获得空指针异常 [英] Getting NullPointer Exception
本文介绍了获得空指针异常的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
这code是制作标签:
进口android.app.ActionBar;
进口android.app.FragmentManager;
进口android.app.FragmentTransaction;
进口android.content.Intent;
进口android.media.Image;
进口android.support.v4.app.Fragment;
进口android.support.v4.app.FragmentActivity;
进口android.support.v4.app.FragmentPagerAdapter;
进口android.support.v4.view.ViewPager;
进口android.support.v7.app.ActionBarActivity;
进口android.support.v4.app.Fragment;进口android.os.Bundle;
进口android.widget.FrameLayout;公共类MainActivity扩展FragmentActivity实现ActionBar.TabListener {动作条动作条;ViewPager viewPager;保护无效的onCreate(捆绑savedInstanceState){
super.onCreate(savedInstanceState);
的setContentView(R.layout.activity_main);
viewPager =(ViewPager)findViewById(R.id.pager);
viewPager.setAdapter(新MyAdapter(getSupportFragmentManager()));
动作条= getActionBar(); //这是错误空指针
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(真);
ActionBar.Tab TAB1 = actionBar.newTab();
Tab1.setText(文本);
Tab1.setTabListener(本);
ActionBar.Tab TAB2 = actionBar.newTab();
Tab2.setText(图像);
Tab2.setTabListener(本);
ActionBar.Tab TAB3 = actionBar.newTab();
Tab3.setText(关于我们);
Tab3.setTabListener(本);
actionBar.addTab(TAB1);
actionBar.addTab(TAB2);
actionBar.addTab(TAB3);}
@覆盖
公共无效onTabSelected(ActionBar.Tab选项卡,FragmentTransaction英尺){}@覆盖
公共无效onTabUnselected(ActionBar.Tab选项卡,FragmentTransaction英尺){}@覆盖
公共无效onTabReselected(ActionBar.Tab选项卡,FragmentTransaction英尺){}
}类MyAdapter扩展FragmentPagerAdapter
{公共MyAdapter(android.support.v4.app.FragmentManager FM){
超(FM);
}@覆盖
公共片段的getItem(INT位置){
片段片段= NULL;
如果(位置== 0)
{
片段=新FragmentAFragment();
}
如果(位置== 1)
{
片段=新FragmentBFragment();
}
如果(位置== 2)
{
片段=新FragmentCFragment();
}
返回片段;
}@覆盖
公众诠释的getCount(){
返回3;
}
}
我也用 ActionBarActivity
和 getSupportActivity
,但另一个不兼容错误。
这是<强> LogCat中输出:
09-12 22:23:10.286 3822-3822 /? I /艺术:不晚启用-Xcheck:JNI(已上)
09-12 22:23:10.325 3822-3829 /? I /艺术:调试程序不再有效
09-12 22:23:10.470 3822-3822 /? D / AndroidRuntime:关闭VM
09-12 22:23:10.471 3822-3822 /? E / AndroidRuntime:致命异常:主要
工艺:com.example.santosh.en code,PID:3822
了java.lang.RuntimeException:无法启动活动ComponentInfo {com.example.santosh.en code / com.example.santosh.en code.MainActivity}:显示java.lang.NullPointerException:尝试调用虚函数在一个空对象引用无效android.app.ActionBar.setNavigationMode(INT)'
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
在android.app.ActivityThread.access $ 800(ActivityThread.java:151)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1303)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5257)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:903)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
显示java.lang.NullPointerException:引起尝试在空对象引用调用虚拟方法无效android.app.ActionBar.setNavigationMode(INT)'
在com.example.santosh.en code.MainActivity.onCreate(MainActivity.java:34)
在android.app.Activity.performCreate(Activity.java:5990)
在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
