如何在改造中使用NullPointer exetpion

Question

我有空指针异常的问题。 2天我什么也做不了。请帮帮我。 NullPointer在线。这是一个问题，但我不知道该怎么做。

        for (AsanaPOJO a : asanas.getAsanas()) {
            Log.d("AsanaPROGRAM LOGS", BuildConfig.FLAVOR + a.getName());
        }

这是JSON：

{

    "asanas": 

[

{

    "id": 34,
    "name": "Easy Pranayama",
    "imgLarge": "/system/photos/asanas/34/large/34.jpg",
    "imgThumb": "/system/photos/asanas/34/thumb/34.jpg",
    "level_id": 1,
    "type_id": 9,
    "audio": "/system/audios/asanas/34/body/en/34.mp3",
    "title_audio": "/system/audios/asanas/34/title/en/34.mp3",
    "duration": 69,
    "fullDesc": "Lie down comfortably on your back so that your abdominal muscles are relaxed. Close your eyes.",
    "photo": "/system/photos/asanas/34/original/34.jpg",
    "sanskrit_name": "Sahaj Pranayama ",
    "sanskrit_audio_title": "/sanskrit_audio_titles/original/missing.png",
    "breathing_video": "/system/videos/asanas/34/breathing/34.mp4",
    "is_paid": false,
    "is_breathing": true,
    "old_identifier": "331",
    "old_pk": 772

},
{

    "id": 35,
    "name": "Easy Pranayama Advanced",
    "imgLarge": "/system/photos/asanas/35/large/35.jpg",
    "imgThumb": "/system/photos/asanas/35/thumb/35.jpg",
    "level_id": 2,
    "type_id": 9,
    "audio": "/system/audios/asanas/35/body/en/35.mp3",
    "title_audio": "/system/audios/asanas/35/title/en/35.mp3",
    "duration": 92,
    "fullDesc": "Lie down comfortably on your back so that your abdominal muscles are relaxed. Close your eyes. Bring your hands behind your head.",
    "photo": "/system/photos/asanas/35/original/35.jpg",
    "sanskrit_name": "Sahaj Pranayama Advanced",
    "sanskrit_audio_title": "/sanskrit_audio_titles/original/missing.png",
    "breathing_video": "/system/videos/asanas/35/breathing/35.mp4",
    "is_paid": true,
    "is_breathing": true,
    "old_identifier": "332",
    "old_pk": 773

}
    ]

}

这是主要活动：

public class MainActivity extends AppCompatActivity {

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

    MYApi myapi = (MYApi) new Builder().setLogLevel(LogLevel.FULL).setEndpoint(MYurl.BASE_URL).build().create(MYApi.class);


    myapi.getAsanas(new Callback<Asanas>() {
        public void success(Asanas asanas,Response response) {


            for (AsanaPOJO a : asanas.getAsanas()) {
                Log.d("AsanaPROGRAM LOGS", BuildConfig.FLAVOR + a.getName());
            }

        }

        public void failure(RetrofitError error) {
        }
    });



}

班级体式：

public class Asanas {

private List<AsanaPOJO> asanaPOJOs;

public Asanas() {
}

public List<AsanaPOJO> getAsanas ()
{
    return this.asanaPOJOs;
}

public void setAsanas (List<AsanaPOJO> asanas)
{
    this.asanaPOJOs = asanaPOJOs;
}

@Override
public String toString()
{
    return "ClassPojo [asanas = "+asanaPOJOs+"]";
}
}

