Holen von Listendaten mit Model-Klasse in Android

Question

Ich habe zwei der Model-Klasse Speciality und SubSpeciality. Wenn ich getsubSpecialityList anrufe, gibt es NullpointerException zurück.

Specialty Modell

public class Speciality 
{ 
public String name; 
public List<SubSpeciality> subSpecialityList; 
public String getname() 
{ 
    return name; 
} 
public void setname(String name) 
{ 
    this.name = name; 
} 
public List<SubSpeciality> getsubSpecialityList() 
{ 
    return subSpecialityList; 
} 
public void setsubSpecialityList(List<SubSpeciality> subSpecialityList) 
{ 
    this.subSpecialityList = subSpecialityList; 
} 
} 

SubSpeciality Modell

public class SubSpeciality 
{ 
public String name; 
public String getnamesub() 
{ 
    return name; 
} 
public void setnamesub(String name) 
{ 
    this.name = name; 
} 
} 

Zugabe Artikel in beiden Modellen mit folgendem Code

List<Speciality> specialityList = new ArrayList<Speciality>(); 
List<SubSpeciality> subspecialityList = new ArrayList<SubSpeciality>(); 
Speciality spe = new Speciality(); 
spe.setname("Othopedic"); 

SubSpeciality sub= new SubSpeciality(); 
sub.setnamesub("---Select speciality---"); 
sub.setnamesub("1"); 
sub.setnamesub("2"); 
sub.setnamesub("3"); 
subspecialityList.add(sub); 
spe.setsubSpecialityList(subspecialityList); 
specialityList.add(spe); 

in folgendem Code bekommen Fehler

for(int j= 0;j<specialityList.size();j++) 
{ 
    Toast.makeText(RegisterActivity.this,specialityList.get(j).getsubSpecialityList().get(j).getnamesub()+"hii",Toast.LENGTH_SHORT).show(); 
} 

Logcat Ausgang:

FATAL EXCEPTION: main Process: careers.app.com.jobssearch, PID: 29880 
java.lang.NullPointerException 
    at careers.app.com.jobssearch.Activity.RegisterActivity$getSpeciality.onPostExecute(RegisterActivity.java:320) 
    at careers.app.com.jobssearch.Activity.RegisterActivity$getSpeciality.onPostExecute(RegisterActivity.java:263) 
    at android.os.AsyncTask.finish(AsyncTask.java:632) 
    at android.os.AsyncTask.access$600(AsyncTask.java:177) 
    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:136) 
    at android.app.ActivityThread.main(ActivityThread.java:5072) 
    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:793) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609) 
    at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Hier ist der Fehler

specialityList.get(j).getsubSpecialityList().get(j) 

Sie davon aus, dass beiden Array gleiche Größe sein, die aber manchmal kann es nicht sein..

so sollte Ihr Code sein

for(int j= 0;j<specialityList.size();j++) 
{ 
    for(int k=0;k<specialityList.get(j).getsubSpecialityList().size();k++) 
     Toast.makeText(getActivity(),specialityList.get(j).getsubSpecialityList().get(k).getnamesub()+"hii",Toast.LENGTH_SHORT).show(); 
}