Java 异步任务和网络丢失问题

在设备上未检测到网络时，我的

AsyncTask

出现问题

正在寻找有关如何修复此问题的建议，谢谢

LogCat似乎指向（inti=0；i的

，我不确定如果网络不可用，如何阻止此代码运行

代码


其中im正在解析位置数据

 private class ProgressTask extends
        AsyncTask<String, Void, ArrayList<String>> {

    ArrayList<String> arrfortextviews;
    private GPSME_Main activity;
    private ProgressBar progressBar1;

    public ProgressTask(GPSME_Main parseMoreDetails) {
        this.activity = parseMoreDetails;
        context = parseMoreDetails;
        progressBar1 = (ProgressBar) findViewById(R.id.progressBar1);

    }

    private Context context;
    protected void onPreExecute() {
        progressBar1.setVisibility(View.VISIBLE);
        Location location = locationManager
                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
        if (location != null) {
            parse_current_location = location.getLatitude() + ","
                    + location.getLongitude();
        }
    }

    @Override
    protected void onPostExecute(ArrayList<String> success) {
        if (arrfortextviews.size() > 0) {
            progressBar1.setVisibility(View.GONE);
            current_address = (success.get(0));
            body_location_address_result.setText(current_address);
        }
    }

    protected ArrayList<String> doInBackground(final String... args) {

        JSONParser jParser = new JSONParser();
        arrfortextviews = new ArrayList<String>();

        JSONArray json = jParser.getJSONFromUrl(google_maps_url + "latlng="
                + parse_current_location + "&sensor=true");

        for (int i = 0; i < json.length(); i++) {

            try {
                JSONObject c = json.getJSONObject(i);
                String parsed_results_formatted_address = c
                        .getString("formatted_address");
arrfortextviews.add(parsed_results_formatted_address);

            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        return arrfortextviews;
    }
}

您得到的是
nullPointerException
，因为您希望得到
JSON
响应，但由于您没有网络，因此没有解析响应

防止此代码运行的一种方法是在进入循环之前简单地进行空检查：

if(json != null){
    for (int i = 0; i < json.length(); i++) {

            try {
                JSONObject c = json.getJSONObject(i);
                String parsed_results_formatted_address = c
                        .getString("formatted_address");
arrfortextviews.add(parsed_results_formatted_address);

            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
}

最终，这取决于如果没有连接，是否需要运行
AsycTask
。
是否在函数getJSONFromUrl（）中进行网络连接。如果是这样，请也发布。此外，当没有网络时，网络api是否会引发异常？你需要处理这个问题。这是我正在考虑的方法。谢谢！！没问题！很高兴我能够帮助你！
: FATAL EXCEPTION: AsyncTask #1
: java.lang.RuntimeException: An error occured while executing doInBackground()
:   at android.os.AsyncTask$3.done(AsyncTask.java:299)
:   at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
:   at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
:   at java.util.concurrent.FutureTask.run(FutureTask.java:239)
:   at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
:   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
:   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
:   at     java.lang.Thread.run(Thread.java:856)
: Caused by: java.lang.NullPointerException
:   at org.greenbot.technologies.gpsme.GPSME_Main$ProgressTask.doInBackground(GPSME_Main.java:575)
:   at org.greenbot.technologies.gpsme.GPSME_Main$ProgressTask.doInBackground(GPSME_Main.java:1)
:   at android.os.AsyncTask$2.call(AsyncTask.java:287)
:   at java.util.concurrent.FutureTask.run(FutureTask.java:234)
:   ... 4 more

if(json != null){
    for (int i = 0; i < json.length(); i++) {

            try {
                JSONObject c = json.getJSONObject(i);
                String parsed_results_formatted_address = c
                        .getString("formatted_address");
arrfortextviews.add(parsed_results_formatted_address);

            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
}

ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    //if there is a connection
    if (netInfo != null && netInfo.isConnectedOrConnecting()){
     ...put your code here...
}