在android.app.ActivityThread.access $ 800(ActivityThread.java:151)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1303)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5257)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:903)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
09-12 22:23:11.142 3822-3834 /? I /艺术:背景部分并发标记扫描GC释放369(79KB)AllocSpace对象,0(0B)LOS对象,53%免费,442KB / 954KB,暂停8.882ms总35.959ms
这是我的Android 的manifest.xml
&LT;?XML版本=1.0编码=UTF-8&GT?;
&LT;清单的xmlns:机器人=http://schemas.android.com/apk/res/android
包=com.example.santosh.en code&GT; &lt;应用
机器人:allowBackup =真
机器人:图标=@的mipmap /应用
机器人:标签=@字符串/ APP_NAME
机器人:主题=@风格/ Theme.AppCompat&GT;
&LT;活动
机器人:名字=。MainActivity
机器人:标签=@字符串/ APP_NAME&GT;
&所述;意图滤光器&gt;
&lt;作用机器人:名字=android.intent.action.MAIN/&GT; &LT;类机器人:名字=android.intent.category.LAUNCHER/&GT;
&所述; /意图滤光器&gt;
&LT; /活性GT;
&LT;活动
机器人:名字=碎裂
机器人:标签=@字符串/ title_activity_fragment&GT;
&LT; /活性GT;
&LT;活动
机器人:名字=。FragmentB
机器人:标签=@字符串/ title_activity_fragment_b&GT;
&LT; /活性GT;
&LT;活动
机器人:名字=。FragmentC
机器人:标签=@字符串/ title_activity_fragment_c&GT;
&LT; /活性GT;
&LT; /用途&gt;&LT; /清单&GT;
现在有些编辑完成,但仍存在这个问题。
包com.example.santosh.en code;
进口com.example.santosh.en code.Base64;进口android.app.ActionBar;
进口android.app.ActionBar;
进口android.app.FragmentManager;
进口android.app.FragmentTransaction;
进口android.content.Intent;
进口android.media.Image;
进口android.support.v4.app.Fragment;
进口android.support.v4.app.FragmentActivity;
进口android.support.v4.app.FragmentPagerAdapter;
进口android.support.v4.view.ViewPager;进口android.os.Bundle;
进口android.support.v7.app.ActionBarActivity;
进口android.view.Window;公共类MainActivity扩展FragmentActivity实现ActionBar.TabListener {
动作条动作条;
ViewPager viewPager; 保护无效的onCreate(捆绑savedInstanceState){ super.onCreate(savedInstanceState); 动作条= getActionBar();
。getWindow()requestFeature(Window.FEATURE_ACTION_BAR);
的setContentView(R.layout.activity_main);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); viewPager =(ViewPager)findViewById(R.id.pager); viewPager.setAdapter(新MyAdapter(getSupportFragmentManager()));
actionBar.setDisplayShowTitleEnabled(真);
ActionBar.Tab TAB1 = actionBar.newTab();
Tab1.setText(文本);
Tab1.setTabListener(本);
ActionBar.Tab TAB2 = actionBar.newTab();
Tab2.setText(图像);
Tab2.setTabListener(本);
ActionBar.Tab TAB3 = actionBar.newTab();
Tab3.setText(关于我们);
Tab3.setTabListener(本);
actionBar.addTab(TAB1);
actionBar.addTab(TAB2);
actionBar.addTab(TAB3); }
@覆盖
公共无效onTabSelected(ActionBar.Tab选项卡,FragmentTransaction英尺){ } @覆盖
公共无效onTabUnselected(ActionBar.Tab选项卡,FragmentTransaction英尺){ } @覆盖
公共无效onTabReselected(ActionBar.Tab选项卡,FragmentTransaction英尺){ }
}类MyAdapter扩展FragmentPagerAdapter
{ 公共MyAdapter(android.support.v4.app.FragmentManager FM){
超(FM);
} @覆盖
公共片段的getItem(INT位置){
片段片段= NULL;
如果(位置== 0)
{
片段=新FragmentAFragment();
}
如果(位置== 1)
{
片段=新FragmentBFragment();
}
如果(位置== 2)
{
片段=新FragmentCFragment();
}
返回片段;
} @覆盖
公众诠释的getCount(){
返回3;
}
}
现在LogCat中显示.....................
