Question

我正在开发一个由view-pager组成的应用程序，而我正在刷View View，所有片段都正确加载，但这是我的问题。当我再一次用相同的片段滑动View分页器时它再次加载，但根据我的要求，之前加载的片段应该恢复。我已经尝试过以下两种方式的代码。

A）这是我的View Pager

mViewPager = (ViewPager)mMyPageFragment.findViewById(R.id.Viewpager);

        myAdapter = new MyAdapter(getFragmentManager());
        mViewPager.setAdapter(myAdapter);
        myAdapter.notifyDataSetChanged();

在适配器中，

public class MyAdapter extends FragmentStatePagerAdapter {
    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public Fragment getItem(int position) {
        System.out.println("MyAdapter="+position);
        switch (position) {
        case 0:
            return new MyPageFirstFragment1();
        case 1:
            return new MyPageFirstFragment2();
        case 2:
            return new MyPageFirstFragment3();

        default:
            return null;
        }
    }
}

第二种方法

private static Hashtable<Integer, Fragment> fragmentItems = new Hashtable<Integer, Fragment>();

    @Override
    public Fragment getItem(int position) {
        System.out.println("MyAdapter=" + position);
        switch (position) {
        case 0: {
            if (!fragmentItems.containsKey(position)) {
                fragmentItems.put(position, new MyPageFirstFragment1());
            }
            return fragmentItems.get(position);
        }
        case 1: {
            if (!fragmentItems.containsKey(position)) {
                fragmentItems.put(position, new MyPageFirstFragment2());
            }
            return fragmentItems.get(position);
        }
        case 2: {
            if (!fragmentItems.containsKey(position)) {
                fragmentItems.put(position, new MyPageFirstFragment3());
            }
            return fragmentItems.get(position);
        }
        case 3: {
            if (!fragmentItems.containsKey(position)) {
                fragmentItems.put(position, new MyPageFirstFragment4());
            }
            return fragmentItems.get(position);
        }

        default:
            return null;
        }
    }

这是我用过的代码，但我不能保留片段。

Answer 1

你不应该将你的片段保存到静态对象中..因为片段管理器会在设备配置更改期间保存有关片段的信息，并在此之后恢复片段..但是将其保存到新的Fragment对象中。而你的“旧”静态对象变得无效。我更喜欢检查片段活动onCreate（）方法，如果savedInstanceState！= null，如果是我恢复视图寻呼机片段的那些标签（findFragmentByTag）并从恢复的片段创建新的适配器..例如 `

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Log.i( LOG_TAG, "onCreate()" );
        //setting view pager
        mViewPager = (ViewPager) findViewById( R.id.mainActivity_viewPager );


        //initializing activity
        if( savedInstanceState == null ) {
            Log.i( LOG_TAG, "onCreate() - savedInstanceState == null" );
            //activity first creation
        } else {
            Log.i( LOG_TAG, "onCreate(), savedInstanceState != null, it is activity start after device reconfiguration.. " );


            //recreating viewpager adapter
            mViewPager.setAdapter( recreateParentFragmentListAdapter() );

        }

和
`

private ParentFragmentListAdapter recreateParentFragmentListAdapter() {
        List<BaseParentFragment> fragments = new ArrayList<BaseParentFragment>(3);
        for( int id = 0; id < 3; id++ ) {
            String fragmentTag = getFragmentTag( R.id.mainActivity_viewPager, id );//int -> long converting
            BaseParentFragment fragment = (BaseParentFragment) (getSupportFragmentManager().findFragmentByTag( fragmentTag ));

            Log.i( LOG_TAG, "onCreate() - finding fragment with tag {" + fragmentTag + "}, found fragment = " + (fragment == null ? "null" : fragment.toString() ) );

            if( fragment == null ){//creating it
                switch( id ) {
                case 0:
                    fragment = new Tab1Fragment();
                case 1:
                    fragment = new Tab2Fragment();
                case 2:
                    fragment = new Tab3Fragment();
                }
            } 
            fragments.add( fragment );
        }

        ParentFragmentListAdapter adapter = new ParentFragmentListAdapter( getSupportFragmentManager(), fragments );
        return adapter;
    }

` 和

private String getFragmentTag( int viewId, long id ) {
        return "android:switcher:" + viewId + ":" + id;
    }

来自sdk

Swipe时，ViewPager不是以前的碎片

1 个答案: