Android 应用程序因切换活动而崩溃
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【中文标题】Android 应用程序因切换活动而崩溃【英文标题】：Android app crashes by switching the activity 【发布时间】：2016-11-09 10:17:08 【问题描述】：我的 android 应用程序有问题。当我按下按钮转到新活动时，它总是崩溃。
错误：
FATAL EXCEPTION: main
Process: PID: 15534
java.lang.RuntimeException: Unable to start activity ComponentInfocom.realliferpgadac.thomas.adacapp/com.realliferpgadac.thomas.adacapp.Feed: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup
at android.app.BackStackRecord.configureTransitions(BackStackRecord.java:1244)
at android.app.BackStackRecord.beginTransition(BackStackRecord.java:978)
at android.app.BackStackRecord.run(BackStackRecord.java:707)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1535)
at android.app.FragmentController.execPendingActions(FragmentController.java:325)
at android.app.Activity.performStart(Activity.java:6252)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
崩溃的activity的源代码：（应该是RSS Feed）
import android.os.AsyncTask;
import android.os.Bundle;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.app.ListFragment;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import java.io.StringReader;
public class Feed extends Activity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_feed);
if (savedInstanceState == null)
getFragmentManager().beginTransaction()
.add(R.id.tvFeed, new PlaceholderFragment())
.commit();
//@Override
// public boolean onCreateOptionsMenu(Menu menu)
// Inflate the menu; this adds items to the action bar if it is present.
//getMenuInflater().inflate(R.menu.main, menu);
//return true;
//
@Override
public boolean onOptionsItemSelected(MenuItem item)
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.tvFeed)
return true;
return super.onOptionsItemSelected(item);
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends ListFragment
// private TextView mRssFeed;
public PlaceholderFragment()
// @Override
// public View onCreateView(LayoutInflater inflater, ViewGroup container,
// Bundle savedInstanceState)
// View rootView = inflater.inflate(R.layout.fragment_main, container, false);
// mRssFeed = (TextView) rootView.findViewById(R.id.rss_feed);
// return rootView;
//
@Override
public void onStart()
super.onStart();
new GetAndroidPitRssFeedTask().execute();
private String getAndroidPitRssFeed() throws IOException
InputStream in = null;
String rssFeed = null;
try
URL url = new URL("http://www.androidpit.com/feed/main.xml");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
in = conn.getInputStream();
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
for (int count; (count = in.read(buffer)) != -1; )
out.write(buffer, 0, count);
byte[] response = out.toByteArray();
rssFeed = new String(response, "UTF-8");
finally
if (in != null)
in.close();
return rssFeed;
private class GetAndroidPitRssFeedTask extends AsyncTask<Void, Void, List<String>>
@Override
protected List<String> doInBackground(Void... voids)
List<String> result = null;
try
String feed = getAndroidPitRssFeed();
result = parse(feed);
catch (XmlPullParserException e)
e.printStackTrace();
catch (IOException e)
e.printStackTrace();
return result;
private List<String> parse(String rssFeed) throws XmlPullParserException, IOException
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
XmlPullParser xpp = factory.newPullParser();
xpp.setInput(new StringReader(rssFeed));
xpp.nextTag();
return readRss(xpp);
private List<String> readRss(XmlPullParser parser)
throws XmlPullParserException, IOException
List<String> items = new ArrayList<>();
parser.require(XmlPullParser.START_TAG, null, "rss");
while (parser.next() != XmlPullParser.END_TAG)
if (parser.getEventType() != XmlPullParser.START_TAG)
continue;
String name = parser.getName();
if (name.equals("channel"))
items.addAll(readChannel(parser));
else
skip(parser);
return items;
private List<String> readChannel(XmlPullParser parser)
throws IOException, XmlPullParserException
List<String> items = new ArrayList<>();
parser.require(XmlPullParser.START_TAG, null, "channel");
while (parser.next() != XmlPullParser.END_TAG)
if (parser.getEventType() != XmlPullParser.START_TAG)
continue;
String name = parser.getName();
if (name.equals("item"))
items.add(readItem(parser));
else
skip(parser);
return items;
private String readItem(XmlPullParser parser) throws XmlPullParserException, IOException
String result = null;
parser.require(XmlPullParser.START_TAG, null, "item");
while (parser.next() != XmlPullParser.END_TAG)
if (parser.getEventType() != XmlPullParser.START_TAG)
continue;
String name = parser.getName();
if (name.equals("title"))
result = readTitle(parser);
else
skip(parser);
return result;
// Processes title tags in the feed.
private String readTitle(XmlPullParser parser)
throws IOException, XmlPullParserException
parser.require(XmlPullParser.START_TAG, null, "title");
String title = readText(parser);
parser.require(XmlPullParser.END_TAG, null, "title");
return title;
private String readText(XmlPullParser parser)
throws IOException, XmlPullParserException
String result = "";
if (parser.next() == XmlPullParser.TEXT)
result = parser.getText();
parser.nextTag();
return result;
private void skip(XmlPullParser parser) throws XmlPullParserException, IOException
if (parser.getEventType() != XmlPullParser.START_TAG)
throw new IllegalStateException();
int depth = 1;
while (depth != 0)
switch (parser.next())
case XmlPullParser.END_TAG:
depth--;
break;
case XmlPullParser.START_TAG:
depth++;
break;
@Override
protected void onPostExecute(List<String> rssFeed)
if (rssFeed != null)
setListAdapter(new ArrayAdapter<>(
getActivity(),
android.R.layout.simple_list_item_1,
android.R.id.text1,
rssFeed));
崩溃活动的 XML 文件：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.realliferpgadac.thomas.adacapp.Feed">
<ScrollView
android:layout_
android:layout_>
<TextView
android:layout_
android:layout_
android:text="New Text"
android:id="@+id/tvFeed"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</ScrollView>
</RelativeLayout>
问题出在哪里，我该如何解决？
我希望你能帮助我。
谢谢，
emt
【问题讨论】：
ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup
您应该查看 logcat 的输出，因为它会告诉您应用程序崩溃的原因。
Caused by: java.lang.ClassCastException: android.widget.TextView cannot be cast to android.view.ViewGroup ... cast it as Textview and try
@IntelliJAmiya 感谢您的回答。我是 Java 开发的新手，所以我很抱歉这个问题，但我没有在我的源代码中找到错误。它在哪里，我该如何解决？谢谢！
if (savedInstanceState == null) getFragmentManager().beginTransaction() .add(R.id.tvFeed, new PlaceholderFragment()) .commit();
【参考方案1】：
将 R.id.tvFeed 替换为 Framelayout 的 id 或默认 id android.R.id.content。
if (savedInstanceState == null)
getFragmentManager().beginTransaction()
.add(android.R.id.content, new PlaceholderFragment())
.commit();
并从 onOptionsItemSelected() 方法中删除代码。
if (id == R.id.tvFeed)
return true;
【讨论】：
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