详解Android.activity销毁流程的工作原理

public void finish() {
 finish(false);
}

private void finish(boolean finishTask) {
  if (mParent == null) {
   int resultCode;
   Intent resultData;
   synchronized (this) {
    resultCode = mResultCode;
    resultData = mResultData;
   }
   if (false) Log.v(TAG, "Finishing self: token=" + mToken);
   try {
    if (resultData != null) {
     resultData.prepareToLeaveProcess();
    }
    if (ActivityManagerNative.getDefault()
      .finishActivity(mToken, resultCode, resultData, finishTask)) {
     mFinished = true;
    }
   } catch (RemoteException e) {
    // Empty
   }
  } else {
   mParent.finishFromChild(this);
  }
 }

@Override
public final boolean finishActivity(IBinder token, int resultCode, Intent resultData, boolean finishTask) {
  ...
  res = tr.stack.requestFinishActivityLocked(token, resultCode,resultData, "app-request", true);
  ...
}

final boolean requestFinishActivityLocked(IBinder token, int resultCode,
   Intent resultData, String reason, boolean oomAdj) {
  ActivityRecord r = isInStackLocked(token);
  if (DEBUG_RESULTS || DEBUG_STATES) Slog.v(TAG_STATES,
    "Finishing activity token=" + token + " r="
    + ", result=" + resultCode + ", data=" + resultData
    + ", reason=" + reason);
  if (r == null) {
   return false;
  }

  finishActivityLocked(r, resultCode, resultData, reason, oomAdj);
  return true;
 }

final boolean finishActivityLocked(ActivityRecord r, int resultCode, Intent resultData,
   String reason, boolean oomAdj) {
  ...
  startPausingLocked(false, false, false, false);
  ...
  return false;
 }

final boolean startPausingLocked(boolean userLeaving, boolean uiSleeping, boolean resuming, boolean dontWait) {
  ...
   try {
    EventLog.writeEvent(EventLogTags.AM_PAUSE_ACTIVITY,
      prev.userId, System.identityHashCode(prev),
      prev.shortComponentName);
    mService.updateUsageStats(prev, false);
    prev.app.thread.schedulePauseActivity(prev.appToken, prev.finishing,
      userLeaving, prev.configChangeFlags, dontWait);
   } catch (Exception e) {
    // Ignore exception, if process died other code will cleanup.
    Slog.w(TAG, "Exception thrown during pause", e);
    mPausingActivity = null;
    mLastPausedActivity = null;
    mLastNoHistoryActivity = null;
   }
  ...
 }

public final void schedulePauseActivity(IBinder token, boolean finished, boolean userLeaving, int configChanges, boolean dontReport) {
 sendMessage(
  finished &＃63; H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
  token, (userLeaving &＃63; 1 : 0) | (dontReport &＃63; 2 : 0),
     configChanges);
}

private void sendMessage(int what, Object obj, int arg1, int arg2) {
  sendMessage(what, obj, arg1, arg2, false);
 }

private void sendMessage(int what, Object obj, int arg1, int arg2, boolean async) {
  if (DEBUG_MESSAGES) Slog.v(
   TAG, "SCHEDULE " + what + " " + mH.codeToString(what)
   + ": " + arg1 + " / " + obj);
  Message msg = Message.obtain();
  msg.what = what;
  msg.obj = obj;
  msg.arg1 = arg1;
  msg.arg2 = arg2;
  if (async) {
   msg.setAsynchronous(true);
  }
  mH.sendMessage(msg);
 }

private void handlePauseActivity(IBinder token, boolean finished,
   boolean userLeaving, int configChanges, boolean dontReport) {
  ActivityClientRecord r = mActivities.get(token);
  if (r != null) {
   //Slog.v(TAG, "userLeaving=" + userLeaving + " handling pause of " + r);
   if (userLeaving) {
    performUserLeavingActivity(r);
   }

   r.activity.mConfigChangeFlags |= configChanges;
   performPauseActivity(token, finished, r.isPreHoneycomb());

   // Make sure any pending writes are now committed.
   if (r.isPreHoneycomb()) {
    QueuedWork.waitToFinish();
   }

   // Tell the activity manager we have paused.
   if (!dontReport) {
    try {
     ActivityManagerNative.getDefault().activityPaused(token);
    } catch (RemoteException ex) {
    }
   }
   mSomeActivitiesChanged = true;
  }
 }

@Override
 public final void activityPaused(IBinder token) {
  final long origId = Binder.clearCallingIdentity();
  synchronized(this) {
   ActivityStack stack = ActivityRecord.getStackLocked(token);
   if (stack != null) {
    stack.activityPausedLocked(token, false);
   }
  }
  Binder.restoreCallingIdentity(origId);
 }

final void activityPausedLocked(IBinder token, boolean timeout) {
  ...
  completePauseLocked(true);
  ...
}

private void completePauseLocked(boolean resumeNext) {
 ...     mStackSupervisor.resumeTopActivitiesLocked(topStack, null, null);
 ...
 }

