Question

我正在开发一个记事本应用程序。我的列表项目显示在NoteList中，当我点击它们时出现此错误。我不知道如何解决这个问题。有谁知道为什么会这样？

logcat的

   04-18 18:20:53.430: E/AndroidRuntime(26517): FATAL EXCEPTION: main
   04-18 18:20:53.430: E/AndroidRuntime(26517): java.lang.ClassCastException:          com.example.note.contentprovider.NoteItem cannot be cast to android.database.Cursor
   04-18 18:20:53.430: E/AndroidRuntime(26517):     at com.example.note.contentprovider.NoteList.onListItemClick(NoteList.java:89)
   04-18 18:20:53.430: E/AndroidRuntime(26517):     at android.app.ListActivity$2.onItemClick(ListActivity.java:319)
   04-18 18:20:53.430: E/AndroidRuntime(26517):     at android.widget.AdapterView.performItemClick(AdapterView.java:298)
   04-18 18:20:53.430: E/AndroidRuntime(26517):     at android.widget.AbsListView.performItemClick(AbsListView.java:1110)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:2894)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at android.widget.AbsListView$1.run(AbsListView.java:3722)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at android.os.Handler.handleCallback(Handler.java:615)
   04-18 18:20:53.430: E/AndroidRuntime(26517):     at android.os.Handler.dispatchMessage(Handler.java:92)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at android.os.Looper.loop(Looper.java:137)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at android.app.ActivityThread.main(ActivityThread.java:4929)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at  java.lang.reflect.Method.invoke(Method.java:511)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:798)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:565)
  04-18 18:20:53.430: E/AndroidRuntime(26517):  at dalvik.system.NativeStart.main(Native Method)

NoteList.java

public class NoteList extends ListActivity implements LoaderManager.LoaderCallbacks < Cursor > {

private SimpleCursorAdapter dataAdapter;

private static final int ACTIVITY_CREATE = 0;
private static final int ACTIVITY_EDIT = 1;

private static final int DELETE_ID = Menu.FIRST;
private NotesDbAdapter mDbHelper;
private ArrayList < NoteItem > notes;
private NoteClassAdapter aa;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.notelist);
    notes = new ArrayList < NoteItem > ();
    int resID = R.layout.notes_row;
    aa = new NoteClassAdapter(this, resID, notes);
    setListAdapter(aa);
    getLoaderManager().initLoader(0, null, this);
    //registerForContextMenu(getListView());
    Button addnote = (Button) findViewById(R.id.addnotebutton);
    addnote.setOnClickListener(new View.OnClickListener() {@
        Override
        public void onClick(View v) {
            createNote();
        }
    });
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    return super.onOptionsItemSelected(item);
}


private void createNote() {
    Intent i = new Intent(this, NoteEdit.class);
    Bundle bundle = new Bundle();
    bundle.putString("mode", "add");
    i.putExtras(bundle);
    startActivityForResult(i, ACTIVITY_CREATE);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);
    Cursor cursor = (Cursor) l.getItemAtPosition(position);
    long row_id = cursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_ROWID);
    Intent i = new Intent(this, NoteEdit.class);
    Bundle bundle = new Bundle();
    bundle.putString("mode", "update");
    bundle.putLong(NotesDbAdapter.KEY_ROWID, row_id);
    i.putExtras(bundle);
    //  i.putExtra(NotesDbAdapter.KEY_ROWID, id);
    startActivityForResult(i, ACTIVITY_EDIT);
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v,
    ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);
    menu.add(0, DELETE_ID, 0, R.string.menu_delete);
}

@Override
public boolean onContextItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case DELETE_ID:
        AdapterContextMenuInfo info = (AdapterContextMenuInfo) item.getMenuInfo();
        // mDbHelper.deleteNote(info.id);

        Uri uri = Uri.parse(NotesDbAdapter.CONTENT_URI + "/" + info.id);
        getContentResolver().delete(uri, null, null);
        return true;
    }
    return super.onContextItemSelected(item);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
    super.onActivityResult(requestCode, resultCode, intent);
}

protected void onResume() {
    super.onResume();
    //Starts a new or restarts an existing Loader in this manager
    getLoaderManager().restartLoader(0, null, this);
}

// This is called when a new Loader needs to be created.
@Override
public Loader < Cursor > onCreateLoader(int id, Bundle args) {
    CursorLoader cursorLoader = new CursorLoader(this,
        NotesDbAdapter.CONTENT_URI, null, null, null, null);
    return cursorLoader;
}

@Override
public void onLoadFinished(Loader < Cursor > loader, Cursor cursor) {

    // dataAdapter.swapCursor(cursor);
    int keyTaskIndex = cursor.getColumnIndexOrThrow(NotesDbAdapter.KEY_TITLE);
    notes.clear();
    while (cursor.moveToNext()) {
        NoteItem newItem = new NoteItem(cursor.getString(keyTaskIndex));

        notes.add(newItem);
    }
    aa.notifyDataSetChanged();
}

@Override
public void onLoaderReset(Loader < Cursor > loader) {
    // This is called when the last Cursor provided to onLoadFinished()
    // above is about to be closed.  We need to make sure we are no
    // longer using it.
    //  dataAdapter.swapCursor(null);
}

}

NoteItem.java

 public class NoteItem {

 String task;
  Date created;

  public String getTask() {
    return task;
  }

  public Date getCreated() {
    return created;
  }

  public NoteItem(String _task) {
    this(_task, new Date(java.lang.System.currentTimeMillis()));
  }

  public NoteItem(String _task, Date _created) {
    task = _task;
    created = _created;
  }

  @Override
  public String toString() {
    SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");
    String dateString = sdf.format(created); 
    return "(" + dateString + ") " + task;
  }
}

Answer 1

Cursor cursor = (Cursor) l.getItemAtPosition(position);不返回游标，它应返回ListItem。更改您的引用以使用ListItem，并将该行更改为：

ListItem item = (ListItem) l.getItemAtPosition(position);

致命异常 - java.lang.ClassCastException

1 个答案: