Question

我的活动中有editText的（用户名，名字，姓氏和电子邮件地址），供用户注册。用户有权通过单击搜索按钮来搜索他输入的用户名是否已存在。如果用户名已存在，则将显示与该用户名相关的所有信息，例如用户名。但是，如果用户单击按钮，如果它不存在，我的应用程序崩溃，我收到CursorIndexOutOfBoundsException错误。我该如何调试那个？

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;

}

Answer 1

所以...如果您的光标为空或没有元素会发生什么？你还在尝试访问它......

尝试类似......

if (cursor != null && cursor.moveToFirst())  {    

...

Answer 2

试试这个：

MainActivity.java

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

        ConsUserRegistration consUserRegistration = db.searchUser(searchableUser);
        if (consUserRegistration != null){

           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);
        }else{
         Toast.makeText(getApplicationContext(), "Username Not Found", Toast.LENGTH_LONG).show();
        }               
    }
});

DatabaseHandler.java

public ConsUserRegistration searchUser(String username){
    ConsUserRegistration search;
    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()){
            search = new ConsUserRegistration (cursor.getString(0), cursor.getString(1), cursor.getString(2), cursor.getString(3));
        }else{
            search = null;
        }

    return search;

}

在Android中单击“搜索”按钮时从数据库中检索数据

2 个答案: