Android(安卓)View 相关源码分析之二继LayoutInflater来说

继Android View 相关源码分析之一从setContentView说起继续说

之前我们分析了setContentView方法的相关代码接下来说说LayoutInflater的方法

LayoutInflater源码分析

与setContentView相关

在PhoneWindow的generateLayout中调用了

  View in = mLayoutInflater.inflate(layoutResource, null);

LayoutInflater中获取实例化方法

  /**   * Obtains the LayoutInflater from the given context.   */  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;  }

inflate方法相关

  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) {      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();      }  }

最后发现都需要调用

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;            //定义返回值 初始化传入形参 root            View result = root;            try {                // 找到根节点                int type;                while ((type = parser.next()) != XmlPullParser.START_TAG &&                        type != XmlPullParser.END_DOCUMENT) {                }                //验证type是否为Start_Tag  保证xml文件正确                if (type != XmlPullParser.START_TAG) {                    throw new InflateException(parser.getPositionDescription()                            + ": No start tag found!");                }                //type为 root node                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)) {                    //处理 merge相关                    //root需要非空 且attachToRoot为空                    if (root == null || !attachToRoot) {                        throw new InflateException(" can be used only with a valid "                                + "ViewGroup root and attachToRoot=true");                    }                    //递归inflate 方法调用                    rInflate(parser, root, inflaterContext, attrs, false);                } else {                    //根据tag节点创建view对象                    final View temp = createViewFromTag(root, name, inflaterContext, attrs);                    ViewGroup.LayoutParams params = null;                    if (root != null) {                        if (DEBUG) {                            System.out.println("Creating params from root: " +                                    root);                        }                        //根据root生成LayoutParams                        params = root.generateLayoutParams(attrs);                        if (!attachToRoot) {                            //如果attachToRoot为flase 则调用setLayoutParams                            temp.setLayoutParams(params);                        }                    }                    if (DEBUG) {                        System.out.println("-----> start inflating children");                    }                    //递归inflate剩下的children                    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.                    if (root != null && attachToRoot) {                        //root非空且attachToRoot=true则将xml文件的root view加到形参提供的root里                        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) {                        //返回xml里解析的root view                        result = temp;                    }                }            } catch (XmlPullParserException e) {                InflateException ex = new InflateException(e.getMessage());                ex.initCause(e);                throw ex;            } catch (Exception e) {                InflateException ex = new InflateException(                        parser.getPositionDescription()                                + ": " + e.getMessage());                ex.initCause(e);                throw ex;            } finally {                // Don't retain static reference on context.                mConstructorArgs[0] = lastContext;                mConstructorArgs[1] = null;            }            Trace.traceEnd(Trace.TRACE_TAG_VIEW);            //返回参数root或xml文件里的root view            return result;        }    }

相关inflate参数的结果

inflate参数分析

相关方法解析
在Inflate中多次被调用的rInflate

   void rInflate(XmlPullParser parser, View parent, Context context,           AttributeSet attrs, boolean finishInflate) throws XmlPullParserException, IOException {       final int depth = parser.getDepth();       int type;       //XmlPullParser解析器的标准解析模式       while (((type = parser.next()) != XmlPullParser.END_TAG ||               parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) {           //找到start_tag节点           if (type != XmlPullParser.START_TAG) {               continue;           }           //获取Name标记           final String name = parser.getName();           //private static final String TAG_REQUEST_FOCUS = "requestFocus";           //处理requestFocus           if (TAG_REQUEST_FOCUS.equals(name)) {               parseRequestFocus(parser, parent);           // private static final String TAG_TAG = "tag";           //处理tag           } else if (TAG_TAG.equals(name)) {               parseViewTag(parser, parent, attrs);           //private static final String TAG_INCLUDE = "include";           //处理include           } else if (TAG_INCLUDE.equals(name)) {               //如果是根节点则抛出异常               if (parser.getDepth() == 0) {                   throw new InflateException(" cannot be the root element");               }               parseInclude(parser, context, parent, attrs);           //private static final String TAG_MERGE = "merge";           //处理merge merge需要是xml中的根节点           } 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);           }       }        //parent的所有子节点都处理完毕的时候回onFinishInflate方法       if (finishInflate) {           parent.onFinishInflate();       }   }   //可以添加自定义逻辑    protected void onFinishInflate() {    }

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