Aurimas Liutikas | 88c7ff1 | 2023-08-10 12:42:26 -0700 | [diff] [blame] | 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.os; |
| 18 | |
| 19 | import android.annotation.NonNull; |
| 20 | import android.annotation.Nullable; |
| 21 | import android.compat.annotation.UnsupportedAppUsage; |
| 22 | import android.util.Log; |
| 23 | import android.util.Printer; |
| 24 | import android.util.Slog; |
| 25 | import android.util.proto.ProtoOutputStream; |
| 26 | |
| 27 | /** |
| 28 | * Class used to run a message loop for a thread. Threads by default do |
| 29 | * not have a message loop associated with them; to create one, call |
| 30 | * {@link #prepare} in the thread that is to run the loop, and then |
| 31 | * {@link #loop} to have it process messages until the loop is stopped. |
| 32 | * |
| 33 | * <p>Most interaction with a message loop is through the |
| 34 | * {@link Handler} class. |
| 35 | * |
| 36 | * <p>This is a typical example of the implementation of a Looper thread, |
| 37 | * using the separation of {@link #prepare} and {@link #loop} to create an |
| 38 | * initial Handler to communicate with the Looper. |
| 39 | * |
| 40 | * <pre> |
| 41 | * class LooperThread extends Thread { |
| 42 | * public Handler mHandler; |
| 43 | * |
| 44 | * public void run() { |
| 45 | * Looper.prepare(); |
| 46 | * |
| 47 | * mHandler = new Handler(Looper.myLooper()) { |
| 48 | * public void handleMessage(Message msg) { |
| 49 | * // process incoming messages here |
| 50 | * } |
| 51 | * }; |
| 52 | * |
| 53 | * Looper.loop(); |
| 54 | * } |
| 55 | * }</pre> |
| 56 | */ |
| 57 | public final class Looper { |
| 58 | /* |
| 59 | * API Implementation Note: |
| 60 | * |
| 61 | * This class contains the code required to set up and manage an event loop |
| 62 | * based on MessageQueue. APIs that affect the state of the queue should be |
| 63 | * defined on MessageQueue or Handler rather than on Looper itself. For example, |
| 64 | * idle handlers and sync barriers are defined on the queue whereas preparing the |
| 65 | * thread, looping, and quitting are defined on the looper. |
| 66 | */ |
| 67 | |
| 68 | private static final String TAG = "Looper"; |
| 69 | |
| 70 | // sThreadLocal.get() will return null unless you've called prepare(). |
| 71 | @UnsupportedAppUsage |
| 72 | static final ThreadLocal<Looper> sThreadLocal = new ThreadLocal<Looper>(); |
| 73 | @UnsupportedAppUsage |
| 74 | private static Looper sMainLooper; // guarded by Looper.class |
| 75 | private static Observer sObserver; |
| 76 | |
| 77 | @UnsupportedAppUsage |
| 78 | final MessageQueue mQueue; |
| 79 | final Thread mThread; |
| 80 | private boolean mInLoop; |
| 81 | |
| 82 | @UnsupportedAppUsage |
| 83 | private Printer mLogging; |
| 84 | private long mTraceTag; |
| 85 | |
| 86 | /** |
| 87 | * If set, the looper will show a warning log if a message dispatch takes longer than this. |
| 88 | */ |
| 89 | private long mSlowDispatchThresholdMs; |
| 90 | |
| 91 | /** |
| 92 | * If set, the looper will show a warning log if a message delivery (actual delivery time - |
| 93 | * post time) takes longer than this. |
| 94 | */ |
| 95 | private long mSlowDeliveryThresholdMs; |
| 96 | |
| 97 | /** |
| 98 | * True if a message delivery takes longer than {@link #mSlowDeliveryThresholdMs}. |
| 99 | */ |
| 100 | private boolean mSlowDeliveryDetected; |
| 101 | |
| 102 | /** Initialize the current thread as a looper. |
| 103 | * This gives you a chance to create handlers that then reference |
| 104 | * this looper, before actually starting the loop. Be sure to call |
| 105 | * {@link #loop()} after calling this method, and end it by calling |
| 106 | * {@link #quit()}. |
| 107 | */ |
| 108 | public static void prepare() { |
| 109 | prepare(true); |
| 110 | } |
| 111 | |
