but 284 // at the end of retaining everything our owner is 285 // no longer started... so make it stop. 286 stop(); 287 } 288 } 289 } 290 291 if (mStarted && mData != null) { 292 // This loader has retained its data, either completely across 293 // a configuration change or just whatever the last data set 294 // was after being restarted from a stop, and now at the point of 295 // finishing the retain we find we remain started, have 296 // our data, and the owner has a new callback... so 297 // let's deliver the data now. 298 callOnLoadFinished(mLoader, mData); 299 } 300 } 301 302 void stop() { 303 if (DEBUG) Log.v(TAG, " Stopping: " + this); 304 mStarted = false; 305 if (!mRetaining) { 306 if (mLoader != null && mListenerRegistered) { 307 // Let the loader know we're done with it 308 mListenerRegistered = false; 309 mLoader.unregisterListener(this); 310 mLoader.stopLoading(); 311 } 312 } 313 } 314 315 void destroy() { 316 if (DEBUG) Log.v(TAG, " Destroying: " + this); 317 mDestroyed = true; 318 boolean needReset = mDeliveredData != null; 319 mDeliveredData = null; 320 if (mCallbacks != null && mLoader != null && mData != null && needReset) { 321 if (DEBUG) Log.v(TAG, " Reseting: " + this); 322 String lastBecause = null; 323 if (mActivity != null) { 324 lastBecause = mActivity.mFragments.mNoTransactionsBecause; 325 mActivity.mFragments.mNoTransactionsBecause = "onLoaderReset"; 326 } 327 try { 328 mCallbacks.onLoaderReset(mLoader); 329 } finally { 330 if (mActivity != null) { 331 mActivity.mFragments.mNoTransactionsBecause = lastBecause; 332 } 333 } 334 } 335 mCallbacks = null; 336 mData = null; 337 if (mLoader != null) { 338 if (mListenerRegistered) { 339 mListenerRegistered = false; 340 mLoader.unregisterListener(this); 341 } 342 mLoader.reset(); 343 } 344 } 345 346 @Override public void onLoadComplete(Loader<Object> loader, Object data) { 347 if (DEBUG) Log.v(TAG, "onLoadComplete: " + this); 348 349 if (mDestroyed) { 350 if (DEBUG) Log.v(TAG, " Ignoring load complete -- destroyed"); 351 return; 352 } 353 354 // Notify of the new data so the app can switch out the old data before 355 // we try to destroy it. 356 if (mData != data) { 357 mData = data; 358 if (mStarted) { 359 callOnLoadFinished(loader, data); 360 } 361 } 362 363 //if (DEBUG) Log.v(TAG, " onLoadFinished returned: " + this); 364 365 // We have now given the application the new loader with its 366 // loaded data, so it should have stopped using the previous 367 // loader. If there is a previous loader on the inactive list, 368 // clean it up. 369 LoaderInfo info = mInactiveLoaders.get(mId); 370 if (info != null && info != this) { 371 info.mDeliveredData = null; 372 info.destroy(); 373 mInactiveLoaders.remove(mId); 374 } 375 } 376 377 void callOnLoadFinished(Loader<Object> loader, Object data) { 378 if (mCallbacks != null) { 379 String lastBecause = null; 380 if (mActivity != null) { 381 lastBecause = mActivity.mFragments.mNoTransactionsBecause; 382 mActivity.mFragments.mNoTransactionsBecause = "onLoadFinished"; 383 } 384 try { 385 if (DEBUG) Log.v(TAG, " onLoadFinished in " + loader + ": " 386 + loader.dataToString(data)); 387 mCallbacks.onLoadFinished(loader, data); 388 } finally { 389 if (mActivity != null) { 390 mActivity.mFragments.mNoTransactionsBecause = lastBecause; 391 } 392 } 393 mDeliveredData = data; 394 } 395 } 396 397 @Override 398 public String toString() { 399 StringBuilder sb = new StringBuilder(64); 400 sb.append("LoaderInfo{"); 401 sb.append(Integer.toHexString(System.identityHashCode(this))); 402 sb.append(" #"); 403 sb.append(mId); 404 sb.append(" : "); 405 DebugUtils.buildShortClassTag(mLoader, sb); 406 sb.append("}}"); 407 return sb.toString(); 408 } 409 410 public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { 411 writer.print(prefix); writer.print("mId="); writer.print(mId); 412 writer.print(" mArgs="); writer.println(mArgs); 