java - 如何在android中的自定义列表适配器中显示来自服务器的带有标题和描述的图像

Question

我正在使用 PHP 和 Mysql 创建一个应用程序，该应用程序在选项卡 fragment 中显示带有图像、标题、描述和价格的自定义 ListView 。

为了实现这一目标，我创建了一个带有 ItemList AsyncTask 内部类的 ProductTabs 类，该类用于获取除图像下载之外的项目详细信息。

ProductTabs 类:

public class ProductTabs extends Fragment {

    HttpHandler httpHandler = new HttpHandler();
    JSONArray items = null;
    ArrayList<HashMap<String,String>> list;
    ProgressDialog progressDialog = null;
    private static String url_products = "";
    private static final String TAG_SUCCESS = "success";
    private static final String TAG_PRODUCTS = "products";
    private static String JSON_PRODUCT_ID = "product_id";
    private static String JSON_PRODUCT_NAME = "product_name";
    private static String JSON_PRODUCT_PRICE = "product_price";
    private static String JSON_PRODUCT_DESC = "product_desc";
    private static String JSON_PRODUCT_URL = "url";
    private static String JSON_PRODUCT_IMAGE = "product_image";

    ListView productList;

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

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.product_tabs, container, false);
        productList = (ListView) v.findViewById(R.id.productList);

        if(this.getTag() == "Popular") {
            url_products = "http://kamalevent.com/cakeshop/products.php";
        } else {
            url_products = "http://kamalevent.com/cakeshop/products.php?sort_by=product_price";
        }

        list = new ArrayList<HashMap<String, String>>();

        new ItemList().execute();
        return v;
    }

    class ItemList extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            progressDialog = new ProgressDialog(getActivity());
            progressDialog.setMessage("Fetching Cakelist...");
            progressDialog.setIndeterminate(false);
            progressDialog.setCancelable(false);
            progressDialog.show();
        }

        @Override
        protected String doInBackground(String... args) {

            String json = httpHandler.makeHttpRequest(url_products, "GET");
            Log.d("Response :", json);

            if(json != null) {
                try {
                    JSONObject jsonObject = new JSONObject(json);
                    items = jsonObject.getJSONArray(TAG_PRODUCTS);

                    for(int i=0; i < items.length(); i++) {
                        JSONObject product = items.getJSONObject(i);

                        String id = product.getString(JSON_PRODUCT_ID);
                        String name = product.getString(JSON_PRODUCT_NAME);
                        String price = product.getString(JSON_PRODUCT_PRICE);
                        String desc = product.getString(JSON_PRODUCT_DESC);
                        String url = product.getString(JSON_PRODUCT_URL);

                        HashMap<String,String> products = new HashMap<String,String>();
                        products.put(JSON_PRODUCT_ID, id);
                        products.put(JSON_PRODUCT_NAME, name);
                        products.put(JSON_PRODUCT_DESC, desc);
                        products.put(JSON_PRODUCT_PRICE, price);
                        products.put(JSON_PRODUCT_URL, url);

                        list.add(products);

                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            progressDialog.dismiss();

            ProductAdapter productAdapter = new ProductAdapter(getActivity(), R.layout.item_list, list);
            productList.setAdapter(productAdapter);
            productAdapter.notifyDataSetChanged();
        }
    }



}

现在这里是自定义 ProductAdapter 的代码，用于创建自定义列表，在此适配器中我创建了一个新的内部 GetImage AsyncTask 类来从 url 下载图像。

ProductAdapter 类:

public class ProductAdapter extends ArrayAdapter<HashMap<String, String>> {

    private ArrayList<HashMap<String,String>> products;
    private Context context;
    private View view;
    private int resource;
    private HashMap<String,String> hashMap;

    public ProductAdapter(Context context, int resource, ArrayList<HashMap<String, String>> products) {
        super(context, resource, products);
        this.context = context;
        this.resource = resource;
        this.products = products;
    }

    public class ValueHolder {
        TextView name, desc, price;
        ImageView image;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = layoutInflater.inflate(resource, parent, false);

        ValueHolder valueHolder = new ValueHolder();
        valueHolder.name = (TextView) view.findViewById(R.id.item_title);
        valueHolder.desc = (TextView) view.findViewById(R.id.item_desc);
        valueHolder.price = (TextView) view.findViewById(R.id.item_price);
        valueHolder.image = (ImageView) view.findViewById(R.id.itemImage);

        hashMap = products.get(position);

        valueHolder.name.setText(hashMap.get("product_name"));
        valueHolder.desc.setText(hashMap.get("product_desc"));
        valueHolder.price.setText("Rs. " + hashMap.get("product_price"));
        if(valueHolder.image != null) {
            new GetImage(valueHolder.image).execute(hashMap.get("url"));
        }

        return view;
    }

    class GetImage extends AsyncTask<String, Void, Bitmap> {
        private final WeakReference<ImageView> imageViewWeakReference;

        public GetImage(ImageView imageView) {
            imageViewWeakReference = new WeakReference<ImageView>(imageView);
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected Bitmap doInBackground(String... args) {
            URL url = null;
            Bitmap image = null;

            String urlToImage = args[0];

            try {
                Log.d("Image :", urlToImage);
                url = new URL(urlToImage);
                image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return image;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            super.onPostExecute(bitmap);
            if(imageViewWeakReference != null) {
                ImageView imageView = imageViewWeakReference.get();
                if(imageView != null) {
                    if(bitmap != null) {
                        Log.d("Image :", "Image found");
                        imageView.setImageBitmap(bitmap);
                    }
                }
            }
        }
    }

}

现在，当我运行这个应用程序时，自定义适配器成功显示项目列表，一段时间后它显示 3-4 个下载的图像而不是整个图像，当我滚动 ListView 时，上面下载的图像也消失了，并且在 logcat GetImage AsyncTask 中像无限进程一样继续运行。

因此，如果有人可以建议我更好的解决方案，或者可以告诉我我在这里做错了什么，那将对我非常有帮助。

提前致谢。

Answer 1

请使用 Android-Universal-Image-Loader 而不是 asynctasks 从 url 加载图像。

显示以下链接: https://github.com/nostra13/Android-Universal-Image-Loader