結合上一篇的SharedPreferences建立一個簡易歷史紀錄的工具
MainActivity UI
拉兩個帳號密碼的輸入跟checkbox+button 以及一個顯示歷史紀錄的textview

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <EditText
        android:id="@+id/username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="帳號"
        android:inputType="text" />

    <EditText
        android:id="@+id/password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="密碼"
        android:inputType="textPassword" />

    <CheckBox
        android:id="@+id/rememberMe"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="記住我" />

    <Button
        android:id="@+id/loginButton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登入" />

    <TextView
        android:id="@+id/loginHistory"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="16dp" />

</LinearLayout>

MainActivity

先宣告變數跟綁定元件

private EditText usernameEditText, passwordEditText;
private CheckBox rememberMeCheckBox;
private Button loginButton;
private TextView loginHistory;
    
usernameEditText = findViewById(R.id.username);
passwordEditText = findViewById(R.id.password);
rememberMeCheckBox = findViewById(R.id.rememberMe);
loginButton = findViewById(R.id.loginButton);
loginHistory = findViewById(R.id.loginHistory);

設定SharedPreferences 的檔案名稱
private static final String PREF_NAME = "LoginPrefs";

建立SharedPreferences 並設定檔案櫃模式
SharedPreferences sharedPreferences = getSharedPreferences(PREF_NAME, MODE_PRIVATE);

boolean isRemembered = sharedPreferences.getBoolean("rememberMe", false);

    // 如果使用者選擇了記住密碼，則自動填充用戶名和密碼
    if (isRemembered) {
        String savedUsername = sharedPreferences.getString("username", "");
        String savedPassword = sharedPreferences.getString("password", "");
        usernameEditText.setText(savedUsername);
        passwordEditText.setText(savedPassword);
        rememberMeCheckBox.setChecked(true);
    }

    // 顯示登入紀錄
    String history = sharedPreferences.getString("loginHistory", "No login history");
    loginHistory.setText(history);

button的點擊事件

            loginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String username = usernameEditText.getText().toString();
                String password = passwordEditText.getText().toString();
                boolean rememberMe = rememberMeCheckBox.isChecked();

                if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {
                    Toast.makeText(MainActivity.this, "Please enter both username and password", Toast.LENGTH_SHORT).show();
                } else {
                    // 保存登入狀態和記住密碼的選擇
                    SharedPreferences.Editor editor = sharedPreferences.edit();
                    editor.putString("username", username);
                    editor.putString("password", password);
                    editor.putBoolean("rememberMe", rememberMe);

                    // 紀錄登入時間
                    String currentTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault()).format(new Date());
                    String loginRecord = username + " logged in at " + currentTime + "\n";

                    // 更新登入歷史
                    String existingHistory = sharedPreferences.getString("loginHistory", "");
                    editor.putString("loginHistory", existingHistory + loginRecord);
                    editor.apply();

                    // 更新 UI 顯示登入紀錄
                    loginHistory.setText(existingHistory + loginRecord);

                    // 跳轉到歡迎頁面
                    startActivity(new Intent(MainActivity.this, WelcomeActivity.class));
                    finish();  // 結束當前 Activity
                }
            }
        });

成果展覽