android如何显示一个对象列表的片段

Question

Button b = (Button) findViewById(R.id.button); 
      b.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        Log.i("hi","onClick()"); 
        Fragment f = ProductListFragment.newInstance(productArray); 
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction(); 
        ft.replace(R.id.fragment, f); 
        ft.commit(); 
       } 
      }); 

这是主要的活动，让用户点击按钮来创建一个包含productArray数据的片段。

import android.support.v4.app.Fragment; 
import android.os.Bundle; 
import android.support.annotation.Nullable; 
import android.util.Log; 
import android.view.Gravity; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.GridView; 

import java.util.ArrayList; 

public class ProductListFragment extends Fragment{ 

    private ArrayList<Product> productArray; 

    public ArrayList<Product> getProductArray() { 
     return productArray; 
    } 

    public void setProductArray(ArrayList<Product> productArray) { 
     this.productArray = productArray; 
    } 

    public static Fragment newInstance(ArrayList<Product> productArray){ 

     ProductListFragment productListFragment = new ProductListFragment(); 
     productListFragment.setProductArray(productArray); 

     return productListFragment; 
    } 


    @Nullable 
    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     GridView gridView = (GridView) inflater.inflate(R.layout.product_list_fragment, container, false); 
     gridView.setNumColumns(2); 
     gridView.setGravity(Gravity.CENTER); 
     gridView.setAdapter( new CustomGridAdapter(getActivity(), getProductArray())); 
     return gridView; 
    } 
} 

这是将productArray中的数据放入网格视图的片段类，这在以前的测试中很好。

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
       android:layout_width="wrap_content" 
       android:layout_height="wrap_content" 
       android:orientation="vertical" 
       android:padding="10dp"> 

    <Button 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="open fragment" 
     android:id="@+id/button"/> 

    <fragment 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:name="com.it.fyp.fyprestaurant.ProductListFragment" 
     android:id="@+id/fragment"/> 


</LinearLayout> 

这是activity_main.xml。我知道如果我以这种方式创建片段，将会发生错误，因为productArray为null。是否需要片段标签，用于保留片段的位置或其他原因？我如何显示新的片段？请帮忙！

Answer 1

您应该添加productArray进行捆绑并从捆绑中获取productArray，Product模型需要实现Parcelable。

private static final String BUNDLE_PRODUCT_LIST = "bundle_product_list";  

public static Fragment newInstance(ArrayList<Product> productArray){ 

    ProductListFragment productListFragment = new ProductListFragment(); 
    Bundle bundle = new Bundle(); 
    bundle.putParcelableArrayList(BUNDLE_PRODUCT_LIST, productArray); 
    productListFragment.setArguments(bundle); 
    return productListFragment; 
} 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 

    if (getArguments() != null) { 
     productArray = getArguments().getParcelableArrayList(BUNDLE_PRODUCT_LIST); 
    } 
} 

========================================

更新：

Parcelable例如：

public class Product implements Parcelable { 
    private String id; 
    private String name; 

    public Product(String id, String name) { 
     this.id = id; 
     this.name = name; 
    } 

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

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

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

    private Product(Parcel in) { 
     id = in.readString(); 
     name = in.readString(); 
    } 

    @Override 
    public void writeToParcel(Parcel out, int i) { 
     // Make sure the order of writeString must be the same order 
     // as in.readString of the constructor above. 
     out.writeString(id); 
     out.writeString(name); 
    } 
}