android - 如何从url获取JSON数据？

Question

这是我在 textview 中获取 JSON 数据的代码。JSON 数据仅在我的代码中。现在，如果我的数据在某个 URL 中，那么我该如何获取这些数据？
旧的答案使用不再支持的 defaultHTTPClient，我尝试使用 retrofit 和 volley 但无法理解。

public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    TextView output = (TextView) findViewById(R.id.textView1);

    String strJson="{ \"Employee\" :[{\"id\":\"101\",\"name\":\"Sonoo Jaiswal\",\"salary\":\"50000\"},{\"id\":\"102\",\"name\":\"Vimal Jaiswal\",\"salary\":\"60000\"}] }";

    String data = "";
    try {
        // Create the root JSONObject from the JSON string.
        JSONObject  jsonRootObject = new JSONObject(strJson);

        //Get the instance of JSONArray that contains JSONObjects
        JSONArray jsonArray = jsonRootObject.optJSONArray("Employee");

        //Iterate the jsonArray and print the info of JSONObjects
        for(int i=0; i < jsonArray.length(); i++){
            JSONObject jsonObject = jsonArray.getJSONObject(i);

            int id = Integer.parseInt(jsonObject.optString("id").toString());
            String name = jsonObject.optString("name").toString();
            float salary = Float.parseFloat(jsonObject.optString("salary").toString());

            data += "Node"+i+" : \n id= "+ id +" \n Name= "+ name +" \n Salary= "+ salary +" \n ";
        }
        output.setText(data);
    } catch (JSONException e) {e.printStackTrace();}
}

Answer 1

编辑

使用Volley如果找不到 httpclient。

此外，解析脚本与下面提到的相同。

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 public class GridUI extends Activity {
 ArrayList<Persons> personsList;
 GridView gridView;
 GridAdapter gridAdapter;
private static final String   url="http://www.zippytrailers.com/funlearn/topicsMap";
   @Override
   protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.gridview);
    personsList= new ArrayList<Persons>();
 new JSONAsyncTask().execute(url);
 gridView=(GridView)findViewById(R.id.gridview);
 gridAdapter = new GridAdapter(this, R.layout.gridview_row, personsList);
 gridView.setAdapter(gridAdapter);

 }
 class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {
 ProgressDialog dialog;
 @Override
  protected void onPreExecute() {
  // TODO Auto-generated method stub
  super.onPreExecute();
  dialog=new ProgressDialog(GridUI.this);
  dialog.setMessage("Loading, please wait");
  dialog.setTitle("Connecting server");
  dialog.show();
  dialog.setCancelable(false);

  }


   @Override
  protected Boolean doInBackground(String... urls) {
      try {

//------------------>>
HttpGet httppost = new HttpGet(urls[0]);
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = httpclient.execute(httppost);

// StatusLine stat = response.getStatusLine();
int status = response.getStatusLine().getStatusCode();

 if(status==200){
 HttpEntity entity = response.getEntity();
 String data = EntityUtils.toString(entity);
  JSONObject jsono=new JSONObject(data);
  JSONArray jarray = jsono.getJSONArray("results");
  for (int i = 0; i < jarray.length(); i++) {
   JSONObject object = jarray.getJSONObject(i);

   Persons name = new Persons();

   name.setName(object.getString("syllabus"));
   name.setDescription(object.getString("grade"));
   name.setDob(object.getString("subject"));
   name.setCountry(object.getString("topic"));
   name.setHeight(object.getString("id"));

   personsList.add(name);
  }
  return true;
 }

} catch (ParseException e1) {
 e1.printStackTrace();
} catch (IOException e) {
 e.printStackTrace();
} catch (JSONException e) {
 e.printStackTrace();
}
return false;

   @Override
  protected void onPostExecute(Boolean result) {
  super.onPostExecute(result);
  dialog.cancel();
  gridAdapter.notifyDataSetChanged();
  if(result == false)
Toast.makeText(getApplicationContext(), "Unable to fetch data from   server", Toast.LENGTH_LONG).show();
 }

}