在标记上粘贴时强制关闭

Question

我有这段代码可以在点击标记时显示 AlertDialog：

public void showOverlay (OverlayItem overlay)
        {
        db = openHelper.getWritableDatabase();

        String[] columns_descri = new String[] {COL_DESCRI};

        Cursor cur = db.query(true, TABLE_COORD, columns_descri,null, null, null, null, null, null);

        String description = cur.getString(cur.getColumnIndexOrThrow(COL_DESCRI));
        AlertDialog.Builder dialog = new AlertDialog.Builder(Geo.this);
        dialog.setTitle("Infos.");
        dialog.setMessage(description);
        dialog.setPositiveButton("OK", new OnClickListener() {    
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
            }
        });
        dialog.show();
        db.close();


    }

        @Override
        public boolean onTap(int index)

        {
 showOverlay(getItem(index)) ;
 return super.onTap(index) ;
 }

奇怪的是我有一个带有 logcat 错误的 FC：

08-24 20:51:42.466: ERROR/AndroidRuntime(265): Uncaught handler: thread main exiting due to uncaught exception
08-24 20:51:42.486: ERROR/AndroidRuntime(265): android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 4

有什么想法吗？ 谢谢。

Answer 1

当第一次创建游标时，它的索引是-1（在列表的开头之前）。在尝试从中检索任何数据之前，您需要调用 cur.moveToFirst()。如果光标为空，moveToFirst() 也会返回 false，这可能很有用：

public void showOverlay (OverlayItem overlay, int index)
{
   db = openHelper.getWritableDatabase();

   String[] columns_descri = new String[] {COL_DESCRI};

   Cursor cur = db.query(true, TABLE_COORD, columns_descri,null, null, null, null, null, null);

   if (cur.moveToPosition(index)) {
         String description = cur.getString(cur.getColumnIndexOrThrow(COL_DESCRI));
         AlertDialog.Builder dialog = new AlertDialog.Builder(Geo.this);
         dialog.setTitle("Infos.");
         dialog.setMessage(description);
         dialog.setPositiveButton("OK", new OnClickListener() {    
             @Override
             public void onClick(DialogInterface dialog, int which) {
                 dialog.dismiss();
             }
         });
         dialog.show();
   }
   else {
        //ERROR!  cursor is empty, throw a toast or something
   }

   db.close();
}