Question

我已对代码进行了更改，因为我在this.setContentView(sv);的开头给出了onCreate()，但是只有在执行try catch之后才会加载视图。是否真的可以在执行try catch之前显示视图？

public class viewstoryActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        /** Create a new layout to display the view */
        ScrollView sv = new ScrollView(this);
        LinearLayout layout1 = new LinearLayout(this);
        layout1.setOrientation(LinearLayout.VERTICAL);
        this.setContentView(sv);
        /** Create a new textview array to display the results */

        try {
            LinearLayout layout[];
            TextView name[];
            ImageView website[];
            TextView category[];
            URL url = new URL("http://gdata.youtube.com/feeds/api/videos?start-index=1&max-results=25&vq=itsaperfectstory&orderby=relevance");

            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document doc = db.parse(new InputSource(url.openStream()));

            NodeList nodeList = doc.getElementsByTagName("entry");

            /** Assign textview array lenght by arraylist size */
            layout = new LinearLayout[nodeList.getLength()];
            name = new TextView[nodeList.getLength()];
            website = new ImageView[nodeList.getLength()];
            category = new TextView[nodeList.getLength()];

            for (int i = 0; i < nodeList.getLength(); i++) {
                Node node = nodeList.item(i);
                layout[i]= new LinearLayout(this);
                layout[i].setOrientation(LinearLayout.VERTICAL);
                layout[i].setBackgroundResource(R.drawable.allicon_bg);
                layout[i].setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,150));
                name[i] = new TextView(this);
                website[i] = new ImageView(this);
                category[i] = new TextView(this);

                name[i].setPadding(50, 20,0,0);
                Element fstElmnt = (Element) node;
                NodeList nameList = fstElmnt.getElementsByTagName("title");
                Element nameElement = (Element) nameList.item(0);
                nameList = nameElement.getChildNodes();
                name[i].setText(((Node) nameList.item(0)).getNodeValue());

                NodeList websiteList = fstElmnt.getElementsByTagName("media:content");
                Element websiteElement = (Element) websiteList.item(0);
                websiteList = websiteElement.getChildNodes();

                final String url1 = websiteElement.getAttribute("url");
                NodeList websiteList1 = fstElmnt.getElementsByTagName("media:thumbnail");
                Element websiteElement1 = (Element) websiteList1.item(1);
                String test=websiteElement1.getAttribute("url");

                Bitmap bm = null;
                URL aURL = new URL(test);
                URLConnection conn = aURL.openConnection();
                conn.connect();
                InputStream is = conn.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(is); 
                bm = BitmapFactory.decodeStream(bis);
                bis.close();
                is.close();  // TODO: handle exception

                website[i].setImageBitmap(bm);
                website[i].setMaxWidth(50);
                website[i].setPadding(380, 0, 0, 0);
                layout[i].addView(name[i]);
                layout[i].addView(website[i]);
                layout1.addView(layout[i]);
                layout[i].setOnClickListener(new OnClickListener() {
                    public void onClick(View v) {
                        Bundle bundle = new Bundle();
                        // add data to bundle
                        bundle.putString("url", url1);
                        Intent intent=new Intent(viewstoryActivity.this, VidActivity.class);
                        intent.putExtras(bundle);
                        startActivityForResult(intent, 0);
                        overridePendingTransition (R.anim.right_slide_out, R.anim.right_slide_out);
                    }
                });
            }
        } catch (Exception e) {
            System.out.println("XML Parsing Exception = " + e);
        }

        /** Set the layout view to display */
        sv.addView(layout1);
    }
}

Answer 1

在分析了您的onCreate()后，很明显您的活动需要一段时间才能展示。您的所有UI都是动态设计和添加的，必须（根据您的代码）等待数据加载并进行解析和组织。换句话说，您通过数据处理阻止了UI。

考虑将数据加载移至AsyncTask。还可以考虑在数据之前设计/加载UI 。这将允许您的用户看到某些内容，即使它不完整。您始终可以在onCreate()之后添加视图或更改显示属性。它也会减少对UI滞后的感知。

Answer 2

建议将big try块移到另一个线程，不要阻止ui。

Answer 3

正如其他人所说，将你的工作转移到AsyncTask中，这样它就不会阻塞主线程。如果你有兴趣了解到究竟有什么需要，那么我建议花点时间阅读TraceView - 这是一个很好的分析工具。

如何解决加载活动的延迟？

3 个答案: