在 Android 上使用 Fragments

Question

我已经完成了一些简单的应用程序，但对于 Android 开发来说还是新手。我一直在尝试使片段工作，但每次尝试加载片段时我的应用程序似乎都会崩溃。我正在尝试制作游戏。我构建它的方式是每个菜单屏幕都是一个片段（主菜单、选项、游戏内）。我继续研究如何编写片段。找到了一些不错的文章和视频。几乎他们都做同样的事情，但对他们来说，这似乎工作。它真的对我不起作用。我希望它工作的方式是，加载一个活动并在该活动上根据菜单更改或替换片段。

在崩溃时，logcat 有时会显示错误，有时不会。

如果您需要 XML 文件，请告诉我（非常怀疑。不添加带有片段标签的片段）。

这是我迄今为止尝试过的：

主活动：

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

        FragmentManager fragmentManager = getFragmentManager();

        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

        BlankFragment blankFragment= new BlankFragment();

        fragmentTransaction.add(android.R.id.content,blankFragment);

        fragmentTransaction.commit();   

    }
}

空白片段：

private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    private static Button startBtn,
    optionsBtn;

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    private OnFragmentInteractionListener mListener;

    // TODO: Rename and change types and number of parameters
    public static BlankFragment newInstance(String param1, String param2) {
        BlankFragment fragment = new BlankFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    public BlankFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState)
    {
        View  view = inflater.inflate(R.layout.fragment_blank, container, false);

        // Inflate the layout for this fragment
        return view;
    }

    // TODO: Rename method, update argument and hook method into UI event
    public void onButtonPressed(Uri uri) {
        if (mListener != null) {
            mListener.onFragmentInteraction(uri);
        }
    }

    @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);
    }

LogCat：

07-07 23:03:20.120    8978-8978/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.marybel.myapplication, PID: 8978
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.marybel.myapplication/com.example.marybel.myapplication.MainActivity}: java.lang.ClassCastException: com.example.marybel.myapplication.MainActivity@3275aea8 must implement OnFragmentInteractionListener
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            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:5021)
            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:827)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.ClassCastException: com.example.marybel.myapplication.MainActivity@3275aea8 must implement OnFragmentInteractionListener
            at com.example.marybel.myapplication.BlankFragment.onAttach(BlankFragment.java:83)
            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:5240)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
            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:5021)
            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:827)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:643)
            at dalvik.system.NativeStart.main(Native Method)

任何解释和建议将不胜感激，谢谢。

Answer 1

我第一次看到 Activity > onCreate() 你的setContentView()被评论了。

要将任何片段添加到您的活动中，首先要通过调用setContentView() 设置活动视图。

请将setContentView() 移动到super.onCreate(savedInstanceState) 之后，并告诉我们接下来的情况，例如

@Override
protected void onCreate(Bundle bundle) {
    super.onCreate(bundle);

    setContentView(R.layout.YOUR_LAYOUT_FILE_NAME);
    ...
}

Answer 2

设法让它工作，我添加片段的方式是右键单击 Layout>New>Fragment。似乎其中一种自动生成的方法或覆盖使其崩溃。删除了除OnCreateView 之外的所有内容，并且工作正常。谢谢