我尝试在模拟器中打开我的Android Studio应用，但出现错误:
12-06 00:50:30.993 1198-1198/com.coding.nero E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.coding.nero, PID: 1198
java.lang.NullPointerException
at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:394)
at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:389)
at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:832)
at android.support.v4.view.ViewPager.populate(ViewPager.java:982)
at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at com.android.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
at android.view.View.measure(View.java:16497)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:544)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
我不知道这意味着什么或如何解决。如果需要，我可以提供更多代码。当我在模拟器中打开它时，它说应用程序崩溃了并且关闭了。
这是我的主要 Activity XML文件
<android.support.v4.view.ViewPager
android:layout_height="match_parent"
android:layout_width="match_parent"
android:id="@+id/pager"
xmlns:android="http://schemas.android.com/apk/res/android">
这是我的MainActivity Java
package com.coding.nero;
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.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class MainActivity extends FragmentActivity {
ViewPager viewPager=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager= (ViewPager) findViewById(R.id.pager);
FragmentManager fragmentManager=getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentB extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentC extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentD extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_d, container, false);
}
}
}
class MyAdapter extends FragmentPagerAdapter{
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment=null;
if(i==0){
fragment=new FragmentA_1();
}
if(i==1){
fragment=new FragmentB_1();
}
if(i==2){
fragment=new FragmentC_1();
}
if(i==3){
fragment=new FragmentD_1();
}
return null;
}
@Override
public int getCount() {
return 4;
}
适配器代码:
package com.coding.nero;
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.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class MainActivity extends FragmentActivity {
ViewPager viewPager=null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager= (ViewPager) findViewById(R.id.pager);
FragmentManager fragmentManager=getSupportFragmentManager();
viewPager.setAdapter(new MyAdapter(fragmentManager));
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentA extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentB extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentC extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_a, container, false);
}
}
/**
* Created by John on 12/5/14.
*/
//Links class to layout file fragment_a
public static class FragmentD extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_d, container, false);
}
}
}
class MyAdapter extends FragmentPagerAdapter{
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
Fragment fragment=null;
if(i==0){
fragment=new FragmentA_1();
}
if(i==1){
fragment=new FragmentB_1();
}
if(i==2){
fragment=new FragmentC_1();
}
if(i==3){
fragment=new FragmentD_1();
}
return null;
}
@Override
public int getCount() {
return (4);
}
}
最佳答案
因为您的适配器“getItem()”返回null。
关于android - 这是什么意思？我如何解决它？致命异常:主要，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/27328809/