问题
线上异常：
android.util.SuperNotCalledException: Activity {com.xxx.app/com.xxx.TestActivity} did not call through to super.onCreate()
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:4037)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:4247)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:91)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:149)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:103)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2613)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:219)
at android.app.ActivityThread.main(ActivityThread.java:8668)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1109)
分析
看起来是派生的 Activity 中没有调用超类的 onCreate() ，也就是派生类中没有 super.onCreate() 导致的问题。追一下代码：
搜索“did not call through to super.onCreate()”：
// ActivityThread.java
/** Core implementation of activity launch. */
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
...
try {
...
if (activity != null) {
...
// 显示的将mCalled设置为false
activity.mCalled = false;
// 若要不抛出下面的‘SuperNotCalledException’，只可能是callActivityOnCreate过程中对mCalled赋值为true了
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
// 检查mCalled，false的情况下就会抛出此异常
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onCreate()");
}
r.activity = activity;
mLastReportedWindowingMode.put(activity.getActivityToken(),
config.windowConfiguration.getWindowingMode());
}
...
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}
可以看出，SuperNotCalledException 正是在 performLaunchActivity 中抛出的，而这与错误堆栈完全符合。至于从 ZygoteInit.main 到 ActivityThread.performLaunchActivity 的启动过程这里不做详细分析，我们直接从 performLaunchActivity 之后的流程分析。
既然我们已经分析出了若要正常启动Activity，就一定要在 callActivityOnCreate 过程中为 mCalled 赋值 true，那我们就继续往下追踪：
// Instrumentation.java
/**
* Perform calling of an activity's {@link Activity#onCreate}
* method. The default implementation simply calls through to that method.
*
* @param activity The activity being created.
* @param icicle The previously frozen state (or null) to pass through to onCreate().
*/
public void callActivityOnCreate(Activity activity, Bundle icicle) {
// 分别查看以下3个方法，得出对 mCalled 的赋值操作是在 activity.performCreate 过程中
prePerformCreate(activity);
activity.performCreate(icicle);
postPerformCreate(activity);
}
final void performCreate(Bundle icicle) {
performCreate(icicle, null);
}
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
final void performCreate(Bundle icicle, PersistableBundle persistentState) {
if (Trace.isTagEnabled(Trace.TRACE_TAG_WINDOW_MANAGER)) {
Trace.traceBegin(Trace.TRACE_TAG_WINDOW_MANAGER, "performCreate:"
+ mComponent.getClassName());
}
dispatchActivityPreCreated(icicle);
mCanEnterPictureInPicture = true;
// initialize mIsInMultiWindowMode and mIsInPictureInPictureMode before onCreate
final int windowingMode = getResources().getConfiguration().windowConfiguration
.getWindowingMode();
mIsInMultiWindowMode = inMultiWindowMode(windowingMode);
mIsInPictureInPictureMode = windowingMode == WINDOWING_MODE_PINNED;
restoreHasCurrentPermissionRequest(icicle);
if (persistentState != null) {
// 双参数的 onCreate 实际上也是调用的 单参数 onCreate
onCreate(icicle, persistentState);
} else {
onCreate(icicle);
}
EventLogTags.writeWmOnCreateCalled(mIdent, getComponentName().getClassName(),
"performCreate");
mActivityTransitionState.readState(icicle);
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
dispatchActivityPostCreated(icicle);
Trace.traceEnd(Trace.TRACE_TAG_WINDOW_MANAGER);
}
public void onCreate(@Nullable Bundle savedInstanceState,
@Nullable PersistableBundle persistentState) {
onCreate(savedInstanceState);
}
/**
* Called when the activity is starting. This is where most initialization
* should go: calling {@link #setContentView(int)} to inflate the
* activity's UI, using {@link #findViewById} to programmatically interact
* with widgets in the UI, calling
* {@link #managedQuery(android.net.Uri , String[], String, String[], String)} to retrieve
* cursors for data being displayed, etc.
*
* <p>You can call {@link #finish} from within this function, in
* which case onDestroy() will be immediately called after {@link #onCreate} without any of the
* rest of the activity lifecycle ({@link #onStart}, {@link #onResume}, {@link #onPause}, etc)
* executing.
*
* <p><em>Derived classes must call through to the super class's
* implementation of this method. If they do not, an exception will be
* thrown.</em></p>
*
* @param savedInstanceState If the activity is being re-initialized after
* previously being shut down then this Bundle contains the data it most
* recently supplied in {@link #onSaveInstanceState}. <b><i>Note: Otherwise it is null.</i></b>
*
* @see #onStart
* @see #onSaveInstanceState
* @see #onRestoreInstanceState
* @see #onPostCreate
*/
@MainThread
@CallSuper
protected void onCreate(@Nullable Bundle savedInstanceState) {
if (DEBUG_LIFECYCLE) Slog.v(TAG, "onCreate " + this + ": " + savedInstanceState);
if (mLastNonConfigurationInstances != null) {
mFragments.restoreLoaderNonConfig(mLastNonConfigurationInstances.loaders);
}
if (mActivityInfo.parentActivityName != null) {
if (mActionBar == null) {
mEnableDefaultActionBarUp = true;
} else {
mActionBar.setDefaultDisplayHomeAsUpEnabled(true);
}
}
if (savedInstanceState != null) {
mAutoFillResetNeeded = savedInstanceState.getBoolean(AUTOFILL_RESET_NEEDED, false);
mLastAutofillId = savedInstanceState.getInt(LAST_AUTOFILL_ID,
View.LAST_APP_AUTOFILL_ID);
if (mAutoFillResetNeeded) {
getAutofillManager().onCreate(savedInstanceState);
}
Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);
mFragments.restoreAllState(p, mLastNonConfigurationInstances != null
? mLastNonConfigurationInstances.fragments : null);
}
mFragments.dispatchCreate();
dispatchActivityCreated(savedInstanceState);
if (mVoiceInteractor != null) {
mVoiceInteractor.attachActivity(this);
}
mRestoredFromBundle = savedInstanceState != null;
// 这里执行完 Activity 的 onCreate 后，会修改 mCalled
mCalled = true;
}
至此，就确认了这个异常的触发链，不仅从整个代码的执行流程上能得到验证，从 onCreate 的另外两个地方也能看到端倪：
- onCreate 的注解 @CallSuper：标记该方法，任何派生类若要重写该方法，则必须调用超类的方法，即 super.xxx()
// CallSuper.java
/**
* Denotes that any overriding methods should invoke this method as well.
* <p>
* Example:
*
* <pre>
* <code>
* @CallSuper
* public abstract void onFocusLost();
* </code>
* </pre>
*
* @memberDoc If you override this method you <em>must</em> call through to the
* superclass implementation.
* @hide
*/
@Retention(SOURCE)
@Target({METHOD})
public @interface CallSuper {
}
- onCreate 的注释也明确说明了
* <p><em>Derived classes must call through to the super class's
* <p><em>Derived classes must call through to the super class's
* implementation of this method. If they do not, an exception will be
* thrown.</em></p>
结论
检查相应的 Activity ，确保 onCreate 中调用了 super.onCreate() 。如果不调用，IDE 会有提示，但就算不按照提示做，编译是能通过的，只是运行时，肯定就会抛出异常了。
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