| 112 | private static void prepare(boolean quitAllowed) { |
| 113 | if (sThreadLocal.get() != null) { |
| 114 | throw new RuntimeException("Only one Looper may be created per thread"); |
| 115 | } |
| 116 | sThreadLocal.set(new Looper(quitAllowed)); |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * Initialize the current thread as a looper, marking it as an |
| 121 | * application's main looper. See also: {@link #prepare()} |
| 122 | * |
| 123 | * @deprecated The main looper for your application is created by the Android environment, |
| 124 | * so you should never need to call this function yourself. |
| 125 | */ |
| 126 | @Deprecated |
| 127 | public static void prepareMainLooper() { |
| 128 | prepare(false); |
| 129 | synchronized (Looper.class) { |
| 130 | if (sMainLooper != null) { |
| 131 | throw new IllegalStateException("The main Looper has already been prepared."); |
| 132 | } |
| 133 | sMainLooper = myLooper(); |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | /** |
| 138 | * Returns the application's main looper, which lives in the main thread of the application. |
| 139 | */ |
| 140 | public static Looper getMainLooper() { |
| 141 | synchronized (Looper.class) { |
| 142 | return sMainLooper; |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | /** |
| 147 | * Set the transaction observer for all Loopers in this process. |
| 148 | * |
| 149 | * @hide |
| 150 | */ |
| 151 | public static void setObserver(@Nullable Observer observer) { |
| 152 | sObserver = observer; |
| 153 | } |
| 154 | |
| 155 | /** |
| 156 | * Poll and deliver single message, return true if the outer loop should continue. |
| 157 | */ |
| 158 | @SuppressWarnings({"UnusedTokenOfOriginalCallingIdentity", |
| 159 | "ClearIdentityCallNotFollowedByTryFinally"}) |
| 160 | private static boolean loopOnce(final Looper me, |
| 161 | final long ident, final int thresholdOverride) { |
| 162 | Message msg = me.mQueue.next(); // might block |
| 163 | if (msg == null) { |
| 164 | // No message indicates that the message queue is quitting. |
| 165 | return false; |
| 166 | } |
| 167 | |
| 168 | // This must be in a local variable, in case a UI event sets the logger |
| 169 | final Printer logging = me.mLogging; |
| 170 | if (logging != null) { |
| 171 | logging.println(">>>>> Dispatching to " + msg.target + " " |
| 172 | + msg.callback + ": " + msg.what); |
| 173 | } |
| 174 | // Make sure the observer won't change while processing a transaction. |
| 175 | final Observer observer = sObserver; |
| 176 | |
| 177 | final long traceTag = me.mTraceTag; |
| 178 | long slowDispatchThresholdMs = me.mSlowDispatchThresholdMs; |
| 179 | long slowDeliveryThresholdMs = me.mSlowDeliveryThresholdMs; |
| 180 | |
| 181 | final boolean hasOverride = thresholdOverride >= 0; |
| 182 | if (hasOverride) { |
| 183 | slowDispatchThresholdMs = thresholdOverride; |
| 184 | slowDeliveryThresholdMs = thresholdOverride; |
| 185 | } |
| 186 | final boolean logSlowDelivery = (slowDeliveryThresholdMs > 0 || hasOverride) |
| 187 | && (msg.when > 0); |
| 188 | final boolean logSlowDispatch = (slowDispatchThresholdMs > 0 || hasOverride); |
| 189 | |
| 190 | final boolean needStartTime = logSlowDelivery || logSlowDispatch; |
| 191 | final boolean needEndTime = logSlowDispatch; |
| 192 | |
| 193 | if (traceTag != 0 && Trace.isTagEnabled(traceTag)) { |
| 194 | Trace.traceBegin(traceTag, msg.target.getTraceName(msg)); |
| 195 | } |
| 196 | |
| 197 | final long dispatchStart = needStartTime ? SystemClock.uptimeMillis() : 0; |
| 198 | final long dispatchEnd; |
| 199 | Object token = null; |
| 200 | if (observer != null) { |
| 201 | token = observer.messageDispatchStarting(); |
| 202 | } |
| 203 | long origWorkSource = ThreadLocalWorkSource.setUid(msg.workSourceUid); |
| 204 | try { |
| 205 | msg.target.dispatchMessage(msg); |
