拖放列表视图在片段中崩溃

Question

我希望这是显而易见的。我试着把一切都改回常规的"listView"(而不是使用DragNDragList库)，它仍然崩溃。

我试着用一些通用的例子资源代替这些东西，但我仍然会崩溃。我觉得有一些基本的我忽略了关于ListViewCursorAdaptor，导致崩溃，我的问题不是专属于dragNdrop库。

问题是否与它在片段中有关?

我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;

My list fragment:

<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>

My List Item:

<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

和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

你的日志说这是一个null点异常，它在listview中。请尝试替换

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

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

您正在使用getactivity()请使用您的充气视图名称，在您的情况下，它是myFragmentView，为什么一个零点异常正在发生

Answer 2

您需要将下面的代码移动到onViewCreated()。我的猜测是findViewById返回null，因为视图仍在创建中。

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();

和替换

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

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