java.lang.NullPointerException：尝试在空对象引用上调用虚方法

时间：2016-12-01 18:02:54

标签： android nullpointerexception

我正在开发一个应用程序，用户可以在网格视图中显示电影海报并查看电影详细信息。我的问题是当我运行应用程序并点击海报时出现此错误 引起：java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.Long com.example.android.movi​​es.Movies.getMposter_id（）＆＃39;在null对象引用上 在这一行id = movie.getMposter_id（）;

我不知道如何解决它。 对不起，如果我不称职，但我无法理解如何修复它。感谢。

这里是DetailsFragment.java 

package com.example.android.movies;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ExpandableListView;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.ToggleButton;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import static com.example.android.movies.R.id.favoriteButton;
import static com.example.android.movies.R.id.iv_poster;


/**
 * A placeholder fragment containing a simple view.
 */
public class DetailsFragment extends Fragment{


    Long id;
    String title, overview, poster, date;
    String vote;
    ImageView posterIV;
    TextView titleTV, dateTV, overviewTV, voteTV;
    static Context mContext;

    ExpandableListAdapter listAdapter;
    static ExpandableListView expListView;
    static List<String> listDataHeader;
    static HashMap<String, List<Trailers>> listDataChild;

    static ArrayList<Trailers> arrTrailers;
    static ArrayList<Trailers> arrReviews;

    ToggleButton favorite;
    private MoviesDB db;

    Trailers t;


    public static DetailsFragment newInstance() {
        return new DetailsFragment();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_details, container, false);

        // get the listview
        expListView = (ExpandableListView) rootView.findViewById(R.id.lvExp);

        // receiving intent

        Intent gIntent = getActivity().getIntent();
        Movies movie = null;
        if (gIntent != null && gIntent.hasExtra("movie")) {
            movie = gIntent.getParcelableExtra("movie");


            id = movie.getMposter_id();

            title = movie.getMtitle();
            titleTV = (TextView) rootView.findViewById(R.id.tv_title);
            titleTV.setText(title);

            date=movie.getMdate();
            dateTV = (TextView) rootView.findViewById(R.id.tv_date);
            dateTV.setText(date);

            vote=String.valueOf(movie.getMvote());
            voteTV= (TextView) rootView.findViewById(R.id.tv_vote);
            voteTV.setText(vote);


            overview=movie.getMoverview();
            overviewTV = (TextView) rootView.findViewById(R.id.tv_overview);
            overviewTV.setText(overview);

            poster = movie.getMposter_path();
            posterIV = (ImageView) rootView.findViewById(iv_poster);
            Picasso.with(getActivity())
                    .load("http://image.tmdb.org/t/p/w185".concat(poster)).into(posterIV);

            favorite= (ToggleButton) rootView.findViewById(favoriteButton);

        }
        favorite.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                db.insert(id,title,poster,date, Double.parseDouble(vote),overview,t.getContent1());

            }
        });

        return rootView;
    }

    private void settingAdapter() {
        // preparing list data
        prepareListData();

        listAdapter = new ExpandableListAdapter(getActivity(), listDataHeader, listDataChild);

        // setting list adapter
        expListView.setAdapter(listAdapter);
    }

    /*
     * Preparing the list data
     */
    private void prepareListData() {
        listDataHeader = new ArrayList<String>();
        listDataChild = new HashMap<String, List<Trailers>>();


        // Adding child data
        listDataHeader.add("Reviews");
        listDataHeader.add("Trailers");

        listDataChild.put(listDataHeader.get(0), arrReviews); // Header, Child data
        listDataChild.put(listDataHeader.get(1), arrTrailers);
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        mContext=getActivity();

        new TrailersFetcher(getActivity(), id,this).execute();
    }

    public void updateTrailers(ArrayList<Trailers> trailers){

        arrTrailers = new ArrayList<>();
        for (int i = 0; i <trailers.size() ; i++) {
            arrTrailers.add(trailers.get(i));

        }
        new ReviewsFetcher(mContext, id,this).execute();
    }

    public void updateReviews(ArrayList<Trailers> reviews){
        arrReviews = new ArrayList<>();

        for (int i = 0; i <reviews.size() ; i++) {
            arrReviews.add(reviews.get(i));

        }

        settingAdapter();
    }
}

这里是Movies.java 

package com.example.android.movies;

import android.os.Parcel;
import android.os.Parcelable;

