Question

CAB无法从游标适配器中删除数据

public class History extends ListActivity{

private ReminderDB mDbHelper;
List selections = new ArrayList();
int count = 0;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.history);

    mDbHelper = new ReminderDB(this);
    mDbHelper.open();
    fillData();
    registerForContextMenu(getListView());
}

private void fillData() {
    final Cursor remindersCursor = mDbHelper.fetchAllHistoryEvents();
    startManagingCursor(remindersCursor);
    // an array for the fields to show in the list row (now only the TITLE)
    String[] from = new String[]{ReminderDB.KEY_TITLE};
    // and an array of the fields for each list row
    int[] to = new int[]{R.id.row1};
    // a simple cursor adapter and set it to display
    final HistoryCustomCursorAdapter history = new HistoryCustomCursorAdapter(this, R.layout.history_list_row, remindersCursor, from, to);
    setListAdapter(history);
    getListView().setChoiceMode(AbsListView.CHOICE_MODE_MULTIPLE_MODAL);
    getListView().setMultiChoiceModeListener(new AbsListView.MultiChoiceModeListener() {
        @Override
        public void onItemCheckedStateChanged(ActionMode mode, int position, long id, boolean checked) {
            if(checked){
                selections.add(history.getItem(position));
                count++;
                mode.setTitle(count+ " Selected");
            }else{
                selections.remove(history.getItem(position));
                count--;
                mode.setTitle(count+ " Selected");
            }
        }

        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            MenuInflater menuInflater = getMenuInflater();
            menuInflater.inflate(R.menu.contextual_menu, menu);
            return true;
        }

        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            return false;
        }

        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            if (item.getItemId()==R.id.item_delete){
                AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
                mDbHelper.deleteHistory(info.id);
                history.notifyDataSetChanged();
                mode.finish();
            }
            fillData();
            return true;
        }

        @Override
        public void onDestroyActionMode(ActionMode mode) {
            count = 0;
            selections.clear();
        }
    });
}

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

这是我收到的错误消息：

11-08 14：24：03.475 6934-6934 / com.example.windchin.digitalbrain E / AndroidRuntime：致命异常：主要显示java.lang.NullPointerException at com.example.windchin.digitalbrain.History $ 1.onActionItemClicked（History.java:83）在android.widget.AbsListView $ MultiChoiceModeWrapper.onActionItemClicked（AbsListView.java:7680）在com.android.internal.policy.impl.PhoneWindow $ DecorView $ ActionModeCallbackWrapper.onActionItemClicked（PhoneWindow.java:3299） at com.android.internal.app.ActionBarImpl $ ActionModeImpl.onMenuItemSelected（ActionBarImpl.java:1009）在com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected（MenuBuilder.java:735）在com.android.internal.view.menu.MenuItemImpl.invoke（MenuItemImpl.java:152）在com.android.internal.view.menu.MenuBuilder.performItemAction（MenuBuilder.java:874）在com.android.internal.view.menu.ActionMenuView.invokeItem（ActionMenuView.java:630）在com.android.internal.view.menu.ActionMenuItemView.onClick（ActionMenuItemView.java:200）在android.view.View.performClick（View.java:4475）在android.view.View $ PerformClick.run（View.java:18786）在android.os.Handler.handleCallback（Handler.java:730）在android.os.Handler.dispatchMessage（Handler.java:92）在android.os.Looper.loop（Looper.java:176）在android.app.ActivityThread.main（ActivityThread.java:5419） at java.lang.reflect.Method.invokeNative（Native Method）在java.lang.reflect.Method.invoke（Method.java:525）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1046）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:862）在dalvik.system.NativeStart.main（本地方法）

这是游标适配器类

public class HistoryCustomCursorAdapter extends SimpleCursorAdapter {
    private Context context;
    private ReminderDB mDbHelper;
    private int layout;

    public HistoryCustomCursorAdapter (Context context, int layout, Cursor c, String[] from, int[] to) {
        super(context, layout, c, from, to);
        this.context = context;
        this.layout = layout;
        mDbHelper = new ReminderDB(context);
        mDbHelper.open();
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {

        final LayoutInflater inflater = LayoutInflater.from(context);
        View rowView = inflater.inflate(layout, parent, false);

        int titleCol = cursor.getColumnIndex(ReminderDB.KEY_TITLE);
        String title = cursor.getString(titleCol);
        TextView textView1 = (TextView) rowView.findViewById(R.id.row1);
        TextView textView2 = (TextView) rowView.findViewById(R.id.row2);
        ImageView imageView = (ImageView) rowView.findViewById(R.id.icon);

        textView1.setText(title);

        String Hdate = cursor.getString(cursor.getColumnIndex(ReminderDB.KEY_DATE_TIME));
        String latitude = cursor.getString(cursor.getColumnIndex(ReminderDB.KEY_LATITUDE));
        String longitude = cursor.getString(cursor.getColumnIndex(ReminderDB.KEY_LONGITUDE));

        if(Hdate != null)
            imageView.setImageResource(R.drawable.cclock);
        else
            imageView.setImageResource(R.drawable.maps);

        if(Hdate != null)
        {
            textView2.setText(Hdate);
        }
        else
        {
            Cursor c = mDbHelper.fetchLocation(latitude, longitude);
            String location = c.getString(c.getColumnIndex(ReminderDB.KEY_LOCATION));
            int option = Integer.parseInt(cursor.getString(cursor.getColumnIndex(ReminderDB.KEY_LOCATIONOPTION)));
            String locationOption;
            if (option == 0){
                locationOption = "When I Arrive";
            } else {
                locationOption = "When I Leave";
            }
            textView2.setText(locationOption + ": " + location);
        }
        return rowView;
    }
}

Answer 1

根据您的评论，您会遇到以下问题：

            AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) item.getMenuInfo();
            mDbHelper.deleteHistory(info.id);

这意味着您的info对象为null，而您对item.getMenuInfo()的调用无效。

这意味着您的HistoryCustomCursorAdapter未正确设置此值。您尚未发布该对象的代码，但我认为这应该足以让您找到错误。

上下文操作栏无法从SQLite

1 个答案: