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片段之间进行更改。

我正在使用Android Studio，基本上我所做的是这样的：

• 使用内置模板“导航抽屉活动”创建了一个新项目
• 创建了一个空白片段

然后我更改了onNavigationDrawerItemSelected方法中的一些代码。

@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();  
}  

我的程序崩溃了，给了我很多我不理解的错误。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

使用向导创建片段时，您选中了一个框来创建侦听器。

所以你得到了这个错误：

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");
}

或者在您的活动中，您可以实现侦听器。