如何在片段中使用GetJsonFromUrlTask​​.java

Question

我从网站上找到了下面的代码，看起来它可能对我的Android应用程序有所帮​​助。但问题是，下面的代码仅用于活动，我需要在片段中运行代码。 BTW我的应用程序是从在线数据库下载图像并将其存储到列表视图。

我该怎么办？

这是我想要使用的代码：

public class GetJsonFromUrlTask extends AsyncTask<Void, Void, String> {

private Activity activity;
private String url;
private ProgressDialog dialog;
private final static String TAG = GetJsonFromUrlTask.class.getSimpleName();

public GetJsonFromUrlTask(Activity activity, String url) {
    super();
    this.activity = activity;
    this.url = url;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
    // Create a progress dialog
    dialog = new ProgressDialog(activity);
    // Set progress dialog title
    dialog.setTitle("Getting JSON DATA");
    // Set progress dialog message
    dialog.setMessage("Loading...");
    dialog.setIndeterminate(false);
    // Show progress dialog
    dialog.show();
}

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

    // call load JSON from url method
    return loadJSON(this.url).toString();
}

@Override
protected void onPostExecute(String result) {
    ((CategoryListViewActivity) activity).parseJsonResponse(result);
    dialog.dismiss();
    Log.i(TAG, result);
}

public JSONArray loadJSON(String url) {
    // Creating JSON Parser instance
    JSONGetter jParser = new JSONGetter();

    // getting JSON string from URL
    JSONArray json = jParser.getJSONFromUrl(url);

    return json;
}

private class JSONGetter {

    private InputStream is = null;
    private JSONArray jObj = null;
    private String json = "";

    // constructor
    public JSONGetter() {

    }

    public JSONArray getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"),
                    8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONArray(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}
}

Answer 1

在片段中使用AsyncTask很简单，如下所示

将代码放在activityCreateview

上

new GetJsonFromUrlTask(getActivity(), mListView).execute("");

getActivity()是将您的活动上下文放入Fragment类

的方法

  

注意：当您从网站上找到代码时，此代码是AsyncTask类，您可以将此代码调用到Activity，Fragment，任何其他类也

更改代码

public class GetJsonFromUrlTask extends AsyncTask<Void, Void, String> {

private Context activity;
private String url;
private ProgressDialog dialog;
private final static String TAG = GetJsonFromUrlTask.class.getSimpleName();

public GetJsonFromUrlTask(Context activity, String url) {
    super();
    this.activity = activity;
    this.url = url;
}

@Override
protected void onPreExecute() {
    super.onPreExecute();
    // Create a progress dialog
    dialog = new ProgressDialog(activity);
    // Set progress dialog title
    dialog.setTitle("Getting JSON DATA");
    // Set progress dialog message
    dialog.setMessage("Loading...");
    dialog.setIndeterminate(false);
    // Show progress dialog
    dialog.show();
}

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

    // call load JSON from url method
    return loadJSON(this.url).toString();
}

@Override
protected void onPostExecute(String result) {

    dialog.dismiss();
    Log.i(TAG, result);
}

public JSONArray loadJSON(String url) {
    // Creating JSON Parser instance
    JSONGetter jParser = new JSONGetter();

    // getting JSON string from URL
    JSONArray json = jParser.getJSONFromUrl(url);

    return json;
}

private class JSONGetter {

    private InputStream is = null;
    private JSONArray jObj = null;
    private String json = "";

    // constructor
    public JSONGetter() {

    }

    public JSONArray getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"),
                    8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONArray(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}
}