在导航抽屉中切换片段

Question

我希望能够使用导航抽屉并根据导航中的选择在不同的片段之间进行切换。

我正在使用 Android Studio，基本上我所做的是：

• 使用内置模板“Navigation Drawer Activity”创建了一个新项目。
• 创建了一个空白片段。

然后我在 onNavigationDrawerItemSelected 方法中更改一些代码。

@Override  
public void onNavigationDrawerItemSelected(int position) {  
    // update the main content by replacing fragments  
    FragmentManager fragmentManager = getSupportFragmentManager();  
    Fragment fragment = new BlankFragment();  
    fragmentManager.beginTransaction()  
            .replace(R.id.container, fragment)  
            .commit();  
}  

我的程序崩溃并给了我很多我不明白的错误。我做错了什么？

4168-4168/com.dev.kim.mytestapplication E/AndroidRuntime﹕ FATAL
EXCEPTION: main
    Process: com.dev.kim.mytestapplication, PID: 4168
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dev.kim.mytestapplication/com.dev.kim.mytestapplication.MainActivity}:
java.lang.ClassCastException:
com.dev.kim.mytestapplication.MainActivity@e71881c must implement
OnFragmentInteractionListener
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.ClassCastException: com.dev.kim.mytestapplication.MainActivity@e71881c must implement
OnFragmentInteractionListener
            at com.dev.kim.mytestapplication.BlankFragment.onAttach(BlankFragment.java:83)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:903)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
            at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1220)
            at android.app.Activity.performStart(Activity.java:5949)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

当您使用向导创建 Fragment 时，您选中了一个框以创建侦听器。

所以你得到这个错误：

must implement
OnFragmentInteractionListener

如果你不想使用监听器，那么在“onAttach”中你可以删除这段代码：

try {
    mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
    throw new ClassCastException(activity.toString()
            + " must implement OnFragmentInteractionListener");
}

或者在你的活动中你可以实现监听器。