717 lines
17 KiB
Markdown
717 lines
17 KiB
Markdown
# 性能优化最佳实践
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性能优化是Android应用开发的重要环节，直接影响用户体验和应用质量。本文档介绍Android应用性能优化的最佳实践。
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## 目录
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- [性能优化策略](#性能优化策略)
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- [启动优化实践](#启动优化实践)
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- [内存优化实践](#内存优化实践)
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- [布局优化实践](#布局优化实践)
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- [网络优化实践](#网络优化实践)
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- [性能监控](#性能监控)
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---
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## 性能优化策略
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### 1. 性能优化原则
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#### 测量优先
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```kotlin
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// ✅ 好的做法：先测量，再优化
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class PerformanceMonitor {
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fun measureTime(block: () -> Unit): Long {
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val startTime = System.currentTimeMillis()
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block()
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return System.currentTimeMillis() - startTime
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}
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fun measureMemory(block: () -> Unit): Long {
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val runtime = Runtime.getRuntime()
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val beforeMemory = runtime.totalMemory() - runtime.freeMemory()
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block()
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val afterMemory = runtime.totalMemory() - runtime.freeMemory()
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return afterMemory - beforeMemory
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}
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}
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// 使用
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val monitor = PerformanceMonitor()
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val time = monitor.measureTime {
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// 执行代码
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}
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Log.d("Performance", "执行时间: ${time}ms")
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```
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#### 优化关键路径
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```kotlin
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// 识别关键路径并优化
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class AppInitializer {
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fun initialize() {
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// 关键路径：必须立即初始化
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initCriticalComponents()
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// 非关键路径：可以延迟初始化
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Handler(Looper.getMainLooper()).postDelayed({
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initNonCriticalComponents()
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}, 100)
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}
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}
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```
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### 2. 性能指标
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#### 关键指标
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```kotlin
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// 启动时间
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class StartupTimeTracker {
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private var appStartTime: Long = 0
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fun onAppStart() {
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appStartTime = System.currentTimeMillis()
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}
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fun onFirstFrame() {
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val startupTime = System.currentTimeMillis() - appStartTime
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Log.d("Performance", "启动时间: ${startupTime}ms")
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}
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}
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// 内存使用
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class MemoryTracker {
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fun getMemoryUsage(): MemoryInfo {
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val runtime = Runtime.getRuntime()
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val totalMemory = runtime.totalMemory()
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val freeMemory = runtime.freeMemory()
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val usedMemory = totalMemory - freeMemory
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return MemoryInfo(
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total = totalMemory,
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used = usedMemory,
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free = freeMemory
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)
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}
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}
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```
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---
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## 启动优化实践
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### 1. Application优化
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#### 延迟初始化
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```kotlin
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// ✅ 好的做法：延迟初始化非关键组件
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class MyApplication : Application() {
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override fun onCreate() {
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super.onCreate()
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// 关键初始化：必须立即执行
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initCriticalComponents()
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// 非关键初始化：延迟执行
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initNonCriticalComponentsAsync()
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}
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private fun initCriticalComponents() {
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// 初始化关键组件
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CrashReporting.init(this)
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}
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private fun initNonCriticalComponentsAsync() {
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// 使用后台线程初始化
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Thread {
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// 初始化非关键组件
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Analytics.init(this)
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ImageLoader.init(this)
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}.start()
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}
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}
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```
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#### 使用App Startup
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```kotlin
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// 使用App Startup统一管理初始化
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class MyInitializer : Initializer<Unit> {
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override fun create(context: Context) {
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// 初始化组件
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Analytics.init(context)
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}
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override fun dependencies(): List<Class<out Initializer<*>>> {
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// 定义依赖关系
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return listOf(OtherInitializer::class.java)
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}
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}
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// 在AndroidManifest.xml中注册
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// <provider
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// android:name="androidx.startup.InitializationProvider"
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// android:authorities="${applicationId}.androidx-startup"
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// android:exported="false"
