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我正在尝试在我的应用程序中使用 walfram alpha 我已经让我的代码在 java 项目中工作，但是当我尝试在 android 中使用它时，我得到“异常下载 URL”

这是我的代码

public class AlphaAPISample extends Activity{

// PUT YOUR APPID HERE:
private static String appid = MYAPPID;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    String input = "who is the president";
    WAEngine engine = new WAEngine();
    engine.setAppID(appid);
    engine.addFormat("plaintext");
    WAQuery query = engine.createQuery();
    query.setInput(input);
    try {
        System.out.println("Query URL:");
        System.out.println(engine.toURL(query));
        WAQueryResult queryResult = engine.performQuery(query);

        if (queryResult.isError()) {
            System.out.println("Query error");
            System.out.println("  error code: " + queryResult.getErrorCode());
            System.out.println("  error message: " + queryResult.getErrorMessage());

        } else if (!queryResult.isSuccess()) {
            System.out.println("Query was not understood; no results available.");

        } else {

            // Got a result.
            System.out.println("Successful query. Pods follow:\n");
            for (WAPod pod : queryResult.getPods()) {
                if (!pod.isError()) {
                    if(pod.getTitle().equals("Result")) {
                        System.out.println(pod.getTitle());
                        for (WASubpod subpod : pod.getSubpods()) {
                            for (Object element : subpod.getContents()) {
                                if (element instanceof WAPlainText) {
                                    System.out.println(((WAPlainText) element).getText());
                                }
                            }
                        }
                    }
                }
            }
            // We ignored many other types of Wolfram|Alpha output, such as warnings, assumptions, etc.
            // These can be obtained by methods of WAQueryResult or objects deeper in the hierarchy.
        }
    } catch (WAException e) {
        e.printStackTrace();
    }


   }
}

这是我的日志猫

    07-21 05:13:23.276  30688-30688/com.assist.me I/System.out﹕ Query URL:
07-21 05:13:23.276  30688-30688/com.assist.me I/System.out﹕ http://api.wolframalpha.com/v2/query?appid=MYAPPID&input=who+is+the+president&format=plaintext&async=false&reinterpret=true
07-21 05:13:23.276  30688-30688/com.assist.me I/URLFetcher﹕ Downloading url http://api.wolframalpha.com/v2/query?appid=MYAPPID&input=who+is+the+president&format=plaintext&async=false&reinterpret=true
07-21 05:13:23.286  30688-30688/com.assist.me W/URLFetcher﹕ Exception downloading URL http://api.wolframalpha.com/v2/query?appid=MYAPPID&input=who+is+the+president&format=plaintext&async=false&reinterpret=true. com.wolfram.alpha.net.WAHttpException: android.os.NetworkOnMainThreadException
07-21 05:13:23.286  30688-30688/com.assist.me I/URLFetcher﹕ Finished downloading URL http://api.wolframalpha.com/v2/query?appid=MYAPPID&input=who+is+the+president&format=plaintext&async=false&reinterpret=true. Elapsed millis: 8
07-21 05:13:23.286  30688-30688/com.assist.me W/System.err﹕ com.wolfram.alpha.WAException: com.wolfram.alpha.net.WAHttpException: android.os.NetworkOnMainThreadException
07-21 05:13:23.286  30688-30688/com.assist.me W/System.err﹕ at com.wolfram.alpha.WAEngine.performQuery(WAEngine.java:128)
07-21 05:13:23.286  30688-30688/com.assist.me W/System.err﹕ at com.pin.assistme.AlphaAPISample.onCreate(AlphaAPISample.java:83)

代码中每个带有我的应用程序 ID 的地方都被替换为短语“MYAPPID”

解决了：

问题是当我应该使用 AsyncTask 时，我试图从主线程获取互联网数据，正如您在异常中看到的那样

android.os.NetworkOnMainThreadException

有关执行此操作的正确方法，请参见下面的代码。

4

1 回答 1

1

好的，我想通了！

public class AlphaAPISample extends Activity {

// PUT YOUR APPID HERE:
private static String appid = "APPID";

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    new YourTask().execute();
}


WAQueryResult queryResult;

private class YourTask extends AsyncTask<WAQueryResult, Void, WAQueryResult> {


    protected void onPreExecute() {

    }

    @Override
    protected WAQueryResult doInBackground(WAQueryResult... urls) {
        String input = "who is the president";
        WAEngine engine = new WAEngine();
        engine.setAppID(appid);
        engine.addFormat("plaintext");

        // Create the query.
        WAQuery query = engine.createQuery();
        query.setInput(input);
        queryResult = null;
        try {
            queryResult = engine.performQuery(query);
        } catch (WAException e) {
            e.printStackTrace();
        }
        return queryResult;
    }

    @Override
    protected void onPostExecute(WAQueryResult response) {
        if (queryResult.isError()) {
            System.out.println("Query error");
            System.out.println("  error code: " + queryResult.getErrorCode());
            System.out.println("  error message: " + queryResult.getErrorMessage());

        } else if (!queryResult.isSuccess()) {
            System.out.println("Query was not understood; no results available.");

        } else {

            // Got a result.
            System.out.println("Successful query. Pods follow:\n");
            for (WAPod pod : queryResult.getPods()) {
                if (!pod.isError()) {
                    if (pod.getTitle().equals("Result")) {
                        System.out.println(pod.getTitle());
                        for (WASubpod subpod : pod.getSubpods()) {
                            for (Object element : subpod.getContents()) {
                                if (element instanceof WAPlainText) {
                                    System.out.println(((WAPlainText) element).getText());
                                    Toast.makeText(getApplicationContext(),((WAPlainText) element).getText(),Toast.LENGTH_SHORT).show();
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

}

于 2014-07-21T02:57:52.390 回答