feat: migrate to MVVM architecture with ViewBinding

- Replace old MainActivity with MVVM structure
- Add MainViewModel for business logic separation
- Implement ViewBinding for type-safe UI access
- Move MainActivity to ui.main package
- Remove Kotlin DSL files (build.gradle.kts, settings.gradle.kts)
- Add Chinese localization support

This refactoring improves code maintainability, testability, and follows modern Android development standards.

app/build.gradle

@@ -0,0 +1,39 @@
+plugins {
+    alias(libs.plugins.android.application)
+}
+
+android {
+    namespace 'com.example.mobile_pda'
+    compileSdk 36
+
+    defaultConfig {
+        applicationId "com.example.mobile_pda"
+        minSdk 26
+        targetSdk 36
+        versionCode 1
+        versionName "1.0"
+
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+    }
+
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+        }
+    }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+}
+
+dependencies {
+    implementation libs.appcompat
+    implementation libs.material
+    implementation libs.activity
+    implementation libs.constraintlayout
+    testImplementation libs.junit
+    androidTestImplementation libs.ext.junit
+    androidTestImplementation libs.espresso.core
+}

app/src/main/java/com/example/mobile_pda/ui/main/MainActivity.java

@@ -0,0 +1,67 @@
+package com.example.mobile_pda.ui.main;
+
+import android.os.Bundle;
+import android.widget.Toast;
+
+import androidx.activity.EdgeToEdge;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.lifecycle.ViewModelProvider;
+
+import com.example.mobile_pda.R;
+import com.example.mobile_pda.databinding.ActivityMainBinding;
+
+public class MainActivity extends AppCompatActivity {
+
+    private ActivityMainBinding binding;
+    private MainViewModel viewModel;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        EdgeToEdge.enable(this);
+        
+        // 1. 使用 ViewBinding 极简初始化，淘汰 findViewById
+        binding = ActivityMainBinding.inflate(getLayoutInflater());
+        setContentView(binding.getRoot());
+
+        // 2. 初始化 ViewModel，状态隔离
+        viewModel = new ViewModelProvider(this).get(MainViewModel.class);
+        
+        setupObservers();
+        setupListeners();
+    }
+
+    private void setupObservers() {
+        // 观察运行状态的变化
+        viewModel.getIsRunning().observe(this, isRunning -> {
+            if (isRunning) {
+                // UI状态随着数据改变（只是模拟示例）
+                binding.btnStartHeader.setEnabled(false);
+                binding.btnPauseHeader.setEnabled(true);
+            } else {
+                binding.btnStartHeader.setEnabled(true);
+                binding.btnPauseHeader.setEnabled(false);
+            }
+        });
+    }
+
+    private void setupListeners() {
+        // 使用 Binding 直接访问控件
+        binding.btnActionStart.setOnClickListener(v -> {
+            Toast.makeText(this, getString(R.string.toast_start_clicked), Toast.LENGTH_SHORT).show();
+            viewModel.startOperation();
+        });
+        
+        binding.btnActionFinish.setOnClickListener(v -> {
+            Toast.makeText(this, getString(R.string.toast_finish_clicked), Toast.LENGTH_SHORT).show();
+            viewModel.finishOperation();
+        });
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        // 清理 binding 引用防止内存泄漏
+        binding = null;
+    }
+}

app/src/main/java/com/example/mobile_pda/ui/main/MainViewModel.java

@@ -0,0 +1,23 @@
+package com.example.mobile_pda.ui.main;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.ViewModel;
+
+public class MainViewModel extends ViewModel {
+    
+    // 模拟的业务运行状态，LiveData实现生命周期感知
+    private final MutableLiveData<Boolean> isRunning = new MutableLiveData<>(false);
+    
+    public LiveData<Boolean> getIsRunning() {
+        return isRunning;
+    }
+
+    public void startOperation() {
+        isRunning.setValue(true);
+    }
+
+    public void finishOperation() {
+        isRunning.setValue(false);
+    }
+}

build.gradle

@@ -0,0 +1,4 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+plugins {
+    alias(libs.plugins.android.application) apply false
+}

settings.gradle

@@ -0,0 +1,23 @@
+pluginManagement {
+    repositories {
+        google {
+            content {
+                includeGroupByRegex("com\\.android.*")
+                includeGroupByRegex("com\\.google.*")
+                includeGroupByRegex("androidx.*")
+            }
+        }
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.name = "Mobile_PDA"
+include ':app'