android - 异步任务类不适用于较新的 Android 版本

Question

我想解析 xml，所以我编写了代码，它可以工作到 2.3，但在最新版本上它不起作用，所以我阅读了 asynctask 并修改了我的代码，但我的 imageview 仍然是空白的，我在 logcat 上没有收到任何错误表示 Asynctask 的实现有问题。

{
    setContentView(R.layout.actionbar);
    String URL = "http://ws.audioscrobbler.com/2.0/?method=artist.search&artist=ricky_martin&api_key=97855e265470056987425832aa9aa81&limit=" + 1 + "&page=" + 1;
    new FetchXMLAsyncTask().execute(URL);
    icon = (ImageView) findViewById(R.id.icon);
}

class FetchXMLAsyncTask extends AsyncTask<String, Void, Void> {
    String name;
    @Override
    protected Void doInBackground(String... params) {
        try {
            // TODO Auto-generated method stub
            final String Artist = "artist";
            final String KEY_NAME = "name";
            final String API = "b25b959554ed76058ac220b7b2e0a026";
            final String KEY_IMAGE ="image";
            //final String KEY_COST = "cost";
            //final String KEY_DESC = "description";
            String URL = params[0]; 
            XmlParser parser = new XmlParser();
            String xml = parser.getXmlFromUrl(URL); // getting XML
            Document doc = parser.getDomElement(xml); // getting DOM element
            XPathFactory xPathfactory = XPathFactory.newInstance();
            XPath xpath = xPathfactory.newXPath();
            XPathExpression expr;
            expr = xpath.compile("//image[@size=\"large\"]");
            NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);
            // looping through all item nodes <item>
            for (int i = 0; i < nl.getLength(); i++) {
                Element e = (Element) nl.item(i);
                String name = parser.getValue(e, KEY_NAME);// name child value
                image = parser.getValue(e, KEY_IMAGE);
                // Toast.makeText(this, "name"+name+"url"+image, Toast.LENGTH_SHORT).show();
            } }catch (XPathExpressionException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        return null;
    }
    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        //do something after parsing is done
        URL thumb_u;
        try {
            thumb_u = new URL(image);
            Drawable thumb_d = Drawable.createFromStream(thumb_u.openStream(), "src");
            icon.setImageDrawable(thumb_d);
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }   
}

Answer 1

Starting Honeycomb AsyncTasks 默认一次启动一个。也许您还有其他一些任务挂起并阻止了这个任务的运行(新任务正在等待旧任务完成，因为它不会并行运行)。

启动 android 3.0 你应该在 THREAD_POOL_EXECUTOR 中启动任务

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
    task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, params);
} else {
    task.execute(params);
}