Android Activity window（7.1）解析（一）

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本章介绍 activity window的组成
这里写图片描述
1、 Activity内部使用phoneWIndow来管理UI，PhoneWindow保持DecorView对象，来管理actionbar和 mian content
2、 PhoneWindow继承Window，用于管理窗口的UI display、事件分发等
3、content部分是activity的main view，当activity中调用setContentView方法时，此时是将View添加到content container部分

Activity被创建后，首先会调用Activity.attach方法，这里将创建PhoneWindow

 final void attach(Context context, ActivityThread aThread,            Instrumentation instr, IBinder token, int ident,            Application application, Intent intent, ActivityInfo info,            CharSequence title, Activity parent, String id,            NonConfigurationInstances lastNonConfigurationInstances,            Configuration config, String referrer, IVoiceInteractor voiceInteractor,            Window window) {        attachBaseContext(context);        mFragments.attachHost(null /*parent*/);        mWindow = new PhoneWindow(this, window);        mWindow.setWindowControllerCallback(this);        mWindow.setCallback(this);        mWindow.setOnWindowDismissedCallback(this);        mWindow.getLayoutInflater().setPrivateFactory(this);        if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {            mWindow.setSoftInputMode(info.softInputMode);        }        if (info.uiOptions != 0) {            mWindow.setUiOptions(info.uiOptions);        }       .......................    }

这里创建PhoneWindow对象mWindow，然后设置一些回调函数，我们知道，对UI的操作都是由PhoneWindow来管理的

下面我们看一下当activity调用setContentView方法里，PhoneWindow做了哪些操作：

PhoneWindow.java    public void setContentView(View view, ViewGroup.LayoutParams params) {        if (mContentParent == null) {            installDecor();        } 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);        }        mContentParent.requestApplyInsets();        final Callback cb = getCallback();        if (cb != null && !isDestroyed()) {            cb.onContentChanged();        }        mContentParentExplicitlySet = true;      }

这里，我们把重点放在installDecor方法上

 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);            ................     }

通过generateDecor()方法生成DecorView对象mDecor，generateLayout方法找到content container

protected ViewGroup generateLayout(DecorView decor) {       ....................       //step1        int layoutResource;        int features = getLocalFeatures();        // System.out.println("Features: 0x" + Integer.toHexString(features));        if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {            layoutResource = R.layout.screen_swipe_dismiss;        } else if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogTitleIconsDecorLayout, res, true);                layoutResource = res.resourceId;            } else {                layoutResource = R.layout.screen_title_icons;            }            // XXX Remove this once action bar supports these features.            removeFeature(FEATURE_ACTION_BAR);            // System.out.println("Title Icons!");        } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0                && (features & (1 << FEATURE_ACTION_BAR)) == 0) {            // Special case for a window with only a progress bar (and title).            // XXX Need to have a no-title version of embedded windows.            layoutResource = R.layout.screen_progress;            // System.out.println("Progress!");        } else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {            // Special case for a window with a custom title.            // If the window is floating, we need a dialog layout            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogCustomTitleDecorLayout, res, true);                layoutResource = res.resourceId;            } else {                layoutResource = R.layout.screen_custom_title;            }            // XXX Remove this once action bar supports these features.            removeFeature(FEATURE_ACTION_BAR);        } else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {            // If no other features and not embedded, only need a title.            // If the window is floating, we need a dialog layout            if (mIsFloating) {                TypedValue res = new TypedValue();                getContext().getTheme().resolveAttribute(                        R.attr.dialogTitleDecorLayout, res, true);                layoutResource = res.resourceId;            } else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {                layoutResource = a.getResourceId(                        R.styleable.Window_windowActionBarFullscreenDecorLayout,                        R.layout.screen_action_bar);            } else {                layoutResource = R.layout.screen_title;            }            // System.out.println("Title!");        } else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {            layoutResource = R.layout.screen_simple_overlay_action_mode;        } else {            // Embedded, so no decoration is needed.            layoutResource = R.layout.screen_simple;            // System.out.println("Simple!");        }//step2        mDecor.startChanging();        mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);        //step3        ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);        ..................        mDecor.finishChanging();        return contentParent;    }

1、这里在step1～step2之间的code是根据当前设置的feature来获取要加载的xml的layoutId，默认情况下加载的是R.layout.screen_simple
2、step3获取content container

到这里，activity window的大致组成讲解完毕

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