Class AsanaPOJO

public class AsanaPOJO {

private int id;
private String name;
private String imgLarge;
private String imgThumb;
private int level_id;
private int type_id;
private String audio;
private String title_audio;
private int duration;
private String fullDesc;
private String photo;
private String sanskrit_name;
private String sanskrit_audio_title;
private String breathing_video;
private String is_paid;
private String is_breathing;
private int old_identifier;
private int old_pk;

public AsanaPOJO() {
}

public String getSanskrit_audio_title ()
{
    return sanskrit_audio_title;
}

public void setSanskrit_audio_title (String sanskrit_audio_title)
{
    this.sanskrit_audio_title = sanskrit_audio_title;
}

public String getAudio ()
{
    return audio;
}

public void setAudio (String audio)
{
    this.audio = audio;
}

public String getImgThumb ()
{
    return imgThumb;
}

public void setImgThumb (String imgThumb)
{
    this.imgThumb = imgThumb;
}

public String getFullDesc ()
{
    return fullDesc;
}

public void setFullDesc (String fullDesc)
{
    this.fullDesc = fullDesc;
}

public String getImgLarge ()
{
    return imgLarge;
}

public void setImgLarge (String imgLarge)
{
    this.imgLarge = imgLarge;
}

public int getLevel_id ()
{
    return level_id;
}

public void setLevel_id (int level_id)
{
    this.level_id = level_id;
}

public String getPhoto ()
{
    return photo;
}

public void setPhoto (String photo)
{
    this.photo = photo;
}

public int getType_id ()
{
    return type_id;
}

public void setType_id (int type_id)
{
    this.type_id = type_id;
}

public int getOld_pk ()
{
    return old_pk;
}

public void setOld_pk (int old_pk)
{
    this.old_pk = old_pk;
}

public int getId ()
{
    return id;
}

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

public int getDuration ()
{
    return duration;
}

public void setDuration (int duration)
{
    this.duration = duration;
}

public String getTitle_audio ()
{
    return title_audio;
}

public void setTitle_audio (String title_audio)
{
    this.title_audio = title_audio;
}

public String getIs_breathing ()
{
    return is_breathing;
}

public void setIs_breathing (String is_breathing)
{
    this.is_breathing = is_breathing;
}

public String getName ()
{
    return name;
}

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

public int getOld_identifier ()
{
    return old_identifier;
}

public void setOld_identifier (int old_identifier)
{
    this.old_identifier = old_identifier;
}

public String getIs_paid ()
{
    return is_paid;
}

public void setIs_paid (String is_paid)
{
    this.is_paid = is_paid;
}

public String getSanskrit_name ()
{
    return sanskrit_name;
}

public void setSanskrit_name (String sanskrit_name)
{
    this.sanskrit_name = sanskrit_name;
}

public String getBreathing_video ()
{
    return breathing_video;
}

public void setBreathing_video (String breathing_video)
{
    this.breathing_video = breathing_video;
}

@Override
public String toString(){
    return "Asana"+name+","+"id";


}

public int checkBool(String s){
    if (s.equals("true")){
        return 1;
    }
    else return 0;
}


}

改造界面

public interface MYApi {
@GET("/asanas")
void getAsanas(Callback<Asanas> response);
}

和日志：

"is_paid":true,"is_breathing":false,"old_identifier":"248","old_pk":1044}]}
09-24 12:06:16.049  20971-20998/com.example.user.asanasproject D/Retrofit﹕ <--- END HTTP (261559-byte body)
09-24 12:06:16.539  20971-20971/com.example.user.asanasproject D/AndroidRuntime﹕ Shutting down VM
09-24 12:06:16.539  20971-20971/com.example.user.asanasproject W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x40c0aa68)
09-24 12:06:16.539  20971-20971/com.example.user.asanasproject E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at com.example.user.asanasproject.MainActivity$1.success(MainActivity.java:37)
            at com.example.user.asanasproject.MainActivity$1.success(MainActivity.java:27)
            at retrofit.CallbackRunnable$1.run(CallbackRunnable.java:45)
            at android.os.Handler.handleCallback(Handler.java:605)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4517)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

通过查看您的JSON响应，字段el_GR和is_paid是布尔值，但在您的班级is_breathing中，您将其声明为AsanaPOJO。

尝试将它们更改为布尔值。

修改

同样@NaviRamyle说 - 您的String类ArrayList变量名称与JSON响应不匹配。

Answer 2

将private List<AsanaPOJO> asanaPOJOs;更改为private List<AsanaPOJO> asanas;

模型变量名称必须与JSON密钥名称完全相同

{
    "asanas": [..]
}