SQLite相关用户信息检索

Question

我正在使用SQLite数据库开发一个登录系统。我已经有了一个注册表单，它可以很好地创建所有用户，我还创建了一个方法来检查输入到EditText中的用户名是否存在。但是现在我的问题是，你将如何从那个用户检索所有相关信息，例如，我还需要检查那个特定用户的密码是否匹配，我还需要从数据库中的用户那里检索一些测试分数，然后在主页中显示它们。下面是用于登录用户的主要活动中的代码：

public void loginUser() {
        EditText usernameInput = findViewById(R.id.login_username);
        EditText passwordInput = findViewById(R.id.login_password);
        String loginUsername = usernameInput.getText().toString();
        String loginPassword = passwordInput.getText().toString();

        if(loginUsername.matches("") || loginPassword.matches("")) {
            Toast.makeText(this, "Fields cannot be empty", Toast.LENGTH_SHORT).show();
        } else {
            if (dbHelper.ifUserExists(loginUsername)) {
                //password verification and login
                //how to retrieve relevant users password and compare to password input?
            } else {
                Toast.makeText(this, "Incorrect username or password", Toast.LENGTH_SHORT).show();
            }
        }
    }

下面是来自databaseHelper的检查用户是否存在的方法：

public boolean ifUserExists(String user) {
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.query(TABLE_USERS,
                new String[]{KEY_ID, KEY_USERNAME, KEY_PASSWORD, KEY_SAT_READING, KEY_SAT_MATH, KEY_ACT_READING, KEY_ACT_MATH},
                KEY_USERNAME + "=?",
                new String[]{user},
                null, null, null);
        if(cursor != null && cursor.moveToFirst()&& cursor.getCount() > 0) {
            return true;
        } else {
            return false;
        }
    }

Answer 1

您可以使用的方法之一是拥有一个包含保存数据的变量的用户对象。使用进程而不是返回布尔值时，这个inconjuction返回用户或null。

也许可以根据您的代码来考虑这个演示应用程序，为了简洁起见，它在数据库帮助程序中包含了一个用户类。

DatabaseHelper.java :-

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "mydb";
    public static final int DBVERSION = 1;
    public static final String TABLE_USERS = "users";
    public static final String KEY_ID = BaseColumns._ID;
    public static final String KEY_USERNAME = "username";
    public static final String KEY_PASSWORD = "password";
    public static final String KEY_SAT_READING = "reading";
    public static final String KEY_SAT_MATH = "satmath";
    public static final String KEY_ACT_READING = "actreading";
    public static final String KEY_ACT_MATH = "actmath";

    SQLiteDatabase db;

    public DatabaseHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        db = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String users_crt_sql = "CREATE TABLE IF NOT EXISTS " + TABLE_USERS +
                "(" +
                KEY_ID + " INTEGER PRIMARY KEY," +
                KEY_USERNAME + " TEXT UNIQUE," +
                KEY_PASSWORD + " TEXT," +
                KEY_SAT_READING + " TEXT," +
                KEY_SAT_MATH + " TEXT," +
                KEY_ACT_READING + " TEXT," +
                KEY_ACT_MATH + " TEXT" +
                ")";
        db.execSQL(users_crt_sql);
    }

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

    }

    public long insertNewUser(String name, String password) {
        ContentValues cv = new ContentValues();
        cv.put(KEY_USERNAME,name);
        cv.put(KEY_PASSWORD,password);
        return db.insert(TABLE_USERS,null,cv);
    }

    public User checkUser(String name, String password) {
        User rv = null;
        Cursor csr = db.query(
                TABLE_USERS,
                null,
                KEY_USERNAME + "=? AND " + KEY_PASSWORD + "=?",
                new String[]{name,password},
                null,null,null
        );
        if (csr.moveToFirst()) {
            rv = new User();
            rv.setUserId(csr.getLong(csr.getColumnIndex(KEY_ID)));
            rv.setUserName(name);
            rv.setUserPassword("");
            rv.setUserSatReading(csr.getString(csr.getColumnIndex(KEY_SAT_READING)));
            rv.setUserSatMath(csr.getString(csr.getColumnIndex(KEY_SAT_MATH)));
            rv.setUserActReading(csr.getString(csr.getColumnIndex(KEY_ACT_READING)));
            rv.setUserActMath(csr.getString(csr.getColumnIndex(KEY_ACT_MATH)));
        }
        csr.close();
        return rv;
    }

