getActivity（）中出错。RunonUithReadNew Runnable（）

Question

致命异常：Timer-0进程：com.example.tanis.MyApplication，PID:9918 java.lang.NullPointerException：尝试在com.example.tanis.MyApplication.Menuitems.Home$MyTime.Run（Home.java:158)处的java.util.TimerThread.MainLoop（Timer.java:555)处的null对象引用上html" target="_blank">调用虚拟方法“void android.support.v4.app.FragmentActivity.RunonUithRead（java.lang.Runnable）”

它显示了getActivity（）中的一个错误。runonuithread（new Runnable（）我不知道为什么会出现这个错误，请帮助，谢谢

package com.example.tanis.myapplication.MenuItems;

import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.Fragment;
import android.support.v4.content.res.ResourcesCompat;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import com.example.tanis.myapplication.Adapters.CardItemString;
import com.example.tanis.myapplication.Adapters.CardPagerAdapterS;
import com.example.tanis.myapplication.Adapters.ViewPagerAdapter;
import com.example.tanis.myapplication.R;
import com.example.tanis.myapplication.Services.website_designing;

import java.util.Timer;
import java.util.TimerTask;
public class Home extends Fragment {


        ViewPager mViewPager;
        CardPagerAdapterS mCardAdapter;
        ShadowTransformer mCardShadowTransformer;



private Context context;
        ViewPager viewPager;


        String titlesText [] = {" Website Design", " Digital Marketing", " Domain Registration", "Graphics Design", " Mobile Apps", " Server Hosting",
        " Software Development", " Content Marketing", " Security (SSl)"};
        String  detailsArray [] = {
        "Your website is your digital home. We create, design, redesign, develop, improvise, and implement. We make beautiful websites",
        "We help your business reach potential customers on every possible digital device through all possible media channels    ",
        "To  launch  your  website  the  first  thing  you  need  is  the  domain  name.  You  can  choose  your  domain  name  with  us  here  ",
        "We  generate  creative  solutions  and  can  create  a  wide  range  of  graphic  for  your  clients  which  match  their  business         ",
        "We are mobile. And we make you mobile. We make responsive websites and mobile apps which compliment your business       ",
        "When  you  are  hosting  your     website  in  the  India  you   will  benefit  from  a      higher  ping  rate  and   lowest             latency              ",
        "Our team is competent at coding web apps with keen attention to detail & intuitive functionality that is high on design & creativity",
        "Content  is  the  heart  of  your  digital  presence. We  create  the right            content  with  the  right  focus   for   your  business",
        "Secure your site with the world's leading   provider of online security and get    these exclusive features at no added   cost",
        };
        int[] images = {R.drawable.website_design, R.drawable.digita,R.drawable.domain_registration,R.drawable.gric,
        R.drawable.mob,R.drawable.server,R.drawable.software_development,R.drawable.ontent,R.drawable.ssl};

private static final String KEY_MOVIE_TITLE = "key_title";

public Home() {
        // Required empty public constructor
        }

/**
 * Use this factory method to create a new instance of
 * this fragment.
 *
 * @return A new instance of fragment FragmentAction.
 */


@Override
public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);


        }

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState)
        {


        View v = inflater.inflate(R.layout.home,container,false);
        TextView txt = (TextView)v.findViewById( R.id.textView12 );
        txt.setText("\u25BA Creative & Dedicated Team");
        TextView txt1 = (TextView)v.findViewById( R.id.textView13 );
        txt1.setText("\u25BA Affordable Cost");
        TextView txt2 = (TextView)v.findViewById( R.id.textView14 );
        txt2.setText("\u25BA Maintain Long Relationship");
        TextView txt3 = (TextView)v.findViewById( R.id.textView15 );
        txt3.setText("\u25BA Timely Deliverly ");

        context = this.getContext();

        Button b = (Button) v.findViewById( R.id.button7 ) ;
        b.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View view) {
        Intent intent=new Intent( getActivity(), website_designing.class);
        }
        } );


        mViewPager = (ViewPager)v.findViewById(R.id.viewpager1);

        mCardAdapter = new CardPagerAdapterS();




        for (int i=0; i<titlesText.length; i++){

        mCardAdapter.addCardItemS(new CardItemString( titlesText[i], detailsArray[i],images[i]));
        }

        mCardShadowTransformer = new ShadowTransformer(mViewPager, mCardAdapter);

        mViewPager.setAdapter(mCardAdapter);
        mViewPager.setPageTransformer(false, mCardShadowTransformer);
        mViewPager.setOffscreenPageLimit(3);



        viewPager = (ViewPager)v.findViewById( R.id.viewpager );
        ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter( this.getContext() );
        viewPager.setAdapter( viewPagerAdapter );

        Timer timer = new Timer(  );
        timer.scheduleAtFixedRate( new Mytime(),2000,4000 );



        FloatingActionButton floatingActionButton = (FloatingActionButton)v.findViewById( R.id.floatingActionButton );
        floatingActionButton.setOnClickListener( new View.OnClickListener() {
@Override
public void onClick(View view) {
        startActivity( new Intent( getActivity(),Registration.class ) );
        }
        } );




        return v;

        }



public class Mytime extends TimerTask {
    @Override
    public void run() {

       //here it is showing me error//

           **getActivity().runOnUiThread( new Runnable() {
            @Override
            public void run() {

                if(viewPager.getCurrentItem() == 0) {
                    viewPager.setCurrentItem( 1 );
                }
                else if (viewPager.getCurrentItem()== 1){
                    viewPager.setCurrentItem( 2 );

                }
                else if (viewPager.getCurrentItem()== 2){
                    viewPager.setCurrentItem( 3 );

                }
                else if (viewPager.getCurrentItem()== 3){
                    viewPager.setCurrentItem( 4 );

                }
                else {
                    viewPager.setCurrentItem(0);
                }
            }
        } );
    }
}

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);


    }


}

Answer 1

java.lang.NullPointerException：尝试调用虚拟方法“void android.support.v4.app.FragmentActivity.RunonUithRead（java.lang.Runnable）”

当应用程序尝试使用具有空值的对象引用时，会引发NullPointerException。

您应该在下面添加检查。

if (getActivity()!=null)

   if (getActivity()!=null)
   {
    getActivity().runOnUiThread( new Runnable() {
            @Override
            public void run() {
            ......
   }