413 writer.print(prefix); writer.print("mCallbacks="); writer.println(mCallbacks); 414 writer.print(prefix); writer.print("mLoader="); writer.println(mLoader); 415 if (mLoader != null) { 416 mLoader.dump(prefix + " ", fd, writer, args); 417 } 418 writer.print(prefix); writer.print("mData="); writer.println(mData); 419 writer.print(prefix); writer.print("mDeliveredData="); writer.println(mDeliveredData); 420 writer.print(prefix); writer.print("mStarted="); writer.print(mStarted); 421 writer.print(" mRetaining="); writer.print(mRetaining); 422 writer.print(" mDestroyed="); writer.println(mDestroyed); 423 writer.print(prefix); writer.print("mListenerRegistered="); 424 writer.println(mListenerRegistered); 425 } 426 } 427 428 LoaderManagerImpl(Activity activity, boolean started) { 429 mActivity = activity; 430 mStarted = started; 431 } 432 433 void updateActivity(Activity activity) { 434 mActivity = activity; 435 } 436 437 private LoaderInfo createLoader(int id, Bundle args, 438 LoaderManager.LoaderCallbacks<Object> callback) { 439 LoaderInfo info = new LoaderInfo(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 440 mLoaders.put(id, info); 441 Loader<Object> loader = callback.onCreateLoader(id, args); 442 info.mLoader = (Loader<Object>)loader; 443 if (mStarted) { 444 // The activity will start all existing loaders in it's onStart(), 445 // so only start them here if we're past that point of the activitiy's 446 // life cycle 447 info.start(); 448 } 449 return info; 450 } 451 452 @SuppressWarnings("unchecked") 453 public <D> Loader<D> initLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 454 LoaderInfo info = mLoaders.get(id); 455 456 if (DEBUG) Log.v(TAG, "initLoader in " + this + ": args=" + args); 457 458 if (info == null) { 459 // Loader doesn't already exist; create. 460 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 461 if (DEBUG) Log.v(TAG, " Created new loader " + info); 462 } else { 463 if (DEBUG) Log.v(TAG, " Re-using existing loader " + info); 464 info.mCallbacks = (LoaderManager.LoaderCallbacks<Object>)callback; 465 } 466 467 if (info.mData != null && mStarted) { 468 // If the loader has already generated its data, report it now. 469 info.callOnLoadFinished(info.mLoader, info.mData); 470 } 471 472 return (Loader<D>)info.mLoader; 473 } 474 475 @SuppressWarnings("unchecked") 476 public <D> Loader<D> restartLoader(int id, Bundle args, LoaderManager.LoaderCallbacks<D> callback) { 477 LoaderInfo info = mLoaders.get(id); 478 if (DEBUG) Log.v(TAG, "restartLoader in " + this + ": args=" + args); 479 if (info != null) { 480 LoaderInfo inactive = mInactiveLoaders.get(id); 481 if (inactive != null) { 482 if (info.mData != null) { 483 // This loader now has data... we are probably being 484 // called from within onLoadComplete, where we haven't 485 // yet destroyed the last inactive loader. So just do 486 // that now. 487 if (DEBUG) Log.v(TAG, " Removing last inactive loader: " + info); 488 inactive.mDeliveredData = null; 489 inactive.destroy(); 490 mInactiveLoaders.put(id, info); 491 } else { 492 // We already have an inactive loader for this ID that we are 493 // waiting for! Now we have three active loaders... let's just 494 // drop the one in the middle, since we are still waiting for 495 // its result but that result is already out of date. 496 if (DEBUG) Log.v(TAG, " Removing intermediate loader: " + info); 497 info.destroy(); 498 } 499 } else { 500 // Keep track of the previous instance of this loader so we can destroy 501 // it when the new one completes. 