| 206 | if (observer != null) { |
| 207 | observer.messageDispatched(token, msg); |
| 208 | } |
| 209 | dispatchEnd = needEndTime ? SystemClock.uptimeMillis() : 0; |
| 210 | } catch (Exception exception) { |
| 211 | if (observer != null) { |
| 212 | observer.dispatchingThrewException(token, msg, exception); |
| 213 | } |
| 214 | throw exception; |
| 215 | } finally { |
| 216 | ThreadLocalWorkSource.restore(origWorkSource); |
| 217 | if (traceTag != 0) { |
| 218 | Trace.traceEnd(traceTag); |
| 219 | } |
| 220 | } |
| 221 | if (logSlowDelivery) { |
| 222 | if (me.mSlowDeliveryDetected) { |
| 223 | if ((dispatchStart - msg.when) <= 10) { |
| 224 | Slog.w(TAG, "Drained"); |
| 225 | me.mSlowDeliveryDetected = false; |
| 226 | } |
| 227 | } else { |
| 228 | if (showSlowLog(slowDeliveryThresholdMs, msg.when, dispatchStart, "delivery", |
| 229 | msg)) { |
| 230 | // Once we write a slow delivery log, suppress until the queue drains. |
| 231 | me.mSlowDeliveryDetected = true; |
| 232 | } |
| 233 | } |
| 234 | } |
| 235 | if (logSlowDispatch) { |
| 236 | showSlowLog(slowDispatchThresholdMs, dispatchStart, dispatchEnd, "dispatch", msg); |
| 237 | } |
| 238 | |
| 239 | if (logging != null) { |
| 240 | logging.println("<<<<< Finished to " + msg.target + " " + msg.callback); |
| 241 | } |
| 242 | |
| 243 | // Make sure that during the course of dispatching the |
| 244 | // identity of the thread wasn't corrupted. |
| 245 | final long newIdent = Binder.clearCallingIdentity(); |
| 246 | if (ident != newIdent) { |
| 247 | Log.wtf(TAG, "Thread identity changed from 0x" |
| 248 | + Long.toHexString(ident) + " to 0x" |
| 249 | + Long.toHexString(newIdent) + " while dispatching to " |
| 250 | + msg.target.getClass().getName() + " " |
| 251 | + msg.callback + " what=" + msg.what); |
| 252 | } |
| 253 | |
| 254 | msg.recycleUnchecked(); |
| 255 | |
| 256 | return true; |
| 257 | } |
| 258 | |
| 259 | /** |
| 260 | * Run the message queue in this thread. Be sure to call |
| 261 | * {@link #quit()} to end the loop. |
| 262 | */ |
| 263 | @SuppressWarnings({"UnusedTokenOfOriginalCallingIdentity", |
| 264 | "ClearIdentityCallNotFollowedByTryFinally", |
| 265 | "ResultOfClearIdentityCallNotStoredInVariable"}) |
| 266 | public static void loop() { |
| 267 | final Looper me = myLooper(); |
| 268 | if (me == null) { |
| 269 | throw new RuntimeException("No Looper; Looper.prepare() wasn't called on this thread."); |
| 270 | } |
| 271 | if (me.mInLoop) { |
| 272 | Slog.w(TAG, "Loop again would have the queued messages be executed" |
| 273 | + " before this one completed."); |
| 274 | } |
| 275 | |
| 276 | me.mInLoop = true; |
| 277 | |
| 278 | // Make sure the identity of this thread is that of the local process, |
| 279 | // and keep track of what that identity token actually is. |
| 280 | Binder.clearCallingIdentity(); |
| 281 | final long ident = Binder.clearCallingIdentity(); |
| 282 | |
| 283 | // Allow overriding a threshold with a system prop. e.g. |
| 284 | // adb shell 'setprop log.looper.1000.main.slow 1 && stop && start' |
| 285 | final int thresholdOverride = |
| 286 | SystemProperties.getInt("log.looper." |
| 287 | + Process.myUid() + "." |
| 288 | + Thread.currentThread().getName() |
| 289 | + ".slow", -1); |
| 290 | |
| 291 | me.mSlowDeliveryDetected = false; |
| 292 | |
| 293 | for (;;) { |
| 294 | if (!loopOnce(me, ident, thresholdOverride)) { |
| 295 | return; |
| 296 | } |
| 297 | } |
| 298 | } |
| 299 | |
| 300 | private static boolean showSlowLog(long threshold, long measureStart, long measureEnd, |
| 301 | String what, Message msg) { |
| 302 | final long actualTime = measureEnd - measureStart; |
| 303 | if (actualTime < threshold) { |
| 304 | return false; |
| 305 | } |
| 306 | // For slow delivery, the current message isn't really important, but log it anyway. |
