2019-11-11：请谈谈View.inflate和LayoutInflater.inflate的区别？

[Moosphan]

[weikano]

没区别

[hyyaoming]

1. 实际上没有区别，View.inflate实际上是对LayoutInflater.inflate做了一层包装，在功能上，LayoutInflate功能更加强大。

2. View.inflate实际上最终调用的还是LayoutInflater.inflate(@LayoutRes int resource, @nullable ViewGroup root)三个参数的方法，这里如果传入的root如果不为空，那么解析出来的View会被添加到这个ViewGroup当中去。

3. 而LayoutInflater.inflate方法则可以指定当前View是否需要添加到ViewGroup中去。

总结一下：

• 如果root为null，attachToRoot将失去作用，设置任何值都没有意义。

• 如果root不为null，attachToRoot设为true，则会给加载的布局文件的指定一个父布局，即root。

• 如果root不为null，attachToRoot设为false，则会将布局文件最外层的所有layout属性进行设置，当该view被添加到父view当中时，这些layout属性会自动生效。

• 在不设置attachToRoot参数的情况下，如果root不为null，attachToRoot参数默认为true。

不管调用的几个参数的方法，最终都会调用如下方法：

    /**
     * Inflate a new view hierarchy from the specified XML node. Throws
     * {@link InflateException} if there is an error.
     * <p>
     * <em><strong>Important</strong></em>&nbsp;&nbsp;&nbsp;For performance
     * reasons, view inflation relies heavily on pre-processing of XML files
     * that is done at build time. Therefore, it is not currently possible to
     * use LayoutInflater with an XmlPullParser over a plain XML file at runtime.
     *
     * @param parser       XML dom node containing the description of the view
     *                     hierarchy.
     * @param root         Optional view to be the parent of the generated hierarchy (if
     *                     <em>attachToRoot</em> is true), or else simply an object that
     *                     provides a set of LayoutParams values for root of the returned
     *                     hierarchy (if <em>attachToRoot</em> is false.)
     * @param attachToRoot Whether the inflated hierarchy should be attached to
     *                     the root parameter? If false, root is only used to create the
     *                     correct subclass of LayoutParams for the root view in the XML.
     * @return The root View of the inflated hierarchy. If root was supplied and
     * attachToRoot is true, this is root; otherwise it is the root of
     * the inflated XML file.
     */
    public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
        synchronized (mConstructorArgs) {
            Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate");

            final Context inflaterContext = mContext;
            final AttributeSet attrs = Xml.asAttributeSet(parser);
            Context lastContext = (Context) mConstructorArgs[0];
            mConstructorArgs[0] = inflaterContext;
            //最终返回的View
            View result = root;

            try {
                // Look for the root node.
                int type;
                while ((type = parser.next()) != XmlPullParser.START_TAG &&
                    type != XmlPullParser.END_DOCUMENT) {
                    // Empty
                }

                if (type != XmlPullParser.START_TAG) {
                    throw new InflateException(parser.getPositionDescription()
                        + ": No start tag found!");
                }

                final String name = parser.getName();

                if (DEBUG) {
                    System.out.println("**************************");
                    System.out.println("Creating root view: "
                        + name);
                    System.out.println("**************************");
                }

                if (TAG_MERGE.equals(name)) {
                    if (root == null || !attachToRoot) {
                        throw new InflateException("<merge /> 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;

                    //root不为空，并且attachToRoot为false时则给当前View设置LayoutParams
                    if (root != null) {
                        if (DEBUG) {
                            System.out.println("Creating params from root: " +
                                root);
                        }
                        // 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);
                        }
                    }

                    if (DEBUG) {
                        System.out.println("-----> start inflating children");
                    }

                    // Inflate all children under temp against its context.
                    rInflateChildren(parser, temp, attrs, true);

                    if (DEBUG) {
                        System.out.println("-----> done inflating children");
                    }

                    // We are supposed to attach all the views we found (int temp)
                    // to root. Do that now.
                    //如果root不为空，并且attachToRoot为ture，那么将解析出来当View添加到当前到root当中，最后返回root
                    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.
                    //如果root等于空，那么将解析完的布局赋值给result最后返回,大部分用的都是这个。
                    if (root == null || !attachToRoot) {
                        result = temp;
                    }
                }
            } catch (XmlPullParserException e) {
                final InflateException ie = new InflateException(e.getMessage(), e);
                ie.setStackTrace(EMPTY_STACK_TRACE);
                throw ie;
            } catch (Exception e) {
                final InflateException ie = new InflateException(parser.getPositionDescription()
                    + ": " + e.getMessage(), e);
                ie.setStackTrace(EMPTY_STACK_TRACE);
                throw ie;
            } finally {
                // Don't retain static reference on context.
                mConstructorArgs[0] = lastContext;
                mConstructorArgs[1] = null;

                Trace.traceEnd(Trace.TRACE_TAG_VIEW);
            }

            return result;
        }
    }

[nealkafuly]

主要是参数的区别

[nealkafuly]

View不用担心上下文，LayoutInflate需要Context

[gabyallen]

+!

[mlinqirong]

没有区别 view.inflate里面还是执行了LayoutInflater.inflate 只是一层封装