java.lang.ClassCastException 无法转换为 android.app.Fragment

Question

我有 MainActivity 类，它具有实例化 ApplicationBar 的方法，所有其他 Activity 都是从此 MainActivity 继承的，因此它们可以使用此方法。

但是我还有一个 MapHolder 类，它必须从 FragmentActivity 扩展，因为在 xml 中它使用 fragment 来显示 map 。问题是，如果我从 FragmentActivity 扩展它，我无法显示 ApplicationBar 选项卡，如果我从 MainActivity 扩展它，我就无法显示 map ，并且会出现以下错误:

LogCat 输出:

    09-29 17:52:10.107: E/GooglePlayServicesUtil(3788): Google Play services is invalid. Cannot recover.
09-29 17:52:43.536: E/AndroidRuntime(3832): FATAL EXCEPTION: main
09-29 17:52:43.536: E/AndroidRuntime(3832): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mydomain.myproj/com.mydomain.myproj.MapHolder }: android.view.InflateException: Binary XML file line #2: Error inflating class fragment
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.os.Looper.loop(Looper.java:137)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread.main(ActivityThread.java:5103)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at java.lang.reflect.Method.invokeNative(Native Method)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at java.lang.reflect.Method.invoke(Method.java:525)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at dalvik.system.NativeStart.main(Native Method)
09-29 17:52:43.536: E/AndroidRuntime(3832): Caused by: android.view.InflateException: Binary XML file line #2: Error inflating class fragment
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:713)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.view.LayoutInflater.inflate(LayoutInflater.java:469)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.view.LayoutInflater.inflate(LayoutInflater.java:353)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:267)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Activity.setContentView(Activity.java:1895)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at com.mydomain.myproj.MapHolder .onCreate(MapHolder .java:19)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Activity.performCreate(Activity.java:5133)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
09-29 17:52:43.536: E/AndroidRuntime(3832):     ... 11 more
09-29 17:52:43.536: E/AndroidRuntime(3832): Caused by: java.lang.ClassCastException: com.google.android.gms.maps.SupportMapFragment cannot be cast to android.app.Fragment
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Fragment.instantiate(Fragment.java:585)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Fragment.instantiate(Fragment.java:560)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.app.Activity.onCreateView(Activity.java:4738)
09-29 17:52:43.536: E/AndroidRuntime(3832):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:689)
09-29 17:52:43.536: E/AndroidRuntime(3832):     ... 20 more

Answer 1

您正在尝试转换 SupportMapFragment成为 native API 级别 11 android.app.Fragment 。这是行不通的。要么:

• 设置您的android:minSdkVersion到 11 或更高，并使用 MapFragment而不是SupportMapFragment ，或

• 转换您的SupportMapFragment成为android.support.v4.app.Fragment

The issue is if I extend it from FragmentActivity I cannot display ApplicationBar Tabs

操作栏已在 API 级别 11 中添加到 Android。如果您希望在旧版本的 Android 上使用操作栏，则需要使用向后移植，ActionBarSherlock或the AppCompat backport in the Android Support package .