Android 登录界面开发指南

基本实现步骤

1. 创建布局文件 (activity_login.xml)

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="登录"
        android:textSize="24sp"
        android:textStyle="bold"
        android:layout_gravity="center_horizontal"
        android:layout_marginBottom="24dp"/>

    <com.google.android.material.textfield.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp">

        <com.google.android.material.textfield.TextInputEditText
            android:id="@+id/etUsername"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="用户名"
            android:inputType="text"/>
    </com.google.android.material.textfield.TextInputLayout>

    <com.google.android.material.textfield.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp">

        <com.google.android.material.textfield.TextInputEditText
            android:id="@+id/etPassword"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="密码"
            android:inputType="textPassword"/>
    </com.google.android.material.textfield.TextInputLayout>

    <Button
        android:id="@+id/btnLogin"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登录"
        android:layout_marginBottom="16dp"/>

    <TextView
        android:id="@+id/tvForgotPassword"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="忘记密码?"
        android:layout_gravity="end"/>

    <TextView
        android:id="@+id/tvRegister"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="注册新账号"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="16dp"/>
</LinearLayout>

2. 创建Activity类 (LoginActivity.kt/java)

Kotlin版本:

class LoginActivity : AppCompatActivity() {

    private lateinit var binding: ActivityLoginBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityLoginBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.btnLogin.setOnClickListener {
            val username = binding.etUsername.text.toString()
            val password = binding.etPassword.text.toString()

            if (validateInput(username, password)) {
                // 执行登录逻辑
                performLogin(username, password)
            }
        }

        binding.tvForgotPassword.setOnClickListener {
            // 跳转到找回密码页面
            startActivity(Intent(this, ForgotPasswordActivity::class.java))
        }

        binding.tvRegister.setOnClickListener {
            // 跳转到注册页面
            startActivity(Intent(this, RegisterActivity::class.java))
        }
    }

    private fun validateInput(username: String, password: String): Boolean {
        if (username.isEmpty()) {
            binding.etUsername.error = "用户名不能为空"
            return false
        }

        if (password.isEmpty()) {
            binding.etPassword.error = "密码不能为空"
            return false
        }

        if (password.length < 6) {
            binding.etPassword.error = "密码长度至少6位"
            return false
        }

        return true
    }

    private fun performLogin(username: String, password: String) {
        // 显示加载进度条
        val progressDialog = ProgressDialog(this).apply {
            setMessage("正在登录...")
            setCancelable(false)
        }
        progressDialog.show()

        // 模拟网络请求
        Handler(Looper.getMainLooper()).postDelayed({
            progressDialog.dismiss()

            if (username == "admin" && password == "123456") {
                // 登录成功，跳转到主页面
                startActivity(Intent(this, MainActivity::class.java))
                finish()
            } else {
                // 登录失败，显示错误提示
                Toast.makeText(this, "用户名或密码错误", Toast.LENGTH_SHORT).show()
            }
        }, 2000)
    }
}

Java版本:

public class LoginActivity extends AppCompatActivity {

    private ActivityLoginBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityLoginBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        binding.btnLogin.setOnClickListener(v -> {
            String username = binding.etUsername.getText().toString();
            String password = binding.etPassword.getText().toString();

            if (validateInput(username, password)) {
                performLogin(username, password);
            }
        });

        binding.tvForgotPassword.setOnClickListener(v -> {
            startActivity(new Intent(this, ForgotPasswordActivity.class));
        });

        binding.tvRegister.setOnClickListener(v -> {
            startActivity(new Intent(this, RegisterActivity.class));
        });
    }

    private boolean validateInput(String username, String password) {
        if (username.isEmpty()) {
            binding.etUsername.setError("用户名不能为空");
            return false;
        }

        if (password.isEmpty()) {
            binding.etPassword.setError("密码不能为空");
            return false;
        }

        if (password.length() < 6) {
            binding.etPassword.setError("密码长度至少6位");
            return false;
        }

        return true;
    }

    private void performLogin(String username, String password) {
        ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("正在登录...");
        progressDialog.setCancelable(false);
        progressDialog.show();

        new Handler(Looper.getMainLooper()).postDelayed(() -> {
            progressDialog.dismiss();

            if (username.equals("admin") && password.equals("123456")) {
                startActivity(new Intent(this, MainActivity.class));
                finish();
            } else {
                Toast.makeText(this, "用户名或密码错误", Toast.LENGTH_SHORT).show();
            }
        }, 2000);
    }
}

高级功能实现

1. 使用ViewModel和LiveData

class LoginViewModel : ViewModel() {
    private val _loginResult = MutableLiveData<LoginResult>()
    val loginResult: LiveData<LoginResult> = _loginResult

    fun login(username: String, password: String) {
        viewModelScope.launch {
            try {
                // 模拟网络请求
                delay(2000)
                if (username == "admin" && password == "123456") {
                    _loginResult.value = LoginResult(success = true)
                } else {
                    _loginResult.value = LoginResult(error = "用户名或密码错误")
                }
            } catch (e: Exception) {
                _loginResult.value = LoginResult(error = "网络错误: ${e.message}")
            }
        }
    }
}

data class LoginResult(
    val success: Boolean = false,
    val error: String? = null
)

2. 使用数据绑定

在build.gradle中启用数据绑定:

android {
    ...
    buildFeatures {
        dataBinding true
    }
}

更新布局文件:

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="viewModel"
            type="com.example.app.LoginViewModel" />
    </data>

    <!-- 原有布局内容 -->
</layout>

3. 添加记住密码功能

在布局中添加CheckBox:

<CheckBox
    android:id="@+id/cbRemember"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="记住密码"/>

在Activity中添加处理逻辑:

private val sharedPref by lazy { 
    getSharedPreferences("login_prefs", Context.MODE_PRIVATE) 
}

// 在onCreate中
binding.cbRemember.isChecked = sharedPref.getBoolean("remember", false)
if (binding.cbRemember.isChecked) {
    binding.etUsername.setText(sharedPref.getString("username", ""))
    binding.etPassword.setText(sharedPref.getString("password", ""))
}

// 在登录成功后
if (binding.cbRemember.isChecked) {
    sharedPref.edit().apply {
        putString("username", username)
        putString("password", password)
        putBoolean("remember", true)
        apply()
    }
} else {
    sharedPref.edit().clear().apply()
}

安全注意事项

1. 密码安全:

   • 不要在日志或调试信息中输出密码
   • 使用HTTPS传输敏感数据
   • 考虑使用加密存储记住的密码

2. 输入验证:

   • 客户端和服务端都要进行验证
   • 防止SQL注入和XSS攻击

3. 用户体验:

   • 添加加载指示器
   • 提供清晰的错误提示
   • 考虑添加密码可见性切换按钮

完整项目结构建议

com.example.app
├── auth
│   ├── LoginActivity.kt
│   ├── RegisterActivity.kt
│   ├── ForgotPasswordActivity.kt
│   └── viewmodel
│       ├── LoginViewModel.kt
│       └── AuthRepository.kt
├── ui
│   └── MainActivity.kt
└── data
    ├── model
    │   └── User.kt
    └── ApiService.kt

希望这个指南对您开发Android登录界面有所帮助！根据您的具体需求，可以进一步扩展和定制这个基础实现。