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// tools:node="merge">
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// <meta-data
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// android:name="com.example.MyInitializer"
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// android:value="androidx.startup" />
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// </provider>
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```
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### 2. 首屏优化
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#### 减少首屏布局复杂度
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```xml
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<!-- ✅ 好的做法：简化首屏布局 -->
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<androidx.constraintlayout.widget.ConstraintLayout
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android:layout_width="match_parent"
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android:layout_height="match_parent">
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<!-- 只显示关键内容 -->
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<TextView
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android:id="@+id/title"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:text="欢迎"
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app:layout_constraintTop_toTopOf="parent"
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app:layout_constraintStart_toStartOf="parent"
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app:layout_constraintEnd_toEndOf="parent"/>
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</androidx.constraintlayout.widget.ConstraintLayout>
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<!-- ❌ 不好的做法：首屏包含过多内容 -->
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```
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#### 使用ViewStub延迟加载
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```xml
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<!-- 使用ViewStub延迟加载非关键视图 -->
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<ViewStub
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android:id="@+id/viewStub"
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android:layout_width="match_parent"
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android:layout_height="wrap_content"
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android:layout="@layout/expensive_view"/>
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```
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```kotlin
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// 在需要时加载
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class MainActivity : AppCompatActivity() {
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private lateinit var viewStub: ViewStub
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override fun onCreate(savedInstanceState: Bundle?) {
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super.onCreate(savedInstanceState)
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setContentView(R.layout.activity_main)
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viewStub = findViewById(R.id.viewStub)
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// 延迟加载
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button.setOnClickListener {
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if (viewStub.parent != null) {
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viewStub.inflate()
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}
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}
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}
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}
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```
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### 3. 启动时间测量
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#### 使用Trace API
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```kotlin
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// 使用Trace API标记启动流程
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class MainActivity : AppCompatActivity() {
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override fun onCreate(savedInstanceState: Bundle?) {
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Trace.beginSection("MainActivity.onCreate")
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super.onCreate(savedInstanceState)
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setContentView(R.layout.activity_main)
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Trace.beginSection("initViews")
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initViews()
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Trace.endSection()
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Trace.beginSection("loadData")
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loadData()
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Trace.endSection()
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Trace.endSection()
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}
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}
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// 使用Systrace分析
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// python systrace.py -t 10 -o trace.html sched freq idle am wm gfx view binder_driver hal dalvik camera input res
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```
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---
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## 内存优化实践
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### 1. 内存泄漏预防
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#### 避免静态引用
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```kotlin
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// ❌ 不好的做法：静态引用Context
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object AppContext {
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var context: Context? = null // 可能导致内存泄漏
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}
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// ✅ 好的做法：使用Application Context
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object AppContext {
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fun getContext(): Context {
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return MyApplication.instance
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}
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}
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```
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#### 正确处理生命周期
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```kotlin
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// ✅ 好的做法：正确处理生命周期
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class MainActivity : AppCompatActivity() {
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private var handler: Handler? = null
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override fun onCreate(savedInstanceState: Bundle?) {
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super.onCreate(savedInstanceState)
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// 使用静态内部类+WeakReference
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handler = MyHandler(this)
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}
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override fun onDestroy() {
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super.onDestroy()
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handler?.removeCallbacksAndMessages(null)
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handler = null
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}
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private class MyHandler(activity: MainActivity) : Handler(Looper.getMainLooper()) {
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private val activityRef = WeakReference(activity)
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override fun handleMessage(msg: Message) {
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activityRef.get()?.let {
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// 处理消息
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}
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}
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}
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}
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```
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### 2. 内存使用优化
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#### 使用对象池
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```kotlin
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// 对象池：复用对象，减少GC
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class ObjectPool<T>(private val factory: () -> T, private val maxSize: Int = 10) {
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private val pool = mutableListOf<T>()
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fun acquire(): T {
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return if (pool.isNotEmpty()) {
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pool.removeAt(pool.size - 1)
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} else {
