android - 当我输入相同的用户名时它给了我 "Wrong input"？

Question

我正在尝试使用 SQL 编写用于登录和注册的 android 代码，当我运行该应用程序并尝试使用我注册时使用的相同用户名登录时，它不会转到主页，但会执行 else 语句在显示“错误输入”的登录类中。请问有谁知道原因吗？

这是我的代码:

登录

public class Login extends AppCompatActivity {

    EditText edt_username, edt_pass,edt_email;
    TextView tv_username, tv_pass;
    Button btn_login, btn_signUp;
    Login_SQLHelper login_sqlHelper;
    SQLiteDatabase db;
    User user;

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

        login_sqlHelper = new Login_SQLHelper(this);
        edt_username = (EditText) findViewById(R.id.edt_username);
        edt_pass = (EditText) findViewById(R.id.edt_pass);
        tv_username = (TextView) findViewById(R.id.tv_username);
        tv_pass = (TextView) findViewById(R.id.tv_pass);
        btn_login = (Button) findViewById(R.id.button);
        btn_signUp = (Button) findViewById(R.id.button2);

        btn_signUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent goSignup = new Intent(Login.this, SignUp.class);
                startActivity(goSignup);
            }
        });
        login();
        //viewData();
    }

    public void login() {
        btn_login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                user = new User();
                String name = edt_username.getText().toString();
                String pass = edt_pass.getText().toString();
                user.setUser_name(name);
                user.setPassword(pass);

                if ( name.equals(login_sqlHelper.get_data().getUser_name())){
                    Intent goHome = new Intent(Login.this, Home.class);
                    startActivity(goHome);
                } else
                    Toast.makeText(Login.this, "Wrong input", Toast.LENGTH_SHORT).show();
                edt_username.setText("");
                edt_pass.setText("");

Login_SQLHelper

public class Login_SQLHelper extends SQLiteOpenHelper {

    public static final String database_name = "user_log";
    public static final String table_name = "user_table";
    public static final String col_username = "username";
    public static final String col_userEmail = "user_email";
    public static final String col_userPass = "user_pass";

    User user = new User();

    public Login_SQLHelper(Context context) {
        super(context, database_name, null, 1);
        SQLiteDatabase db = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(" create table " + table_name + "(" + col_username + " TEXT," + col_userEmail + " TEXT," + col_userPass + " TEXT )");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        db.execSQL("DROP TABLE IF EXISTS " + table_name);
    }

    public boolean insert_data(User user) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(col_username, user.getUser_name());
        contentValues.put(col_userEmail, user.getEmail());
        contentValues.put(col_userPass, user.getPassword());
        Long res = db.insert(table_name, null, contentValues);
        if (res == -1)
            return false;
        else
            return true;
    }

    public User get_data() {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery("select * from " + table_name, null);
       User user2 = new User();
        return user2;
    }

注册

public class SignUp extends AppCompatActivity {

    EditText edt_username, edt_pass, edt_email;
    Button btn3;
    User user;
    Login_SQLHelper login_db;

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

        edt_username = (EditText) findViewById(R.id.edtS_username);
        edt_pass = (EditText) findViewById(R.id.edtS_pass);
        edt_email = (EditText) findViewById(R.id.edtS_email);
        btn3 = (Button) findViewById(R.id.button3);
        user = new User();
        login_db = new Login_SQLHelper(this);
        signUp();
    }

    public void signUp() {
        btn3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                user.setUser_name(edt_username.getText().toString());
                user.setEmail(edt_email.getText().toString());
                user.setPassword(edt_pass.getText().toString());
                boolean isInserted = login_db.insert_data(user);
                if (isInserted == true) {
                    Toast.makeText(SignUp.this, "Inserted", Toast.LENGTH_SHORT).show();
                    Intent goLogin = new Intent(SignUp.this, Login.class);
                    startActivity(goLogin);
                }else
                    Toast.makeText(SignUp.this, "Not inserted", Toast.LENGTH_SHORT).show();
                }
            });
        }
    }

用户

public class User {

    String user_name , email , password;

    public String getUser_name() {
        return user_name;
    }

    public void setUser_name(String user_name) {
        this.user_name = user_name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

Answer 1

问题出在这个方法上。

public User get_data() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery("select * from " + table_name, null);
   User user2 = new User();
    return user2;
}

您正在从数据库中获取数据并创建新的用户对象并返回此空对象。

尝试此代码或根据需要做出一些改变。

public User get_data() {
   SQLiteDatabase db = this.getWritableDatabase();
   Cursor cursor = db.rawQuery("select * from " + table_name, null);
   if ((mCursor.moveToFirst()) || mCursor.getCount() !=0){
     User user2 = new User();
     user2.setUser_name(cursor.getString(0));
     user2.setEmail(cursor.getString(1));
     user2.setPassword(cursor.getString(2));
     cursor.close();
   }
  return user2;
}