如何与适配器共享 arraylist class

Question

我创建了一个数组列表，它从给定的 URL 中获取数据，现在我希望这个 ArrayList 显示在 GridView 中。我在 [=15] 中传递了它=] 但 ArrayList 显示 null.The API 响应 List 正在获取数据，因为在项目上单击它显示数据。

public ArrayList<String> images, urlResponse;
    FloatingActionButton fab;
    public String Data_Url = "http://gurbaaj.16mb.com/photos.php";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        GridView gallery = (GridView) findViewById(R.id.gridview);
        fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(MainActivity.this, "FAB clicked", Toast.LENGTH_SHORT).show();
                Intent intent = new Intent(MainActivity.this, ImageCheckActivity.class);
                intent.putStringArrayListExtra("stock_list", urlResponse);
                startActivity(intent);
            }
        });
        //Action On item click
        gallery.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1,
                                    int position, long arg3) {
                if (null != images && !images.isEmpty())
                    Toast.makeText(
                            getApplicationContext(),
                            "position " + position + " " + urlResponse, Toast.LENGTH_SHORT).show();
            }
        });
        gallery.setAdapter(new ImageAdapter(this, urlResponse));
    }

    @Override
    protected void onStart() {
        Toast.makeText(this, "On Start" , Toast.LENGTH_SHORT).show();
        super.onStart();
        final ProgressDialog loading = ProgressDialog.show(MainActivity.this,"Data is Loading", "Please wait...",false,false);
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Data_Url, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                loading.dismiss();
                parseData(response);

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                error.printStackTrace();
                Toast.makeText(getApplicationContext(), "Network error", Toast.LENGTH_SHORT).show();
            }
        });
// Creating RequestQueue
        CustomVolleyRequestQueue.getInstance(getApplicationContext()).addToRequestQueue(jsonArrayRequest);
    }

    private void parseData(JSONArray response) {
        urlResponse = new ArrayList<>();
        for (int i = 0; i < response.length(); i++) {
            JSONObject jsonObject;
            try {
                jsonObject = response.getJSONObject(i);
                String Images = jsonObject.getString("Image");
                urlResponse.add(Images);
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }



 private class ImageAdapter extends BaseAdapter {

        /**
         * The context.
         */
        private Activity context;
        ArrayList<String> urlImages;

        /**
         * Instantiates a new image adapter.
         *
         * @param localContext the local context
         */

        public ImageAdapter(Activity localContext, ArrayList<String> urlImages) {
            context = localContext;
            images = getAllShownImagesPath(context);
            this.urlImages = urlImages;
        }

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

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

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

        public View getView(final int position, View convertView,
                            ViewGroup parent) {
            ImageView picturesView;
            if (convertView == null) {
                picturesView = new ImageView(context);
                picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER);
                picturesView
                        .setLayoutParams(new GridView.LayoutParams(270, 270));

            } else {
                picturesView = (ImageView) convertView;
            }
            try {
                Glide.with(context).load(urlImages.get(position))
                        .placeholder(R.mipmap.ic_launcher_round).centerCrop()
                        .into(picturesView);
            } catch (Exception e) {
                e.printStackTrace();
            }
            return picturesView;
        }

Answer 1

解析数据后添加此行：

gallery.setAdapter(new ImageAdapter(this, urlResponse));

像那样:

private void parseData(JSONArray response) {
    urlResponse = new ArrayList<>();
    for (int i = 0; i < response.length(); i++) {
        JSONObject jsonObject;
        try {
            jsonObject = response.getJSONObject(i);
            String Images = jsonObject.getString("Image");
            urlResponse.add(Images);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
    gallery.setAdapter(new ImageAdapter(this, urlResponse));
}

Answer 2

您应该像在 ArrayList 中一样在 ImageAdapter 中创建方法（add、addAll 等），并在 ImageAdapter 中的 ArrayList 发生更改后调用 notifyDataSetChanged。

public void add(String text) {
    urlImages.add(text);
    notifyDataSetChanged();
}

public void addAll(List<String> text) {
    urlImages.addAll(text);
    notifyDataSetChanged();
}

此外，您将 null 对象作为 urlImages 传递给 ItemAdapter，您应该考虑创建构造函数，它将使用新的空列表初始化 urlImages，或者传递一个非 null 对象。

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