片段 UI 未显示答案

【问题标题】：Fragment UI not displayed片段 UI 未显示
【发布时间】：2014-05-27 16:06:46
【问题描述】：

所以我正在开发这个 android 应用程序，并在其中输入了 NavigatonDrawer，它运行良好。当从抽屉中选择一个项目时，MainActivity 应该替换FrameLayout，它在activity_main.xml 中定义。问题是当我用片段替换FrameLayout 时，应用程序强制关闭。我究竟做错了什么？我该如何解决这个问题？

以下是当您从抽屉中选择项目时调用的方法：

    @Override
public void onNavigationDrawerItemSelected(int position) {
    FragmentTransaction transaction=getFragmentManager().beginTransaction();
    switch (position){
        case 0: //cal
            calFragment cal=new calFragment().newInstance();
            transaction.replace(R.id.container, cal);
            break;
        case 1: //note
            noteFragment note=new noteFragment();
            transaction.replace(R.id.container, note);
            break;
        case 2: //con
            conFragment con=new conFragment();
            transaction.replace(R.id.container, con);
            break;
        case 3: //TODO login
            break;
        case 4: //TODO settings
            break;
        default:break;
    }
    transaction.commit();
}

这里是activity_main.xml：

<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.arandum.syncc.MainActivity">

<!-- As the main content view, the view below consumes the entire
     space available using match_parent in both dimensions. -->
<FrameLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

<fragment android:id="@+id/navigation_drawer"
    android:layout_width="@dimen/navigation_drawer_width"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:name="com.arandum.syncc.NavigationDrawerFragment" />

还有 calFragment.java 和 fragment_cal.xml 供参考

public class calFragment extends Fragment {

private OnFragmentInteractionListener mListener;

public static calFragment newInstance() {
    calFragment fragment = new calFragment();
    return fragment;
}
public calFragment() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_cal, container, false);
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnFragmentInteractionListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

public interface OnFragmentInteractionListener {

    public void onFragmentInteraction(Uri uri);
}

}

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.arandum.syncc.calFragment">

<TextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="@string/title_section1"
    android:textSize="30sp"
    />

提前致谢！

新的

    04-15 11:23:49.385  22325-22325/com.arandum.syncc D/dalvikvm﹕ Late-enabling CheckJNI
    04-15 11:23:49.445  22325-22325/com.arandum.syncc D/dalvikvm﹕ DexOpt: couldn't find field Landroid/app/ActivityThread;.mActiveResources
    04-15 11:23:49.445  22325-22325/com.arandum.syncc W/dalvikvm﹕ VFY: unable to resolve instance field 1
    04-15 11:23:49.445  22325-22325/com.arandum.syncc D/dalvikvm﹕ VFY: replacing opcode 0x54 at 0x0006
    04-15 11:23:49.445  22325-22325/com.arandum.syncc D/dalvikvm﹕ DexOpt: couldn't find field Landroid/app/ActivityThread;.mPackages
    04-15 11:23:49.445  22325-22325/com.arandum.syncc W/dalvikvm﹕ VFY: unable to resolve instance field 4
    04-15 11:23:49.445  22325-22325/com.arandum.syncc D/dalvikvm﹕ VFY: replacing opcode 0x54 at 0x0000
    04-15 11:23:49.560  22325-22325/com.arandum.syncc D/AndroidRuntime﹕ Shutting down VM
    04-15 11:23:49.560  22325-22325/com.arandum.syncc W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41fd9ba8)
    04-15 11:23:49.565  22325-22325/com.arandum.syncc E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.arandum.syncc, PID: 22325
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.arandum.syncc/com.arandum.syncc.MainActivity}: java.lang.ClassCastException: com.arandum.syncc.MainActivity@42315fe8 must implement OnFragmentInteractionListener
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2207)
                at     android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
                at android.app.ActivityThread.access$800(ActivityThread.java:135)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:136)
                at android.app.ActivityThread.main(ActivityThread.java:5029)
                at java.lang.reflect.Method.invokeNative(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:515)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
                at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
                at dalvik.system.NativeStart.main(Native Method)
         Caused by: java.lang.ClassCastException: com.arandum.syncc.MainActivity@42315fe8 must implement OnFragmentInteractionListener
                at com.arandum.syncc.calFragment.onAttach(calFragment.java:36)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:849)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
            at android.app.BackStackRecord.run(BackStackRecord.java:684)
            at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
            at android.app.Activity.performStart(Activity.java:6050)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
            at android.app.ActivityThread.access$800(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5029)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:132)
            at dalvik.system.NativeStart.main(Native Method)
04-15 11:23:51.490  22325-22325/com.arandum.syncc I/Process﹕ Sending signal. PID: 22325 SIG: 9

