从URL到ViewPager加载图像

Question

我已经实现了pageradapter，但它显示空白的活动，这是我的代码

Adapter.java

public class MarketingViewPagerAdapter extends PagerAdapter {
    private List<MarketingImagesList> marketingImagesLists;
    private LayoutInflater inflater;
    private Context context;

    public MarketingViewPagerAdapter(List<MarketingImagesList> marketingImagesLists,  Context context) {
        this.marketingImagesLists = marketingImagesLists;
        this.inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        this.context = context;
    }
    @Override
    public int getCount() {
        return marketingImagesLists.size();
    }
    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == ((View) object);
    }
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        final MarketingImagesList listItem = marketingImagesLists.get(position);
        View itemView = inflater.inflate(R.layout.marketingswiper, container, false);
        ImageView imageView = (ImageView) itemView.findViewById(R.id.swipeImagesMarketing);
        Picasso.with(context).load(listItem.getFilePath())
                .into(imageView);
        container.addView(itemView);
        return itemView;
    }
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        ((ViewPager) container).removeView((ImageView) object);
    }
}

成像师

public class MarketingImagesList {
    String filePath;
    public MarketingImagesList(String filePath) {
        this.filePath = filePath;
    }
    public String getFilePath() {
        return filePath;
    }

}

营销活动

public class MarketingActivity extends AppCompatActivity {
    private static final String URL_DATA = "http://cognoamobileapp.com/api/products";
//    private RecyclerView recyclerView;
//
//    private RecyclerView.Adapter adapter;
    private List<MarketingImagesList> listMarketingList;
    ViewPager viewPager;
    //MarketingAdapter adapter;
    MarketingViewPagerAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_marketing);

        viewPager = (ViewPager) findViewById(R.id.marketing_viewPager);
        listMarketingList = new ArrayList<>();
        fetchImages();

    }
    private void fetchImages() {
        final ProgressDialog progressDialog = new ProgressDialog(this);
        progressDialog.setMessage("Loading presentations..");
        progressDialog.show();
        StringRequest stringRequest = new StringRequest(Request.Method.GET, URL_DATA,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        progressDialog.dismiss();
                        try {
                            JSONObject jsonObject = new JSONObject(response);
                            JSONArray jsonArray = jsonObject.getJSONArray("products");
                            for (int i =0; i<jsonArray.length(); i++) {
                                JSONObject o = jsonArray.getJSONObject(i);
                                MarketingImagesList item = new MarketingImagesList(
                                    o.getString("filepath")
                                );
                                listMarketingList.add(item);
                            }
                            adapter = new MarketingViewPagerAdapter(listMarketingList, getApplicationContext());
                            viewPager.setAdapter(adapter);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                progressDialog.dismiss();
                Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
            }

        });
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        requestQueue.add(stringRequest);
    }
}

Answer 1

您需要致电adapter.notifyDataSetChanged();