在 ViewPager 中获取活动页面并更新内容

Question

我按照下面的教程（向下滚动到“全屏图像幻灯片”部分）来实现全屏幻灯片，除了在幻灯片中不使用图像，我使用的是视频：

http://www.androidhive.info/2016/04/android-glide-image-library-building-image-gallery-app/

这是我对 DialogFragment 和 PagerAdapter 的实现：

public class SlideshowDialogFragment extends DialogFragment {

    private ArrayList<Video> videos;

    private ViewPager viewPager;

    private MyViewPagerAdapter myViewPagerAdapter;

    private int selectedPosition = 0;

    public static SlideshowDialogFragment newInstance() {
        SlideshowDialogFragment fragment = new SlideshowDialogFragment();

        return fragment;
    }

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

        videos = (ArrayList<Video>) getArguments().getSerializable("videos");
        selectedPosition = getArguments().getInt("position");

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

        myViewPagerAdapter = new MyViewPagerAdapter();
        viewPager.setAdapter(myViewPagerAdapter);

        setCurrentItem(selectedPosition);

        return v;
    }

    private void setCurrentItem(int position) {
        viewPager.setCurrentItem(position, false);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setStyle(DialogFragment.STYLE_NORMAL, android.R.style.Theme_Black_NoTitleBar_Fullscreen);
    }

    public class MyViewPagerAdapter extends PagerAdapter {

        private LayoutInflater layoutInflater;

        public MyViewPagerAdapter() {

        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            layoutInflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            View view = layoutInflater.inflate(R.layout.video_layout, container, false);

            Video video = videos.get(position);

            TextureVideoView videoView = (TextureVideoView) view.findViewById(R.id.videoView);

            Uri videoUri = Uri.parse(video.getUrl());

            videoView.setVideoURI(videoUri);
            videoView.setMediaController(null);
            videoView.requestFocus();

            container.addView(view);

            return view;
        }

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

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

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View) object);
        }
    }
}

问题是，现在，视频一加载就会自动播放。而且，由于 ViewPager 加载了下一张和上一张幻灯片（我希望它这样做），幻灯片也会自动播放下一张和上一张视频（我不希望它这样做)。

所以我的问题是，如何修改我的代码，使其仅在当前幻灯片处于活动状态时播放视频，然后在幻灯片变为非活动状态时暂停/停止视频？

仅供参考：开始和停止视频的方法是videoView.start() 和videoView.stop()。

Answer 1

您可以使用我的其他答案 here 中的相同方法。

在 ViewPager 适配器中保留一组视频视图引用，以便您可以启动当前正在显示的视频，并暂停所有已实例化但当前未显示的视频视图。

对适配器的更改：

public class MyViewPagerAdapter extends PagerAdapter {

    private LayoutInflater layoutInflater;

    //Added:
    public TextureVideoView[] videoViews = new TextureVideoView[videos.size()];

    public MyViewPagerAdapter() {

    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        layoutInflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View view = layoutInflater.inflate(R.layout.video_layout, container, false);

        Video video = videos.get(position);

        TextureVideoView videoView = (TextureVideoView) view.findViewById(R.id.videoView);

        Uri videoUri = Uri.parse(video.getUrl());

        videoView.setVideoURI(videoUri);
        videoView.setMediaController(null);
        videoView.requestFocus();

        container.addView(view);

        //Added:
        videoViews[position] = videoView;

        return view;
    }

    //.............
}

然后，在适配器之外，使用 ViewPager.OnPageChangeListener 启动当前视频，并暂停任一侧的视频：

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
  @Override
  public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { }

  @Override
  public void onPageSelected(int position) {

    for (int i = 0; i < videos.size(); i++) {
      TextureVideoView videoView = myViewPagerAdapter.videoViews[i];
      if (videoView == null) continue;
      if (i == position) {
        videoView.start();
      } else {
        videoView.stop();
      }
    }
  }

  @Override
  public void onPageScrollStateChanged(int state) {  }
});