xxxActivity did not call through to super.onStart()等方法SuperNotCalledException的源码分析

在编写activity的过程中，会遇到类似以下异常信息：

throw new SuperNotCalledException("Activity " + mComponent.toShortString() +" did not call through to super.onStart()");

一眼看去，知道是关于super.onCreate，super.onStart，super.onPause等方法的未被调用问题

往往是在生命周期方法中，添加调用super类对应的方法即可。那么，好奇的是，为什么一定要调用父类的方法呢？

从activity的方法说起，

onCreate方法里，涉及到ActionBar的设置，Bundle数据的操作，与Fragment的交互，Application中activity create后的回调

    @MainThread@CallSuperprotected void onCreate(@Nullable Bundle savedInstanceState) {//...if (mActivityInfo.parentActivityName != null) {if (mActionBar == null) {mEnableDefaultActionBarUp = true;} else {mActionBar.setDefaultDisplayHomeAsUpEnabled(true);}}if (savedInstanceState != null) {Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);mFragments.restoreAllState(p, mLastNonConfigurationInstances != null? mLastNonConfigurationInstances.fragments : null);}mFragments.dispatchCreate();getApplication().dispatchActivityCreated(this, savedInstanceState);if (mVoiceInteractor != null) {mVoiceInteractor.attachActivity(this);}mCalled = true;}

onStart方法里，涉及与Fragment的交互，Application中activity start后的回调

    @CallSuperprotected void onStart() {mCalled = true;mFragments.doLoaderStart();getApplication().dispatchActivityStarted(this);}

onResume方法里，涉及与Application中activity resume后的回调

    @CallSuperprotected void onResume() {getApplication().dispatchActivityResumed(this);mCalled = true;}

onPause方法里，涉及与Application中activity pause后的回调

    @CallSuperprotected void onPause() {getApplication().dispatchActivityPaused(this);mCalled = true;}

onStop方法里，涉及与Application中activity stop后的回调

    @CallSuperprotected void onStop() {if (mActionBar != null) mActionBar.setShowHideAnimationEnabled(false);getApplication().dispatchActivityStopped(this);mCalled = true;}

onDestroy方法里，涉及到资源的释放，涉及与Application中activity destroy后的回调

    @CallSuperprotected void onDestroy() {mCalled = true;// dismiss any dialogs we are managing.if (mManagedDialogs != null) {final int numDialogs = mManagedDialogs.size();for (int i = 0; i < numDialogs; i++) {final ManagedDialog md = mManagedDialogs.valueAt(i);if (md.mDialog.isShowing()) {md.mDialog.dismiss();}}mManagedDialogs = null;}// close any cursors we are managing.synchronized (mManagedCursors) {int numCursors = mManagedCursors.size();for (int i = 0; i < numCursors; i++) {ManagedCursor c = mManagedCursors.get(i);if (c != null) {c.mCursor.close();}}mManagedCursors.clear();}// Close any open search dialogif (mSearchManager != null) {mSearchManager.stopSearch();}getApplication().dispatchActivityDestroyed(this);}

由此看出，对于父类的生命周期方法调用是必要的，不可少的

另外，在Activity中，有调用生命周期方法的方法，比如：

    final void performCreate(Bundle icicle) {onCreate(icicle);mActivityTransitionState.readState(icicle);performCreateCommon();}

还有performStart()，performResume()，performPause()，performStop()，performDestroy()等，称之为performXXX()，

performXXX()方法直接或者间接的调用对应的Activity生命周期方法，

而performXXX()方法是由系统去调用

在performXXX()内，会用一个成员变量mCalled，调用Activity生命周期方法之前，mCalled是false，mCalled最终会在Activity的生命周期方法内设置为true，如果为false，校验不通过，抛出SuperNotCalledException异常。也就是说，如果开发时自定义activity重写生命周期方法时，如果没有调用Super的对应方法，异常就会出现，如下：

    final void performStart() {//...mCalled = false;mInstrumentation.callActivityOnStart(this);//内部调用onStart()方法,mCalled变为trueif (!mCalled) {throw new SuperNotCalledException("Activity " + mComponent.toShortString() + " did not call through to super.onStart()");}//...}

可以看出，mCalled机制是一种强制措施，父类Activity中生命周期方法做了一些公共性的操作，这些操作对子类Activity来说是必不可少的。

这种代码设计，针对上述场景的需要，是一种不错的选择