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

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。

其他回答

我想,我有ViewPager的逻辑。

如果我需要刷新一组页面并基于新的数据集显示它们,我调用notifyDataSetChanged()。 然后,ViewPager对getItemPosition()进行多次调用,将Fragment作为对象传递给那里。这个片段可以来自旧数据集(我想要丢弃的数据集),也可以来自新数据集(我想要显示的数据集)。因此,我重写了getItemPosition(),在那里我必须以某种方式确定我的片段是来自旧数据集还是来自新数据集。

In my case I have a 2-pane layout with a list of top items on the left pane and a swipe view (ViewPager) on the right. So, I store a link to my current top item inside my PagerAdapter and also inside of each instantiated page Fragment. When the selected top item in the list changes, I store the new top item in PagerAdapter and call notifyDataSetChanged(). And in the overridden getItemPosition() I compare the top item from my adapter to the top item from my fragment. And only if they are not equal, I return POSITION_NONE. Then, PagerAdapter reinstantiates all the fragments that have returned POSITION_NONE.

请注意。存储顶部项id而不是引用可能是一个更好的主意。

下面的代码片段有点示意图,但我从实际工作的代码中改编了它。

public class SomeFragment extends Fragment {
  private TopItem topItem;
}

public class SomePagerAdapter extends FragmentStatePagerAdapter {
  private TopItem topItem;

  public void changeTopItem(TopItem newTopItem) {
    topItem = newTopItem;
    notifyDataSetChanged();
  }

  @Override
  public int getItemPosition(Object object) {
    if (((SomeFragment) object).getTopItemId() != topItem.getId()) {
      return POSITION_NONE;
    }
    return super.getItemPosition(object);
  }
}

感谢之前所有的研究人员!

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。

After a lot of searching for this problem, I found a really good solution that I think is the right way to go about this. Essentially, instantiateItem only gets called when the view is instantiated and never again unless the view is destroyed (this is what happens when you override the getItemPosition function to return POSITION_NONE). Instead, what you want to do is save the created views and either update them in the adapter, generate a get function so someone else can update it, or a set function which updates the adapter (my favorite).

所以,在你的MyViewPagerAdapter中添加一个变量:

private View updatableView;

在你的instantiateItem:

 public Object instantiateItem(View collection, int position) {
        updatableView = new TextView(ctx); //My change is here
        view.setText(data.get(position));
        ((ViewPager)collection).addView(view);
        return view;
    }

通过这种方式,你可以创建一个函数来更新你的视图:

public updateText(String txt)
{
    ((TextView)updatableView).setText(txt);
}

希望这能有所帮助!

你可以动态更新所有的片段,你可以在三个步骤中看到。

在适配器中:

public class MyPagerAdapter extends FragmentPagerAdapter {
private static int NUM_ITEMS = 3;
private Map<Integer, String> mFragmentTags;
private FragmentManager mFragmentManager;

public MyPagerAdapter(FragmentManager fragmentManager) {
    super(fragmentManager);
    mFragmentManager = fragmentManager;
    mFragmentTags = new HashMap<Integer, String>();
}

// Returns total number of pages
@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 FirstFragment.newInstance();
        case 1:
            return SecondFragment.newInstance();
        case 2:
            return ThirdFragment.newInstance();
        default:
            return null;
    }
}

// Returns the page title for the top indicator
@Override
public CharSequence getPageTitle(int position) {
    return "Page " + position;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    Object object = super.instantiateItem(container, position);
    if (object instanceof Fragment) {
        Fragment fragment = (Fragment) object;
        String tag = fragment.getTag();
        mFragmentTags.put(position, tag);
    }
    return object;
}

public Fragment getFragment(int position) {
    Fragment fragment = null;
    String tag = mFragmentTags.get(position);
    if (tag != null) {
        fragment = mFragmentManager.findFragmentByTag(tag);
    }
    return fragment;
}}

现在在你的活动中:

public class MainActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener{

MyPagerAdapter mAdapterViewPager;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ViewPager viewPager = (ViewPager) findViewById(R.id.vpPager);
    mAdapterViewPager = new MyPagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(mAdapterViewPager);
    viewPager.addOnPageChangeListener(this);
}

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

}

@Override
public void onPageSelected(int position) {

    Fragment fragment = mAdapterViewPager.getFragment(position);
    if (fragment != null) {
        fragment.onResume();
    }
}

@Override
public void onPageScrollStateChanged(int state) {

}}

最后在你的片段中,是这样的:

public class YourFragment extends Fragment {

// newInstance constructor for creating fragment with arguments
public static YourFragment newInstance() {

    return new YourFragment();
}

// Store instance variables based on arguments passed
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
}

// Inflate the view for the fragment based on layout XML
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    return inflater.inflate(R.layout.fragment, container, false);
}


@Override
public void onResume() {
    super.onResume();

    //to refresh your view
    refresh();

}}

您可以在这里看到完整的代码。

谢谢阿尔瓦罗·路易斯·布斯塔曼特。

无论如何,在KitKat+上,适配器. notifydatasetchanged()似乎足以导致新视图显示,前提是你已经将toffscreenpagelimit设置得足够高。我能够通过执行viewpage . setoffscreenpagelimit(2)来获得所需的行为。