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factory()
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}
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}
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fun release(obj: T) {
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if (pool.size < maxSize) {
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pool.add(obj)
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}
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}
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}
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// 使用
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val viewPool = ObjectPool({ View(context) })
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val view = viewPool.acquire()
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// 使用view
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viewPool.release(view)
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```
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#### 优化图片加载
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```kotlin
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// 使用Glide等图片加载库
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Glide.with(context)
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.load(imageUrl)
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.placeholder(R.drawable.placeholder)
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.error(R.drawable.error)
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.override(800, 600) // 指定尺寸
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.into(imageView)
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// 使用WebP格式
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// WebP格式比PNG/JPG更小，加载更快
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// 使用图片压缩
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fun compressBitmap(bitmap: Bitmap, quality: Int = 80): ByteArray {
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val stream = ByteArrayOutputStream()
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bitmap.compress(Bitmap.CompressFormat.WEBP, quality, stream)
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return stream.toByteArray()
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}
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```
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### 3. 内存监控
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#### 使用LeakCanary
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```gradle
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// build.gradle
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dependencies {
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debugImplementation 'com.squareup.leakcanary:leakcanary-android:2.12'
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}
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```
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```kotlin
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// 自动检测内存泄漏
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// LeakCanary会自动检测并报告内存泄漏
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```
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#### 手动内存分析
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```kotlin
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// 获取内存信息
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class MemoryAnalyzer {
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fun getMemoryInfo(): String {
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val runtime = Runtime.getRuntime()
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val maxMemory = runtime.maxMemory()
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val totalMemory = runtime.totalMemory()
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val freeMemory = runtime.freeMemory()
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val usedMemory = totalMemory - freeMemory
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return """
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Max Memory: ${maxMemory / 1024 / 1024}MB
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Total Memory: ${totalMemory / 1024 / 1024}MB
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Used Memory: ${usedMemory / 1024 / 1024}MB
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Free Memory: ${freeMemory / 1024 / 1024}MB
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""".trimIndent()
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}
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fun dumpHeap(): File {
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val heapDumpFile = File(cacheDir, "heap_dump.hprof")
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Debug.dumpHprofData(heapDumpFile.absolutePath)
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return heapDumpFile
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}
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}
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```
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---
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## 布局优化实践
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### 1. 减少布局层级
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#### 使用ConstraintLayout
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```xml
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<!-- ✅ 好的做法：使用ConstraintLayout减少层级 -->
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<androidx.constraintlayout.widget.ConstraintLayout
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android:layout_width="match_parent"
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android:layout_height="match_parent">
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<TextView
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android:id="@+id/title"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:text="标题"
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app:layout_constraintStart_toStartOf="parent"
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app:layout_constraintTop_toTopOf="parent"/>
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<TextView
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android:id="@+id/subtitle"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:text="副标题"
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app:layout_constraintStart_toStartOf="parent"
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app:layout_constraintTop_toBottomOf="@id/title"/>
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</androidx.constraintlayout.widget.ConstraintLayout>
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<!-- ❌ 不好的做法：嵌套过多 -->
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<LinearLayout>
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<LinearLayout>
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<TextView/>
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</LinearLayout>
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</LinearLayout>
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```
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### 2. 避免过度绘制
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#### 减少背景绘制
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```xml
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<!-- ✅ 好的做法：移除不必要的背景 -->
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<LinearLayout
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android:layout_width="match_parent"
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android:layout_height="wrap_content"
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android:background="@android:color/white">
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<!-- 子视图不需要再设置背景 -->
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</LinearLayout>
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<!-- ❌ 不好的做法：多层背景 -->
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<LinearLayout android:background="@color/background1">
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<LinearLayout android:background="@color/background2">
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<!-- 导致过度绘制 -->
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</LinearLayout>
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</LinearLayout>
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```
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#### 使用clipToPadding
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```xml
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<!-- 使用clipToPadding减少绘制区域 -->
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<RecyclerView
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android:layout_width="match_parent"
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android:layout_height="match_parent"
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android:clipToPadding="false"
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android:padding="16dp"/>
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```
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### 3. RecyclerView优化