    public class User {
        long userId;
        String userName;
        String userPassword;
        String userSatReading;
        String userSatMath;
        String userActReading;
        String userActMath;

        public User() {
        }

        public User(String name, String password) {
            this(-1L, name, password, null, null, null, null);
        }

        public User(long id, String name, String password, String satReading, String satMath, String actReading, String actmath) {
            this.userId = id;
            this.userName = name;
            this.userPassword = password;
            this.userSatReading = satReading;
            this.userSatMath = satMath;
            this.userActReading = actReading;
            this.userActMath = actmath;
        }

        public long getUserId() {
            return userId;
        }

        public void setUserId(long userId) {
            this.userId = userId;
        }

        public String getUserName() {
            return userName;
        }

        public void setUserName(String userName) {
            this.userName = userName;
        }

        public String getUserPassword() {
            return userPassword;
        }

        public void setUserPassword(String userPassword) {
            this.userPassword = userPassword;
        }

        public String getUserSatReading() {
            return userSatReading;
        }

        public void setUserSatReading(String userSatReading) {
            this.userSatReading = userSatReading;
        }

        public String getUserSatMath() {
            return userSatMath;
        }

        public void setUserSatMath(String userSatMath) {
            this.userSatMath = userSatMath;
        }

        public String getUserActReading() {
            return userActReading;
        }

        public void setUserActReading(String userActReading) {
            this.userActReading = userActReading;
        }

        public String getUserActMath() {
            return userActMath;
        }

        public void setUserActMath(String userActMath) {
            this.userActMath = userActMath;
        }
    }
}

• 注释checkUser方法相当于idUserExists方法，但是如果找不到用户，则返回的用户对象将为null。使用游标时，您应该关闭游标。如果游标由一个returns.
• Lilewise方法返回，则
• 检查游标为null，因为如果方法为Check moveTofirst，而游标的计数为0，则将始终返回有效的游标，而如果计数为0 moveToFirst将返回false，则只有其中一个检查为needed.

。

​

在下面的活动中使用上述内容，这反映了您现有的代码和您想要实现的目标。

在最初启动时，应用程序添加了一个用户(用于妖魔化)，该用户的名字是Admin，密码是UI由一个显示未登录的textView ！(显示顶部)、两个编辑文本(按照您的代码)和一个登录按钮组成。

MainActivity.java

public class MainActivity extends AppCompatActivity {

    DatabaseHelper dbHelper;
    DatabaseHelper.User current_user = null;
    EditText loginUsername, loginPassword;
    TextView status;
    Button login;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        status = this.findViewById(R.id.status);
        loginUsername = this.findViewById(R.id.login_username);
        loginPassword = this.findViewById(R.id.login_password);
        login = this.findViewById(R.id.login);
        login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                loginUser();
            }
        });

        dbHelper = new DatabaseHelper(this);
        dbHelper.insertNewUser("Admin","adminpassword");

    }

    private void loginUser() {
        if (
                loginUsername.getText().toString() == null
                        || loginUsername.getText().toString().length() < 1
                        ||loginPassword.getText().toString() == null
                        || loginPassword.getText().toString().length() < 1) {
            Toast.makeText(this, "Fields cannot be empty", Toast.LENGTH_SHORT).show();
            return;
        }
        if ((current_user = dbHelper.checkUser(loginUsername.getText().toString(),loginPassword.getText().toString())) != null) {
            loginUsername.setVisibility(View.GONE);
            loginPassword.setVisibility(View.GONE);
            login.setText("DO SOMETHNG");
            login.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(v.getContext(),"Hello " +
                            current_user.getUserName() +
                            " you are logged in so you can do something!",Toast.LENGTH_SHORT).show();
                }
            });
            status.setText("Successfully Logged-In as " + current_user.getUserName());
        } else {
            Toast.makeText(this, "Incorrect username or password", Toast.LENGTH_SHORT).show();
        }
    }
}

结果

初始运行

​

​

• ，如果编辑文本中没有任何内容，并且单击了Login按钮，则*字段不能空消息。如果输入了无效的用户和密码组合并单击Login>E 238>按钮，则会对e 139不正确的用户名或密码消息进行烤烤。

<代码142输入有效的用户名和密码:- F 143<>H144在E 145的topd处被完全记录为E 145记录在哪里？<？<？是用于用户名和密码被删除的username).

• The编辑文本。
• ，Login按钮更改为，根据:-

做某事

​

​

​