Android DataBinding 与 MVVM使用详解

android {
    buildFeatures {
        dataBinding = true
    }
}

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable 
            name="user" 
            type="com.example.User" />
    </data>
    <LinearLayout>
        <TextView
            android:text="@{user.name}"  <!-- 单向绑定 -->
            android:visibility="@{user.isAdult ? View.VISIBLE : View.GONE}"/>
        <EditText
            android:text="@={user.email}" />  <!-- 双向绑定 -->
    </LinearLayout>
</layout>

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        // 数据绑定初始化
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        // 设置数据对象
        binding.user = User("John", "john@example.com", true)
        // 设置生命周期所有者（用于LiveData）
        binding.lifecycleOwner = this
    }
}

[View] ---(观察)---> [ViewModel] <---(管理)---> [Model]
   ↑                      |
   └──(DataBinding绑定)──┘

class UserViewModel : ViewModel() {
    // 使用 LiveData 实现数据观察
    private val _user = MutableLiveData<User>()
    val user: LiveData<User> = _user
    // 双向绑定的可观察字段
    val inputText = ObservableField<String>("")
    init {
        _user.value = User("Alice", "alice@domain.com", true)
    }
    // 处理 UI 事件
    fun updateUser() {
        _user.value = User(inputText.get() ?: "", "", true)
    }
}

<data>
    <variable 
        name="viewModel" 
        type="com.example.UserViewModel" />
</data>
<TextView
    android:text="@{viewModel.user.name}" />
<EditText
    android:text="@={viewModel.inputText}" />  <!-- 双向绑定到ViewModel -->
<Button
    android:onClick="@{() -> viewModel.updateUser()}" />  <!-- 绑定点击事件 -->

class MainActivity : AppCompatActivity() {
    private val viewModel: UserViewModel by viewModels()
    override fun onCreate(savedInstanceState: Bundle?) {
        val binding: ActivityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        // 绑定 ViewModel
        binding.viewModel = viewModel
        // 设置生命周期所有者
        binding.lifecycleOwner = this
    }
}