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84 lines
1.9 KiB
84 lines
1.9 KiB
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谈谈你对 Context 的理解？
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---
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1. 了解 Context 的作用
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2. 熟悉 Context 初始化流程
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3. 深入理解不同应用组件之间 Context 的区别
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#### 问题
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1. 应用里面有多少个 Context？不同的 Context 之间有什么区别？
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2. Activity 里的 this 和 getBaseContext 有什么区别？
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3. getApplication 和 getApplicationContext 有什么区别？
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4. 应用组件的构造，onCreate、attachBaseContext 调用顺序？
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```java
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class ContextImpl extends Context {
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final ActivityThread mMainThread;
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final LoadedApk mPackageInfo;
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private final ResourcesManager mResourcesManager;
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private final Resource mResources;
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private Resources.Theme mTheme = null;
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private PackageManager mPackageManager;
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final Object[] mServiceCache = SystemServiceRegistry.createServiceCache();
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}
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```
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#### Context 是在哪创建的？
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Application ：
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1. 继承关系
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Application <- ContextWrapper <- Context
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2. 调用顺序
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\<init> -> attachBaseContext -> onCreate
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Activity：
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```java
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private Activity performLaunchActivity() {
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Activity activity = null;
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activity = mInstrumentation.newActivity();
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Application app = r.packageInfo.makeApplication();
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Context appContext = createBaseContextForActivity(r, activity);
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activity.attach(appContext, app, ...);
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activity.onCreate();
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return activity;
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}
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```
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1. 继承关系
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Activity <- ContextThemeWrapper <- ContextWrapper
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2. 调用顺序
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\<init> -> attachBaseContext -> onCreate
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Service:
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```java
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private void handleCreateService(CreateServiceData data) {
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Service service = null;
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service = (Service) cl.loadClass(data.info.name).newInstance();
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ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
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context.setOuterContext(service);
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Application app = packageInfo.makeApplication();
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service.attach(context, app);
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service.onCreate();
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}
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```
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