Android 性能优化—— 启动优化提升60%

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<!-- Base application theme. -->  
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">  
        <item name="android:windowFullscreen">true</item>  
        <item name="android:windowIsTranslucent">true</item>  
    </style>

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<!-- Base application theme. -->  
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">  
    <item name="android:windowBackground">@mipmap/launch</item>   //闪屏页图片  
    <item name="android:windowFullscreen">true</item>  
    <item name="android:windowContentOverlay">@null</item>  
</style>

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C:\Android\Demo>adb shell am start -S -W com.example.moneyqian.demo/com.example.moneyqian.demo.MainActivity  
Stopping: com.example.moneyqian.demo  
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.example.moneyqian.demo/.MainActivity }  
Status: ok  
Activity: com.example.moneyqian.demo/.MainActivity  
ThisTime: 2247  
TotalTime: 2247  
WaitTime: 2278  
Complete

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//ActivityRecord  
  
private void reportLaunchTimeLocked(final long curTime) {  
    ``````  
    final long thisTime = curTime - displayStartTime;  
    final long totalTime = stack.mLaunchStartTime != 0 ?  
                 (curTime - stack.mLaunchStartTime) : thisTime;  
}

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new Thread(new Runnable() {  
    @Override  
    public void run() {  
        //设置线程的优先级，不与主线程抢资源  
        Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);  
        //子线程初始化第三方组件  
        Thread.sleep(5000);//建议延迟初始化，可以发现是否影响其它功能，或者是崩溃！  
    }  
}).start();

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handler.postDelayed(new Runnable() {  
    @Override  
    public void run() {  
        //延迟初始化组件  
    }  
}, 3000);

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//Application  
  
@Override  
protected void attachBaseContext(Context base) {  
    super.attachBaseContext(base);  
    SPUtil.putLong("application_attach_time",   
        System.currentTimeMillis());//记录Application初始化时间  
}

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//入口Activity  
  
@Override  
public void onWindowFocusChanged(boolean hasFocus) {  
    super.onWindowFocusChanged(hasFocus);  
  
      long appAttachTime = SPUtil.getLong("application_attach_time");  
      long diffTime = System.currentTimeMillis() - appAttachTime;//从application到入口Acitity的时间  
  
     //所以闪屏页展示的时间为 2000ms - diffTime.  
}

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1. 广告页的下载，由于这个是一个异步过程，所以往往不知道加载到页面的合适时机。  
  2. 广告页的保存，因为保存是 I/O 流操作，很有可能被用户中断，下次拿到破损的图片。

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1.  在入口 Acitivity 中开启 IntentService 来下载广告页。 或者是其它异步下载操作。  
  2.  在广告页图片 文件流完全写入后 记录图片大小，或者记录一个标识。

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//ActivityStack  
final void startActivityLocked(ActivityRecord r, boolean newTask, boolean keepCurTransition,  
        ActivityOptions options) {  
  
    ``````  
    if (!isHomeStack() || numActivities() > 0) {//HOME_STACK表示Launcher桌面所在的Stack  
        // 1.首先当前启动栈不在Launcher的桌面栈里,并且当前系统已经有激活过Activity  
  
        boolean doShow = true;  
        if (newTask) {  
            // 2.要将该Activity组件放在一个新的任务栈中启动  
            if ((r.intent.getFlags() & Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED) != 0) {  
                resetTaskIfNeededLocked(r, r);  
                doShow = topRunningNonDelayedActivityLocked(null) == r;  
            }  
        } else if (options != null && options.getAnimationType()  
                == ActivityOptions.ANIM_SCENE_TRANSITION) {  
            doShow = false;  
        }  
        if (r.mLaunchTaskBehind) {  
            //3. 热启动，不需要启动窗口  
          mWindowManager.setAppVisibility(r.appToken, true);  
            ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);  
        } else if (SHOW_APP_STARTING_PREVIEW && doShow) {  
  
            ``````  
            //4. 显示启动窗口  
            r.showStartingWindow(prev, showStartingIcon);  
        }  
    } else {  
        // 当前启动的是桌面Launcher (开机启动)  
        // If this is the first activity, don't do any fancy animations,  
        // because there is nothing for it to animate on top of.  
        ``````  
    }  
  
