我正在使用兼容性库中的ViewPager。我已经成功地让它显示几个视图,我可以通过页面。

但是,我很难弄清楚如何用一组新的视图更新ViewPager。

我已经尝试了各种各样的事情,比如调用mAdapter.notifyDataSetChanged(), mviewpage .invalidate(),甚至在每次我想使用新的数据列表时创建一个全新的适配器。

没有任何帮助,textviews保持不变,从原始数据。

更新: 我做了一个小测试项目,我几乎能够更新视图。我将在下面粘贴这个类。

然而,似乎没有更新的是第二个视图,“B”仍然存在,它应该在按下更新按钮后显示“Y”。

public class ViewPagerBugActivity extends Activity {

    private ViewPager myViewPager;
    private List<String> data;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        data = new ArrayList<String>();
        data.add("A");
        data.add("B");
        data.add("C");

        myViewPager = (ViewPager) findViewById(R.id.my_view_pager);
        myViewPager.setAdapter(new MyViewPagerAdapter(this, data));

        Button updateButton = (Button) findViewById(R.id.update_button);
        updateButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                updateViewPager();
            }
        });
    }

    private void updateViewPager() {
        data.clear();
        data.add("X");
        data.add("Y");
        data.add("Z");
        myViewPager.getAdapter().notifyDataSetChanged();
    }

    private class MyViewPagerAdapter extends PagerAdapter {

        private List<String> data;
        private Context ctx;

        public MyViewPagerAdapter(Context ctx, List<String> data) {
            this.ctx = ctx;
            this.data = data;
        }

        @Override
        public int getCount() {
            return data.size();
        }

        @Override
        public Object instantiateItem(View collection, int position) {
            TextView view = new TextView(ctx);
            view.setText(data.get(position));
            ((ViewPager)collection).addView(view);
            return view;
        }

        @Override
        public void destroyItem(View collection, int position, Object view) {
             ((ViewPager) collection).removeView((View) view);
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == object;
        }

        @Override
        public Parcelable saveState() {
            return null;
        }

        @Override
        public void restoreState(Parcelable arg0, ClassLoader arg1) {
        }

        @Override
        public void startUpdate(View arg0) {
        }

        @Override
        public void finishUpdate(View arg0) {
        }
    }
}

当前回答

This is for all those like me, which need to update the Viewpager from a service (or other background thread) and none of the proposals have worked: After a bit of logchecking i realized, that the notifyDataSetChanged() method never returns. getItemPosition(Object object) is called an all ends there without further processing. Then i found in the docs of the parent PagerAdapter class (is not in the docs of the subclasses), "Data set changes must occur on the main thread and must end with a call to notifyDataSetChanged() ". So, the working solution in this case was (using FragmentStatePagerAdapter and getItemPosition(Object object) set to return POSITION_NONE) :

然后调用notifyDataSetChanged():

runOnUiThread(new Runnable() {
         @Override
         public void run() {
             pager.getAdapter().notifyDataSetChanged();
         }
     });

其他回答

所有这些解决办法对我都没有帮助。于是我找到了一个可行的解决方案: 您可以每次都设置适配器,但这是不够的。 在更换适配器之前,你应该做这些事情:

FragmentManager fragmentManager = slideShowPagerAdapter.getFragmentManager();
FragmentTransaction transaction = fragmentManager.beginTransaction();
List<Fragment> fragments = fragmentManager.getFragments();
for (Fragment f : fragments) {
    transaction.remove(f);
}
transaction.commit();

在这之后:

viewPager.setAdapter(adapter);

我发现这个问题的决定很有趣。 我们可以使用FragmentStatePagerAdapter (android.support.v4.app.FragmentStatePagerAdapter),而不是使用FragmentPagerAdapter将所有片段保存在内存中,当我们每次选择fragment时,它都会重新加载fragment。

两个适配器的实现是相同的。我们只需要在extend FragmentStatePagerAdapter上修改extend FragmentPagerAdapter

这是一个可怕的问题,我很乐意提出一个极好的解决方案;简单、高效、有效!

如下所示,代码显示了使用一个标志来指示何时返回POSITION_NONE

public class ViewPagerAdapter extends PagerAdapter
{
    // Members
    private boolean mForceReinstantiateItem = false;

    // This is used to overcome terrible bug that Google isn't fixing
    // We know that getItemPosition() is called right after notifyDataSetChanged()
    // Therefore, the fix is to return POSITION_NONE right after the notifyDataSetChanged() was called - but only once
    @Override
    public int getItemPosition(Object object)
    {
        if (mForceReinstantiateItem)
        {
            mForceReinstantiateItem = false;
            return POSITION_NONE;
        }
        else
        {
            return super.getItemPosition(object);
        }
    }

    public void setData(ArrayList<DisplayContent> newContent)
    {
        mDisplayContent = newContent;
        mForceReinstantiateItem = true;
        notifyDataSetChanged();
    }

}

我认为我已经创建了一种简单的方法来通知数据集的更改:

首先,稍微改变一下instantiateItem函数的工作方式:

    @Override
    public Object instantiateItem(final ViewGroup container, final int position) {
        final View rootView = mInflater.inflate(...,container, false);
        rootView.setTag(position);
        updateView(rootView, position);
        container.addView(rootView, LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
        mViewPager.setObjectForPosition(rootView, position);
        return rootView;
    }

对于“updateView”,用你想要填充的所有数据填充视图(setText,setBitmapImage,…)

验证destroyView是这样工作的:

    @Override
    public void destroyItem(final ViewGroup container, final int position, final Object obj) {
        final View viewToRemove = (View) obj;
        mViewPager.removeView(viewToRemove);
    }

现在,假设你需要更改数据,然后调用PagerAdapter上的下一个函数:

    public void notifyDataSetChanged(final ViewPager viewPager, final NotifyLocation fromPos,
            final NotifyLocation toPos) {
        final int offscreenPageLimit = viewPager.getOffscreenPageLimit();
        final int fromPosInt = fromPos == NotifyLocation.CENTER ? mSelectedPhotoIndex
                : fromPos == NotifyLocation.MOST_LEFT ? mSelectedPhotoIndex - offscreenPageLimit
                        : mSelectedPhotoIndex + offscreenPageLimit;
        final int toPosInt = toPos == NotifyLocation.CENTER ? mSelectedPhotoIndex
                : toPos == NotifyLocation.MOST_LEFT ? mSelectedPhotoIndex - offscreenPageLimit
                        : mSelectedPhotoIndex + offscreenPageLimit;
        if (fromPosInt <= toPosInt) {
            notifyDataSetChanged();
            for (int i = fromPosInt; i <= toPosInt; ++i) {
                final View pageView = viewPager.findViewWithTag(i);
                mPagerAdapter.updateView(pageView, i);
            }
        }
    }

public enum NotifyLocation {
    MOST_LEFT, CENTER, MOST_RIGHT
}

例如,如果你希望通知viewPager所显示的所有视图,有一些东西发生了变化,你可以调用:

notifyDataSetChanged(mViewPager,NotifyLocation.MOST_LEFT,NotifyLocation.MOST_RIGHT);

就是这样。

下面的代码对我有用。

创建一个扩展FragmentPagerAdapter类的类,如下所示。

public class Adapter extends FragmentPagerAdapter {

private int tabCount;
private Activity mActivity;
private Map<Integer, String> mFragmentTags;
private FragmentManager mFragmentManager;
private int container_id;
private ViewGroup container;
private List<Object> object;

public Adapter(FragmentManager fm) {
    super(fm);
}

public Adapter(FragmentManager fm, int numberOfTabs , Activity mA) {
    super(fm);
    mActivity = mA;
    mFragmentManager = fm;
    object = new ArrayList<>();
    mFragmentTags = new HashMap<Integer, String>();
    this.tabCount = numberOfTabs;
}

@Override
public Fragment getItem(int position) {
    switch (position) {
        case 0:
            return Fragment0.newInstance(mActivity);
        case 1:
            return Fragment1.newInstance(mActivity);
        case 2:
            return Fragment2.newInstance(mActivity);
        default:
            return null;
    }}


@Override
public Object instantiateItem(ViewGroup container, int position) {
    Object object = super.instantiateItem(container, position);
    if (object instanceof Fragment) {
        Log.e("Already defined","Yes");
        Fragment fragment = (Fragment) object;
        String tag = fragment.getTag();
        Log.e("Fragment Tag","" + position + ", " + tag);
        mFragmentTags.put(position, tag);
    }else{
        Log.e("Already defined","No");
    }
    container_id = container.getId();
    this.container = container;
    if(position == 0){
        this.object.add(0,object);
    }else if(position == 1){
        this.object.add(1,object);
    }else if(position == 2){
        this.object.add(2,object);
    }
    return object;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    super.destroyItem(container, position, object);
    if (object instanceof Fragment) {
        Log.e("Removed" , String.valueOf(position));
    }
}

@Override
public int getItemPosition (Object object)
{   int index = 0;
    if(this.object.get(0) == object){
        index = 0;
    }else if(this.object.get(1) == object){
        index = 1;
    }else if(this.object.get(2) == object){
        index = 2;
    }else{
        index = -1;
    }
    Log.e("Index" , "..................." + String.valueOf(index));
    if (index == -1)
        return POSITION_NONE;
    else
        return index;
}

public String getFragmentTag(int pos){
    return "android:switcher:"+R.id.pager+":"+pos;
}

public void NotifyDataChange(){
    this.notifyDataSetChanged();
}

public int getcontainerId(){
    return container_id;
}

public ViewGroup getContainer(){
    return this.container;
}

public List<Object> getObject(){
    return this.object;
}

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

然后在您创建的每个Fragment中,创建一个updateFragment方法。在这个方法中,您可以更改片段中需要更改的内容。例如,在我的例子中,Fragment0包含了一个GLSurfaceView,它显示了一个基于.ply文件路径的3d对象,所以在我的updateFragment方法中,我改变了这个ply文件的路径。

然后创建一个ViewPager实例,

viewPager = (ViewPager) findViewById(R.id.pager);

和一个Adpater实例,

adapter = new Adapter(getSupportFragmentManager(), 3, this);

然后这样做,

viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(1);

然后在类内部初始化了上面的Adapter类并创建了一个viewPager,每次你想要更新你的一个片段(在我们的例子中是Fragment0)时,使用以下方法:

adapter.NotifyDataChange();

adapter.destroyItem(adapter.getContainer(), 0, adapter.getObject().get(0)); // destroys page 0 in the viewPager.

fragment0 = (Fragment0) getSupportFragmentManager().findFragmentByTag(adapter.getFragmentTag(0)); // Gets fragment instance used on page 0.

fragment0.updateFragment() method which include the updates on this fragment

adapter.instantiateItem(adapter.getContainer(), 0); // re-initialize page 0.

这个解决方案是基于Alvaro Luis Bustamante提出的技术。