在应用中自定义一个view，需要获取这个view的布局，需要用到

(LinearLayout) LayoutInflater.from(context).inflate(R.layout.contentitem, null);

这个方法。

一般的资料中的第二个参数会是一个null。通常情况下没有问题，但是如果我想给这个view设置一个对应的类，然后通过这个类来操作的话就会出问题。

先看下面的例子

1 
      2  3 
     
       8  9     
      15 16     
      21 22     
      28 29     
      34 35     
      
       40     
      
     41 42     
     48 

对应的类是

1 public class ContentItemView extends LinearLayout { 2  3     private TextView title; 4     private TextView author; 5     private TextView content; 6     private TextView otherInfo; 7     private ImageView contentImage; 8  9     private ContentInfo info;10 11     public ContentItemView(Context context) {12         super(context);13         init(context);14     }15 16     private void init(Context context) {17         LinearLayout convertView =18         (LinearLayout) LayoutInflater.from(context).inflate(R.layout.contentitem, null);19         title = (TextView) convertView.findViewById(R.id.textViewTitle);20         author = (TextView) convertView.findViewById(R.id.textViewAuthor);21         content = (TextView) convertView.findViewById(R.id.textViewContent);22         otherInfo = (TextView) convertView.findViewById(R.id.textViewOtherInfo);23         contentImage = (ImageView) convertView.findViewById(R.id.imageView);24     }25 }

 

这个自定义view我想将它添加到一个listview中。

1     public void add(final ContentInfo info) { 2         ContentItemView contentItemView  = new ContentItemView(context); 3         contentItemView.setContentInfo(info); 4         contentItemView.setLayoutParams(new AbsListView.LayoutParams(AbsListView.LayoutParams.MATCH_PARENT, AbsListView.LayoutParams.WRAP_CONTENT)); 5  6         data.add(contentItemView); 7     } 8  9     @Override10     public View getView(int position, View convertView, ViewGroup parent) {11         return data.get(position);12     }

程序运行起来以后，没有任何问题，但是界面没有显示出来，仅仅是在listview中多了一系列黑色的条条

 

如果将

(LinearLayout) LayoutInflater.from(context).inflate(R.layout.contentitem, null);

修改为

(LinearLayout) LayoutInflater.from(context).inflate(R.layout.contentitem, this);

显示就会正常

 

上面的东西很多资料里面都有，但是原因是什么？我在网络上找了很久都没有找到，于是就自己研究了下代码

1     public View inflate(int resource, ViewGroup root) { 2         return inflate(resource, root, root != null); 3     } 4  5     public View inflate(int resource, ViewGroup root, boolean attachToRoot) { 6         if (DEBUG) System.out.println("INFLATING from resource: " + resource); 7         XmlResourceParser parser = getContext().getResources().getLayout(resource); 8         try { 9             return inflate(parser, root, attachToRoot);10         } finally {11             parser.close();12         }13     }14     public View inflate(XmlPullParser parser, ViewGroup root, boolean attachToRoot) {15 ........16                 if (TAG_MERGE.equals(name)) {17                     if (root == null || !attachToRoot) {18                         throw new InflateException("
      can be used only with a valid "19                                 + "ViewGroup root and attachToRoot=true");20                     }21 22                     rInflate(parser, root, attrs, false);23                 } else {24                     // Temp is the root view that was found in the xml25                     View temp;26                     if (TAG_1995.equals(name)) {27                         temp = new BlinkLayout(mContext, attrs);28                     } else {29                         temp = createViewFromTag(root, name, attrs);30                     }31 32                     ViewGroup.LayoutParams params = null;33 34                     if (root != null) {35                         if (DEBUG) {36                             System.out.println("Creating params from root: " +37                                     root);38                         }39                         // Create layout params that match root, if supplied40                         params = root.generateLayoutParams(attrs);41                         if (!attachToRoot) {42                             // Set the layout params for temp if we are not43                             // attaching. (If we are, we use addView, below)44                             temp.setLayoutParams(params);45                         }46                     }47 48                   ..............49                     if (root != null && attachToRoot) {50                         root.addView(temp, params);51                     }52 53                     // Decide whether to return the root that was passed in or the54                     // top view found in xml.55                     if (root == null || !attachToRoot) {56                         result = temp;57                     }58                 }59 .....60 }

可以看到在inflate(XmlPullParser parser, ViewGroup root, boolean attachToRoot)函数中，只有root不等于空的情况下才能够真正的把view添加到listview中。

看看参数root的含义：@param root Optional view to be the parent of the generated hierarchy 

就是说这个表示的事view的容器是什么。如果不告诉SDK你要把这个view放到哪里，当然就不能生成view了。