Viewpager使用3片段使用FragmentPagerAdapter

我寫了一個使用ViewPager和3片段的程序。我的問題是：Viewpager使用3片段使用FragmentPagerAdapter

當活動創建時，首先調用2個片段。當從片段1到片段2時，當片段2被點擊或滾動時，片段3的newInstance()方法被調用。而且，當我從片段3向後移動到片段2時，片段1調用方法onCreateView()。

我的代碼：

ViewPagerAdapter.java

public class ViewPagerAdapter extends FragmentPagerAdapter { 

private static int NUM_ITEMS = 3; 
Context context; 

public ViewPagerAdapter(FragmentManager manager,Context context) { 
    super(manager); 
    this.context = context; 
} 

@Override 
public int getCount() { 
    return NUM_ITEMS; 
} 

// Returns the fragment to display for that page 
@Override 
public Fragment getItem(int position) { 
    switch (position) { 
     case 0: 
      return Fragment_About.newInstance("About",20); 
     case 1: 
      return Fragment_EditSkills.newInstance ("Skills",30); 
     case 2: 
      return Fragment_EditActivities.newInstance("Activities",40); 

     default: 
      return null; 
    } 
} 
}

Fragment_About.java

public class Fragment_About extends Fragment { 

public static Fragment_About newInstance(String name, int age) { 
    Bundle bundle = new Bundle(); 
    bundle.putString("name", name); 
    bundle.putInt("age", age); 

    Fragment_About fragment = new Fragment_About(); 
    fragment.setArguments(bundle); 

    Log.i("FragmentAbout instance","instance"); 
    Log.i("name",""+name); 
    Log.i("age",""+age); 
    return fragment; 
} 

private void readBundle(Bundle bundle) { 
    if (bundle != null) { 
     name = bundle.getString("name"); 
     age = bundle.getInt("age"); 
     Log.i("readBundle oncreateview","readBundle oncreateview"); 
     Log.i("name",""+name); 
     Log.i("age",""+age); 
    } 
} 

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

    txtEditAbout = (TextView) view.findViewById(R.id.textEditAbout); 
    about = (TextView) view.findViewById(R.id.about); 

    readBundle(getArguments()); 

} 
}

日誌：

// when the activity is created. 
I/FragmentAbout instance: instance 
I/EditSkills instance: instance 


// When I click on page 2 
I/FragActivity instance: instance

從3向後移動至片段2至fragmen噸1被稱爲但此時newInstance()不要求任何片段

I/readBundle oncreateview: readBundle oncreateview

請說明上述處理的。

來源

2017-01-15 narahari_arjun

'getItem'總是在您的代碼中返回一個新實例。當您滑動時，下一個最接近的碎片將加載到內存中。你可以像陣列適配器那樣存儲Fragment對象列表 –

Viewpager根據OffscreenPageLimit參數預加載相鄰片段。缺省情況下它被設置爲1（DEFAULT_OFFSCREEN_PAGES = 1）

您使用FragmentPagerAdapter，這意味着，如果它們更遠然後離屏限制片段視圖可能被破壞。

來源

2017-01-15 13:09:14

Viewpager使用3片段使用FragmentPagerAdapter

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