/**
 */
public class Movies implements Parcelable {
    String Mposter_path;
    Long Mposter_id;
    String Mtitle;
    String Moverview;
    String Mdate;
    Double Mvote;
    Long id;

    public Movies(String mposter_path, Long mposter_id, String mtitle,
                  String moverview, String mdate, Double mvote) {
        Mposter_path = mposter_path;
        Mposter_id = mposter_id;
        Mtitle = mtitle;
        Moverview = moverview;
        Mdate = mdate;
        Mvote = mvote;
    }

    public Movies() {

    }

    public String getMposter_path() {
        return Mposter_path;
    }

    public Long getMposter_id() {return Mposter_id;}

    public String getMtitle() {
        return Mtitle;
    }

    public String getMoverview() {
        return Moverview;
    }

    public String getMdate() {
        return Mdate;
    }

    public Double getMvote() {
        return Mvote;
    }


    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(this.Mposter_path);
        dest.writeValue(this.Mposter_id);
        dest.writeString(this.Mtitle);
        dest.writeString(this.Moverview);
        dest.writeString(this.Mdate);
        dest.writeValue(this.Mvote);
    }

    private Movies(Parcel in) {
        this.Mposter_path = in.readString();
        this.Mposter_id = (Long) in.readValue(Long.class.getClassLoader());
        this.Mtitle = in.readString();
        this.Moverview = in.readString();
        this.Mdate = in.readString();
        this.Mvote = (Double) in.readValue(Double.class.getClassLoader());
    }

    public static final Parcelable.Creator<Movies> CREATOR = new Parcelable.Creator<Movies>() {
        @Override
        public Movies createFromParcel(Parcel source) {
            return new Movies(source);
        }

        @Override
        public Movies[] newArray(int size) {
            return new Movies[size];
        }
    };
}

MovieAdapter.java 

package com.example.android.movies;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;

/**
 *
 */
public class MovieAdapter extends BaseAdapter{
    ArrayList<Movies> MovieList=new ArrayList<Movies>();
    Context mContext;

    public MovieAdapter(Context context,ArrayList<Movies> movieArrayList) {
        this.mContext=context;
        this.MovieList=movieArrayList;
    }

    @Override
    public int getCount() {
        return MovieList == null ? 0 : MovieList.size();
    }

    @Override
    public Object getItem(int position) {
        return MovieList.get(position);
    }

    @Override
    public long getItemId(int id) {return MovieList.get(id).getMposter_id(); }

    @Override
    public View getView(int position, View ConvertedView, ViewGroup viewGroup) {
        View view=ConvertedView;
        if (view==null)
        {
            LayoutInflater inflater=(LayoutInflater)
                    mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view=inflater.inflate(R.layout.grid_item,null);
        }
        ImageView ivMovieName= (ImageView) view.findViewById(R.id.image_view);

        Picasso.with(mContext)
                .load("http://image.tmdb.org/t/p/w185"+MovieList.get(position).getMposter_path()).into(ivMovieName);


        return view;
    }
}

2 个答案:

答案 0 :(得分：0)

您的意图中可能有一部电影，但mPoster_id为空。您需要检查您的电影是否具有不为空的mPoster_id，或者默认情况下将其设置为非空值。

答案 1 :(得分：0)

您的活动代码在哪里？你真的把这个电影对象放在你的活动的意图上，比如getIntent（）。putExtra（movie）？看起来Movie类没有问题。 这是我测试的工作代码： MainActivity.java：

public class MainActivity extends AppCompatActivity {

Movie movie;

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    TextView test = (TextView) findViewById(R.id.test);

    movie = new Movie("Awesome", (long) 123);
    String about = movie.getName() + "\n" + movie.getId();
    test.setText(about);

    test.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            getIntent().putExtra("movie", movie);

            if (savedInstanceState == null)
                getSupportFragmentManager()
                        .beginTransaction()
                        .replace(R.id.container_view, new DetailFragment())
                        .commit();

        }
    });

}
}

DetailFragment.java：

public class DetailFragment extends Fragment{

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.fragment_detail,container,false);

    TextView textView = (TextView)root.findViewById(R.id.textView2);

    Movie movie = getActivity().getIntent().getParcelableExtra("movie");

    String about = movie.getName()+"\n"+movie.getId();
    textView.setText(about);

    return root;
}
}

Movie.java：

public class Movie implements Parcelable{

private Long id;
private String name;

public Movie(String n, Long i){
    name = n;
    id = i;
}

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

protected Movie(Parcel in) {
    this.name = in.readString();
    this.id = (Long) in.readValue(Long.class.getClassLoader());
}

public static final Creator<Movie> CREATOR = new Creator<Movie>() {
    @Override
    public Movie createFromParcel(Parcel in) {
        return new Movie(in);
    }

    @Override
    public Movie[] newArray(int size) {
        return new Movie[size];
    }
};

@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel parcel, int i) {
    parcel.writeString(this.name);
    parcel.writeValue(this.id);
}
}
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