Android-应用启动过程

一.在桌面或抽屉显示应用图标

桌面或抽屉就是一个普通APP应用，用于显示所有应用图标含有以下intent意图的Activity会显示在桌面或抽屉<intent-filter>    <action android:name="android.intent.action.MAIN" />    <category android:name="android.intent.category.LAUNCHER" /></intent-filter>

二.点击桌面或抽屉的应用图标

Launcher.java{    ...    public void onClick(View v)        ...                 // 新建任务栈Stack,用于存放目标应用的Activity        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);        startActivity(intent)    }   }

三.startActivity(…)过程

1.启功目标应用的任务栈Stack

2.通知源应用的主线程ActivityThread-调用Activity的onPause方法

3.调用Process_start创建新进程,加入目标应用主线程ActivityThread,执行main方法

ActivityThread.java{    // java程序入口    public static void main(String[] args) {        ...        Looper.prepareMainLooper();        ActivityThread thread = new ActivityThread();        thread.attach(false);        // handle处理消息分发        if (sMainThreadHandler == null) {            sMainThreadHandler = thread.getHandler();        }        // End of event ActivityThreadMain.        Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);        Looper.loop();        throw new RuntimeException("Main thread loop unexpectedly exited");    }}

4.在目标应用主线程中loadClass加载Activity类

Instrumentation.java{ // 监控应用与系统的交互    // 创建Activity实例对象    newActivity(...)    // 调用Activity生命周期的各种方法    callActivityOnCreate(...)    callActivityOnStart(...)    callActivityOnReStart(...)    callActivityOnResume(...)    callActivityOnPause(...)    callActivityOnStop(...)    callActivityOnDestroy(...)    callActivityOnSaveInstanceState(...)    callActivityOnRestoreInstanceState(...)    ...}

5.在Activity类setContentView加载布局

Activity.java{    attach(...) {        ...        // 创建PhoneWindow extends Window类        mWindow = new PhoneWindow(this, window);        ...    }    onCreate(...){        setContentView(...)     }    setContentView(...) {        getWindow().setContentView(...);    }    getWindow(){        return mWindow;    }}PhoneWindow.java{       public void setContentView(int layoutResID) {               if (mContentParent == null) {            installDecor();// 初始化父布局mContentParent        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            mContentParent.removeAllViews();        }        if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,                    getContext());            transitionTo(newScene);        } else {            mLayoutInflater.inflate(layoutResID, mContentParent);        }        ...           }    public void setContentView(View view) {        setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));    }    public void setContentView(View view, ViewGroup.LayoutParams params) {        if (mContentParent == null) {            installDecor(); // 初始化父布局mContentParent        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            mContentParent.removeAllViews();        }        if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {            view.setLayoutParams(params);            final Scene newScene = new Scene(mContentParent, view);            transitionTo(newScene);        } else {            mContentParent.addView(view, params);        }        ...    }    // 初始化父布局mContentParent    private void installDecor() {        mForceDecorInstall = false;        if (mDecor == null) {            mDecor = generateDecor(-1);            mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);            mDecor.setIsRootNamespace(true);            if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {                mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);            }        } else {            mDecor.setWindow(this);        }        if (mContentParent == null) {            mContentParent = generateLayout(mDecor);            ...        }           }    protected ViewGroup generateLayout(DecorView decor) {        ...        ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);        ...        return contentParent;    }}

简书: http://www.jianshu.com/p/30f61733fdaf
CSDN博客: http://blog.csdn.net/qq_32115439/article/details/72905465
GitHub博客：http://lioil.win/2017/06/07/Android_Launcher.html
Coding博客：http://c.lioil.win/2017/06/07/Android_Launcher.html