【问题讨论】：

标签： android layout android-fragments fragment

【解决方案1】：

要调用FragmentTransaction 和添加/替换/显示/隐藏 Fragment，您始终需要按如下方式调用commit：

fragmentManager.beginTransaction().replace(R.id.container, cal).commit();

然后，你的代码应该为你的片段使用一个通用变量：

FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransac = fragmentManager.beginTransaction();
// init the fragment (with the a default fragment, not null)
Fragment frag = new calFragment().newInstance();
switch (position){
    case 0:
        // init with the 1st fragment
        frag = new calFragment().newInstance();
        break;
    case 1:
        // init with the 2nd fragment
        frag = new noteFragment();
        break;
    case 2:
        // same for others
        frag = new conFragment();
        break;
    case 3: //TODO login
        break;
    case 4: //TODO settings
        break;
    default:break;
}
// THEN replace with the fragment variable
fragmentTransac.replace(R.id.container, frag, null);
// commit the transaction
fragmentTransac.commit();

正如你的 Logcat 所说：com.arandum.syncc.MainActivity@42316ed0 must implement OnFragmentInteractionListener 然后尝试添加这个实现：

public class MainActivity extends FragmentActivity (or ActionBarActivity) implements calFragment.OnFragmentInteractionListener {

对于每个 Fragment 将使用一个，您必须在您的 MainActivity 中实现其自己的 Interface，如下所示：

implements calFragment.OnFragmentInteractionListener, noteFragment.PublicInterface, conFragment.AnotherInterface, ...etc

【讨论】：

我试过这个，现在我的应用程序只要事务提交就强制关闭。我应该使用与替换不同的东西吗？我会立即编辑帖子。
@NDTS 我更新了答案。我怀疑是 FragmentTransaction 错误，该错误被同一个变量多次调用。您只需要始终更改片段而不是 commit() 。无论如何，如果这仍然不起作用，您应该按照您所说的编辑您的帖子并提供 logcat。
我马上试试这个。我正在尝试发布 logcat，但网站说我有错误（？）
我用 logcat 上传了一个文件...希望没问题
@NDTS 太好了！那挺好的！真的很高兴能提供帮助。请你接受我的回答好吗？ :) 为下一步编写愉快的代码。

【解决方案2】：

你需要有

FramentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.commit();

要将事务应用到活动，您必须调用 commit()。

@Override
public void onNavigationDrawerItemSelected(int position) {

FragmentManager fragmentManager = getFragmentManager();
FramentTransaction fragmentTransaction = fragmentManager.beginTransaction();
switch (position){
    case 0: //cal
        calFragment cal=new calFragment().newInstance();
        fragmentTransaction.replace(R.id.container, cal);
        fragmentTransaction.commit();  
        break;
    case 1: //note
        noteFragment note=new noteFragment();
        fragmentTransaction.replace(R.id.container, note);
        fragmentTransaction.commit();
        break;
    case 2: //con
        conFragment con=new conFragment();
        fragmentTransaction.replace(R.id.container, con);
        fragmentTransaction.commit();
        break;
    case 3: //TODO login
        break;
    case 4: //TODO settings
        break;
    default:break;
}

【讨论】：