Android6.0 旋转屏幕（三）应用是否要重启



上篇博客我们分析了WMS中的updateRotationUnchecked函数，当旋转角度有变化时会调用sendNewConfiguration函数。这篇博客我们就来分析下这个函数。

    public void updateRotationUnchecked(boolean alwaysSendConfiguration, boolean forceRelayout) {
        if(DEBUG_ORIENTATION) Slog.v(TAG, "updateRotationUnchecked("
                   + "alwaysSendConfiguration=" + alwaysSendConfiguration + ")");

        long origId = Binder.clearCallingIdentity();
        boolean changed;
        synchronized(mWindowMap) {
            changed = updateRotationUncheckedLocked(false);
            if (!changed || forceRelayout) {
                getDefaultDisplayContentLocked().layoutNeeded = true;
                performLayoutAndPlaceSurfacesLocked();
            }
        }

        if (changed || alwaysSendConfiguration) {
            sendNewConfiguration();
        }

        Binder.restoreCallingIdentity(origId);
    }

AMS的updateConfiguration函数

这个函数最后是调用了AMS的updateConfiguration函数。

    void sendNewConfiguration() {
        try {
            mActivityManager.updateConfiguration(null);
        } catch (RemoteException e) {
        }
    }

我们再来看AMS的updateConfiguration函数，这个时候参数values是空，所以会调用WMS的computeNewConfiguration来获取一些配置信息。然后会调用updateConfigurationLocked函数。

    public void updateConfiguration(Configuration values) {
        enforceCallingPermission(android.Manifest.permission.CHANGE_CONFIGURATION,
                "updateConfiguration()");

        synchronized(this) {
            if (values == null && mWindowManager != null) {
                // sentinel: fetch the current configuration from the window manager
                values = mWindowManager.computeNewConfiguration();
            }

            if (mWindowManager != null) {
                mProcessList.applyDisplaySize(mWindowManager);
            }

            final long origId = Binder.clearCallingIdentity();
            if (values != null) {
                Settings.System.clearConfiguration(values);
            }
            updateConfigurationLocked(values, null, false, false);
            Binder.restoreCallingIdentity(origId);
        }
    }

我们再来看updateConfigurationLocked函数，先把Configuration数据保存在mConfiguration，然后会调用ActivityThread的scheduleConfigurationChanged。紧接着会发送ACTION_CONFIGURATION_CHANGED广播，然后获取当前最上面活动的Activity，调用ActivityStack的ensureActivityConfigurationLocked函数和ActivityStackSupervisor的ensureActivitiesVisibleLocked函数。

    boolean updateConfigurationLocked(Configuration values,
            ActivityRecord starting, boolean persistent, boolean initLocale) {
        int changes = 0;

        if (values != null) {
            Configuration newConfig = new Configuration(mConfiguration);
            changes = newConfig.updateFrom(values);
            if (changes != 0) {
                if (!initLocale && values.locale != null && values.userSetLocale) {
                    final String languageTag = values.locale.toLanguageTag();
                    SystemProperties.set("persist.sys.locale", languageTag);
                    mHandler.sendMessage(mHandler.obtainMessage