在 super.onCreate 上添加内容错误之前必须调用 requestFeature()

Question

我有一个扩展ActionBarActivity 的抽象类。在onCreate，我有：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    supportRequestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    ...
}

由于内容错误之前的 requestFeature() 导致应用程序崩溃，特别是在 super.onCreate(savedInstanceState) 行。在阅读了一些类似的帖子后，我想出了这个解决方案：

@Override
protected void onCreate(Bundle savedInstanceState) {
    requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    super.onCreate(savedInstanceState);
    ...
}

我的问题是：为什么它在超级调用时崩溃？另外，在我调用super.onCreate 之前，我不是扩展此类的类中的settingContentView。它仍然偶尔崩溃。

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myapp/com.myapp.cycle.Cycle}: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2351)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$600(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1331)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:155)
at android.app.ActivityThread.main(ActivityThread.java:5454)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1029)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:796)
at dalvik.system.NativeStart.main(Native Method)

Caused by: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
at com.android.internal.policy.impl.PhoneWindow.requestFeature(PhoneWindow.java:320)
at android.app.Activity.requestWindowFeature(Activity.java:3283)
at android.support.v7.app.ActionBarActivityDelegateICS.onCreate(ActionBarActivityDelegateICS.java:63)
at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:98)
at com.myapp.core.activity.MyActivity.onCreate(MyActivity.java:83)
at com.myapp.cycle.Cycle.onCreate(Cycle.java:55)
at android.app.Activity.performCreate(Activity.java:5066)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1101)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
... 11 more

Answer 1

因为android.support.v7.app.ActionBarActivity 通过添加ActionBar 来改变窗口内容。
请看以

开头的代码

@Override
protected void onCreate(Bundle savedInstanceState) {
    mImpl = ActionBarActivityDelegate.createDelegate(this);
    super.onCreate(savedInstanceState);
    mImpl.onCreate(savedInstanceState);
}

详情请联系https://android.googlesource.com/platform/frameworks/support/+/master/v7/appcompat/src/android/support/v7/app/ActionBarActivity.java。
FEATURE_INDETERMINATE_PROGRESS 的外观取决于 ActionBar 是否存在。所以需要在 super 调用之前设置。