阅读源码查看系统如何加载布局

Acticity setContentView源码阅读

public void setContentView(@LayoutRes int layoutResID) {
        getWindow().setContentView(layoutResID);
        initWindowDecorActionBar();
        }

点击去发现是个抽象类

  public abstract void setContentView(@LayoutRes int layoutResID);

1、通过getWindow()找到具体的实现类PhoneWindow

mWindow = new PhoneWindow(this, window);

2、查看PhoneWindow如何具体加载布局 继续看代码

@Override
    public void setContentView(int layoutResID) {
       
        if (mContentParent == null) {
            installDecor(); 
        } 
       mLayoutInflater.inflate(layoutResID, mContentParent);
       

3、查看installDecor(); 里面代码 返回一个DecorView，DecorView继承FrameLayout

//赋值给了Phonewindow成员变量 mDecor 

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

4、继续看里面installDecor又干了什么事情

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) {
        // 构建布局
            mContentParent = generateLayout(mDecor);
			。。。

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

       // 构建布局主要代码
    mDecor.startChanging();
        mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);
        ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
// 构建系统布局

``

标签：ViewGroup,setContentView,void,layoutResID,DecorView,源码,Android,mDecor
来源： https://blog.csdn.net/fc289738973/article/details/120418145