Question

我在Android Fragment类中执行AsyncTask时遇到了一些问题。在onClick方法中，我使用以下代码new BackgroundTaskPost().execute();

调用了我的执行

我试图以不同的方式形成我的AsyncTask，但它们都不起作用。

我最近的尝试如下：

public class BackgroundTaskPost extends AsyncTask<String, String, String> {
    @Override
    protected void onPreExecute(){
        SharedPreferences preferenceLogin = getActivity().getSharedPreferences(loginPreference, Context.MODE_PRIVATE);
        userName = preferenceLogin.getString("UserName", null);
        password = preferenceLogin.getString("Password", null);

        SharedPreferences sharedPreferences = getActivity().getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
        radioId1 = sharedPreferences.getString("check1", " ");
        radioId2 = sharedPreferences.getString("check2", " ");
        radioId3 = sharedPreferences.getString("check3", " ");
        radioId4 = sharedPreferences.getString("check4", " ");
        radioId5 = sharedPreferences.getString("check5", " ");
        radioId6 = sharedPreferences.getString("check6", " ");
        radioId7 = sharedPreferences.getString("check7", " ");
        radioId8 = sharedPreferences.getString("check8", " ");
        radioId9 = sharedPreferences.getString("check9", " ");
        radioId10 = sharedPreferences.getString("check10", " ");
        radioId11 = sharedPreferences.getString("check11", " ");
        //fev1 = pref.getFloat("Result", 0);

        outputs = new Outputs[13];
        outputs[0] = new Outputs("387.WEIGHT", "Float", "25.3");
        outputs[1] = new Outputs("383.FIELD", "String", radioId1);
        outputs[2] = new Outputs("384.FIELD", "String", radioId2);
        outputs[3] = new Outputs("381.FIELD", "String", radioId3);
        outputs[4] = new Outputs("389.FIELD", "String", radioId4);
        outputs[5] = new Outputs("388.LF#FEV1", "Float", "0.99");
        outputs[6] = new Outputs("390.FIELD", "String", radioId5);
        outputs[7] = new Outputs("378.FIELD", "String", radioId6);
        outputs[8] = new Outputs("379.FIELD", "String", radioId7);
        outputs[9] = new Outputs("380.FIELD", "String", radioId8);
        outputs[10] = new Outputs("382.FIELD", "String", radioId9);
        outputs[11] = new Outputs("385.FIELD", "String", radioId10);
        outputs[12] = new Outputs("386.FIELD", "String", radioId11);
    }

    @Override
    protected String doInBackground(String... params){
        postRequest = new HttpPostRequest(userName, password);

        String content = postRequest.postQuestionnaire(59, "Månedkontrol", "1.0", outputs);
        return content;
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
        Toast.makeText(getActivity(), result, Toast.LENGTH_LONG).show();
    }
}

我的问题是，我从未来过onPostExecute，因为应用程序崩溃，导致logcat出现错误。

    java.lang.RuntimeException: An error occured while executing doInBackground()
        at android.os.AsyncTask$3.done(AsyncTask.java:300)
        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
        at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
        at java.util.concurrent.FutureTask.run(FutureTask.java:242)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
        at java.lang.Thread.run(Thread.java:841)
 Caused by: java.lang.RuntimeException: Failed : HTTP error code : 500
        at com.example.OpenTeleStandaloneApplication.HttpIntegration.HttpPostRequest.postRequest(HttpPostRequest.java:55)
        at com.example.OpenTeleStandaloneApplication.HttpIntegration.HttpPostRequest.postQuestionnaire(HttpPostRequest.java:104)
        at com.example.OpenTeleStandaloneApplication.ApplicationInterface.cfqrlunge7$BackgroundTaskPost.doInBackground(cfqrlunge7.java:169)
        at com.example.OpenTeleStandaloneApplication.ApplicationInterface.cfqrlunge7$BackgroundTaskPost.doInBackground(cfqrlunge7.java:128)
        at android.os.AsyncTask$2.call(AsyncTask.java:288)
        at java.util.concurrent.FutureTask.run(FutureTask.java:237)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
        at java.lang.Thread.run(Thread.java:841)

我可以告诉我有几次尝试在Eclipse的控制台应用程序中使用相同的代码，它在没有问题的情况下工作得很好。所以我可以得出结论，问题出现在AsyncTask。

HttpRequest：

public String getInput(int id, String name, String version, Outputs[] outputs){
    DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");

    String retVal = "{\"QuestionnaireId\":" + id + "," +
            "\"date\":\"" + dateFormat.format(new Date()) + "\"," +
            "\"name\":\"" + name + "\"," +
            "\"version\":\"" + version + "\"," +
            "\"output\":[";
    for (int i = 0; i < outputs.length; i++) {
        retVal += "{\"name\":\""+ outputs[i].getName() +
                "\",\"type\":\"" + outputs[i].getType() +
                "\",\"value\":" + outputs[i].getValue() +
                "}";
        if(i < outputs.length - 1)
            retVal += ",";
    }
    retVal += "]}";

    return retVal;
}

public String postQuestionnaire(int id, String name, String version, Outputs[] outputs){
    return postRequest("rest/questionnaire/listing", getInput(id, name, version, outputs));
}

希望任何人都可以帮助我，过去两天我在这个问题上花了很多时间。非常感谢。

Answer 1

观察 - 有几个非常好的网络/休息库，所以没有理由用低级别的HttpRequest和朋友推出自己的库。处理简单HTTP 500错误的问题强调了这一点。

此外，尽管获得了很多＆＃34;积极的新闻＆＃34;，AsyncTask是一个尝试进行网络访问的糟糕地方。我认为它是一个根本不应该被使用的结构，因为它不是活动生命周期意识，但我离题了。

我建议您查看上述库中的一个，例如Retrofit或Volley。他们将为您提供一个处理许多问题的框架，而不是重新发明轮子。

无法正确执行AsyncTask

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