Paryllable與arraylist <CustomClass>從活動傳遞價值到片段android

Question

我想從一個活動傳遞一個自定義ArrayList到一個片段，但不明白代碼有什麼問題。沒有錯誤，但即使是他們我也無法獲得預期的輸出。 我努力修復它近3天后完全失去了（是的，但我只是一個初學者）。請幫我解決它。目的是爲了將片段用於其他活動。

這裏是我的活動課：

public class CityDetailsActivity extends AppCompatActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     // Create a list of City Details 
     ArrayList<CityDetails> cityDetail = new ArrayList<CityDetails>(); 
     cityDetail.add(new CityDetails("information", "near", "local food", R.drawable.img1, R.drawable.img1, R.drawable.img6)); 
     Bundle args = new Bundle(); 
     args.putParcelableArrayList("key", cityDetail); 
     CityInformationFragment myFragment = new CityInformationFragment(); 
     myFragment.setArguments(args); 

     // Set the content of the activity to use the activity_main.xml layout file 
     setContentView(R.layout.fragment_main); 
     ViewPager vpPager = (ViewPager) findViewById(R.id.vpPager); 
     FragmentPagerAdapter adapterViewPager; 
     adapterViewPager = new CityDetailsPagerAdapter(getSupportFragmentManager()); 
     vpPager.setAdapter(adapterViewPager); 
     // Give the TabLayout the ViewPager 
     TabLayout tabLayout = (TabLayout) findViewById(R.id.sliding_tabs); 
     tabLayout.setupWithViewPager(vpPager); 
    } 
} 

我的自定義Parcelable類是爲下：

public class CityDetails implements Parcelable { 
    private String mInformation; 
    private String mNearPlace; 
    private String mLocalFood; 
    private int mItemImageResourceId; 
    private int mNear_place_image_ResourceId; 
    private int mLocal_food_image_ResourceId; 

    public CityDetails(String information, String nearPlace, String localFood, int itemImageResourceId 
      , int near_place_image_ResourceId, int local_food_image_ResourceId) { 
     mInformation = information; 
     mNearPlace = nearPlace; 
     mLocalFood = localFood; 
     mItemImageResourceId = itemImageResourceId; 
     mNear_place_image_ResourceId = near_place_image_ResourceId; 
     mLocal_food_image_ResourceId = local_food_image_ResourceId; 

    } 

    @Override 
    public void writeToParcel(Parcel out, int flags) { 
     out.writeString(mInformation); 
     out.writeString(mNearPlace); 
     out.writeString(mLocalFood); 
     out.writeInt(mItemImageResourceId); 
     out.writeInt(mNear_place_image_ResourceId); 
     out.writeInt(mLocal_food_image_ResourceId); 

    } 

    private CityDetails(Parcel in) { 
     mItemImageResourceId = in.readInt(); 
     mNear_place_image_ResourceId = in.readInt(); 
     mLocal_food_image_ResourceId = in.readInt(); 
     mNearPlace = in.readString(); 
     mLocalFood = in.readString(); 
     mInformation = in.readString(); 
    } 

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

    // After implementing the `Parcelable` interface, we need to create the 
    // `Parcelable.Creator<MyParcelable> CREATOR` constant for our class; 
    // Notice how it has our class specified as its type. 
    public static final Parcelable.Creator<CityDetails> CREATOR 
      = new Parcelable.Creator<CityDetails>() { 

     // This simply calls our new constructor (typically private) and 
     // passes along the unmarshalled `Parcel`, and then returns the new object! 
     @Override 
     public CityDetails createFromParcel(Parcel in) { 
      return new CityDetails(in); 
     } 

     // We just need to copy this and change the type to match our class. 
     @Override 
     public CityDetails[] newArray(int size) { 
      return new CityDetails[size]; 
     } 
    }; 

    public String getInformation() { 
     return mInformation; 
    } 

    public String getNearPlace() { 
     return mNearPlace; 
    } 

    public String getLocalFood() { 
     return mLocalFood; 
    } 

    public int getItemImageResourceId() { 
     return mItemImageResourceId; 
    } 

    public int getNear_place_image_ResourceId() { 
     return mNear_place_image_ResourceId; 
    } 

    public int getLocal_food_image_ResourceId() { 
     return mLocal_food_image_ResourceId; 
    } 
} 

最後一點我的片段是：

public class CityInformationFragment extends Fragment { 

    public CityInformationFragment() { 
     // Required empty public constructor 
    } 

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

     Bundle bundle = getArguments(); 

     if ((bundle != null)) { 
      ArrayList<CityDetails> city = getArguments().getParcelable("key"); 

      // Create an {@link WordAdapter}, whose data source is a list of {@link Word}s. The 
      // adapter knows how to create list items for each item in the list. 
      CityDetailsAdapter adapter = new CityDetailsAdapter(getActivity(), city); 

