在片段之間傳遞ArrayList和Parcelable

Question

在使用Retrofit並使用非同步回調消費了json之後，我無法將ArrayList從MainActivity傳遞到片段。從MainActivity

代碼：

lFragmentManager = getFragmentManager(); 
      lFragment = lFragmentManager.findFragmentById(R.id.frame_container); 
      lFragment = new Fragment_Categories(); 
      Bundle bundle = new Bundle(); 
      bundle.putParcelableArrayList("list_categories", Categories_.getCategories()); 
      //for(int a = 0 ; a < Categories_.getCategories().size(); a++) 
      // Log.d("billy",Categories_.getCategories().get(a).getTitle()); 
      lFragment.setArguments(bundle); 
     lFragmentManager.beginTransaction().replace(R.id.frame_container ,lFragment).commit(); 

注意，在註釋日誌並打印清單的背景下，所以我把ArrayList與此代碼片段裏面onCreateView：

if(savedInstanceState != null) 
     categories = savedInstanceState.getParcelableArrayList("list_categories"); 

    /* 
    * initialize the Recycler view 
    */ 
    mRecycler = (RecyclerView)view.findViewById(R.id.categories_list); 
    mAdapter = new AdapterCategories(categories,getActivity()); 
    mRecycler.setAdapter(mAdapter); 

這是我的班級類別：

public class Categories implements Parcelable{ 

private ArrayList<NavDrawerItem> categories; 

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

@Override 
public void writeToParcel(Parcel dest, int flags) { 
    dest.writeTypedList(categories); 

} 

public static final Parcelable.Creator<Categories> CREATOR = new Parcelable.Creator<Categories>() { 

    public Categories createFromParcel(Parcel in) { 
     return new Categories(in); 

    } 

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

private Categories(Parcel in){ 

    categories = in.createTypedArrayList(NavDrawerItem.CREATOR); 
} 

public ArrayList<NavDrawerItem> getCategories() { 
    return categories; 
} 
} 

這裏是類NavDrawerItem：

public class NavDrawerItem implements Parcelable { 

private String title; 
private String description; 
private String image; 
private String post_count; 
private String id; 
private String slug; 
private int parent; 

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

@Override 
public void writeToParcel(Parcel dest, int flags) { 
    dest.writeString(title); 
    dest.writeString(description); 
    dest.writeString(image); 
    dest.writeString(post_count); 
    dest.writeString(id); 
    dest.writeString(slug); 
    dest.writeInt(parent); 
} 

public static final Parcelable.Creator<NavDrawerItem> CREATOR = new Parcelable.Creator<NavDrawerItem>() { 

    public NavDrawerItem createFromParcel(Parcel in) { 
     return new NavDrawerItem(in); 

    } 

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

private NavDrawerItem(Parcel in){ 
    title = in.readString(); 
    description = in.readString(); 
    image = in.readString(); 
    post_count = in.readString(); 
    id = in.readString(); 
    slug = in.readString(); 
    parent = in.readInt(); 
} 

的問題是，內部片段（試圖通過列表的RecyclerView的適配器時）或RecyclerView我拿一個空異常的轉接器內：

顯示java.lang.NullPointerException：嘗試上的空對象引用調用虛擬方法的java.util.ArrayList android.os.Bundle.getParcelableArrayList（java.lang.String中）'

謝謝你的幫助！

Answer 1

您不會使用savedInstanceState來獲取您的參數，因爲它們不作爲saveInstanceState()操作的一部分傳遞。你想用來代替。所以試試這個...

categories = getArguments().getParcelableArrayList("list_categories");