Question

我要做的是只使用一个Activity作为许多片段的宿主，例如，活动一次只能托管一个片段，片段应按特定顺序附加到活动。
我的片段代码：

public class FirstFragment extends Fragment{

    //some code here to instantiate FirstFragment here.

    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.main, container, false);
    Button button = (Button) view.findViewById(R.id.button1);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            ((MainActivity) getActivity()).onFirstFragmentFinished(position);
        }
    });
    return view;
}

    // Container Activity must implement this interface
    public interface FirstFragmentListener {
        public void onFirstFragmentFinished(int position);
    }
}

简单地说，在每个片段中，按下它时会有一个按钮，它将获得主机活动并调用FirstFragmentListener接口的实现方法。

public class MainActivity extends AppCompatActivity implements FirstFragmentListener {

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

       FragmentManager fragmentManager =  getSupportFragmentManager();
       FragmentTransaction fragmentTra = fragmentManager.beginTransaction();
       fragmentTra .replace(R.id.main_layout, new FirstFragment());
       fragmentTra.commit(); 
    }

    @Override
    public void onFirstFragmentFinished(int position)
    {
        if(position == 1)
        {
            FragmentManager fragmentManager =  getSupportFragmentManager();
            FragmentTransaction fragmentTra = fragmentManager.beginTransaction();
            fragmentTra .replace(R.id.main_layout, new SecondFragment());
            fragmentTra.commit(); 
        }
    }
}

创建活动时，请始终使用FirstFragment布局替换此活动内的任何内容当FirstFragment完成其工作并按下该片段上的按钮时，它将在此活动上调用FirstFragment接口的实现方法，然后检查位置是否有值，如果条件正确则转到并将SecondFragment替换为SecondFragment实例。
调用commit()方法时，应用程序崩溃。

Answer 1

在Fragment中，你需要View来绑定像这样的片段：

public class FirstFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.main, container, false);

        Button button = (Button) view.findViewById(R.id.button1);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(position == 1){
                     SecondFragment secondFrag= new SecondFragment();
                     getActivity().getFragmentManager().beginTransaction()
                           .replace(R.id.main_layout, secondFrag)
                           .addToBackStack(null)
                           .commit();
                }
            }
        });
        return view;
    }

}

Answer 2

使用onFirstFragmentFinished是错误的。看看官方文件： android-comunication-activity-ffragment

更喜欢覆盖onAttach（）方法。

Answer 3

我看看我的堆栈跟踪，我发现了这个异常：

com.example.exchange.msbexchange E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.exchange.msbexchange, PID: 17975
java.lang.RuntimeException: com.example.exchange.msbexchange.MainActivity@1e7d93b must implement OnFragmentInteractionListener
at com.example.exchange.msbexchange.CurrencyFragment.onAttach(CurrencyFragment.java:83)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1030)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1259)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1624)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6117)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

很明显，因为我的MainActivity没有实现SecondFragment类的接口。我不知道碎片是否必须使用。我只需要实现界面，现在它正在运行。

Answer 4

您需要在片段

中的onAttach中实现您的界面FirstFragmentListener

FirstFragmentListener mCallback;

@Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (FirstFragmentListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnHeadlineSelectedListener");
        }
    }

然后像点击或任何你想要的那样使用它

Android在调用FragmentTransaction Replace方法时崩溃了吗？

4 个答案: