本文介绍了setUserVisibleHint在Fragment中的onCreateView之前调用的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

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

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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09-09 08:40