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我有两个片段。（其中一个有一个编辑文本和一个按钮，另一个只有一个列表视图）我想使用片段事务动态创建它们。但是当我尝试这样做时，我的应用程序无法启动。我的代码做错了什么？

AddToDoFragment.java

public class AddToDoFragment extends Fragment {

public interface OnToDoAddedListener {

    public void OnToDoAdded (String newToDo);

}

private OnToDoAddedListener onToDoAddedListener;

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

    final EditText edittext = (EditText) view.findViewById(R.id.editText);
    Button button = (Button) view.findViewById(R.id.addButton);
    button.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            String text = edittext.getText().toString();
            onToDoAddedListener.OnToDoAdded(text);
            edittext.setText("");
        }
    });

    return view;

}

 @Override
    public void onAttach(Activity activity) {
      super.onAttach(activity);
      if (activity instanceof OnToDoAddedListener) {
        onToDoAddedListener = (OnToDoAddedListener) activity;
      } else {
        throw new ClassCastException(activity.toString()
            + " must implemenet AddToDoFragment.OnToDoAddedListener");
      }
    }

}

MainActivity.java

public class MainActivity extends Activity implements AddToDoFragment.OnToDoAddedListener {



private ArrayList<String> todoItems;
private ArrayAdapter<String> adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if(savedInstanceState == null) {
        todoItems = new ArrayList<String>();
    } else {
        todoItems = savedInstanceState.getStringArrayList("todoItemTag");//the tag must match what the variable was saved with in onSaveInstanceState
    }

    FragmentManager fm = getFragmentManager();

    ToDoListFragment listToDo = new ToDoListFragment();
    listToDo = (ToDoListFragment) fm.findFragmentById(R.id.list_view_fragment);

    if(listToDo == null)
    {
        FragmentTransaction ft = fm.beginTransaction();
        ft.add(R.id.add_to_do_fragment, new AddToDoFragment());
        ft.add(R.id.list_view_fragment, new ToDoListFragment());
        ft.commit();

    }

    adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, todoItems);
    listToDo.setListAdapter(adapter);
}

public void OnToDoAdded(String newToDo) {
    todoItems.add(newToDo);
    adapter.notifyDataSetChanged();

}

@Override
protected void onSaveInstanceState(Bundle outState) {
    // TODO Auto-generated method stub
    super.onSaveInstanceState(outState);

    outState.putStringArrayList("todoItemTag", todoItems);

}

   }

ToDoListFragment.java

public class ToDoListFragment extends ListFragment{

}

activity_main.xml

<LinearLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" 
android:orientation="vertical">

<FrameLayout 
    android:name="com.example.todolistwithconfiguration.AddToDoFragment"
    android:id="@+id/add_to_do_fragment"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="0.5"/>

<FrameLayout 
    android:name="com.example.todolistwithconfiguration.ToDoListFragment"
    android:id="@+id/list_view_fragment"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1.5"
    android:visibility="gone"/>

日志猫

  • 10-29 17:21:59.783: D/AndroidRuntime(788): 关闭虚拟机
  • 10-29 17:21:59.783: W/dalvikvm(788): threadid=1: 线程以未捕获的异常退出 (group=0x414c4700)
  • 10-29 17:21:59.863：E/AndroidRuntime(788)：致命异常：主要
  • 10-29 17:21:59.863: E/AndroidRuntime(788): java.lang.RuntimeException: 无法启动活动 ComponentInfo{com.example.todolistwithdynamicfragments/com.example.todolistwithdynamicfragments.MainActivity}: java.lang.NullPointerException
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread.access$600(ActivityThread.java:141)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.os.Handler.dispatchMessage(Handler.java:99)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.os.Looper.loop(Looper.java:137)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread.main(ActivityThread.java:5103)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 java.lang.reflect.Method.invokeNative(Native Method)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 java.lang.reflect.Method.invoke(Method.java:525)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): at dalvik.system.NativeStart.main(Native Method)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 由: java.lang.NullPointerException 引起
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 com.example.todolistwithdynamicfragments.MainActivity.onCreate(MainActivity.java:40)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.Activity.performCreate(Activity.java:5133)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
  • 10-29 17:21:59.863: E/AndroidRuntime(788): ... 11 更多
  • 10-29 17:22:27.032: I/Process(788): 发送信号。PID：788 SIG：9
4

2 回答 2

0

尝试setListAdapter()在你的ToDoListFragment而不是在当前做Activity

于 2013-10-29T17:26:20.783 回答
0

将您的 MainAcitivity.java 更改为：

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if(savedInstanceState == null) {
            FragmentManager fm = getFragmentManager();
            FragmentTransaction ft = fm.beginTransaction();
            ft.add(R.id.add_to_do_fragment, new AddToDoFragment());
            ft.add(R.id.list_view_fragment, new ToDoListFragment());
            ft.commit();
        }
    }   
}

和你的 ToDoListFragment.java 到这个：

    public class ToDoListFragment extends ListFragment {

    private List<String> todoItems;

    @Override
    protected void onViewCreated(View view, Bundle savedInstanceState) {
        SharedPreferences preferences = this.getActivity().getSharedPreferences("pref",0);      
        this.todoItems = new ArrayList<String>();

        HashSet<String> savedItems = preferences.getStringSet("todoItems", new HashSet<String>());
        this.todoItems.addAll(savedItems);

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, this.todoItems);
        this.setListAdapter(adapter);
    }
}

我使用 SharedPreferences 来保存 todoItems。您可以从 AddToDoFragment 访问 SharedPreferences 并将项目添加到列表中。

于 2013-10-29T17:00:48.530 回答