| 307 | Slog.w(TAG, "Slow " + what + " took " + actualTime + "ms " |
| 308 | + Thread.currentThread().getName() + " h=" |
| 309 | + msg.target.getClass().getName() + " c=" + msg.callback + " m=" + msg.what); |
| 310 | return true; |
| 311 | } |
| 312 | |
| 313 | /** |
| 314 | * Return the Looper object associated with the current thread. Returns |
| 315 | * null if the calling thread is not associated with a Looper. |
| 316 | */ |
| 317 | public static @Nullable Looper myLooper() { |
| 318 | return sThreadLocal.get(); |
| 319 | } |
| 320 | |
| 321 | /** |
| 322 | * Return the {@link MessageQueue} object associated with the current |
| 323 | * thread. This must be called from a thread running a Looper, or a |
| 324 | * NullPointerException will be thrown. |
| 325 | */ |
| 326 | public static @NonNull MessageQueue myQueue() { |
| 327 | return myLooper().mQueue; |
| 328 | } |
| 329 | |
| 330 | private Looper(boolean quitAllowed) { |
| 331 | mQueue = new MessageQueue(quitAllowed); |
| 332 | mThread = Thread.currentThread(); |
| 333 | } |
| 334 | |
| 335 | /** |
| 336 | * Returns true if the current thread is this looper's thread. |
| 337 | */ |
| 338 | public boolean isCurrentThread() { |
| 339 | return Thread.currentThread() == mThread; |
| 340 | } |
| 341 | |
| 342 | /** |
| 343 | * Control logging of messages as they are processed by this Looper. If |
| 344 | * enabled, a log message will be written to <var>printer</var> |
| 345 | * at the beginning and ending of each message dispatch, identifying the |
| 346 | * target Handler and message contents. |
| 347 | * |
| 348 | * @param printer A Printer object that will receive log messages, or |
| 349 | * null to disable message logging. |
| 350 | */ |
| 351 | public void setMessageLogging(@Nullable Printer printer) { |
| 352 | mLogging = printer; |
| 353 | } |
| 354 | |
| 355 | /** {@hide} */ |
| 356 | @UnsupportedAppUsage |
| 357 | public void setTraceTag(long traceTag) { |
| 358 | mTraceTag = traceTag; |
| 359 | } |
| 360 | |
| 361 | /** |
| 362 | * Set a thresholds for slow dispatch/delivery log. |
| 363 | * {@hide} |
| 364 | */ |
| 365 | public void setSlowLogThresholdMs(long slowDispatchThresholdMs, long slowDeliveryThresholdMs) { |
| 366 | mSlowDispatchThresholdMs = slowDispatchThresholdMs; |
| 367 | mSlowDeliveryThresholdMs = slowDeliveryThresholdMs; |
| 368 | } |
| 369 | |
| 370 | /** |
| 371 | * Quits the looper. |
| 372 | * <p> |
| 373 | * Causes the {@link #loop} method to terminate without processing any |
| 374 | * more messages in the message queue. |
| 375 | * </p><p> |
| 376 | * Any attempt to post messages to the queue after the looper is asked to quit will fail. |
| 377 | * For example, the {@link Handler#sendMessage(Message)} method will return false. |
| 378 | * </p><p class="note"> |
| 379 | * Using this method may be unsafe because some messages may not be delivered |
| 380 | * before the looper terminates. Consider using {@link #quitSafely} instead to ensure |
| 381 | * that all pending work is completed in an orderly manner. |
| 382 | * </p> |
| 383 | * |
| 384 | * @see #quitSafely |
| 385 | */ |
| 386 | public void quit() { |
| 387 | mQueue.quit(false); |
| 388 | } |
| 389 | |
| 390 | /** |
| 391 | * Quits the looper safely. |
| 392 | * <p> |
| 393 | * Causes the {@link #loop} method to terminate as soon as all remaining messages |
| 394 | * in the message queue that are already due to be delivered have been handled. |
| 395 | * However pending delayed messages with due times in the future will not be |
| 396 | * delivered before the loop terminates. |
| 397 | * </p><p> |
| 398 | * Any attempt to post messages to the queue after the looper is asked to quit will fail. |
| 399 | * For example, the {@link Handler#sendMessage(Message)} method will return false. |
| 400 | * </p> |
| 401 | */ |
| 402 | public void quitSafely() { |
| 403 | mQueue.quit(true); |
| 404 | } |
| 405 | |
| 406 | /** |
| 407 | * Gets the Thread associated with this Looper. |
| 408 | * |
| 409 | * @return The looper's thread. |
| 410 | */ |
| 411 | public @NonNull Thread getThread() { |
| 412 | return mThread; |
| 413 | } |
| 414 | |
| 415 | /** |
| 416 | * Gets this looper's message queue. |
| 417 | * |
| 418 | * @return The looper's message queue. |
| 419 | */ |
| 420 | public @NonNull MessageQueue getQueue() { |
| 421 | return mQueue; |
| 422 | } |
| 423 | |
| 424 | /** |
| 425 | * Dumps the state of the looper for debugging purposes. |
| 426 | * |
| 427 | * @param pw A printer to receive the contents of the dump. |
| 428 | * @param prefix A prefix to prepend to each line which is printed. |
| 429 | */ |
| 430 | public void dump(@NonNull Printer pw, @NonNull String prefix) { |
| 431 | pw.println(prefix + toString()); |
| 432 | mQueue.dump(pw, prefix + " ", null); |
| 433 | } |
| 434 | |
| 435 | /** |
| 436 | * Dumps the state of the looper for debugging purposes. |
| 437 | * |
| 438 | * @param pw A printer to receive the contents of the dump. |
| 439 | * @param prefix A prefix to prepend to each line which is printed. |
| 440 | * @param handler Only dump messages for this Handler. |
| 441 | * @hide |
| 442 | */ |
| 443 | public void dump(@NonNull Printer pw, @NonNull String prefix, Handler handler) { |
| 444 | pw.println(prefix + toString()); |
| 445 | mQueue.dump(pw, prefix + " ", handler); |
| 446 | } |
| 447 | |
| 448 | /** @hide */ |
| 449 | public void dumpDebug(ProtoOutputStream proto, long fieldId) { |
| 450 | final long looperToken = proto.start(fieldId); |
| 451 | proto.write(LooperProto.THREAD_NAME, mThread.getName()); |
| 452 | proto.write(LooperProto.THREAD_ID, mThread.getId()); |
| 453 | if (mQueue != null) { |
| 454 | mQueue.dumpDebug(proto, LooperProto.QUEUE); |
| 455 | } |
| 456 | proto.end(looperToken); |
| 457 | } |
| 458 | |
| 459 | @Override |
| 460 | public String toString() { |
| 461 | return "Looper (" + mThread.getName() + ", tid " + mThread.getId() |
| 462 | + ") {" + Integer.toHexString(System.identityHashCode(this)) + "}"; |
| 463 | } |
| 464 | |
| 465 | /** {@hide} */ |
| 466 | public interface Observer { |
| 467 | /** |
| 468 | * Called right before a message is dispatched. |
| 469 | * |
| 470 | * <p> The token type is not specified to allow the implementation to specify its own type. |
| 471 | * |
| 472 | * @return a token used for collecting telemetry when dispatching a single message. |
| 473 | * The token token must be passed back exactly once to either |
| 474 | * {@link Observer#messageDispatched} or {@link Observer#dispatchingThrewException} |
| 475 | * and must not be reused again. |
| 476 | * |
| 477 | */ |
| 478 | Object messageDispatchStarting(); |
| 479 | |
| 480 | /** |
| 481 | * Called when a message was processed by a Handler. |
| 482 | * |
| 483 | * @param token Token obtained by previously calling |
| 484 | * {@link Observer#messageDispatchStarting} on the same Observer instance. |
| 485 | * @param msg The message that was dispatched. |
| 486 | */ |
| 487 | void messageDispatched(Object token, Message msg); |
| 488 | |
| 489 | /** |
| 490 | * Called when an exception was thrown while processing a message. |
| 491 | * |
| 492 | * @param token Token obtained by previously calling |
| 493 | * {@link Observer#messageDispatchStarting} on the same Observer instance. |
| 494 | * @param msg The message that was dispatched and caused an exception. |
| 495 | * @param exception The exception that was thrown. |
| 496 | */ |
| 497 | void dispatchingThrewException(Object token, Message msg, Exception exception); |
| 498 | } |
| 499 | } |