語境操作欄無法從SQLite的

Question

刪除選定的項目

CAB無法刪除光標適配器數據

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(); 
} 
} 

這是錯誤消息我得到：

11-08 14/24：03.475 6934-6934/com.example.windchin.digitalbrain E/AndroidRuntime：致命例外：main java.lang.NullPointerException at com.example.windchin.d igitalbrain.History $ 1.onActionItemClicked（History.java:83） at android.widget.AbsListView $ MultiChoiceModeWrapper.onActionItemClicked（AbsListView.java:7680） at com.android.internal.policy.impl.PhoneWindow $ DecorView $ ActionModeCallbackWrapper.onActionItemClicked （PhoneWindow.java:3299） at com.android.internal.app.ActionBarImpl $ ActionModeImpl.onMenuItemSelected（ActionBarImpl.java:1009） at 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） （android.view.java:4475） at android.view.View $ PerformClick.run（View .java：18786） at android.os.Handler.handleCallback（Handler.java:730） at android.os.Handler.dispatchMessage（Handler.java:92） at android.os.Looper.loop（Looper.java ：Method.java：176） at android.app.ActivityThread.main（ActivityThread.java:5419） at java.lang.reflect.Method.invokeNative（Native Method） at java.lang.reflect.Method.invoke（Method.java： 525） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1046） at com.android.internal.os.ZygoteInit.main（Zy goteInit.java:862） 在dalvik.system.NativeStart.main（本機方法）

這是光標適配器類

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

基於您的評論，那麼你必須在這些線路有問題：

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

這意味着你的info對象是null和你的item.getMenuInfo()電話無法正常工作。

這意味着您的HistoryCustomCursorAdapter未正確設置此值。您尚未發佈該對象的代碼，但我認爲這應該足以讓您找到該錯誤。