好吧，在经过许多其他问题之后，我终于把它归结为这个在我尝试打开应用程序时不断发生的错误。我已经尝试过NullPointerExceptions的其他解决方案，但它们似乎不起作用。
这是一个LogCat：
12-08 03:03:40.222: E/AndroidRuntime(1974): FATAL EXCEPTION: main
12-08 03:03:40.222: E/AndroidRuntime(1974): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.zekfed.minecraft.pro/com.zekfed.minecraft.pro.Main}: java.lang.NullPointerException
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.os.Handler.dispatchMessage(Handler.java:99)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.os.Looper.loop(Looper.java:137)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread.main(ActivityThread.java:5039)
12-08 03:03:40.222: E/AndroidRuntime(1974): at java.lang.reflect.Method.invokeNative(Native Method)
12-08 03:03:40.222: E/AndroidRuntime(1974): at java.lang.reflect.Method.invoke(Method.java:511)
12-08 03:03:40.222: E/AndroidRuntime(1974): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-08 03:03:40.222: E/AndroidRuntime(1974): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-08 03:03:40.222: E/AndroidRuntime(1974): at dalvik.system.NativeStart.main(Native Method)
12-08 03:03:40.222: E/AndroidRuntime(1974): Caused by: java.lang.NullPointerException
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.Activity.initActionBar(Activity.java:1861)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.Activity.getActionBar(Activity.java:1848)
12-08 03:03:40.222: E/AndroidRuntime(1974): at com.zekfed.minecraft.pro.Main.<init>(Main.java:48)
12-08 03:03:40.222: E/AndroidRuntime(1974): at java.lang.Class.newInstanceImpl(Native Method)
12-08 03:03:40.222: E/AndroidRuntime(1974): at java.lang.Class.newInstance(Class.java:1319)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
12-08 03:03:40.222: E/AndroidRuntime(1974): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
12-08 03:03:40.222: E/AndroidRuntime(1974): ... 11 more
12-08 03:04:37.692: W/Trace(2024): Unexpected value from nativeGetEnabledTags: 0
12-08 03:04:37.692: W/Trace(2024): Unexpected value from nativeGetEnabledTags: 0
12-08 03:04:37.692: W/Trace(2024): Unexpected value from nativeGetEnabledTags: 0
12-08 03:04:37.742: W/Trace(2024): Unexpected value from nativeGetEnabledTags: 0
12-08 03:04:37.742: W/Trace(2024): Unexpected value from nativeGetEnabledTags: 0
12-08 03:04:37.762: D/AndroidRuntime(2024): Shutting down VM
12-08 03:04:37.762: W/dalvikvm(2024): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
12-08 03:04:37.772: E/AndroidRuntime(2024): FATAL EXCEPTION: main
12-08 03:04:37.772: E/AndroidRuntime(2024): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.zekfed.minecraft.pro/com.zekfed.minecraft.pro.Main}: java.lang.NullPointerException
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.os.Handler.dispatchMessage(Handler.java:99)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.os.Looper.loop(Looper.java:137)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread.main(ActivityThread.java:5039)
12-08 03:04:37.772: E/AndroidRuntime(2024): at java.lang.reflect.Method.invokeNative(Native Method)
12-08 03:04:37.772: E/AndroidRuntime(2024): at java.lang.reflect.Method.invoke(Method.java:511)
12-08 03:04:37.772: E/AndroidRuntime(2024): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
12-08 03:04:37.772: E/AndroidRuntime(2024): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
12-08 03:04:37.772: E/AndroidRuntime(2024): at dalvik.system.NativeStart.main(Native Method)
12-08 03:04:37.772: E/AndroidRuntime(2024): Caused by: java.lang.NullPointerException
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.Activity.initActionBar(Activity.java:1861)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.Activity.getActionBar(Activity.java:1848)
12-08 03:04:37.772: E/AndroidRuntime(2024): at com.zekfed.minecraft.pro.Main.<init>(Main.java:48)
12-08 03:04:37.772: E/AndroidRuntime(2024): at java.lang.Class.newInstanceImpl(Native Method)
12-08 03:04:37.772: E/AndroidRuntime(2024): at java.lang.Class.newInstance(Class.java:1319)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
12-08 03:04:37.772: E/AndroidRuntime(2024): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
12-08 03:04:37.772: E/AndroidRuntime(2024): ... 11 more
这是我的Main.class：
///////////////////////////////////////////////////////////////////////////////////////////////////
// //
// Zeklandian Minecraft Guide : Pro Version //
// //
// Created by Asher Wood //
// and Khuram Shazad //
// //
// ??2012 Asher Wood and Khuram Shazad //
// //
// Layout Handler / Main Class //
// //
///////////////////////////////////////////////////////////////////////////////////////////////////
package com.zekfed.minecraft.pro;
import android.app.ActionBar;
import android.content.Context;
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.view.ViewPager;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.ViewGroup;
public class Main extends FragmentActivity {
// Create ViewPager, Make sliding screens
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
private static final String ARG_SECTION_NUMBER = null;
SectionsPagerAdapter mSectionsPagerAdapter;
static ViewPager mViewPager;
// ActionBar: Make ActionBar and Buttons
ActionBar actionbar = getActionBar();
// Make Menu
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.main, menu);
return true;
}
// Create Fragments
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment = new SectionFragment();
Bundle args = new Bundle();
args.putInt(SectionFragment.ARG_SECTION_NUMBER, i);
fragment.setArguments(args);
return fragment;
}
@Override
public int getCount() {
return 5;
}
// Create titles
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getString("Blocks").toUpperCase();
case 1:
return getString("Items").toUpperCase();
case 2:
return getString("Tools & Armour").toUpperCase();
case 3:
return getString("Mobs").toUpperCase();
case 4:
return getString("Structures").toUpperCase();
}
return null;
}
private String getString(String string) {
// TODO Auto-generated method stub
return null;
}
}
// Create pages
public static class SectionFragment extends Fragment {
public SectionFragment() {
}
public static final String ARG_SECTION_NUMBER = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LayoutInflater inflater1 = (LayoutInflater) mViewPager.getContext()
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
Bundle args = new Bundle();
int resId = (Integer) getArguments().get(ARG_SECTION_NUMBER);
switch (resId) {
case 0:
resId = R.layout.blocks;
break;
case 1:
resId = R.layout.toolsarmour;
break;
case 2:
resId = R.layout.items;
break;
case 3:
resId = R.layout.mobs;
break;
case 4:
resId = R.layout.structures;
break;
}
View view = inflater1.inflate(resId, null);
return view;
}
}
private Bundle getArguments() {
return null;
}
}
答案 0 :(得分：1)
你确定第48行是这个代码的适当位置吗？
ActionBar actionbar = getActionBar();
答案 1 :(得分：0)
您运行此代码的Android平台版本是什么？
您的uses-sdk清单标记设置为什么？它为android:minSdkVersion指定了什么？ android:targetSdkVersion？这项活动使用了什么主题？
您在getActionBar执行之前调用onCreate，将其称为初始值设定项。这可能不会做你想要的。在致电onCreate和super.onCreate后，您应在setContentView分配此字段。
您已使用名称ViewPager声明了静态mViewPager字段。除了不正确的Android风格（静态字段以s开头，而不是m，）这个范围几乎肯定不是您想要的，因为静态字段对于您可能需要此范围的进程是全局的到你的Activity实例。