Question

所有

感谢您的帮助。我的问题是如何将arrayadapter处理传递给它的listarray，为什么在我将新的arraylist分配给vlist之后它不起作用（请参考注释行之间的代码）？我尝试使用vlist = new ArrayList（）;而不是vlist.clear（）;但它只是不起作用。

import .....


public class MainActivity extends Activity {

    Button load;
    ListView content;
    Context context;
    ArrayAdapter<String> adapter;

    List<String> vlist;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        load = (Button) findViewById(R.id.load);
        content = (ListView) findViewById(R.id.content);
        txtJson = (TextView) findViewById(R.id.txtjson);
        context = this;
        vlist = new ArrayList<String>();
        load.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {

                DataLoader dLdr = new DataLoader();
                try {
                    dLdr.execute(new URI("http://someweb:3000/videolist"));
                } catch (URISyntaxException e) {
                    e.printStackTrace();
                }

            }
        });

        adapter = new ArrayAdapter<String>(context,
                android.R.layout.simple_list_item_1, vlist);
        content.setAdapter(adapter);

    }

    private class DataLoader extends AsyncTask<URI, Integer, List<String>> {

        ProgressDialog wait = new ProgressDialog(context);

        @Override
        protected void onPostExecute(List<String> result) {
            super.onPostExecute(result);



/*******************************************************************/
                vlist.clear();
                for (int i = 0; i < result.size(); i++) {
                    vlist.add(result.get(i));
                }
                adapter.notifyDataSetChanged();

/*******************************************************************/





            wait.dismiss();
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            wait.setTitle("Loading...");
            wait.show();
        }

        @Override
        protected List<String> doInBackground(URI... params) {

            HttpClient client = new DefaultHttpClient();
            HttpGet getter = new HttpGet(params[0]);
            List<String> results = new ArrayList<String>();

            try {
                HttpResponse response = client.execute(getter);
                HttpEntity entity = response.getEntity();
                InputStream is = entity.getContent();
                InputStreamReader isRdr = new InputStreamReader(is);
                BufferedReader bfRdr = new BufferedReader(isRdr);
                StringBuilder strBldr = new StringBuilder();
                String line = null;

                while ((line = bfRdr.readLine()) != null) {
                    strBldr.append(line);
                }

                String result = strBldr.toString();

                JSONObject jObj = new JSONObject(result);
                JSONArray jArray = jObj.getJSONArray("list");
                results = new ArrayList<String>();
                for (int i = 0; i < jArray.length(); i++) {
                    results.add((String) jArray.getString(i));
                }

                return results;

            } catch (IllegalStateException e) {
                e.printStackTrace();
            } catch (ClientProtocolException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            } catch (NullPointerException e) {
                e.printStackTrace();
            }

            return null;
        }
    }

}

Answer 1

您可能想要创建自己的适配器，您可以在其中设置列表。

查看http://www.piwai.info/android-adapter-good-practices/了解详情。

Answer 2

退房 ArrayAdaptor constructor code

您可以看到约束器调用

Arrays.asList(objects)

由它自己创建一个新的ArrayList see function实例。

意味着更改vlist不会更改ArrayAdaptor正在使用的Arraylist。

最简单的解决方法是致电

adapter.clear()
adapter.addAll(result) 
adapter.notifyDataSetChanged();

想知道Arrayadapter是如何工作的

2 个答案: