我在大学的一个小组中工作的 CVS 项目遇到了一个奇怪的问题。我们有一个 Android 项目，一个简单的投票应用程序。一开始，用户必须使用用户名和密码登录应用程序。它实际上适用于该组中的所有人，除了我。我们之间唯一的区别是我使用的是 IntelliJ Idea 12 Community Edition 和所有其他 eclipse。在我的具体情况下，它只是在我输入用户和密码并按下登录按钮后崩溃。它尝试加载应用程序并立即抛出“不幸的是‘应用程序’已停止”异常。
我猜它与库或 .classpath 的 Eclipse 文件有关？我真的不知道这两个 IDE 协同工作的效果如何？！我读到将两者与 CVS 一起使用没有问题。
我也设置了eclipse。错误也出现了？！我不知道为什么这对我不起作用？！...
这是 logcat 输出（过滤错误和“反馈”）：
07-16 22:30:35.305: ERROR/AndroidRuntime(2223): FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity `enter code here`ComponentInfo{de.unikassel.feedbackclient/de.unikassel.feedbackclient.MainActivity}: `enter code here`java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at de.unikassel.feedbackclient.MainActivity.onCreate(MainActivity.java:72)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
... 11 more
和 AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="de.unikassel.feedbackclient"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="16" />
<uses-permission android:name="android.permission.INTERNET" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="de.unikassel.feedbackclient.MainActivity"
android:label="@string/app_name" >
</activity>
<activity
android:name="de.unikassel.feedbackclient.LoginActivity"
android:label="@string/title_activity_login"
android:windowSoftInputMode="adjustResize|stateVisible" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="de.unikassel.feedbackclient.AdminActivity"
android:label="@string/title_activity_admin" >
</activity>
<activity
android:name="de.unikassel.feedbackclient.PollActivity"
android:label="@string/title_activity_open_poll" >
</activity>
<activity
android:name="de.unikassel.feedbackclient.SettingsActivity"
android:label="@string/title_activity_settings" >
</activity>
</application>
</manifest>
和我的 App.iml
<?xml version="1.0" encoding="UTF-8"?>
<module type="JAVA_MODULE" version="4">
<component name="EclipseModuleManager" forced_jdk="true">
<conelement value="com.android.ide.eclipse.adt.DEPENDENCIES" />
<src_description expected_position="1">
<src_folder value="file://$MODULE_DIR$/src" expected_position="0" />
<src_folder value="file://$MODULE_DIR$/gen" expected_position="1" />
<src_folder value="com.android.ide.eclipse.adt.ANDROID_FRAMEWORK" expected_position="2" />
<src_folder value="com.android.ide.eclipse.adt.LIBRARIES" expected_position="3" />
</src_description>
</component>
<component name="FacetManager">
<facet type="android" name="Android">
<configuration />
</facet>
</component>
<component name="NewModuleRootManager" inherit-compiler-output="false">
<output url="file://$MODULE_DIR$/bin/classes" />
<exclude-output />
<content url="file://$MODULE_DIR$">
<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
<sourceFolder url="file://$MODULE_DIR$/gen" isTestSource="false" />
</content>
<orderEntry type="jdk" jdkName="Android 4.2.2 Platform" jdkType="Android SDK" />
<orderEntry type="sourceFolder" forTests="false" />
<orderEntry type="module-library" exported="">
<library>
<CLASSES>
<root url="jar://$MODULE_DIR$/libs/android-support-v4.jar!/" />
</CLASSES>
<JAVADOC />
<SOURCES />
</library>
</orderEntry>
</component>
</module>
谢谢帮助...
编辑：根据logcat和mainactivity中抛出的异常，我也在这里粘贴了它的代码......
package de.unikassel.feedbackclient;
import java.util.Locale;
import de.unikassel.feedbackclient.R;
import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.ListFragment;
import android.support.v4.view.ViewPager;
import android.view.Menu;
/**
* Main Screen where all polls are shown in a tab layout.
*
*/
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
/**
* Define the number of shown tabs in Tab-Bar.
*/
private final int NUMTABS = 3;
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
/**
* Method will be called when Activity will be created by
* Android OS.
*
* @param Bundle savedInstanceState
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab().setText(mSectionsPagerAdapter.getPageTitle(i)).setTabListener(this));
}
}
/**
* Method is called to create the options menu for given activity.
*
* @param Menu menu
* @return boolean
*/
@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;
}
/**
* Method is called if a tab from tab-view is selected.
*
* @param ActionBar.Tab tab
* @param FragmentTransaction fragmentTransaction
*/
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
/**
* Method is called if a tab from tab-view is unselected (switched to next tab, etc.).
*
* @param ActionBar.Tab tab
* @param FragmentTransaction fragmentTransaction
*/
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* Method is called if a tab from tab-view is reselected (switched back from other tab, etc.).
*
* @param ActionBar.Tab tab
* @param FragmentTransaction fragmentTransaction
*/
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
/**
*
* @param fm FragmentManager
*/
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
ListFragment fragment = new ListSectionFragment();
return fragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return NUMTABS;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class DummySectionFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
}
}
问题解决了......操作栏导致了问题。以下将修复它...
在 onCreate 之后的 MainActivity.java 中必须是：
getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
setContentView(R.layout.activity_main);