setContentView中的源码探索（未修订）

来源：互联网发布：显卡超频软件哪里编辑：程序博客网时间：2024/06/08 16:49

PhoneWindow是window的子类
DecorView是整个ViewTree的最顶层View
DecorView和加载了我们提供的布局
ViewRootImpl则负责渲染视图,WindowManager和DecorView的纽带

基于android 25源码进行探索，先从setContentView中进行探索

    public void setContentView(@LayoutRes int layoutResID) {        getWindow().setContentView(layoutResID);        initWindowDecorActionBar();    }    public Window getWindow() {        return mWindow;    }    private Window mWindow;

可以看到主要是从getwindow调用的方法，而getWindow就直接返回了一个window，可以看出window就是一个抽象类,我们的找出真正的实现类，用AS搜索了一下，看到在attach方法中找了实现类

 final void attach(...) {        attachBaseContext(context);        mFragments.attachHost(null /*parent*/);        mWindow = new PhoneWindow(this, window);        mWindow.setWindowControllerCallback(this);        mWindow.setCallback(this);        mWindow.setOnWindowDismissedCallback(this);        mWindow.getLayoutInflater().setPrivateFactory(this);      ...    mWindow.setWindowManager(                (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),                mToken, mComponent.flattenToString(),                (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);        if (mParent != null) {            mWindow.setContainer(mParent.getWindow());        }        mWindowManager = mWindow.getWindowManager();    }

PhoneWindow就是window的实现类，接着我们就重点讲解这里，因为就是这里把我们的View给填充进入了

    public PhoneWindow(Context context, Window preservedWindow) {        this(context); ...        if (preservedWindow != null) {            mDecor = (DecorView) preservedWindow.getDecorView();            mElevation = preservedWindow.getElevation();       ...        }...    }    public final View getDecorView() {        if (mDecor == null || mForceDecorInstall) {            installDecor();        }        return mDecor;    }   private void installDecor() {        if (mDecor == null) {            mDecor = generateDecor(-1);        } else {            mDecor.setWindow(this);        }        if (mContentParent == null) {            mContentParent = generateLayout(mDecor);            final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(                    R.id.decor_content_parent);            if (decorContentParent != null) {                mDecorContentParent = decorContentParent;                mDecorContentParent.setWindowCallback(getCallback());                if (mDecorContentParent.getTitle() == null) {                    mDecorContentParent.setWindowTitle(mTitle);                }            } else {                mTitleView = (TextView) findViewById(R.id.title);                if (mTitleView != null) {                    if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {                        final View titleContainer = findViewById(R.id.title_container);                        if (titleContainer != null) {                            titleContainer.setVisibility(View.GONE);                        } else {                            mTitleView.setVisibility(View.GONE);                        }                        mContentParent.setForeground(null);                    } else {                        mTitleView.setText(mTitle);                    }                }            }            if (mDecor.getBackground() == null && mBackgroundFallbackResource != 0) {                mDecor.setBackgroundFallback(mBackgroundFallbackResource);            }    }

PhoneWindow构造方法创建了DecorView，而我前面所说DecorView是整个ViewTree的最顶层View，installDecor中也设置了标题栏和内容

generateDecor

  protected DecorView generateDecor(int featureId) {      ...        return new DecorView(context, featureId, this, getAttributes());    }

我们在看看具体是怎么填充我们提供的View的

generateLayout

  protected ViewGroup generateLayout(DecorView decor) {        ...       mDecor.startChanging();        mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);        ...  }void onResourcesLoaded(LayoutInflater inflater, int layoutResource) {        mDecorCaptionView = createDecorCaptionView(inflater);        //加载layoutResource        final View root = inflater.inflate(layoutResource, null);        if (mDecorCaptionView != null) {            if (mDecorCaptionView.getParent() == null) {                addView(mDecorCaptionView,                        new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));            }            mDecorCaptionView.addView(root,                    new ViewGroup.MarginLayoutParams(MATCH_PARENT, MATCH_PARENT));        } else {            // Put it below the color views.            addView(root, 0, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));        }        mContentRoot = (ViewGroup) root;        initializeElevation();    }

从generateLayout中的onResourcesLoaded方法中，终于看到了我们想看到的东西。

到目前为止，通过setContentView方法，创建了DecorView和加载了我们提供的布局，但是我们并没有被window添加

Window添加DecorView

每一个Activity组件都有一个关联的Window对象，用来描述一个应用程序窗口。每一个应用程序窗口内部又包含有一个View对象，用来描述应用程序窗口的视图。

首先，在ActivityThread#handleLaunchActivity中启动Activity，在这里面会调用到Activity#onCreate方法，从而完成上面所述的DecorView创建动作，当onCreate()方法执行完毕，在handleLaunchActivity方法会继续调用到ActivityThread#handleResumeActivity方法，我们看看这个方法的源码：

  final void handleResumeActivity(...) {      ...        //这里会调用到onResume()方法        r = performResumeActivity(token, clearHide, reason);            ...                final Activity a = r.activity;                r.window = r.activity.getWindow();// 获得window对象                View decor = r.window.getDecorView();// 获得DecorView对象                decor.setVisibility(View.INVISIBLE);                ViewManager wm = a.getWindowManager(); // 获得windowManager对象                WindowManager.LayoutParams l = r.window.getAttributes();                a.mDecor = decor;                l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;                l.softInputMode |= forwardBit;                if (a.mVisibleFromClient && !a.mWindowAdded) {                    a.mWindowAdded = true;                    wm.addView(decor, l);// 调用addView方法                }        }    }

就在这个方法里，终于看到windowManager将decorView添加进去了,当你准备点进去看addView 方法时，你没猜错它(ViewManager)又TM是抽象或者接口…windowManager都是抽象类，那到底谁实现了他呢…
还记得我为啥说每一个Activity组件都有一个关联的Window对象，请回到我上面说的activity->attach

//设置WindowManager  mWindow.setWindowManager(                (WindowManager)context.getSystemService(Context.WINDOW_SERVICE),                mToken, mComponent.flattenToString(),                (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);   public void setWindowManager(WindowManager wm, IBinder appToken, String appName,            boolean hardwareAccelerated) {      ...        if (wm == null) {            wm = (WindowManager)mContext.getSystemService(Context.WINDOW_SERVICE);        }        mWindowManager = ((WindowManagerImpl)wm).createLocalWindowManager(this);    }

看到这里知道是谁了吧，就是他 WindowManagerImpl,赶紧看看他的addView方法中写了啥

WindowManagerImpl->addView

   @Override    public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {        applyDefaultToken(params);        mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);    }  public void addView(View view, ViewGroup.LayoutParams params,            Display display, Window parentWindow) {        final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams) params;        //创建ViewRootImpl            root = new ViewRootImpl(view.getContext(), display);            view.setLayoutParams(wparams);            mViews.add(view);            mRoots.add(root);            mParams.add(wparams);        //ViewRootImpl.setView            root.setView(view, wparams, panelParentView);    }

ViewRootImpl#setView方法，并把DecorView作为参数传递进去，在这个方法内部，会通过跨进程的方式向WMS（WindowManagerService）发起一个调用，从而将DecorView最终添加到Window上，在这个过程中，ViewRootImpl、DecorView和WMS会彼此关联，至于详细过程这里不展开来说了

ViewRootImpl对他不熟悉的可以看看 Android中的ViewRootImpl类源码解析

参考Android View源码解读：浅谈DecorView与ViewRootImpl

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