Question

我希望它有点明显。我尝试将所有内容更改回常规“listView”（而不是使用DragNDragList库），它仍然崩溃。

我尝试用一些通用示例资源替换这些东西，但我仍然遇到了崩溃。我觉得有一些基本的东西我忽略了导致崩溃的ListViewCursorAdaptor，而且我的问题不是dragNdrop库所独有的。

问题可能与片段中的问题有关吗？

我的onCreateView：

myFragmentView = inflater.inflate(R.layout.todo_fragment, container, false);
    db = new DBAdapter(getActivity());
    db.open();
    Cursor TaskCursor = db.getAllTasks();

    list = (DragNDropListView) getActivity().findViewById(R.id.dragList);

    Log.d("cursor", TaskCursor.getString(1)); //This shows me that my cursor obviously isn't empty

    adapter = new DragNDropCursorAdapter(myFragmentView.getContext(),
                               R.layout.task_list_item,
                               TaskCursor,
                               new String[]{DBAdapter.COLUMN_NAME},
                               new int[]{R.id.TaskItemTitle},
                               R.id.DragHandle);

    Log.d("apater", "test");

    list.setDragNDropAdapter(adapter); //Line 46 (where it crashes)

    Log.d("apater", "test");

    db.close();

    return myFragmentView;

我的列表片段：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<com.terlici.dragndroplist.DragNDropListView
    android:id="@+id/dragList"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    /></LinearLayout>

我的清单项目：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content" >

<ImageView
    android:id="@+id/DragHandle"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/drag_handle" />

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/TaskItemTitle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Large Text"
        android:textSize="20sp" />

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/card_text" >
    </RelativeLayout>

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Medium Text"
        android:textSize="16sp" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:text="Small Text"
        android:textSize="8sp" />

</LinearLayout>

图书馆：https://github.com/terlici/DragNDropList

LogCa：

05-05 12:16:19.456: E/AndroidRuntime(29575): FATAL EXCEPTION: main
05-05 12:16:19.456: E/AndroidRuntime(29575): Process: edu.jcu.cs470.togenda, PID: 29575
05-05 12:16:19.456: E/AndroidRuntime(29575): java.lang.NullPointerException
05-05 12:16:19.456: E/AndroidRuntime(29575):    at edu.jcu.cs470.togenda.ToDoFragment.onCreateView(ToDoFragment.java:46)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.Fragment.performCreateView(Fragment.java:1700)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.BackStackRecord.run(BackStackRecord.java:684)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.os.Handler.handleCallback(Handler.java:733)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.os.Handler.dispatchMessage(Handler.java:95)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.os.Looper.loop(Looper.java:136)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at android.app.ActivityThread.main(ActivityThread.java:5024)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at java.lang.reflect.Method.invokeNative(Native Method)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at java.lang.reflect.Method.invoke(Method.java:515)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:133)
05-05 12:16:19.456: E/AndroidRuntime(29575):    at dalvik.system.NativeStart.main(Native Method)
05-05 12:17:01.898: I/Process(29575): Sending signal. PID: 29575 SIG: 9

Answer 1

你记录说它是一个零点异常，它在listview.please中尝试替换

 list = (DragNDropListView) getActivity().findViewById(R.id.dragList);

到

 list = (DragNDropListView) myFragmentView.findViewById(R.id.dragList);

您正在使用 getactivity（）请在您的情况下使用您的膨胀视图名称 myFragmentView ，了解为什么会出现null point excetin。

Answer 2

您需要将代码移到onViewCreated（）以下。我的猜测是findViewById返回null，因为仍在创建视图。

db = new DBAdapter(getActivity());
    db.open();
    Cursor TaskCursor = db.getAllTasks();

    list = (DragNDropListView) getActivity().findViewById(R.id.dragList);

    Log.d("cursor", TaskCursor.getString(1)); //This shows me that my cursor obviously isn't empty

    adapter = new DragNDropCursorAdapter(myFragmentView.getContext(),
                               R.layout.task_list_item,
                               TaskCursor,
                               new String[]{DBAdapter.COLUMN_NAME},
                               new int[]{R.id.TaskItemTitle},
                               R.id.DragHandle);

    Log.d("apater", "test");

    list.setDragNDropAdapter(adapter); //Line 46 (where it crashes)

    Log.d("apater", "test");

    db.close();

并替换

list = (DragNDropListView) getActivity().findViewById(R.id.dragList);

通过

list = (DragNDropListView) view.findViewById(R.id.dragList);

拖动Drop Listview在片段中崩溃

2 个答案: