Question

我有一个带适配器的常规ViewPager：

public class MyDialogFragment extends DialogFragment {

    private ViewPager viewPager;

    private MyViewPagerAdapter myViewPagerAdapter;

    private City city;

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

        return fragment;
    }

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

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

        city = Parcels.unwrap(getArguments().getParcelable("city"));

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

        viewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                // Page changed
            }
        });

        return v;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    public class MyViewPagerAdapter extends PagerAdapter {

        private Context context;

        private LayoutInflater layoutInflater;

        public MyViewPagerAdapter(Context context) {
            this.context = context;
        }

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

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

            ImageView imageView = (ImageView) view.findViewById(R.id.cityImage);

            Glide.with(context)
                    .load(city.getImage())
                    .into(imageView);
            }

            container.addView(view);

            return view;
        }

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

正如您所看到的，我在ViewPager上设置了一个页面更改侦听器。但是我需要能够在页面发生变化时通知适配器，以便我可以修改适配器的ImageView。我怎么能这样做？

Answer 1

向适配器类添加方法

pm2 logs

在public class MyViewPagerAdapter extends PagerAdapter { ... public void pageChanged(int position) { // Do something } ... }之后使用该方法

OnPageChangeListener

Answer 2

一种方法是在适配器中创建数据结构，以将寻呼机视图映射到其位置。 SparseArray效率最高：

private SparseArray<View> pageMap = new SparseArray<>();

然后在适配器的instantiateItem()方法中，将视图添加到SparseArray：

public Object instantiateItem(ViewGroup container, int position) {
    ...
    pageMap.put(position, view);
    ...
}

现在，在您的OnPageChangeListener中，您可以执行以下操作：

@Override
public void onPageSelected(int position) {
    View view = adapter.getView(pos);
    if (view != null) {
        ImageView iv = (ImageView) view.findViewById(R.id.your_image_view);
        // You now have the image view
    }
}

请务必从适配器SparseArray方法中的destroyItem()删除观看次数：

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

Answer 3

您可以使用带有imagelist的构造函数来传递并在下一页自动调用..在您的代码中将被修改为::: ArrayList imageList = new ArrayList＆lt;＆gt;（）;

imageList.add("ImagePath here");
myViewPagerAdapter = new MyViewPagerAdapter(getContext(),imageList);
viewPager.setAdapter(myViewPagerAdapter);

然后你的适配器就像::

    public class MyViewPagerAdapter extends PagerAdapter {

            private Context context;
            private ArrayList<String> imageList
            private LayoutInflater layoutInflater;

            public MyViewPagerAdapter(Context context,ArrayList<String> imageList) {
                this.context = context;
                this.imageList = imageList;
            }

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

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

                ImageView imageView = (ImageView) view.findViewById(R.id.cityImage);

                Glide.with(context)
                        .load(imageList.get(position))            // This will be changes like 
                        .into(imageView);
                }

                container.addView(view);

                return view;
            }

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

那样做.. 在此之后，有一些建议 - 请在使用viewpager时使用arraylist .. 现在你只是从包中取出parceble对象.. 你可以为arraylist做同样的事，通过立即传递整个arraylist来接收来自同一捆绑的arraylist。所以你不需要找到页面更改事件..viewpager会自动处理.. 这里是如何发送＆amp;收到可分辨的arraylist

 // while sending the list
        Bundle bundle = new Bundle();
        bundle.putParcelableArrayList("citylist", new ArrayList<City>());

        // while receiving the list
        ArrayList<City> citylist = getIntent().getParcelableArrayListExtra("citylist");

之后只需获取所有图像并添加到imagelist数组

       for (int i = 0; i < citylist.size(); i++) {
            imageList.add(citylist.get(i).getImage());
        }

并在

中传递此imageList

myViewPagerAdapter = new MyViewPagerAdapter(getContext(),imageList);
viewPager.setAdapter(myViewPagerAdapter);

告诉我是否需要更多的帮助。

ViewPager适配器中的OnPageChangeListener？

3 个答案:

ViewPager适配器中的O​​nPageChangeListener？

3 个答案:

ViewPager适配器中的OnPageChangeListener？