一月9日至13日:06:13.967 5526-5526 / com.example.santosh.en code I /艺术:不晚启用-Xcheck:JNI(已上)
1月9日至一十三日:06:14.086 5526-5526 / com.example.santosh.en code D / AndroidRuntime:关闭VM
1月9日至一十三日:06:14.087 5526-5526 / com.example.santosh.en code E / AndroidRuntime:致命异常:主要
工艺:com.example.santosh.en code,PID:5526
了java.lang.RuntimeException:无法启动活动ComponentInfo {com.example.santosh.en code / com.example.santosh.en code.MainActivity}:android.util.AndroidRuntimeException:requestFeature()必须所谓的添加内容之前
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
在android.app.ActivityThread.access $ 800(ActivityThread.java:151)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1303)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5257)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:903)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
android.util.AndroidRuntimeException:引起requestFeature()必须添加内容之前调用
在com.android.internal.policy.impl.PhoneWindow.requestFeature(PhoneWindow.java:302)
在com.example.santosh.en code.MainActivity.onCreate(MainActivity.java:36)
在android.app.Activity.performCreate(Activity.java:5990)
在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
在android.app.ActivityThread.access $ 800(ActivityThread.java:151)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1303)
在android.os.Handler.dispatchMessage(Handler.java:102)
在android.os.Looper.loop(Looper.java:135)
在android.app.ActivityThread.main(ActivityThread.java:5257)
在java.lang.reflect.Method.invoke(本机方法)
在java.lang.reflect.Method.invoke(Method.java:372)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:903)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
1月9日至一十三日:06:14.112 5526-5533 / com.example.santosh.en code I /艺术:调试程序不再有效
1月9日至一十三日:06:14.124 5526-5533 / com.example.santosh.en code W /艺术:暂停所有线程了:12.092ms
解决方案
更改您的进口:
进口android.support.v4.app.Fragment;
进口android.support.v4.app.FragmentManager;
进口android.support.v4.app.FragmentPagerAdapter;
进口android.support.v4.app.FragmentStatePagerAdapter;
进口android.support.v4.app.FragmentTransaction;
进口android.support.v4.view.ViewPager;
进口android.support.v7.app.ActionBar;
进口android.support.v7.app.ActionBarActivity;
和做的:
动作条= getSupportActionBar();
This code is for making Tabs:
import android.app.ActionBar;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.media.Image;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.widget.FrameLayout;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
ActionBar actionBar;
ViewPager viewPager;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager= (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(new MyAdapter(getSupportFragmentManager()));
actionBar=getActionBar();//Here is error Null Pointer
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
actionBar.setDisplayShowTitleEnabled(true);
ActionBar.Tab Tab1=actionBar.newTab();
Tab1.setText("Text");
Tab1.setTabListener(this);
ActionBar.Tab Tab2=actionBar.newTab();
Tab2.setText("Image");
Tab2.setTabListener(this);
ActionBar.Tab Tab3=actionBar.newTab();
Tab3.setText("About Us");
Tab3.setTabListener(this);
actionBar.addTab(Tab1);
actionBar.addTab(Tab2);
actionBar.addTab(Tab3);
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
}
class MyAdapter extends FragmentPagerAdapter
{
public MyAdapter(android.support.v4.app.FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment=null;
if(position==0)
{
fragment=new FragmentAFragment();
}
if(position==1)
{
fragment=new FragmentBFragment();
}
if(position==2)
{
fragment=new FragmentCFragment();
}
return fragment;
}
@Override
public int getCount() {
return 3;
}
}
I have Also used ActionBarActivity
and getSupportActivity
but still another incompatibility error.
