我的问题是:
我想知道 xLayout(或一般的 ViewGroup)何时从 XML 添加 subview ？我所说的“何时”是指在代码的哪个点，在 UI 工具包的“遍历”的哪个“ channel ”中？
我应该覆盖 xLayout 或 ViewGroup 的哪个方法？

我做了功课:我看过"Writing Custom Views For Android"在上次 Google I/O 中提出(由 Adam Powell 和 Romain Guy)，我已经阅读了 Adam Powell 对此 Google+ post 的评论.

最佳答案

Looking for the exact point in Android's source code where children are added.

@Override
public void setContentView(int layoutResID) {
    if (mContentParent == null) {
        installDecor();
    } else {
        mContentParent.removeAllViews();
    }
    mLayoutInflater.inflate(layoutResID, mContentParent);
    final Callback cb = getCallback();
    if (cb != null && !isDestroyed()) {
        cb.onContentChanged();
    }
}

I want to know what happens exactly after I set content view to an XML file that contains a custom view. Afer the constructor there has to be a part in the code where the custom view "parse/read/inflate/convert" XML-declared child views to actual views ! (comment by JohnTube)

// Inflate a new view hierarchy from the specified XML node.
public View inflate(XmlPullParser parser, ViewGroup root, boolean attachToRoot)

// Recursive method used to descend down the xml hierarchy and instantiate views,     
// instantiate their children, and then call onFinishInflate().
void rInflate(XmlPullParser parser, View parent, final AttributeSet attrs,
       boolean finishInflate) throws XmlPullParserException, IOException

temp = createViewFromTag(root, name, attrs);

View createViewFromTag(View parent, String name, AttributeSet attrs) {
    ....
    ....
    if (view == null) {
        if (-1 == name.indexOf('.')) {
            view = onCreateView(parent, name, attrs);
        } else {
            view = createView(name, null, attrs);
        }
    }
    ....
}

android.widget: Button, TextView etc.

android.view: ViewStub. SurfaceView, TextureView etc.

android.webkit: WebView

protected View onCreateView(String name, AttributeSet attrs) throws ClassNotFoundException {
    return createView(name, "android.view.", attrs);
}

<android.widget.LinearLayout
    ...
    ... />  

<MyCustomView ../>

public final View createView(String name, String prefix, AttributeSet attrs)
                            throws ClassNotFoundException, InflateException {

    // Try looking for the constructor in cache
    Constructor<? extends View> constructor = sConstructorMap.get(name);
    Class<? extends View> clazz = null;

    try {
        if (constructor == null) {
            // Class not found in the cache, see if it's real, and try to add it
            clazz = mContext.getClassLoader().loadClass(
                 prefix != null ? (prefix + name) : name).asSubclass(View.class);
            ....
            // Get constructor   
            constructor = clazz.getConstructor(mConstructorSignature);
            sConstructorMap.put(name, constructor);
        } else {
            ....
        }

        Object[] args = mConstructorArgs;
        args[1] = attrs;

        // Obtain an instance
        final View view = constructor.newInstance(args);
        ....

        // We finally have a view!
        return view;
    }
    // A bunch of catch blocks: 
        - if the only constructor defined is `CustomView(Context)` - NoSuchMethodException
        - if `com.my.package.CustomView` doesn't extend View - ClassCastException
        - if `com.my.package.CustomView` is not found - ClassNotFoundException

    // All these catch blocks throw the often seen `InflateException`.
}

关于android - 何时将 subview 从 XML 添加到 Layout/ViewGroup，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/17334078/