LayoutInflater中有兩個(gè)inflate方法：

• public View inflate( int resource, ViewGroup root)
• public View inflate(int resource, ViewGroup root, boolean attachToRoot)

測(cè)試
 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    //    setContentView(R.layout.activity_main);
        final LayoutInflater inflater = getLayoutInflater();
        //A
        final View view1 = inflater.inflate(R.layout.activity_main, null);
        //B
        final View view2 = inflater.inflate(R.layout.activity_main, (ViewGroup) findViewById(android.R.id.content),false);
        //C。并且會(huì)顯示在界面上
        final View view3 = inflater.inflate(R.layout.activity_main, (ViewGroup) findViewById(android.R.id.content),true);
        
        // 參數(shù)為Null
        Log.d(TAG, "onCreate() view1: " + view1 +"layoutparam = "+view1.getLayoutParams()); 
        
         // 有參數(shù)FrameLayout$LayoutParams
        Log.d(TAG, "onCreate() view2: " + view2 +"layoutparam = "+view2.getLayoutParams());
        
        //有參數(shù)LinearLayout$LayoutParams
        Log.d(TAG, "onCreate() view3: " + view3 +"layoutparam = "+view3.getLayoutParams());
}

分析ABC
三個(gè)方法最后都會(huì)調(diào)用下面這個(gè)：

 public View inflate(XmlPullParser parser, ViewGroup root, boolean attachToRoot) {
  ...跳過一堆代碼...
   View result = root;
     // Temp 就是我們的xml布局
       final View temp = createViewFromTag(root, name, inflaterContext, attrs);

                    ViewGroup.LayoutParams params = null;
                    //如果是上面的A調(diào)用，則不會(huì)創(chuàng)建layout params
                    if (root != null) {
                       
                        //B和C  根據(jù)root創(chuàng)建layout params
                        params = root.generateLayoutParams(attrs);
                        if (!attachToRoot) {
                            //B 第三個(gè)參數(shù)attachToRoot為 false,則會(huì)設(shè)置layout params                          
                            temp.setLayoutParams(params);
                        }
                    }
                 
                   
                    //C 如果設(shè)置了root并且第三個(gè)參數(shù)為true.則使用params把temp添加 的root上去
                    if (root != null && attachToRoot) {
                        root.addView(temp, params);
                    }

                    //A 如果root沒設(shè)置并且第三參數(shù)為false
                    //則直接返回temp
                    if (root == null || !attachToRoot) {
                        result = temp;
                    }
               
               /*
               A:返回的是temp
               B:返回的是root,temp設(shè)置了params,但沒有添加 到root上
               C：返回的是root并且會(huì)把布局添加到root上
               */
              return result;      
 }

對(duì)定義view的影響

onMeasure()方法都會(huì)根據(jù)測(cè)量模式做不同處理

MeasureSpec.EXACTLY == LayoutParams. MATCH_PARENT或設(shè)置的一個(gè)精確值

MeasureSpec.AT_MOST == LayoutParams. WRAP_CONTENT

可以知曉測(cè)量時(shí)依賴于LayoutParams种柑。而inflate(resId,null)是不會(huì)設(shè)置LayoutParams的核芽。

在listview中出現(xiàn)item設(shè)置的寬高沒有被處理的時(shí)候可以檢查一下是否正確調(diào)用了inflate方法