This is LogCat output:
09-12 22:23:10.286 3822-3822/? I/art﹕ Not late-enabling -Xcheck:jni (already on)
09-12 22:23:10.325 3822-3829/? I/art﹕ Debugger is no longer active
09-12 22:23:10.470 3822-3822/? D/AndroidRuntime﹕ Shutting down VM
09-12 22:23:10.471 3822-3822/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.santosh.encode, PID: 3822
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.santosh.encode/com.example.santosh.encode.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setNavigationMode(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setNavigationMode(int)' on a null object reference
at com.example.santosh.encode.MainActivity.onCreate(MainActivity.java:34)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.Zyg
oteInit.main(ZygoteInit.java:698)
09-12 22:23:11.142 3822-3834/? I/art﹕ Background partial concurrent mark sweep GC freed 369(79KB) AllocSpace objects, 0(0B) LOS objects, 53% free, 442KB/954KB, paused 8.882ms total 35.959ms
This is my android manifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.santosh.encode" >
<application
android:allowBackup="true"
android:icon="@mipmap/app"
android:label="@string/app_name"
android:theme="@style/Theme.AppCompat" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".FragmentA"
android:label="@string/title_activity_fragment" >
</activity>
<activity
android:name=".FragmentB"
android:label="@string/title_activity_fragment_b" >
</activity>
<activity
android:name=".FragmentC"
android:label="@string/title_activity_fragment_c" >
</activity>
</application>
</manifest>
now Some edit done but Still Facing Problem.
package com.example.santosh.encode;
import com.example.santosh.encode.Base64;
import android.app.ActionBar;
import android.app.ActionBar;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.media.Image;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Window;
public class MainActivity extends FragmentActivity implements ActionBar.TabListener {
ActionBar actionBar;
ViewPager viewPager;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
actionBar=getActionBar();
getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
setContentView(R.layout.activity_main);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
viewPager= (ViewPager) findViewById(R.id.pager);
viewPager.setAdapter(new MyAdapter(getSupportFragmentManager()));
actionBar.setDisplayShowTitleEnabled(true);
ActionBar.Tab Tab1=actionBar.newTab();
Tab1.setText("Text");
Tab1.setTabListener(this);
ActionBar.Tab Tab2=actionBar.newTab();
Tab2.setText("Image");
Tab2.setTabListener(this);
ActionBar.Tab Tab3=actionBar.newTab();
Tab3.setText("About Us");
Tab3.setTabListener(this);
actionBar.addTab(Tab1);
actionBar.addTab(Tab2);
actionBar.addTab(Tab3);
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
}
class MyAdapter extends FragmentPagerAdapter
{
public MyAdapter(android.support.v4.app.FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment=null;
if(position==0)
{
fragment=new FragmentAFragment();
}
if(position==1)
{
fragment=new FragmentBFragment();
}
if(position==2)
{
fragment=new FragmentCFragment();
}
return fragment;
}
@Override
public int getCount() {
return 3;
}
}
Now LogCat Shows.....................
09-13 01:06:13.967 5526-5526/com.example.santosh.encode I/art﹕ Not late-enabling -Xcheck:jni (already on)
09-13 01:06:14.086 5526-5526/com.example.santosh.encode D/AndroidRuntime﹕ Shutting down VM
09-13 01:06:14.087 5526-5526/com.example.santosh.encode E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.santosh.encode, PID: 5526
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.santosh.encode/com.example.santosh.encode.MainActivity}: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: android.util.AndroidRuntimeException: requestFeature() must be called before adding content
at com.android.internal.policy.impl.PhoneWindow.requestFeature(PhoneWindow.java:302)
at com.example.santosh.encode.MainActivity.onCreate(MainActivity.java:36)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
09-13 01:06:14.112 5526-5533/com.example.santosh.encode I/art﹕ Debugger is no longer active
09-13 01:06:14.124 5526-5533/com.example.santosh.encode W/art﹕ Suspending all threads took: 12.092ms
解决方案
Change your imports to:
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
and do:
actionBar = getSupportActionBar();
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