private class Idler implements MessageQueue.IdleHandler {
  @Override
  public final boolean queueIdle() {
   ActivityClientRecord a = mNewActivities;
   boolean stopProfiling = false;
   if (mBoundApplication != null && mProfiler.profileFd != null
     && mProfiler.autoStopProfiler) {
    stopProfiling = true;
   }
   if (a != null) {
    mNewActivities = null;
    IActivityManager am = ActivityManagerNative.getDefault();
    ActivityClientRecord prev;
    do {
     if (localLOGV) Slog.v(
      TAG, "Reporting idle of " + a +
      " finished=" +
      (a.activity != null && a.activity.mFinished));
     if (a.activity != null && !a.activity.mFinished) {
      try {
       am.activityIdle(a.token, a.createdConfig, stopProfiling);
       a.createdCOnfig= null;
      } catch (RemoteException ex) {
       // Ignore
      }
     }
     prev = a;
     a = a.nextIdle;
     prev.nextIdle = null;
    } while (a != null);
   }
   if (stopProfiling) {
    mProfiler.stopProfiling();
   }
   ensureJitEnabled();
   return false;
  }
 }

public final void activityIdle(IBinder token, Configuration config, boolean stopProfiling) {
  final long origId = Binder.clearCallingIdentity();
  synchronized (this) {
   ActivityStack stack = ActivityRecord.getStackLocked(token);
   if (stack != null) {
    ActivityRecord r =
      mStackSupervisor.activityIdleInternalLocked(token, false, config);
    if (stopProfiling) {
     if ((mProfileProc == r.app) && (mProfileFd != null)) {
      try {
       mProfileFd.close();
      } catch (IOException e) {
      }
      clearProfilerLocked();
     }
    }
   }
  }
  Binder.restoreCallingIdentity(origId);
 }

final ActivityRecord activityIdleInternalLocked(final IBinder token, boolean fromTimeout, Configuration config) {
 .... 
 stack.destroyActivityLocked(r, true, "finish-idle");
 .... 
}

final boolean destroyActivityLocked(ActivityRecord r, boolean removeFromApp, String reason) {
  ...
  r.app.thread.scheduleDestroyActivity(r.appToken, r.finishing, r.configChangeFlags);
  ...  
}

public final void scheduleDestroyActivity(IBinder token, boolean finishing, int configChanges) {
 sendMessage(H.DESTROY_ACTIVITY, token, finishing &＃63; 1 : 0,
     configChanges);
}

private void handleDestroyActivity(IBinder token, boolean finishing,
   int configChanges, boolean getNonConfigInstance) {
  ActivityClientRecord r = performDestroyActivity(token, finishing,
    configChanges, getNonConfigInstance);
  if (r != null) {
   cleanUpPendingRemoveWindows(r);
   WindowManager wm = r.activity.getWindowManager();
   View v = r.activity.mDecor;
   if (v != null) {
    if (r.activity.mVisibleFromServer) {
     mNumVisibleActivities--;
    }
    IBinder wtoken = v.getWindowToken();
    if (r.activity.mWindowAdded) {
     if (r.onlyLocalRequest) {
      // Hold off on removing this until the new activity's
      // window is being added.
      r.mPendingRemoveWindow = v;
      r.mPendingRemoveWindowManager = wm;
     } else {
      wm.removeViewImmediate(v);
     }
    }
    if (wtoken != null && r.mPendingRemoveWindow == null) {
     WindowManagerGlobal.getInstance().closeAll(wtoken,
       r.activity.getClass().getName(), "Activity");
    }
    r.activity.mDecor = null;
   }
   if (r.mPendingRemoveWindow == null) {
    // If we are delaying the removal of the activity window, then
    // we can't clean up all windows here. Note that we can't do
    // so later either, which means any windows that aren't closed
    // by the app will leak. Well we try to warning them a lot
    // about leaking windows, because that is a bug, so if they are
    // using this recreate facility then they get to live with leaks.
    WindowManagerGlobal.getInstance().closeAll(token,
      r.activity.getClass().getName(), "Activity");
   }

   // Mocked out contexts won't be participating in the normal
   // process lifecycle, but if we're running with a proper
   // ApplicationContext we need to have it tear down things
   // cleanly.
   Context c = r.activity.getBaseContext();
   if (c instanceof ContextImpl) {
    ((ContextImpl) c).scheduleFinalCleanup(
      r.activity.getClass().getName(), "Activity");
   }
  }
  if (finishing) {
   try {
    ActivityManagerNative.getDefault().activityDestroyed(token);
   } catch (RemoteException ex) {
    // If the system process has died, it's game over for everyone.
   }
  }
  mSomeActivitiesChanged = true;
 }

private ActivityClientRecord performDestroyActivity(IBinder token, boolean finishing,
   int configChanges, boolean getNonConfigInstance) {
  ...  
  r.activity.performStop();
  ...
  mInstrumentation.callActivityOnDestroy(r.activity);
  ...
 }

final void performStop() {
  ...
  mInstrumentation.callActivityOnStop(this);
  ...
}

public void callActivityOnStop(Activity activity) {
  activity.onStop();
 }

public void callActivityOnDestroy(Activity activity) {
 ...
 activity.performDestroy();
 ...
}

final void performDestroy() {
  mDestroyed = true;
  mWindow.destroy();
  mFragments.dispatchDestroy();
  onDestroy();
  mFragments.doLoaderDestroy();
  if (mVoiceInteractor != null) {
   mVoiceInteractor.detachActivity();
  }
 }