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#### ViewHolder复用
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```kotlin
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// ✅ 好的做法：正确实现ViewHolder
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class UserAdapter : RecyclerView.Adapter<UserAdapter.ViewHolder>() {
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class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
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val nameTextView: TextView = itemView.findViewById(R.id.name)
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val emailTextView: TextView = itemView.findViewById(R.id.email)
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}
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override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
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val view = LayoutInflater.from(parent.context)
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.inflate(R.layout.item_user, parent, false)
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return ViewHolder(view)
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}
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override fun onBindViewHolder(holder: ViewHolder, position: Int) {
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val user = users[position]
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holder.nameTextView.text = user.name
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holder.emailTextView.text = user.email
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}
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}
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```
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#### 使用DiffUtil
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```kotlin
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// 使用DiffUtil优化列表更新
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class UserDiffCallback(
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private val oldList: List<User>,
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private val newList: List<User>
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) : DiffUtil.Callback() {
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override fun getOldListSize() = oldList.size
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override fun getNewListSize() = newList.size
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override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
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return oldList[oldItemPosition].id == newList[newItemPosition].id
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}
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override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
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return oldList[oldItemPosition] == newList[newItemPosition]
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}
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}
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// 使用
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val diffResult = DiffUtil.calculateDiff(UserDiffCallback(oldList, newList))
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adapter.users = newList
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diffResult.dispatchUpdatesTo(adapter)
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```
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---
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## 网络优化实践
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### 1. 请求优化
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#### 请求合并
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```kotlin
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// ✅ 好的做法：合并请求
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class ApiService {
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@GET("users")
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suspend fun getUsers(@Query("ids") ids: String): List<User>
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// 一次请求获取多个用户，而不是多次请求
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}
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// ❌ 不好的做法：多次请求
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// for (id in userIds) {
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// apiService.getUser(id)
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// }
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```
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#### 使用缓存
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```kotlin
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// 使用OkHttp缓存
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val client = OkHttpClient.Builder()
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.cache(Cache(cacheDir, 10 * 1024 * 1024)) // 10MB缓存
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.build()
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// 使用Retrofit缓存
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@Headers("Cache-Control: max-age=3600")
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@GET("users/{id}")
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suspend fun getUser(@Path("id") id: String): User
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```
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### 2. 数据压缩
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#### 使用Gzip
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```kotlin
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// 服务器端启用Gzip压缩
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// 客户端自动处理Gzip响应
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// OkHttp自动支持Gzip解压
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```
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#### 数据格式优化
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```kotlin
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// 使用Protobuf替代JSON
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// Protobuf更小、更快
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data class User(
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val id: String,
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||
val name: String,
|
||
val email: String
|
||
)
|
||
|
||
// 转换为Protobuf
|
||
val userProto = UserProto.newBuilder()
|
||
.setId(user.id)
|
||
.setName(user.name)
|
||
.setEmail(user.email)
|
||
.build()
|
||
```
|
||
|
||
### 3. 网络监控
|
||
|
||
#### 监控网络请求
|
||
|
||
```kotlin
|
||
// 使用OkHttp Interceptor监控
|
||
class NetworkMonitorInterceptor : Interceptor {
|
||
override fun intercept(chain: Interceptor.Chain): Response {
|
||
val request = chain.request()
|
||
val startTime = System.currentTimeMillis()
|
||
|
||
val response = chain.proceed(request)
|
||
|
||
val duration = System.currentTimeMillis() - startTime
|
||
Log.d("Network", "${request.url} - ${duration}ms")
|
||
|
||
return response
|
||
}
|
||
}
|
||
|
||
val client = OkHttpClient.Builder()
|
||
.addInterceptor(NetworkMonitorInterceptor())
|
||
.build()
|
||
```
|
||
|
||
---
|
||
|
||
## 性能监控
|
||
|
||
### 1. 性能指标收集
|
||
|
||
#### 使用Firebase Performance
|
||
|
||
```gradle
|
||
// build.gradle
|
||
dependencies {
|
||
implementation 'com.google.firebase:firebase-perf-ktx:20.4.1'
|
||
}
|
||
```
|
||
|
||
```kotlin
|
||
// 监控自定义性能指标
|
||
val trace = FirebasePerformance.getInstance().newTrace("load_user_data")
|
||
trace.start()
|
||
|
||
// 执行操作
|
||
loadUserData()
|
||
|
||
trace.stop()
|
||
```
|
||
|
||
#### 自定义性能监控
|
||
|
||
```kotlin
|
||
class PerformanceTracker {
|
||
private val metrics = mutableMapOf<String, Long>()
|
||
|
||
fun startTrace(name: String) {
|
||
metrics[name] = System.currentTimeMillis()
|
||
}
|
||
|
||
fun endTrace(name: String) {
|
||
val startTime = metrics[name]
|
||
if (startTime != null) {
|
||
val duration = System.currentTimeMillis() - startTime
|
||
Log.d("Performance", "$name: ${duration}ms")
|
||
metrics.remove(name)
|
||
}
|
||
}
|
||
}
|
||
|
||
// 使用
|
||
val tracker = PerformanceTracker()
|
||
tracker.startTrace("load_data")
|
||
// 执行操作
|
||
tracker.endTrace("load_data")
|
||
```
|
||
|
||
### 2. 性能分析工具
|
||
|
||
#### 使用Android Profiler
|
||
|
||
```kotlin
|
||
// Android Studio Profiler可以监控：
|
||
// - CPU使用率
|
||
// - 内存使用情况
|
||
// - 网络请求
|
||
// - 电量消耗
|
||
```
|
||
|
||
#### 使用Systrace
|
||
|
||
```bash
|
||
# 使用Systrace分析性能
|
||
python systrace.py -t 10 -o trace.html sched freq idle am wm gfx view binder_driver hal dalvik camera input res
|
||
|
||
# 在代码中标记
|
||
Trace.beginSection("my_section")
|
||
// 执行代码
|
||
Trace.endSection()
|
||
```
|
||
|
||
#### 使用Perfetto
|
||
|
||
```kotlin
|
||
// Perfetto是更强大的性能分析工具
|
||
// 可以分析：
|
||
// - CPU调度
|
||
// - 内存分配
|
||
// - 文件I/O
|
||
// - 网络活动
|
||
```
|
||
|
||
---
|
||
|
||
## 总结
|
||
|
||
性能优化是一个持续的过程，需要：
|
||
|
||
1. **测量优先**：先测量性能，找出瓶颈
|
||
2. **优化关键路径**：优先优化影响用户体验的关键路径
|
||
3. **启动优化**：减少启动时间，提升用户体验
|
||
4. **内存优化**：避免内存泄漏，优化内存使用
|
||
5. **布局优化**：减少布局层级，避免过度绘制
|
||
6. **网络优化**：优化网络请求，使用缓存
|
||
7. **性能监控**：持续监控性能指标，及时发现问题
|
||
|
||
通过遵循这些最佳实践，可以显著提升应用的性能和用户体验。
|