我正在创建一个应用程序,该应用程序在单击按钮时应显示RSS源。链接到新页面的按钮不起作用
我有一个主类,屏幕1和屏幕2 和一个主要的xml文件和屏幕1和屏幕2的布局。
现在我与主要XML和类是RSS源之前试过它工作得很好
然而,现在,当我试图让屏幕1(屏幕截图1),其中显示饲料的地方,我只是得到一个黑色屏幕。
我想知道为什么会发生这种情况,正如我通过Screen1类告诉链接到screen1 xml文件一样。
主类:
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class SImpleRssReader2Activity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button videoNext = (Button) findViewById(R.id.videoButton) ;
videoNext.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.screen2);
// Intent i = new Intent();
// i.setClassName("rahul.application.WunApp", "rahul.application.WunApp.screen1");
// startActivity(i);
}
});
Button newsNext = (Button) findViewById(R.id.newsButton);
newsNext.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.screen1);
// Intent i = new Intent();
// i.setClassName("rahul.application.WunApp", "rahul.application.WunApp.screen1");
// startActivity(i);
}
});
}
}
屏幕1:
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import android.app.ListActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class Screen1 extends ListActivity {
/** Called when the activity is first created. */
List<String> headlines;
List<String> links;
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
Uri uri = Uri.parse((String) links.get(position));
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.screen1);
// Initializing instance variables
headlines = new ArrayList<String>();
links = new ArrayList<String>();
try {
URL url = new URL("http://news.google.com/news?ned=us&topic=h&output=rss");
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
factory.setNamespaceAware(false);
XmlPullParser xpp = factory.newPullParser();
// We will get the XML from an input stream
xpp.setInput(getInputStream(url), "UTF_8");
/* We will parse the XML content looking for the "<title>" tag which appears inside the "<item>" tag.
* However, we should take in consideration that the rss feed name also is enclosed in a "<title>" tag.
* As we know, every feed begins with these lines: "<channel><title>Feed_Name</title>...."
* so we should skip the "<title>" tag which is a child of "<channel>" tag,
* and take in consideration only "<title>" tag which is a child of "<item>"
*
* In order to achieve this, we will make use of a boolean variable.
*/
boolean insideItem = false;
// Returns the type of current event: START_TAG, END_TAG, etc..
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)
headlines.add(xpp.nextText()); //extract the headline
} else if (xpp.getName().equalsIgnoreCase("link")) {
if (insideItem)
links.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();
}
// Binding data
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, headlines);
setListAdapter(adapter);
}
public InputStream getInputStream(URL url) {
try {
return url.openConnection().getInputStream();
} catch (IOException e) {
return null;
}
}
主要的xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:id="@+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:text="@string/welcome" >
<requestFocus />
</EditText>
<TextView
android:id="@+id/textView5"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView7"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<Button
android:id="@+id/newsButton"
android:layout_width="152dp"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:text="@string/button1" />
</RelativeLayout>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" />
</RelativeLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</RelativeLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<Button
android:id="@+id/videoButton"
android:layout_width="156dp"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:text="@string/button3" />
</RelativeLayout>
</LinearLayout>
屏蔽1的xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ListView
android:id="@+android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
所以总结一下:当我只有主类和xml时它工作,但现在我链接到一个新的类和xml,它不起作用。为什么?
我在screen1中的列表数据应该是Screen1.java中提供的RSS源...但是我能够在不使用Asynctask的情况下获得RSS源(不想尝试使用它,因为没有学习了如何使用Asynctask)在我的main.xml中,我所需要的就是能够使用main.xml中的链接在screen1.xml中显示......我知道可能是更有效的方法,但对于我这似乎是最容易理解的。第3点也没有做任何事情。尽管感谢您的帮助。 –