android获取数据库查询的结果

参考：https://www.xuebuyuan.com/3244495.html

原来错误的程序，app会崩溃（请大神指点错误的原因是啥？_(:з)∠)_）

btn_search.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String key = et_username.getText().toString();
                Cursor cursor = dbOpenHelper.getReadableDatabase().query("tb_user",null,"username=?",new String[]{key}, null,null,null);

                if (cursor.getCount() == 0) {
                    Toast.makeText(MainActivity.this,"很遗憾，没有相关记录",Toast.LENGTH_SHORT).show();
                } else {
//                    while (cursor.moveToNext()) {
//                        Log.i("cccccccccc", cursor.getString(1) + " " + cursor.getString(2));
//                    }
                    Log.i("dddddddd",cursor.getString(1));
                }
            }
        });

改正后的程序，用循环来输出

btn_search.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String key = et_username.getText().toString();
                Cursor cursor = dbOpenHelper.getReadableDatabase().query("tb_user",null,"username=?",new String[]{key}, null,null,null);

                if (cursor.getCount() == 0) {
                    Toast.makeText(MainActivity.this,"很遗憾，没有相关记录",Toast.LENGTH_SHORT).show();
                } else {
                    while (cursor.moveToNext()) {
                        Log.i("cccccccccc", cursor.getString(1) + " " + cursor.getString(2));
                    }
//                    Log.i("dddddddd",cursor.getString(1));
                }
            }
        });