我们经常实用的LayoutInflater这样用：

View view = LayoutInflater.from(context).inflate(R.layout.resource,root,flase);

进入inflate进行源码解析

public View inflate(@LayoutRes int resource, [@Nullable](https://my.oschina.net/u/2896689) ViewGroup root, boolean attachToRoot) {    final Resources res = getContext().getResources();    if (DEBUG) {        Log.d(TAG, "INFLATING from resource: \"" + res.getResourceName(resource) + "\" ("                + Integer.toHexString(resource) + ")");    }    final XmlResourceParser parser = res.getLayout(resource);    try {        return inflate(parser, root, attachToRoot);    } finally {        parser.close();    }}

主要做了一件事： 建立XmlResourceParser为后面解析xml文件做准备

继续进入inflate(为方便阅读删除一些调试代码和异常捕获代码，只保留了核心代码)

public View inflate(XmlPullParser parser, [@Nullable](https://my.oschina.net/u/2896689) ViewGroup root, boolean attachToRoot) {    synchronized (mConstructorArgs) {        final Context inflaterContext = mContext;        final AttributeSet attrs = Xml.asAttributeSet(parser);        Context lastContext = (Context) mConstructorArgs[0];        mConstructorArgs[0] = inflaterContext;        View result = root;        try {            if (TAG_MERGE.equals(name)) {                if (root == null || !attachToRoot) {                    throw new InflateException("
     can be used only with a valid "                            + "ViewGroup root and attachToRoot=true");                }                rInflate(parser, root, inflaterContext, attrs, false);            } else {                // Temp is the root view that was found in the xml                final View temp = createViewFromTag(root, name, inflaterContext, attrs);                ViewGroup.LayoutParams params = null;                if (root != null) {                    // Create layout params that match root, if supplied                    params = root.generateLayoutParams(attrs);                    if (!attachToRoot) {                        // Set the layout params for temp if we are not                        // attaching. (If we are, we use addView, below)                        temp.setLayoutParams(params);                    }                }                rInflateChildren(parser, temp, attrs, true);                // We are supposed to attach all the views we found (int temp)                // to root. Do that now.                if (root != null && attachToRoot) {                    root.addView(temp, params);                }                // Decide whether to return the root that was passed in or the                // top view found in xml.                if (root == null || !attachToRoot) {                    result = temp;                }            }        } catch (XmlPullParserException e) {...}

`

这段源码中看出主要逻辑为：

1、判断xml局中标签是否为merge,如果是则走rInflate直接去遍历创建xml所有的View对象

2、进入非merge的逻辑里面，会创建根View，主要的过程在createViewFromTag创建View

3、rInflateChildren创建子View

3、接下来如果传入的root不为null,并且attachToRoot==false，则对创建好的View的ViewGroup.LayoutParams是通过generateLayoutParams生成的。

4、如果root不为null,attachToRoot==true，那么则将整个View作为一个子View加入到父布局中，否则直接返回这个View

继续进入createViewFromTag源码（为方便理解去除异常彩蛋和ignoreThemeAttr属性的代码） `

View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,        boolean ignoreThemeAttr) {    if (name.equals("view")) {        name = attrs.getAttributeValue(null, "class");    }    try {        View view;        if (mFactory2 != null) {            view = mFactory2.onCreateView(parent, name, context, attrs);        } else if (mFactory != null) {            view = mFactory.onCreateView(name, context, attrs);        } else {            view = null;        }        if (view == null && mPrivateFactory != null) {            view = mPrivateFactory.onCreateView(parent, name, context, attrs);        }        if (view == null) {            final Object lastContext = mConstructorArgs[0];            mConstructorArgs[0] = context;            try {                if (-1 == name.indexOf('.')) {                    view = onCreateView(parent, name, attrs);                } else {                    view = createView(name, null, attrs);                }            } finally {                mConstructorArgs[0] = lastContext;            }        }		……

这段源码中看出主要逻辑为：

1、标签为view时获取view的class属性作为要创建的View的name(注意View和view的区别)

2、主要通过不同的Factory通过**createView() **去创建View

3、其中有个逻辑需要在onCreateView执行之前判断是否存在“.”，存在点则表示不是系统的View,需要单独处理，在后面createView的代码可以看到有这样一段加入了“android.view.”，后面会讲这句的用途。