502 if (DEBUG) Log.v(TAG, " Making last loader inactive: " + info); 503 mInactiveLoaders.put(id, info); 504 } 505 } 506 507 info = createLoader(id, args, (LoaderManager.LoaderCallbacks<Object>)callback); 508 return (Loader<D>)info.mLoader; 509 } 510 511 public void destroyLoader(int id) { 512 if (DEBUG) Log.v(TAG, "destroyLoader in " + this + " of " + id); 513 int idx = mLoaders.indexOfKey(id); 514 if (idx >= 0) { 515 LoaderInfo info = mLoaders.valueAt(idx); 516 mLoaders.removeAt(idx); 517 info.destroy(); 518 } 519 idx = mInactiveLoaders.indexOfKey(id); 520 if (idx >= 0) { 521 LoaderInfo info = mInactiveLoaders.valueAt(idx); 522 mInactiveLoaders.removeAt(idx); 523 info.destroy(); 524 } 525 } 526 527 @SuppressWarnings("unchecked") 528 public <D> Loader<D> getLoader(int id) { 529 LoaderInfo loaderInfo = mLoaders.get(id); 530 if (loaderInfo != null) { 531 return (Loader<D>)mLoaders.get(id).mLoader; 532 } 533 return null; 534 } 535 536 void doStart() { 537 if (DEBUG) Log.v(TAG, "Starting in " + this); 538 if (mStarted) { 539 RuntimeException e = new RuntimeException("here"); 540 e.fillInStackTrace(); 541 Log.w(TAG, "Called doStart when already started: " + this, e); 542 return; 543 } 544 545 mStarted = true; 546 547 // Call out to sub classes so they can start their loaders 548 // Let the existing loaders know that we want to be notified when a load is complete 549 for (int i = mLoaders.size()-1; i >= 0; i--) { 550 mLoaders.valueAt(i).start(); 551 } 552 } 553 554 void doStop() { 555 if (DEBUG) Log.v(TAG, "Stopping in " + this); 556 if (!mStarted) { 557 RuntimeException e = new RuntimeException("here"); 558 e.fillInStackTrace(); 559 Log.w(TAG, "Called doStop when not started: " + this, e); 560 return; 561 } 562 563 for (int i = mLoaders.size()-1; i >= 0; i--) { 564 mLoaders.valueAt(i).stop(); 565 } 566 mStarted = false; 567 } 568 569 void doRetain() { 570 if (DEBUG) Log.v(TAG, "Retaining in " + this); 571 if (!mStarted) { 572 RuntimeException e = new RuntimeException("here"); 573 e.fillInStackTrace(); 574 Log.w(TAG, "Called doRetain when not started: " + this, e); 575 return; 576 } 577 578 mRetaining = true; 579 mStarted = false; 580 for (int i = mLoaders.size()-1; i >= 0; i--) { 581 mLoaders.valueAt(i).retain(); 582 } 583 } 584 585 void finishRetain() { 586 if (mRetaining) { 587 if (DEBUG) Log.v(TAG, "Finished Retaining in " + this); 588 589 mRetaining = false; 590 for (int i = mLoaders.size()-1; i >= 0; i--) { 591 mLoaders.valueAt(i).finishRetain(); 592 } 593 } 594 } 595 596 void doDestroy() { 597 if (!mRetaining) { 598 if (DEBUG) Log.v(TAG, "Destroying Active in " + this); 599 for (int i = mLoaders.size()-1; i >= 0; i--) { 600 mLoaders.valueAt(i).destroy(); 601 } 602 } 603 604 if (DEBUG) Log.v(TAG, "Destroying Inactive in " + this); 605 for (int i = mInactiveLoaders.size()-1; i >= 0; i--) { 606 mInactiveLoaders.valueAt(i).destroy(); 607 } 608 mInactiveLoaders.clear(); 609 } 610 611 @Override 612 public String toString() { 613 StringBuilder sb = new StringBuilder(128); 614 sb.append("LoaderManager{"); 615 sb.append(Integer.toHexString(System.identityHashCode(this))); 616 sb.append(" in "); 617 DebugUtils.buildShortClassTag(mActivity, sb); 618 sb.append("}}"); 619 return sb.toString(); 620 } 621 622 @Override 623 public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) { 624 if (mLoaders.size() > 0) { 625 writer.print(prefix); writer.println("Active Loaders:"); 626 String innerPrefix = prefix + " "; 627 for (int i=0; i < mLoaders.size(); i++) { 628 LoaderInfo li = mLoaders.valueAt(i); 629 writer.print(prefix); writer.print(" #"); writer.print(mLoaders.keyAt(i)); 630 writer.print(": "); writer.println(li.toString()); 631 li.dump(innerPrefix, fd, writer, args); 632 } 633 } 634 if (mInactiveLoaders.size() > 0) { 635 writer.print(prefix); writer.println("Inactive Loaders:"); 636 String innerPrefix = prefix + " "; 637 for (int i=0; i < mInactiveLoaders.size(); i++) { 638 LoaderInfo li = mInactiveLoaders.valueAt(i); 639 writer.print(prefix); writer.print(" #"); writer.print(mInactiveLoaders.keyAt(i)); 640 writer.print(": "); writer.println(li.toString()); 641 li.dump(innerPrefix, fd, writer, args); 642 } 643 } 644 } 645} 646