将数据从MainActivity传递到Fragment

Question

我正在尝试使用Parcelable将onDataLoaded函数（位于MainActivity中）的自定义对象列表传递给片段。 但是我得到这个错误...

这是一个MainActivity函数，onDataLoaded

@Override
public void onDataLoaded(List<Grad> gradovi, List<Ponuda> ponude) {

    Spinner spinnerGradovi = (Spinner) findViewById(R.id.gradovi_spinner);
    ArrayAdapter<String> adapterGradovi;
    List<String> listaGradova = new ArrayList<>();
    ArrayList<Ponuda> ponudaArrayList = new ArrayList<Ponuda>();

    ponudaLista = ponude;
    gradLista = gradovi;

    for(Grad grad : gradovi ){
        listaGradova.add(grad.getNaziv());
    }

    for(Ponuda ponuda : ponude){
        ponudaArrayList.add(ponuda);
    }


    //here I want to get arguments which contains ArrayList
    Fragment fragmentGet = svePonudeFragment;
    Bundle bundle = new Bundle();
    bundle.putParcelableArrayList("Ponuda", ponudaArrayList);
    fragmentGet.setArguments(bundle);


    adapterGradovi = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, listaGradova);

    spinnerGradovi.setAdapter(adapterGradovi);


}

这是片段：

public class SvePonudeFragment extends Fragment {

private RecyclerView rv;

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

    rv = (RecyclerView) rootView.findViewById(R.id.rv);
    LinearLayoutManager llm = new LinearLayoutManager(getActivity());
    rv.setLayoutManager(llm);

    Bundle data = getActivity().getIntent().getExtras();
    ArrayList<Ponuda> listaPonuda= data.getParcelable("ponude");


    for(Ponuda ponuda : listaPonuda){
        System.out.println(ponuda.getNaziv());
    }

    initializeAdapter(listaPonuda);

    return rootView;
}

private void initializeAdapter(List<Ponuda> preuzetePonude){
    RVAdapter adapter = new RVAdapter(preuzetePonude);
    rv.setAdapter(adapter);
}

}

这是对象类

@Table(database = MainDatabase.class)
public class Ponuda extends BaseModel implements Parcelable{

@Column
@PrimaryKey int id;
@Column  String tekstPonude;
@Column  int cijena;
@Column  int popust;
@Column  int cijenaOriginal;
@Column  String urlSlike;
@Column  int usteda;
@Column  String kategorija;
@Column  String grad;
@Column  String datumPonude;

public Ponuda() {
}

public Ponuda(int id,String tekstPonude, int cijena, int popust, int cijenaOriginal, String urlSlike, int usteda, String kategorija, String grad, String datumPonude){
    this.id=id;
    this.tekstPonude = tekstPonude;
    this.cijena = cijena;
    this.popust = popust;
    this.cijenaOriginal = cijenaOriginal;
    this.urlSlike = urlSlike;
    this.usteda = usteda;
    this.kategorija = kategorija;
    this.grad = grad;
    this.datumPonude = datumPonude;
}

public String getNaziv() {
    return tekstPonude;
}
public String getCijena() {
    return Integer.toString(cijena);
}
public String getURL() {
    return urlSlike;
}

public void setCijena(int cijena) {
    this.cijena = cijena;
}

public int getId() {
    return id;
}

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

public String getTekstPonude() {
    return tekstPonude;
}

public void setTekstPonude(String tekstPonude) {
    this.tekstPonude = tekstPonude;
}

public int getPopust() {
    return popust;
}

public void setPopust(int popust) {
    this.popust = popust;
}

public int getCijenaOriginal() {
    return cijenaOriginal;
}

public void setCijenaOriginal(int cijenaOriginal) {
    this.cijenaOriginal = cijenaOriginal;
}

public String getUrlSlike() {
    return urlSlike;
}

public void setUrlSlike(String urlSlike) {
    this.urlSlike = urlSlike;
}

public int getUsteda() {
    return usteda;
}

public void setUsteda(int usteda) {
    this.usteda = usteda;
}

public String getKategorija() {
    return kategorija;
}

public void setKategorija(String kategorija) {
    this.kategorija = kategorija;
}

public String getGrad() {
    return grad;
}

public void setGrad(String grad) {
    this.grad = grad;
}

public String getDatumPonude() {
    return datumPonude;
}

public void setDatumPonude(String datumPonude) {
    this.datumPonude = datumPonude;
}
public static List<Ponuda> getAll(){
    List<Ponuda> ponudaList;
    ponudaList= new Select().from(Ponuda.class).queryList();

    return ponudaList;
}


public Ponuda(Parcel in){
    String[] data = new String[9];

    in.readStringArray(data);
    this.id = in.readInt();
    this.tekstPonude = in.readString();
    this.cijena = in.readInt();
    this.popust = in.readInt();
    this.cijenaOriginal = in.readInt();
    this.urlSlike = in.readString();
    this.usteda = in.readInt();
    this.kategorija = in.readString();
    this.grad = in.readString();
    this.datumPonude = in.readString();

}

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

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeInt(id);
    dest.writeString(tekstPonude);
    dest.writeInt(cijena);
    dest.writeInt(popust);
    dest.writeInt(cijenaOriginal);
    dest.writeString(urlSlike);
    dest.writeInt(usteda);
    dest.writeString(kategorija);
    dest.writeString(grad);
    dest.writeString(datumPonude);
}

public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
    public Ponuda createFromParcel(Parcel in) {
        return new Ponuda(in);
    }

    public Ponuda[] newArray(int size) {
        return new Ponuda[size];
    }
};

}

我不明白为什么会出现空指针异常

尝试在空对象引用上调用虚拟方法'android.os.Parcelable android.os.Bundle.getParcelable（java.lang.String）'

Answer 1

是的，您收到此错误。 为什么？ 因为您有2个错误：

Bundle data = getActivity().getIntent().getExtras(); 

->您正在尝试获取Activity而不是片段。 您应该尝试使用getArguments()代替。

您将收到另一个错误，因为调用片段的onCreateView()时，片段中没有参数束（您的束在活动中的onDataLoaded中设置）。 我认为您应该在片段中重新加载数据，例如：

public void reloadData(){
      //getArguments, parse and show in the list 
}
//then in your onDataLoaded of MainActivity:
//here I want to get arguments which contains ArrayList
((YourFragment)fragmentGet).reloadData(); //call after set argument

Answer 2

您可以通过其他方式来实现。 从活动中获取数据。

在主Java中添加updateListInFragment（）。 MainActivity.java

public ArrayList<Ponuda> updateListInFragment(){
       return ponudaArrayList;
    }

SvePonudeFragment.java

private ArrayList<Ponuda> mMyList;
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.sve_ponude_fragment, container, false);

    rv = (RecyclerView) rootView.findViewById(R.id.rv);
    LinearLayoutManager llm = new LinearLayoutManager(getActivity());
    rv.setLayoutManager(llm);

    Bundle data = getActivity().getIntent().getExtras();
    updateArrayList(); //Let's update here


    for(Ponuda ponuda : mMyList){
        System.out.println(ponuda.getNaziv());
    }

    initializeAdapter(listaPonuda);

    return rootView;
    }



// Update your mMyList from activity
public void updateArrayList(){

   MainActivity activity = (MainActivity) activity;
   mMyList = activity.updateListInFragment();

}