在Android中搜索记录并从数据库中检索

在我的活动中，我有editText的用户名、姓氏、姓氏和电子邮件地址。当用户输入现有用户名时，他可以通过单击搜索按钮进行搜索，用户拥有的数据将显示在编辑文本中

MainActivity.java

btn_Search.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View arg0) {
        String searchableUser = txt_User.getText().toString();

        ConsUserRegistration consUserRegistration = db.searchUser(searchableUser);

        String searchUser = consUserRegistration.getUser().toString();
        String searchFirst = consUserRegistration.getFirstName().toString();
        String searchLast = consUserRegistration.getLastName().toString();
        String searchEmail = consUserRegistration.getEmail().toString();

        txt_User.setText(searchUser);
        txt_First.setText(searchFirst);
        txt_Last.setText(searchLast);
        txt_Email.setText(searchEmail);             
    }
});

DatabaseHandler.java

public ConsUserRegistration searchUser(String username){

    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.query(Constants.TABLE_USER, new String[] {Constants.KEY_USER, Constants.KEY_FIRST, 
            Constants.KEY_LAST, Constants.KEY_EMAIL}, Constants.KEY_USER + " =? ", 
            new String[] { String.valueOf(username) }, null, null, null);
    if (cursor != null)
        cursor.moveToFirst();

    ConsUserRegistration search = new ConsUserRegistration (cursor.getString(0), cursor.getString(1), cursor.getString(2), cursor.getString(3));

    return search;

}

但是，当用户单击搜索按钮并且没有输入用户名EditText中的任何字符时，我在DatabaseHandler的第行中得到一个CursorIndexOutOfBoundsException错误：ConsUserRegistration Search=new ConsUserRegistration cursor.getString0，cursor.getString1，cursor.getString2，cursor.getString3

此外，由于数据库崩溃，我无法从中检索数据。

更改

db.searchUser(searchableUser);
ConsUserRegistration consUserRegistration = new ConsUserRegistration();

到

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Button按钮\u SearchbuttonfindViewByIdr.I'd.ItsidYourXML

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按钮可能需要声明或定义，需要查看整个代码，对不起。刚刚编辑了我的问题NullPointerExceptions在哪一行代码？请参阅日志猫。您建议的代码正在运行，但是，当我没有输入用户名时，我在DatabaseHandler的第行中获得了CursorindexOutOfBoundsException：conUserRegistration search=new conUserRegistration cursor.getString0，cursor.getString1，cursor.getString2，cursor.getString3；

ConsUserRegistration consUserRegistration = db.searchUser(searchableUser);