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当我按下一个按钮时，它应该从网页中检索数据并根据我的布局显示它。这样做很好，但只有当我单击返回时，才返回我的主要活动（家庭活动）并再次按下按钮。

我第一次按下按钮时加载需要很长时间，有时不起作用。但第二次是即时加载[工作正常]。

这是代码 - 三个类 - HomeActivity.java、News.Java 和 MyNewsHandler.java

public class HomeActivity extends Activity
{
String username = " ";
Button alog;
Button news;
Button forumTime;
EditText usernameEntry;
SharedPreferences preferences;
ImageView image;
TextView usernametv;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.home);

    forumTime = (Button)findViewById(R.id.timeButton);
    news = (Button) findViewById(R.id.newsButton); // <--- Heres the problem
    alog = (Button) findViewById(R.id.alogButton);
    usernameEntry = (EditText) findViewById(R.id.username);


    //For news button
    OnClickListener newsListener = new OnClickListener()
    {
        public void onClick(View v)
        {
            Intent intent = new Intent(HomeActivity.this, News.class);
            startActivity(intent);
        }
    };

    //Attaching listeners
    //forumTime.setOnClickListener(timeListener);
    //alog.setOnClickListener(alogListener);
    news.setOnClickListener(newsListener);
}

public void display(String string)
{
    Toast.makeText(getBaseContext(), string, 300000).show();
}

}

public class MyNewsHandler extends DefaultHandler
{
private Boolean inTitle = false;
private Boolean inDescription = false;
private Boolean inItem = false;
private Boolean inCategory = false;
static public ArrayList<String> title = new ArrayList<String>(),
    description = new ArrayList<String>(), category = new ArrayList<String>();
private StringBuilder buff = null;
// All methods auto called in this order - start, characters, end
/*
 * Called when an xml tag starts
 * imgView.setImageResource(R.drawable.newImage);
 */
@Override
public void startElement(String uri, String localName, String qName,Attributes attributes) 
{
    if (inItem) 
    {
        if (localName.equals("title")) 
        {
            inTitle = true;
            buff = new StringBuilder();
        }
        if (localName.equals("description")) 
        {
            inDescription = true;
            buff = new StringBuilder();
        }
        if (localName.equals("category")) 
        {
            inCategory = true;
            buff = new StringBuilder();
        }

    }
    if (localName.equals("item")) 
    {
        inItem = true;
    }
}
/*
 * Called when an xml tag ends
 */
@Override
public void endElement(String uri, String localName, String qName)throws SAXException 
{
    if (!inTitle && !inDescription && !inCategory) 
    {
        inItem = false;
    } 
    else 
    {
        if (inTitle) 
        {
            String check = buff.toString().trim();
            title.add(check);
            inTitle = false;
            buff = null;
        }
        if (inDescription) 
        {
            String check2 = buff.toString().trim();
            String array [];
            int index = 0;
            if (check2.contains("/>"))
            {
                array = check2.split("/>");
                index = check2.indexOf("10;");
                description.add(array[array.length - 1].trim());
            }

            else description.add(check2);
            //description.add(array[1]);
            inDescription = false;
            buff = null;
        }
        if(inCategory)
        {
            String check = buff.toString().trim();
            category.add(check);
            inCategory = false;
            buff = null;
        }
    }
}
/*
 * Called to get tag characters
 */
@Override
public void characters(char ch[], int start, int length) 
{
    if (buff != null) 
    {
        for (int i = start; i < start + length; i++) 
        {
            buff.append(ch[i]);
        }
    }
}

}

public class News extends ListActivity
{
String url;
TextView text1;
TextView text2;
static ImageView img;
// newsList contains the list items 
static ArrayList<HashMap<String, Object>> newsList = new ArrayList<HashMap<String, Object>>();
// to store drawable id's
static HashMap<String, Integer> images = new HashMap<String, Integer>();
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    //Load xml containing image view and a linear layout with 2 textviews
    setContentView(R.layout.aloglistview); 

    img = (ImageView)findViewById(R.id.imageView2);
    text1 = (TextView) findViewById(R.id.text1);
    text2 = (TextView) findViewById(R.id.text2);

    // url we are retrieving from
    url = "http://services.runescape.com/m=news/latest_news.rss";

