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

对我有用的是重写finishUpdate方法,它在转换结束时被调用,并在那里执行notifyDataSetChanged():

public class MyPagerAdapter extends FragmentPagerAdapter {
    ...
    @Override
    public void finishUpdate(ViewGroup container) {
        super.finishUpdate(container);
        this.notifyDataSetChanged();
    }
    ...
}

其他回答

对我有用的是重写finishUpdate方法,它在转换结束时被调用,并在那里执行notifyDataSetChanged():

public class MyPagerAdapter extends FragmentPagerAdapter {
    ...
    @Override
    public void finishUpdate(ViewGroup container) {
        super.finishUpdate(container);
        this.notifyDataSetChanged();
    }
    ...
}

在OP提出他的问题两年半之后,这个问题仍然,嗯,仍然是一个问题。显然谷歌在这方面的优先级不是特别高,所以我没有找到解决方案,而是找到了一个变通办法。对我来说,最大的突破是找到了问题的真正原因(见本文中公认的答案)。一旦问题明显是任何活动页面都没有正确刷新,我的解决方法就很明显了:

在我的片段(几页)中:

I took all the code which populates the form out of onCreateView and put it in a function called PopulateForm which may be called from anywhere, rather than by the framework. This function attempts to get the current View using getView, and if that is null, it just returns. It's important that PopulateForm contains only the code that displays - all the other code which creates FocusChange listeners and the like is still in OnCreate Create a boolean which can be used as a flag indicating the form must be reloaded. Mine is mbReloadForm Override OnResume() to call PopulateForm() if mbReloadForm is set.

在我的活动中,我做页面的加载:

Go to page 0 before changing anything. I'm using FragmentStatePagerAdapter, so I know that two or three pages are affected at most. Changing to page 0 ensures I only ever have the problem on pages 0, 1 and 2. Before clearing the old list, take it's size(). This way you know how many pages are affected by the bug. If > 3, reduce it to 3 - if you're using a a different PagerAdapter, you'll have to see how many pages you have to deal with (maybe all?) Reload the data and call pageAdapter.notifyDataSetChanged() Now, for each of the affected pages, see if the page is active by using pager.getChildAt(i) - this tells you if you have a view. If so, call pager.PopulateView(). If not, set the ReloadForm flag.

在此之后,当您重新加载第二组页面时,该错误仍然会导致一些页面显示旧数据。但是,现在它们将被刷新,您将看到新的数据-您的用户不会知道页面是不正确的,因为这种刷新将在他们看到页面之前发生。

希望这能帮助到一些人!

所有这些答案对我都不起作用。

唯一对我有用的是,我必须再次将适配器设置为viewpager,然后它将刷新内容。

removeView(int pos)在我的PagerAdaper

public void removeView(int index) {
       imageFileNames.remove(index);
       notifyDataSetChanged();
}

无论我在哪里删除文件,我都必须这样做

imagePagerAdapter.removeView(currentPosition);
viewPager.setAdapter(imagePagerAdapter);

编辑:

下面的方法是有效的,你可以使用下面的方法。

public void updateView(int pos){
      viewPager.setAdapter(null);
      imagePagerAdapter =new ImagePagerAdapter(YOUR_CONTEXT,YOUR_CONTENT);
      viewPager.setAdapter(imagePagerAdapter);
      viewPager.setCurrentItem(pos);
}

用你的上下文替换你的YOUR_CONTEXT,用你的内容名称替换你的内容,即更新列表或其他东西。

以防任何人使用FragmentStatePagerAdapter的适配器(这将让ViewPager创建显示所需的最小页面,对于我的情况最多2个页面),@rui。araujo在适配器中覆盖getItemPosition的答案不会造成重大浪费,但仍然可以改进。

在伪代码中:

public int getItemPosition(Object object) {
    YourFragment f = (YourFragment) object;
    YourData d = f.data;
    logger.info("validate item position on page index: " + d.pageNo);

    int dataObjIdx = this.dataPages.indexOf(d);

    if (dataObjIdx < 0 || dataObjIdx != d.pageNo) {
        logger.info("data changed, discard this fragment.");
        return POSITION_NONE;
    }

    return POSITION_UNCHANGED;
}

1.首先,您必须在Pageradapter类中设置getItemposition方法 2.您必须阅读您的视图寻呼机的确切位置 3.然后将该位置作为新位置的数据位置发送 4.在setonPageChange监听器中写入更新按钮的点击监听器

我修改了程序代码,只设置了特定的位置元素

public class MyActivity extends Activity {

private ViewPager myViewPager;
private List<String> data;
public int location=0;
public Button updateButton;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

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

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

      updateButton = (Button) findViewById(R.id.update);

    myViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i2) {
             //Toast.makeText(MyActivity.this, i+"  Is Selected  "+data.size(), Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onPageSelected( int i) {
          // here you will get the position of selected page
            final int k = i;
             updateViewPager(k);

        }

        @Override
        public void onPageScrollStateChanged(int i) {

        }
    });
}

private void updateViewPager(final int i) {  
    updateButton.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {

            Toast.makeText(MyActivity.this, i+"  Is Selected  "+data.size(), Toast.LENGTH_SHORT).show();
            data.set(i, "Replaced "+i);         
            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 int getItemPosition(Object object) {
        return POSITION_NONE;
    }

    @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) {
    }
}
}