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111 lines
2.4 KiB
111 lines
2.4 KiB
---
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谈谈你对 Application 的理解
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---
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1. 了解 Application 的作用
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2. 熟悉 Application 的类继承关系以及生命周期
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3. 深入理解 Application 的初始化原理
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#### Application 有什么用？
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1. 应用进程初始化操作
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2. 提供上下文
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#### Application 怎么初始化？
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```java
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// ActivityThread#attach
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private void attach() {
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final IActivityManager mgr = ActivityManagerNative.getDefault();
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mgr.attachAppliation(mAppThread);
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}
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```
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```java
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// AMS
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public final void attachApplication(IApplicationThread thread) {
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synchronized(this) {
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attachApplicationLocked(thread, callingPid);
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}
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}
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```
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```java
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boolean attachApplicationLocked(IApplicationThread thread, ...) {
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//...
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// IPC 调用，回到应用进程
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thread.bindApplication(...);
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}
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```
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```java
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public final void bindApplication(...) {
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AppBindData data = new AppBindData();
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//...
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sendMessage(H.BIND_APPLICATION, data);
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}
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```
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```java
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private void handleBindApplication(AppBindData data) {
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// LoadedApk
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data.info = getPackageInfoNoCheck(data.appInfo, data.compatInfo);
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// LoadedApk#makeApplication
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Application app = data.info.makeApplication(...);
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// Application#onCreate
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mInstrumentation.callApplicationOnCreate(app);
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}
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```
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```java
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public Application makeApplication(...) {
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if(mApplication != null) {
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return mApplication;
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}
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ContextImpl appContext = ContextImpl.createAppContext(...);
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app = mActivityThread.mInstrumentation.newApplication(...);
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return app;
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}
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```
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```java
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Application new Application(ClassLoader cl, String className, Context context) {
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return newApplication(cl.loadClass(className), context);
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}
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```
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```java
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static Application newApplication(Class<?> clazz, Context context) {
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Application app = (Application)clazz.newInstance();
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app.attach(context);
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return app;
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}
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```
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```java
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final void attach(Context context) {
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attachBaseContext(context);
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}
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```
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总结一下 Application 的初始化：
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1. new Application()
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2. Application.attachBaseContext()
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3. Application.onCreate()
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**不要执行耗时操作**
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```java
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boolean attachApplicationLocked(IApplicationThread thread, ...) {
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//...
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// IPC 调用，回到应用进程
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thread.bindApplication(...);
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//...
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// 启动待启动的组件
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mStackSupervisor.attachApplicationLocked(...);
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mServices.attachApplicationLocked(app, processName);
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sendPendingBroadcastsLocked(app);
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}
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```
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