Activity销毁流程

Looper.myQueue().addIdleHandler(new Idler())
ActivityManagerNative.getDefault().activityIdle()
ActivityManagerService.activityIdle()
ActivityStackSupervisor.activityIdleInternalLocked()
ActivityStack.destroyActivityLocked()
IApplicationThread.scheduleDestoryActivity()
ActivityThread.scheduleDestoryActivity()
ActivityThread.sendMessage()
ActivityThread.H.sendMessage()
ActivityThread.H.handleMessage()
ActivityThread.handleDestoryActivity()
ActivityThread.performDestoryActivity()
Activity.performStop()
Instrumentation.callActivityOnStop()
Activity.onStop()
Instrumentation.callActivityOnDestory()
Activity.performDestory()
Acitivity.onDestory()
ActivityManagerNative.getDefault().activityDestoryed()
ActivityManagerService.activityDestoryed()
ActivityStack.activityDestoryedLocked()

我们在ActivityThread.handleResumeActivity方法中调用了Looper.myQueue().addIdleHandler(new Idler())，下面看一下这个方法的实现：

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;
        }
    }

内部有一个queueIdle的回调方法，当它被添加到MessageQueue之后就会回调该方法，我们可以发现在这个方法体中调用了ActivityManagerNative.getDefault.activityIdle方法，通过上一篇文章以及上面的讲解，我们应该知道这了最终调用的是ActivityManagerService.activityIdle方法，好吧，这里看一下activityIdle方法的具体实现：

@Override
    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);
    }

可以发现这里又调用了ActivityStackSupervisor.activityIdleInternalLocked方法，然后我们看一下activityIdleInternalLocked方法的具体实现：

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

可以看到这里调用ActivityStack.destroyActivityLocked方法，可以看一下其具体实现：

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

好吧，这里又开始执行IApplicationThread.scheduleDestoryActivity方法，上文已经做了说明这里最终调用的是ActivityThread.scheduleDestroyActivity方法，好吧，看一下ActivityThread.scheduleDestryActivity方法的实现：

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

这里有开始执行sendMessage方法，通过一系列的调用sendMessage方法最终调用了handleDestroyActivity方法：

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;
    }

可以看到这里调用了performDestroyActivity方法，用来执行Avtivity的onDestroy方法：

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

然后调用了Activity.performStop()方法，查看performStop方法：

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

然后调用了Instrumentation.callActivityOnStop()方法：

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

好吧，终于调用了Activity的onStop方法。。。

我们继续看一下Instrumentation.callActivityOnDestroy()。。。。又是通过Instrumentation来调用Activity的onDestroy方法：

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

然后看一下Activity的performDestroy()方法的实现：

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

O(∩_∩)O哈哈~，终于回调了Activity的onDestroy方法。。。。

总结：