android - Android 如何从 SQLite 游标查询中获取返回值字符串并在 Edittext 中显示？

Question

当我运行 SQLite 游标查询时，它无法在编辑文本中显示结果字符串。

它失败并显示 Logcat 消息：

java.lang.RuntimeException: Unable to start activity
android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1

如何从光标中获取查询结果值字符串并在edittext中显示？

public class Books extends Activity implements OnClickListener {

 private BooksData books;

 @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.books);

        books = new BooksData(this);

        }

        SQLiteDatabase db1 = books.getReadableDatabase();

        SEARCH_TERM = "math";

        EditText edittext = (EditText) findViewById(R.id.edittext1);

        // Get the value from TITLE when the TOPIC value is specified, ie such as "math".

        Cursor cursor_2 = db1.query(TABLE_NAME, new String[] {"_id", "TOPIC", "TITLE"}, "TOPIC = ?", new String[]{ ""+SEARCH_TERM+"" }, null, null, null, null);

        String TEMP_DATA = cursor_2.getString(2);

        edittext.setText(TEMP_DATA);

books.close();
cursor_2.close();
}

Answer 1

您需要先移动到光标中的第一条记录，然后才能从中提取数据。

Cursor cursor_2 = db1.query(TABLE_NAME, new String[] {"_id", "TOPIC", "TITLE"}, "TOPIC = ?", new String[]{ ""+SEARCH_TERM+"" }, null, null, null, null);

if (cursor_2 == null)
   return;

try{
   if (cursor_2.moveToFirst()) // Here we try to move to the first record
        edittext.setText(cursor_2.getString(2)); // Only assign string value if we moved to first record
}finally { 
   cursor_2.close();
}