Activity中的setContentView(R.layout.xxx)源码分析

点进去会看到下图：

其中getWindow()是获取到Window类的唯一子类PhoneWindow的对象

找到PhoneWindow的setContentView()方法点进去：

 1 @Override
 2     public void setContentView(int layoutResID) {
 3         // Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
 4         // decor, when theme attributes and the like are crystalized. Do not check the feature
 5         // before this happens.
 6         if (mContentParent == null) {
 7             installDecor();
 8         } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
 9             mContentParent.removeAllViews();
10         }
11
12         if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
13             final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
14                     getContext());
15             transitionTo(newScene);
16         } else {
17             mLayoutInflater.inflate(layoutResID, mContentParent);
18         }
19         mContentParent.requestApplyInsets();
20         final Callback cb = getCallback();
21         if (cb != null && !isDestroyed()) {
22             cb.onContentChanged();
23         }
24     }

从上述代码中可以看出：把我们的layoutResID放在了mContentParent里面

在类中可以看出mContentParent是一个ViewGroup

点进去查看：installDecor()方法

继续跟进：generateLayout（）方法

protected ViewGroup generateLayout(DecorView decor) {
        // Apply data from current theme.

        TypedArray a = getWindowStyle();

        if (false) {
            System.out.println("From style:");
            String s = "Attrs:";
            for (int i = 0; i < R.styleable.Window.length; i++) {
                s = s + " " + Integer.toHexString(R.styleable.Window[i
![无标题.png](http://upload-images.jianshu.io/upload_images/4658633-9a3a758cbac9f8aa.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)
]) + "="
                        + a.getString(i);
            }
            System.out.println(s);
        }

        //根据style属性做一些列的判断...

      //在做一些列的判断得到layoutResource
       layoutResource = R.layout.screen_swipe_dismiss; //这里用R.layout.screen_simple来分析

        mDecor.startChanging();

        View in = mLayoutInflater.inflate(layoutResource, null);
        //把layoutResource放进decor中去
        decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
        mContentRoot = (ViewGroup) in;

        ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
        if (contentParent == null) {
            throw new RuntimeException("Window couldn't find content container view");
        }

       //......

        mDecor.finishChanging();
        //返回创建的这个布局
        return contentParent;
    }
//贴出这个布局文件

  if (mDecor == null) {
            mDecor = generateDecor();
            mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
            mDecor.setIsRootNamespace(true);
            if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
                mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
            }
        }

 protected DecorView generateDecor() {
        return new DecorView(getContext(), -1);
    }

mDecor 就是DecorView（FragmentLayout）的一个实例
所以最终的图形就是