java - 想要将 ArrayList> 转换为字符串

Question

我读了Universal Image Loader我制作了具有 gridview 的应用程序，并且该 gridview 从 json 获取图像。但我的应用程序加载速度很慢，所以我想使用通用图像加载器，但是 getView ImageAdapeter 类中通用图像加载器中的函数，它的使用方式如下

imageLoader.displayImage(imageUrls[position], imageView, options);或对于公式 imageLoader.displayImage(String, imageView, options);

所以我没有字符串来完成这个公式。我只能创建 Object arr存储Arraylist。

如何转换ArrayList<HashMap<String, Object>>字符串或任何方法来更改我的代码？

请尽可能确认或建议或推荐我。易于阅读my code

下面是我的 ImageAdapter。它工作正常，但太慢了。

public class ImageAdapter extends BaseAdapter {
    private Context context;
    private ArrayList<HashMap<String, Object>> MyArr = new ArrayList<HashMap<String, Object>>();

    public ImageAdapter(Context c, ArrayList<HashMap<String, Object>> myArrList) {
        context = c;
        MyArr = myArrList;
    }

    public int getCount() {
        return MyArr.size();
    }

    public Object getItem(int position) {
        return position;
    }

    public long getItemId(int position) {
        return position;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        viewHolder = new ViewHolder();

        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        if (convertView == null) {
            convertView = inflater.inflate(R.layout.grid_item, null);
        }
        viewHolder.categoryCard = (ImageView) convertView.findViewById(R.id.category_card);
        //==================== change area
        Object arr = new ArrayList<HashMap<String, Object>>(); // make objec arr to store arraylist
        arr = MyArr.get(position).get("categoryid");
        if (arr.equals("1")) {
            viewHolder.categoryCard.setImageResource(R.drawable.card_eat);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageView1);
        } else {
            viewHolder.categoryCard.setImageResource(R.drawable.card_etc);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageView1);
        }
        // =============================
        try {
            viewHolder.imageView.setImageBitmap((Bitmap) MyArr.get(position).get("ImageThumBitmap"));
        } catch (Exception e) {
            viewHolder.imageView.setImageResource(android.R.drawable.ic_menu_report_image);
        }

        return convertView;

    }

}


// Download JSON in Background
public class DownloadJSONFileAsync extends AsyncTask<String, Void, Void> {
    String token = getIntent().getExtras().getString("token1");

    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
    }

    @Override
    protected Void doInBackground(String... params) {

        String url = "http://xxx.xxx.xxx/card/all/20/0/?token="+token;
        JSONArray data = null;
        try {

            JSONObject jsonObject = new JSONObject(getJSONUrl(url));

            MyArrList = new ArrayList<HashMap<String, Object>>();
            HashMap<String, Object> map;
            data = jsonObject.getJSONArray("data");
            for (int i = 0; i < data.length(); i++) {
                JSONObject c = data.getJSONObject(i);
                map = new HashMap<String, Object>();

                // Thumbnail Get ImageBitmap To Object
                map.put("cardimage", (String) c.getString("cardimage"));
                map.put("ImageThumBitmap",(Bitmap) loadBitmap(c.getString("cardimage")));
                map.put("categoryid", (String) c.getString("categoryid"));
                MyArrList.add(map);
            }

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }

    protected void onPostExecute(Void unused) {
        ShowAllContent(); // When Finish Show Content
        dismissDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
        removeDialog(DIALOG_DOWNLOAD_JSON_PROGRESS);
    }

}

这是来自 Universal Image Loader 的 ImageAdapter

public class ImageAdapter extends BaseAdapter {
    @Override
    public int getCount() {
        return imageUrls.length;
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ImageView imageView;
        if (convertView == null) {
            imageView = (ImageView) getLayoutInflater().inflate(R.layout.item_grid_image, parent, false);
        } else {
            imageView = (ImageView) convertView;
        }
                     // I want to do like this
        imageLoader.displayImage(imageUrls[position], imageView, options);

        return imageView;
    }
}

Answer 1

如果您想保留ArrayList<HashMap<String, Object>>你必须创建一个新的 String[]这样:

String[] urls = new String[MyArrList.size()];
for(int i=0; i<MyArrList.size(); i++){
   urls[i] = MyArrList.get(i).get("cardimage");
}

PS。我使用了您在代码中声明的变量名 MyArrList，顺便说一句，以大写字母开头的变量名不是一个好主意。

PS2。我认为如果您想使用通用图像加载器，您可能不再需要将每个位图存储在 HashMap 中