}

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//ActivityRecord  
void showStartingWindow(ActivityRecord prev, boolean createIfNeeded) {  
    final CompatibilityInfo compatInfo =  
            service.compatibilityInfoForPackageLocked(info.applicationInfo);  
    final boolean shown = service.mWindowManager.setAppStartingWindow(  
            appToken, packageName, theme, compatInfo, nonLocalizedLabel, labelRes, icon,  
            logo, windowFlags, prev != null ? prev.appToken : null, createIfNeeded);  
    if (shown) {  
        mStartingWindowState = STARTING_WINDOW_SHOWN;  
    }  
}

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//WindowManagerService  
@Override  
public boolean setAppStartingWindow(IBinder token, String pkg,  
        int theme, CompatibilityInfo compatInfo,  
        CharSequence nonLocalizedLabel, int labelRes, int icon, int logo,  
        int windowFlags, IBinder transferFrom, boolean createIfNeeded) {  
  
    synchronized(mWindowMap) {  
  
        //1. 启动窗口也是需要token的  
        AppWindowToken wtoken = findAppWindowToken(token);  
  
        //2. 如果已经设置过启动窗口了，不继续处理  
        if (wtoken.startingData != null) {  
            return false;  
        }  
  
        if (theme != 0) {  
            AttributeCache.Entry ent = AttributeCache.instance().get(pkg, theme,  
                    com.android.internal.R.styleable.Window, mCurrentUserId);  
  
           //3. 一堆代码对主题判断，不符合要求则不显示启动窗口（如透明主题）  
            if (windowIsTranslucent) {  
                return false;  
            }  
            if (windowIsFloating || windowDisableStarting) {  
                return false;  
            }  
            ``````  
        }  
  
        //4. 创建StartingData，并且通过Handler发送消息  
  
        wtoken.startingData = new StartingData(pkg, theme, compatInfo, nonLocalizedLabel,  
                labelRes, icon, logo, windowFlags);  
        Message m = mH.obtainMessage(H.ADD_STARTING, wtoken);  
  
        mH.sendMessageAtFrontOfQueue(m);  
    }  
    return true;  
}

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//WindowManagerService --> H   
  
public void handleMessage(Message msg) {  
    switch (msg.what) {  
  
        case ADD_STARTING: {  
            final AppWindowToken wtoken = (AppWindowToken)msg.obj;  
            final StartingData sd = wtoken.startingData;  
  
            View view = null;  
            try {  
                final Configuration overrideConfig = wtoken != null && wtoken.mTask != null  
                        ? wtoken.mTask.mOverrideConfig : null;  
                view = mPolicy.addStartingWindow(wtoken.token, sd.pkg, sd.theme,  
                    sd.compatInfo, sd.nonLocalizedLabel, sd.labelRes, sd.icon, sd.logo,  
                    sd.windowFlags, overrideConfig);  
            } catch (Exception e) {  
                Slog.w(TAG_WM, "Exception when adding starting window", e);  
            }  
  
            ``````  
  
        } break;  
}

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//PhoneWindowManager  
@Override  
public View addStartingWindow(IBinder appToken, String packageName, int theme,  
        CompatibilityInfo compatInfo, CharSequence nonLocalizedLabel, int labelRes,  
        int icon, int logo, int windowFlags, Configuration overrideConfig) {  
  
     //可以通过SHOW_STARTING_ANIMATIONS设置不显示启动窗口  
    if (!SHOW_STARTING_ANIMATIONS) {  
        return null;  
    }  
    WindowManager wm = null;  
    View view = null;  
  
    //1. 获取上下文Context和主题theme以及标题  
    Context context = mContext;  
    if (theme != context.getThemeResId() || labelRes != 0) {  
        try {  
            context = context.createPackageContext(packageName, 0);  
            context.setTheme(theme);  
        } catch (PackageManager.NameNotFoundException e) {  
            // Ignore  
        }  
    }  
  
    //2. 创建PhoneWindow 用来显示  
    final PhoneWindow win = new PhoneWindow(context);  
    win.setIsStartingWindow(true);  
  
    //3. 设置当前窗口type和flag,源码注释中描述的很清晰...  
    win.setType(  
        WindowManager.LayoutParams.TYPE_APPLICATION_STARTING);  
  
    win.setFlags(...);  
  
    ``````  
    view = win.getDecorView();  
  
    //4. WindowManager的绘制流程  
    wm.addView(view, params);  
    return view.getParent() != null ? view : null;  
}