android - 异步任务在 2.3.3 中未运行 doInBackground

Question

我正在开发一个 Android 应用程序。现在我想使用 AsyncTask。它在 android 4.1 中完美运行，但 doInBackground 方法在 android 2.3.3 中无法运行。 logcat 中没有错误..

我有一个扩展 vom AsyncTask 的类。所以我从 new Class().execute() 开始。构造函数始终有效。

你知道如何解决 android 2.3.3 中的问题吗？

编辑: 我的代码:

private class TopicList extends AsyncTask<String, Integer, String> {
    private TopicList(){
        Log.e("Constructor","Works");
    }
    @Override
    protected String doInBackground(String... arg0) {
        Log.e("InBackground","Works");
        new Thread(new Runnable() {
            public void run() {
       // Network processes
                }
        }).start();
        return null;
    }
}

我有目标版本 17 和 minSdkVersion 7。您还需要更多信息吗？我使用以下代码执行它:

new TopicList().execute();

logcat中的错误日志仅显示构造函数有效。

Answer 1

异步任务 API: http://developer.android.com/reference/android/os/AsyncTask.html

阅读上面的文档后，很明显 AsyncTask 在 2.3.3 版本中应该可以正常工作(它是在 API 3 = Android 1.5 中添加的)。

您确定传递的参数正确吗？这是一个异步任务的简单示例，它调用 WebService 并在 Activity 的 TextView 中显示结果，我希望这可以帮助您走上正轨:

private class AsyncTaskWebServiceCaller extends AsyncTask<Void, Void, String> {
    private ProgressDialog dialog = new ProgressDialog(MainActivity.this);

    @Override
    protected void onPreExecute() {
        dialog.setMessage("Connecting to Web Service...");
        dialog.show();
    }

    @Override
    protected String doInBackground(Void...voids) {
        //create the envelope for the message
        SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
        envelope.dotNet = false;

        //get the card (SOAPObject) that will be put into the envelope
        SoapObject soapObject = new SoapObject(WSDL_TARGET_NAMESPACE, OPERATION_NAME);
        envelope.setOutputSoapObject(soapObject);

        //put something on the card  
        PropertyInfo propertyInfo = new PropertyInfo();
        propertyInfo.setType(PropertyInfo.STRING_CLASS);
        propertyInfo.setName("macAddress");
        propertyInfo.setValue(macAddress);
        soapObject.addProperty(propertyInfo);

        //call WebService
        try {
            HttpTransportSE httpTransportSE = new HttpTransportSE(SOAP_ADDRESS);
            httpTransportSE.debug = true;
            httpTransportSE.call(SOAP_ACTION, envelope);
            Object response = envelope.getResponse();
            return response.toString();             
        } catch (Exception e) {
            String text = "Oops!! App has crashed with exception: "+e.getMessage() + "\n" + "Stack trace below:\n";
            StackTraceElement[] stackTrace = e.getStackTrace();
            for (StackTraceElement stackTraceElement : stackTrace) {
                text += stackTraceElement.toString() + "\n";
            }
            return text;
        }
    }

    @Override
    protected void onPostExecute(String result) {
        if (dialog.isShowing()) {
            dialog.dismiss();
        }
        TextView textView = (TextView)findViewById(R.id.textView1);
        textView.setText(result);
    }

}

要调用 AsyncTask，只需执行以下操作:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    new AsyncTaskWebServiceCaller().execute();
}