java - 我如何将参数传递给 AsyncTask，并将结果返回给另一个类的字段变量？

Question

我在 android Java 中遇到 asynctask 问题。这是同样的问题:variable returns null outside asynctask android我的异步任务从 url 获取数据，以获取 google maps 的方向!这是我调用我的代码的地方，onrespondre 内部 => myvaraible 有数据，但变量外部是 null。

    public void onResponse(String status, Document doc, final GoogleDirection gd) {
    mMap.addMarker(new MarkerOptions()
            .position(
                    new LatLng(myLocation.getLatitude(), myLocation
                            .getLongitude()))
            .icon(BitmapDescriptorFactory
                    .defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));
    mMap.addMarker(new MarkerOptions().position(Position).icon(
            BitmapDescriptorFactory
                    .defaultMarker(BitmapDescriptorFactory.HUE_RED)));

    mMap.addPolyline(gd.getPolyline(doc, 3, Color.RED));
    MyVariable = gd.getTotalDurationValue(doc);
}

这是类:

    private class RequestTask extends AsyncTask<String, Void, Document> {
    protected Document doInBackground(String... url) {
        try {
            HttpClient httpClient = new DefaultHttpClient();
            HttpContext localContext = new BasicHttpContext();
            HttpPost httpPost = new HttpPost(url[0]);
            HttpResponse response = httpClient.execute(httpPost,
                    localContext);
            InputStream in = response.getEntity().getContent();
            DocumentBuilder builder = DocumentBuilderFactory.newInstance()
                    .newDocumentBuilder();

            return builder.parse(in);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ParserConfigurationException e) {
            e.printStackTrace();
        } catch (SAXException e) {
            e.printStackTrace();
        }

        return null;
    }

    protected void onPostExecute(Document doc) {
        super.onPostExecute(doc);

        if (mDirectionListener != null) {
            mDirectionListener.onResponse(getStatus(doc), doc,
                    GoogleDirection.this);
        }
    }

    private String getStatus(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("status");
        Node node1 = nl1.item(0);

        if (isLogging) {
            Log.i("GoogleDirection", "Status : " + node1.getTextContent());
        }

        return node1.getTextContent();
    }
}

Answer 1

我想 getter setter 是非常基础的。但是对于不知道的人:

一个单独的 getter setter 类

public class getterSetter{

String test;

public getterSetter()
{
    super();
    test= "";
}

public String getStatus()
{
    return test;
}
public setStatus(String input)
{
    test= input;
}
}

在你的Asynctask中:

protected void onPostExecute(Document doc) {
        super.onPostExecute(doc);
        setStatus(getStatus(doc));
        if (mDirectionListener != null) {
            mDirectionListener.onResponse(doc,
                    GoogleDirection.this);
        }

在您的onResponse 方法中:

public void onResponse(Document doc, final GoogleDirection gd) {

String status = getStatus();
mMap.addMarker(new MarkerOptions()
        .position(
                new LatLng(myLocation.getLatitude(), myLocation
                        .getLongitude()))
        .icon(BitmapDescriptorFactory
                .defaultMarker(BitmapDescriptorFactory.HUE_BLUE)));
mMap.addMarker(new MarkerOptions().position(Position).icon(
        BitmapDescriptorFactory
                .defaultMarker(BitmapDescriptorFactory.HUE_RED)));

mMap.addPolyline(gd.getPolyline(doc, 3, Color.RED));
MyVariable = gd.getTotalDurationValue(doc);
}