android 解决.XML提示ava.lang.NullPointerException at错误后XML没显示

提示错误：

 java.lang.NullPointerException
 Exception details are logged in Window > Show View > Error Log

 java.lang.NullPointerException
     at com.xxxx.ui.xxxxview.IphoneTreeView.onLayout(IphoneTreeView.java:236)
     at android.view.View.layout(View.java:14817)
     at android.view.ViewGroup.layout(ViewGroup.java:4631)
     at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
     at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
     at android.view.View.layout(View.java:14817)
     at android.view.ViewGroup.layout(ViewGroup.java:4631)
 ....

意思是提示 指针或对象空，具体列表；

解决方法：点击“IphoneTreeView.java:236”会跳到错误的.JAVA代码中，

对对象或指针进行判断不为NULL再使用。如：

         int state =0;
         if (mAdapter != null)//加上判断就可以解决，之前是没有判断引起的
           state = mAdapter.getTreeHeaderState(groupPos, childPos);