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

继续进入onCreateView源码

public final View createView(String name, String prefix, AttributeSet attrs)        throws ClassNotFoundException, InflateException {    Constructor
     constructor = sConstructorMap.get(name);    if (constructor != null && !verifyClassLoader(constructor)) {        constructor = null;        sConstructorMap.remove(name);    }    Class
     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);            if (mFilter != null && clazz != null) {                boolean allowed = mFilter.onLoadClass(clazz);                if (!allowed) {                    failNotAllowed(name, prefix, attrs);                }            }            constructor = clazz.getConstructor(mConstructorSignature);            constructor.setAccessible(true);            sConstructorMap.put(name, constructor);        } else {            // If we have a filter, apply it to cached constructor            if (mFilter != null) {                // Have we seen this name before?                Boolean allowedState = mFilterMap.get(name);                if (allowedState == null) {                    // New class -- remember whether it is allowed                    clazz = mContext.getClassLoader().loadClass(                            prefix != null ? (prefix + name) : name).asSubclass(View.class);                    boolean allowed = clazz != null && mFilter.onLoadClass(clazz);                    mFilterMap.put(name, allowed);                    if (!allowed) {                        failNotAllowed(name, prefix, attrs);                    }                } else if (allowedState.equals(Boolean.FALSE)) {                    failNotAllowed(name, prefix, attrs);                }            }        }        Object lastContext = mConstructorArgs[0];        if (mConstructorArgs[0] == null) {            // Fill in the context if not already within inflation.            mConstructorArgs[0] = mContext;        }        Object[] args = mConstructorArgs;        args[1] = attrs;        final View view = constructor.newInstance(args);        if (view instanceof ViewStub) {            // Use the same context when inflating ViewStub later.            final ViewStub viewStub = (ViewStub) view;            viewStub.setLayoutInflater(cloneInContext((Context) args[0]));        }        mConstructorArgs[0] = lastContext;        return view;    }

这段源码虽然很复杂，但主要做的事就是 通过反射的方式去加载一个View类

这段代码就能解释上面为什么要加“android.view.”，这段代码会将系统的View的路径拼起来，把类加载进来；

clazz = mContext.getClassLoader().loadClass(prefix != null ? (prefix + name) : name).asSubclass(View.class)

到现在，我们讲完了对于xml根view的创建逻辑，还有个很重要的流程没有讲：

子View创建 的逻辑在inflate中的rInflateChildren

进入rInflateChildren，这里依然会进入到rInflate()

void rInflate(XmlPullParser parser, View parent, Context context,        AttributeSet attrs, boolean finishInflate) throws XmlPullParserException, IOException {    final int depth = parser.getDepth();    int type;    boolean pendingRequestFocus = false;    while (((type = parser.next()) != XmlPullParser.END_TAG ||            parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) {        if (type != XmlPullParser.START_TAG) {            continue;        }        final String name = parser.getName();        if (TAG_REQUEST_FOCUS.equals(name)) {            pendingRequestFocus = true;            consumeChildElements(parser);        } else if (TAG_TAG.equals(name)) {            parseViewTag(parser, parent, attrs);        } else if (TAG_INCLUDE.equals(name)) {            if (parser.getDepth() == 0) {                throw new InflateException("
     cannot be the root element");            }            parseInclude(parser, context, parent, attrs);        } else if (TAG_MERGE.equals(name)) {            throw new InflateException("
     must be the root element");        } else {            final View view = createViewFromTag(parent, name, context, attrs);            final ViewGroup viewGroup = (ViewGroup) parent;            final ViewGroup.LayoutParams params = viewGroup.generateLayoutParams(attrs);            rInflateChildren(parser, view, attrs, true);            viewGroup.addView(view, params);        }    }    if (pendingRequestFocus) {        parent.restoreDefaultFocus();    }    if (finishInflate) {        parent.onFinishInflate();    }}

这段源码的大致可以总结为：

1、总的逻辑为获取xml文档的层级数，解析每一层级的数据

2、解析过程首先进行View的合理性校验，include、merge等标签；

3、最后还是会走到createViewFromTag 创建出 View 对象，如果是 ViewGroup则递归调用rInflateChildren

到这里基本上所有的流程讲完了，这里总结一下加载流程：

**1、拿到Xml解析对象，为后续解析做准备

2、对整个Xml中的布局控制处理由 root、attachToRoot这两个参数控制

3、解析子View，通过createViewFromTag创建实例对象**