      // Find the {@link ListView} object in the view hierarchy of the {@link Activity}. 
      // There should be a {@link ListView} with the view ID called list, which is declared in the 
      // word_list.xml layout file. 
      ListView listView = (ListView) rootView.findViewById(R.id.city_list); 

      // Make the {@link ListView} use the {@link WordAdapter} we created above, so that the 
      // {@link ListView} will display list items for each {@link Word} in the list. 
      listView.setAdapter(adapter); 
     } 

     return rootView; 
    } 

} 

編輯： 這裏是我的FragmentPagerDapter

public class CityDetailsPagerAdapter extends FragmentPagerAdapter { 
final int PAGE_COUNT = 1; 
private String tabTitles[] = new String[] { "City Information"}; 
private Context context; 

public CityDetailsPagerAdapter(FragmentManager fm) { 
    super(fm); 
} 

@Override 
public Fragment getItem(int position) { 
    return new CityInformationFragment(); 
} 
@Override 
public CharSequence getPageTitle(int position) { 
    // Generate title based on item position 
    return tabTitles[position]; 
} 


@Override 
public int getCount() { 
    return PAGE_COUNT; 
} 

} 而且，這裏是我的CityDetailsAdapter：

public class CityDetailsAdapter extends ArrayAdapter<CityDetails> { 
// View lookup cache 
private static class ViewHolder { 
    TextView cityInformation; 
    ImageView city_item_image; 
    TextView city_near_place_Information; 
    ImageView city_item_near_place_image; 
    TextView city_local_food_Information; 
    ImageView city_item_local_food_image; 

} 

public CityDetailsAdapter(Context context, ArrayList<CityDetails> cityDetails) { 
    super(context, 0, cityDetails); 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    // Get the data item for this position 
    CityDetails currentCity = getItem(position); 
    // Check if an existing view is being reused, otherwise inflate the view 
    ViewHolder viewHolder; // view lookup cache stored in tag 
    if (convertView == null) { 
     // If there's no view to re-use, inflate a brand new view for row 
     viewHolder = new ViewHolder(); 
     LayoutInflater inflater = LayoutInflater.from(getContext()); 
     convertView = inflater.inflate(R.layout.city_list_item, parent, false); 
        /*Find the TextView and ImageView and set them on the VIewHolder*/ 
     viewHolder.cityInformation = (TextView) convertView.findViewById(R.id.cityInformation); 
     viewHolder.city_near_place_Information = (TextView) convertView.findViewById(R.id.city_near_place_Information); 
     viewHolder.city_local_food_Information = (TextView) convertView.findViewById(R.id.city_local_food_Information); 
     viewHolder.city_item_image = (ImageView) convertView.findViewById(R.id.city_item_image); 
     viewHolder.city_item_near_place_image = (ImageView) convertView.findViewById(R.id.city_item_near_place_image); 
     viewHolder.city_item_local_food_image = (ImageView) convertView.findViewById(R.id.city_item_local_food_image); 

     // Cache the viewHolder object inside the fresh view 
     convertView.setTag(viewHolder); 
    } else { 
     // View is being recycled, retrieve the viewHolder object from tag 
     viewHolder = (ViewHolder) convertView.getTag(); 
    } 
    // Populate the data into the template view using the data object 
    viewHolder.cityInformation.setText(currentCity.getInformation()); 
    viewHolder.city_item_image.setImageResource(currentCity.getItemImageResourceId()); 
    viewHolder.city_near_place_Information.setText(currentCity.getNearPlace()); 
    viewHolder.city_local_food_Information.setText(currentCity.getLocalFood()); 
    viewHolder.city_item_near_place_image.setImageResource(currentCity.getNear_place_image_ResourceId()); 
    viewHolder.city_item_local_food_image.setImageResource(currentCity.getLocal_food_image_ResourceId()); 

    return convertView; 
} 

要儘可能具體到我正在做的錯誤。因爲作爲初學者我可能無法理解一些概念，但我會嘗試。無論如何，這是我的第一個問題，所以也許我沒有正確地說出問題。 和你的幫助是最受歡迎的。 謝謝。

Answer 1

的問題似乎是與你的FragmentPagerAdapter類。你不通過getItem（）方法返回的片段傳遞任何參數，它只是返回沒有任何參數傳遞給它的片段對象。

因此修改該方法，以下面

@Override 
public Fragment getItem(int position) { 
    CityInfomationFragment fragment = new CityInformationFragment(); 
    Bundle args = new Bundle(); 
    args.putParcelableArrayList("key", your_array_list); 
    fragment.setArguments(args); 
    return fragment; 
} 

傳遞array_list從活性的FragmentPagerAdapter類的構造和使用場變量保存，並在爲getItem（）方法引用它

編輯

您在活動中創建的片段實例完全沒有效果，除非您使用它進行任何片段事務。您可以將該片段實例傳遞給FragmentPagerAdater，並從getItem（）方法返回該片段以在ViewPager中顯示該片段。

Answer 2

試試下面一行

ArrayList<CityDetails> city = getArguments().getParcelableArrayList("key");