LayoutInflater.inflate源码

1.LayoutInflater.form方法

    public static LayoutInflater from(Context context) {
        LayoutInflater LayoutInflater =
                (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (LayoutInflater == null) {
            throw new AssertionError("LayoutInflater not found.");
        }
        return LayoutInflater;
    }

2.inflate方法

 public View inflate(@LayoutRes int resource, @Nullable ViewGroup root) {
        return inflate(resource, root, root != null);
    }
public View inflate(XmlPullParser parser, @Nullable ViewGroup root) {
        return inflate(parser, root, root != null);
    }
public View inflate(@LayoutRes int resource, @Nullable ViewGroup root,       boolean attachToRoot) {
 return inflate(res.getLayout(resource), root, attachToRoot);
}
//这三个方法都调用第四个方法
    public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
                    // ....前面的都是一些非核心代码
                    final View temp = createViewFromTag(root, name, inflaterContext, attrs);//创建view
                    ViewGroup.LayoutParams params = null;
                    if (root != null) {//如果root!=null 则获取temp宽高信息
                        params = root.generateLayoutParams(attrs);
                        if (!attachToRoot) {//如果attachToRoot==false 则temp设置宽高
                            temp.setLayoutParams(params);
                        }
                    }
                    if (root != null && attachToRoot) {//如果root!=null 并attachToRoot=true 直接添加view
                        root.addView(temp, params);
                    }
//如果root == null 或attachToRoot=true 直接返回view
                    if (root == null || !attachToRoot) {
                        result = temp;
                    }
                }
            return result;
        }
    }

3.总结

如果root!=null以及attachToRoot==false 则根据XML的根布局宽高设置根布局的宽高
如果root!=null 并attachToRoot=true 直接添加view(view也会根据XML的根布局宽高设置根布局的宽高)
如果root == null 或attachToRoot=true 直接返回view,不会设置根布局的宽高

1)RecyclerView的item

LayoutInflater.from(this).inflate(R.layout.xxx, parent, false)

2)直接添加

LayoutInflater.from(this).inflate(R.layout.xxx,父view,true);

4.AsyncLayoutInflater类

//封装了一个LayoutInflater,可异步加载
//因为LayoutInflater解析xml也是需要耗时的
new AsyncLayoutInflater(this).inflate(@LayoutRes int resid, @Nullable ViewGroup parent, @NonNull AsyncLayoutInflater.OnInflateFinishedListener callback);
//AsyncLayoutInflater异步加载完通过Handler发送消息