setUserVisibleHint在Fragment中的onCreateView之前调用 [英] setUserVisibleHint called before onCreateView in Fragment

问题描述

我正在使用 ViewPager 并使用碎片，我发现

setUserVisibleHint（）在片段中的onCreateView（）之前调用

我使用片段从支持库 android.support.v4.app.Fragment

这是库的问题吗？

如何摆脱它？

> EDIT

我覆盖setUserVisibleHint（），不调用super来摆脱它。

<$在片段中的onCreateView（）之前调用导致NullPointerException的pre> @Override
public void setUserVisibleHint（boolean isVisibleToUser）{
// FIXED：setUserVisibleHint super.setUserVisibleHint（isVisibleToUser）;
}


解决方案

  //为获取数据创建布尔值
 private boolean isViewShown = false; 
 
 @Override 
 public void setUserVisibleHint（boolean isVisibleToUser）{
 super.setUserVisibleHint（isVisibleToUser）; 
 if（getView（）！= null）{
 isViewShown = true; 
 // fetchdata（）包含当页面被选择时显示数据的逻辑主要asynctask填充数据
 fetchData（）; 
} else {
 isViewShown = false; 
} 
} 
  

使用 isViewShown 实例变量来决定是否在中获取数据onCreateView（）或在 setUserVisibleHint（） p>

以下代码包含的逻辑onCreateView（）：

  @Override 
 public View onCreateView（LayoutInflater inflater，ViewGroup container，
 Bundle savedInstanceState）{
 View view = inflater.inflate（R.layout.main_layout，容器，假）; 
 
 //查看初始化步骤....... 
 
 if（！isViewShown）{
 fetchData（）; 
} 
 //做其他东西
} 
  

会解决你的问题。因为它解决了我的问题。 ：）

这个技巧将从 onCreateView（）中获取数据以直接从一个页面跳转到另一个页面，你刷过视图，它会从 setUserVisibleHint（）方法中获取数据。 :)

I am working on ViewPager and using Fragment there I found

setUserVisibleHint() called before onCreateView() in Fragment

I am using Fragment from support library android.support.v4.app.Fragment

Is this is a problem with Library ?

How can I get rid of it ?

EDIT

I Override setUserVisibleHint() and not calling super to get rid of it.

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    //FIXED: setUserVisibleHint() called before onCreateView() in Fragment causes NullPointerException
    //super.setUserVisibleHint(isVisibleToUser);
}

解决方案

// create boolean for fetching data
private boolean isViewShown = false;

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (getView() != null) {
        isViewShown = true;
        // fetchdata() contains logic to show data when page is selected mostly asynctask to fill the data
        fetchData();
    } else {
        isViewShown = false;
    }
} 

Use isViewShown instance variable to decide whether to fetch data in onCreateView() or in setUserVisibleHint().

Below code contains logic for onCreateView():

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.main_layout, container, false);

   // view initialization steps.......

   if (!isViewShown) {
        fetchData();
   } 
   // do other stuff
}

This code will solve your problem. As It solved my problem. :)

This trick will fetch data in onCreateView() for direct jumping from one page to another, whereas when you swipe the view it will fetch the data from setUserVisibleHint() method. :)

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