    HttpClient httpclient = new DefaultHttpClient();
    HttpGet httpget = new HttpGet(url);
    String result = ""; // result of http Post
    try
    {
        // Execute HTTP get Request
        HttpResponse response = httpclient.execute(httpget);

        // Extract the page content returned from the response
        BufferedReader in = new BufferedReader(new InputStreamReader(
                response.getEntity().getContent()));
        StringBuffer sb = new StringBuffer("");
        String line = "";
        String NL = System.getProperty("line.separator");
        while ((line = in.readLine()) != null)
        {
            sb.append(line + NL);
        }
        in.close();
        result = sb.toString(); // resulting content of the page
    } catch (ClientProtocolException e)
    {
        Log.d("ERROR", "ClientProtocolException=" + e);
        System.err.println("ClientProtocolException=" + e);
    } catch (IOException e)
    {
        Log.d("ERROR", "IOException=" + e);
        System.err.println("IOException=" + e);
    }
    try
    {
        //Parse the resulting page 
        Xml.parse(result, new MyNewsHandler());
    } catch (SAXException e)
    {
        e.printStackTrace();
    } catch (Exception e)
    {
        e.printStackTrace();
    }
    //needs to match formulate list thing
    SimpleAdapter adapter = new SimpleAdapter(this, newsList,
            R.layout.newsitem, new String[] { "Title", "Description", "Image"},
            new int[] { R.id.textnews1, R.id.textnews2, R.id.imageView2});

    populateList(); //Add all items to the newslist 
    setListAdapter(adapter);
}
public  void populateList()
{
    //Method to add to images hashmap 
    initMap();
    //reset each time the list is populated
    newsList = new ArrayList<HashMap<String, Object>>();
    //Display 10 items
    for (int i = 0; i < 11; i++)
    {
        HashMap<String, Object> temp = new HashMap<String, Object>();
        String title = MyNewsHandler.title.get(i);
        String category = MyNewsHandler.category.get(i);
        //default drawable
        int drawable = R.drawable.item;
        //Match title text to hash keys to set correct image
        for (Map.Entry<String, Integer> entry : images.entrySet()) 
        {
            String key = entry.getKey();
            Object value = entry.getValue();
            if(category.contains(entry.getKey()))
            {
                drawable = entry.getValue();
                break;
            }
            else drawable = R.drawable.item;
        }
        temp.put("Title", title);
        temp.put("Description", " " + MyNewsHandler.description.get(i));
        temp.put("Image",drawable);
        newsList.add(temp);
    }
}
public void display(String string)
{
    Toast.makeText(getBaseContext(), string, 1000202).show();
}
public void initMap()
{
    images.put("Behind the Scenes News",R.drawable.behindthescenes);
    images.put("Customer Support News",R.drawable.customerservice);
    images.put("Game Update News",R.drawable.gameupdate);
    images.put("Website News",R.drawable.devblog);
    images.put("Technical News",R.drawable.technicalnews);
}

}

对不起，代码太长了..问题是它可以工作（哈..），但是当我第一次想要它时它不会立即加载。

它这样做：启动应用程序>点击新闻按钮>“不加载，空白屏幕”

但是当我这样做时它会起作用：启动应用程序>点击新闻按钮>回击>点击新闻按钮>“即时加载”

我遵循了一个建议，我在点击按钮之前进行了预解析，还做了另一次尝试，我完全摆脱了图像（认为这可能是延迟）。没有不同。仍然是相同的行为。

任何建议表示赞赏！

4

2 回答 2

1

树点：

  1. 用于AsyncTask与 UI 没有直接关系的任何事物
  2. 缓存一切。从网站获得 XML 后，将其保存在某处，下次在开始下载之前从文件中加载。
  3. 预加载。不要等待用户点击按钮。应用程序启动后，立即启动AsyncTask（参见第 1 页）以执行后台下载和 XML 解析。当用户按下按钮时，结果就准备好了。
于 2012-05-03T06:58:38.200 回答
1

列尼克所说的一切。

我的解决方案只是略有不同。我做了这样的事情：

  1. On（按钮按下或其他触发事件）发出启动 IntentService（而不是 AsyncTask）的 Intent。为什么？它的语法比较简单，我想从几个地方调用它。
  2. 立即开始显示结果并在结果滴入时用结果填充它。我这样做的简单方法是通过 ContentProvider 公开我的所有数据并运行 ListFragment 。
于 2012-05-03T21:45:07.850 回答