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我正在使用 Jsoup，在 Android 中，我想从这个网站的第一个标签“img”中获取属性“src”：http: //www.proyectoglass.com/feeds/posts/default? alt=rss ，由于某种原因，我无法确定程序正在停止，而且我一无所知。这是代码：

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    TextView test=(TextView) findViewById(R.id.testText);

    try {
        Document doc = Jsoup.connect("http://www.proyectoglass.com/feeds/posts/default?alt=rss").ignoreContentType(true).get(); 
        Element img =  doc.select("img").first();
        test.setText(""+img.attr("abs:src"));
    } catch (IOException e) {
        test.setText(e.toString());
    }

}

这是我的 LogCat：

06-14 15:57:48.064: W/dalvikvm(542): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
06-14 15:57:48.106: E/AndroidRuntime(542): FATAL EXCEPTION: main
06-14 15:57:48.106: E/AndroidRuntime(542): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jsoup_test/com.example.jsoup_test.MainActivity}: java.lang.NullPointerException
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.os.Looper.loop(Looper.java:123)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread.main(ActivityThread.java:4627)
06-14 15:57:48.106: E/AndroidRuntime(542):  at java.lang.reflect.Method.invokeNative(Native Method)
06-14 15:57:48.106: E/AndroidRuntime(542):  at java.lang.reflect.Method.invoke(Method.java:521)
06-14 15:57:48.106: E/AndroidRuntime(542):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-14 15:57:48.106: E/AndroidRuntime(542):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-14 15:57:48.106: E/AndroidRuntime(542):  at dalvik.system.NativeStart.main(Native Method)
06-14 15:57:48.106: E/AndroidRuntime(542): Caused by: java.lang.NullPointerException
06-14 15:57:48.106: E/AndroidRuntime(542):  at com.example.jsoup_test.MainActivity.onCreate(MainActivity.java:28)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-14 15:57:48.106: E/AndroidRuntime(542):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
06-14 15:57:48.106: E/AndroidRuntime(542):  ... 11 more

在网络中，我想从 src 获取 url。

<img width="640" height="344" border="0" src="http://4.bp.blogspot.com/-tNEIyl1tTJA/UbRVa2bKpiI/AAAAAAAAAs4/xqW9VPw7b9g/s640/Larry-Page-Google-Project-Glass.jpg"/>
4

2 回答 2

0

您的链接看起来像 rss 提要（http://www.proyectoglass.com/feeds/posts/default?alt=rss）。

假设您拥有 html 并使用 asynctask 的任何方式

<img width="640" height="344" border="0" src="http://4.bp.blogspot.com/-tNEIyl1tTJA/UbRVa2bKpiI/AAAAAAAAAs4/xqW9VPw7b9g/s640/Larry-Page-Google-Project-Glass.jpg"/>

您可以执行以下操作 

String html ="<img width="+640+" height="+344+" border="+0+" src="+"http://4.bp.blogspot.com/-tNEIyl1tTJA/UbRVa2bKpiI/AAAAAAAAAs4/xqW9VPw7b9g/s640/Larry-Page-Google-Project-Glass.jpg"+"/>";
Document doc = Jsoup.parse(html);
Element link = doc.select("img").first();
String s = link.attr("src");

编辑：

public class asynctask extends Activity {

TextView tv;
ArrayList<String> bb = new ArrayList<String>();
ProgressDialog pd;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView) findViewById(R.id.textView1);
pd = new ProgressDialog(asynctask.this);
pd.setMessage("Loading..");
new TheTask().execute(); 
} 
class TheTask extends AsyncTask <Void,Void,Void>
{

@Override
protected void onPreExecute() {
    // TODO Auto-generated method stub
    super.onPreExecute();
    pd.show();
}
@Override
protected Void doInBackground(Void... params) {
    try
    {
    URL url = new URL("http://www.proyectoglass.com/feeds/posts/default?alt=rss");

    XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
    factory.setNamespaceAware(false);
    XmlPullParser xpp = factory.newPullParser();
    xpp.setInput(url.openConnection().getInputStream(), "UTF_8"); 
    //xpp.setInput(getInputStream(url), "UTF-8");   
    boolean insideItem = false;
    int eventType = xpp.getEventType();
    while (eventType != XmlPullParser.END_DOCUMENT) {
        if (eventType == XmlPullParser.START_TAG) {

            if (xpp.getName().equalsIgnoreCase("item")) {
                insideItem = true;
            } else if (xpp.getName().equalsIgnoreCase("title")) {
                if (insideItem)
                {

                }       
            } else if (xpp.getName().equalsIgnoreCase("link")) {
                if (insideItem)
                {

                }
            }
            else if (xpp.getName().equalsIgnoreCase("description")) {
                if (insideItem)
                    bb.add(xpp.nextText()); //extract the link of article
            }
        }else if(eventType==XmlPullParser.END_TAG && xpp.getName().equalsIgnoreCase("item")){
            insideItem=false;
        }

        eventType = xpp.next(); //move to next element
    }


} catch (MalformedURLException e) {
    e.printStackTrace();
} catch (XmlPullParserException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}
    return null;
}
@Override
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
Document doc = Jsoup.parse(bb.get(0).toString());
Element link = doc.select("img").first();
String s = link.attr("src"); 
pd.dismiss();
tv.setText(s);
}
}   
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity"
     >
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

</LinearLayout>

快照

在此处输入图像描述

于 2013-06-14T17:35:22.453 回答
0

谁能告诉我我做错了什么？

您在 MainActivity.java 的第 28 行调用对象引用的方法是一件坏事，该对象引用没有引用任何内容（null）。

于 2013-06-14T16:18:46.977 回答