android - retrofit2返回的response.body() on a null object reference

Question

源码

public class MusicData {
    private SongMusic mSongMusic;
    private Retrofit mRetrofit;
    private static MusicData mData=new MusicData();
    private MusicData(){}
    public HttpApi getHttp(){
        if(mRetrofit==null){
            mRetrofit=new Retrofit.Builder().baseUrl("http://tingapi.ting.baidu.com/")
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return mRetrofit.create(HttpApi.class);
    }
    
    public void getListMusic(int type, int size, int off){
        Call<RecommentBean> mCall=getHttp().getrecomment(type,size,off);
        mCall.enqueue(new Callback<RecommentBean>() {
            @Override
            public void onResponse(Call<RecommentBean> call, Response<RecommentBean> response) {
                mSongMusic.setAdapter(response.body().getSong_list());
            }

            @Override
            public void onFailure(Call<RecommentBean> call, Throwable t) {

            }
        });
    }
//设置接口实现类的对象
    public void setSongServer(SongMusic song){
        mSongMusic=song;
    }
    public static MusicData getMusicData(){
        return mData;
    }
}

错误
E/AndroidRuntime: FATAL EXCEPTION: main

              Process: com.wang.mymusic, PID: 3414
              java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List com.wang.mymusic.model.RecommentBean.getSong_list()' on a null object reference
                  at com.wang.mymusic.data.MusicData$2.onResponse(MusicData.java:50)
                  at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:68)
                  at android.os.Handler.handleCallback(Handler.java:739)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

描述
这块是使用retrofit2请求音乐列表，并将请求放在一个工具类中的方法里，使用接口将返回值传递给需要使用返回数据的页面，但是在编译运行时报错；但是该请求代码放在activity中的时候是正确的，可以正常获得数据，在网上着也没有搜索到解决方法，不知道是哪里出错了

Answer 1

Set the headers parameter User-Agent:Mozilla/5.0 (Windows NT 10.0; WOW64) in the interface file of retrofit (you can check the header parameters of the browser when requesting this address, and then set the parameters to retrofit) ), you can solve the problem

Answer 2

1-It may be that the data structure does not match, just check it
2-It may be that the data in this layer of the null pointer has no value, of course it is the null pointer;