使用RecyclerView適配器更改運行時佈局屏幕

Question

我有兩個佈局文件，如下所示。

如果數據存在於列表中，則顯示此佈局。

，當列表爲空，然後我告訴這個佈局。

現在，我想在運行時更改佈局。當用戶從列表中刪除最後一個項目時，我想將佈局更改爲第二個圖像中顯示的「清空購物車佈局」。

在RecyclerView適配器getItemCount()方法，如果列表爲空或null，則我回算不算1否則我回到list.size()

這是我的適配器代碼。

public class CheckOutAdapter extends RecyclerView.Adapter<CheckOutAdapter.ViewHolder> { 

    public ArrayList<Design> designList; 
    private Context context; 
    private LayoutInflater layoutInflater; 

    public CheckOutAdapter(Context context, ArrayList<Design> designList) { 
     this.designList = designList; 
     this.context = context; 
     this.layoutInflater = LayoutInflater.from(context); 
    } 

    @Override 
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     if(designList.isEmpty() || designList == null || designList.size() == 0) { 
      View view = layoutInflater.inflate(R.layout.empty_cart, parent, false); 
      return new ViewHolder(view); 
     } else { 
      View view = layoutInflater.inflate(R.layout.checkout_single_design, parent, false); 
      return new ViewHolder(view); 
     } 
    } 

    @Override 
    public void onBindViewHolder(final ViewHolder holder, final int position) { 

     final Design design = designList.get(position); 
     holder.tvQuality.setText(design.qualityName); 
     holder.tvDesign.setText(design.designName); 
     holder.tvShade.setText(design.name); 
     holder.tvAmount.setText("₹ " + design.amount); 
     Picasso.with(context).load(design.image).into(holder.ivDesign); 
     if (design.pcs != 0) { 
      holder.btPcsCount.setText(Integer.toString(design.pcs)); 
     } 

     holder.ivDelete.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       openDialog(design); 
      } 
     }); 
     //other ClickListeners. 
    } 

    @Override 
    public int getItemCount() { 
     if (designList == null || designList.isEmpty() || designList.size() == 0) { 
      return 1; 
     } else { 
      return designList.size(); 
     } 
    } 

    public static class ViewHolder extends RecyclerView.ViewHolder { 

     public LinearLayout llPer; 
     public Button btPlus, btMinus, btPcsCount, btAddCart; 
     public ImageView ivDesign, ivDelete; 
     public TextView tvDesign, tvQuality, tvShade, tvAmount, tvDiscAmt, tvDisPer; 

     public ViewHolder(View itemView) { 
      super(itemView); 

      llPer = (LinearLayout) itemView.findViewById(R.id.llPer); 
      btPlus = (Button) itemView.findViewById(R.id.btPlus); 
      //other findViewByIds 
     } 
    } 

    public void openDialog(final Design design) { 
     AlertDialog.Builder builder = new AlertDialog.Builder(context); 
     builder.setTitle("Confirm"); 
     builder.setMessage("Remove item from cart?"); 
     builder.setPositiveButton("YES", new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int which) { 
       designList.remove(design); 
       notifyDataSetChanged(); 
       saveSharedPref(context, "cart", new Gson().toJson(designList)); 
       Toast.makeText(context, "deleted", Toast.LENGTH_SHORT).show(); 
       dialog.dismiss(); 
      } 
     }); 

     builder.setNegativeButton("NO", new DialogInterface.OnClickListener() { 
      @Override 
      public void onClick(DialogInterface dialog, int which) { 
       dialog.dismiss(); 
      } 
     }); 

     AlertDialog alert = builder.create(); 
     alert.show(); 
    } 
} 

我得到NullPointerException接近onBindViewHolder。我不知道它爲什麼會墜毀。請提出建議。

Answer 1

你可以做到這一點覆蓋getItemViewType()：

@Override 
public int getItemViewType(int position) { 
    if (designList.size() == 0) return R.layout.empty; 
    else return R.layout.normal_layout; 
} 

@Override 
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    View view = LayoutInflater.from(parent.getContext()).inflate(viewType, parent, false); 
    ViewHolder viewHolder = null; 
    if (viewType == R.layout.empty) { 
     viewHolder = new EmptyViewHolder(view); 
    } else { 
     viewHolder = new NormalViewHolder(view); 
    } 
    return viewholder; 
} 

@Override 
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) { 
    if (holder instanceOf EmptyViewHolder){ 
     // this is empty item, update view appropriately if needed 
    } else { 
     // this is normal item, update view appropriately if needed 
    } 
} 

現在，當數據集變化並有1只在您的適配器的項目，你會得到顯示所需的佈局。

Answer 2

看看..當您重新創建1時，即使您的數據集沒有任何數據..您的適配器嘗試綁定來自空數據集的視圖，因此您得到一個空指針。

**而現在你可以在你的bindView做到這一點**

@Override //add this method to your adapter 
public int getItemViewType(int position) { 
    if(designList.size()==0){ 
     return 1; 
     }else{ 
     return 2; 
    } 
} 

也在你onCreateView持有人做..

@Override // modify your onCreate based on viewtype 
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    if(viewType == 1) { //for empty layout 
     View view = layoutInflater.inflate(R.layout.empty_cart, parent, false); 
     return new ViewHolder(view); 
    } else { 
     View view = layoutInflater.inflate(R.layout.checkout_single_design, parent, false); 
     return new ViewHolder(view); 
    } 
} 

（）做到這一點：

@Override/
public void onBindViewHolder(final ViewHolder holder, final int position) { 

    if(designList.size()>0){ 
     final Design design = designList.get(position); 
    holder.tvQuality.setText(design.qualityName); 
    holder.tvDesign.setText(design.designName); 
    holder.tvShade.setText(design.name); 
    holder.tvAmount.setText("₹ " + design.amount); 
    Picasso.with(context).load(design.image).into(holder.ivDesign); 
    if (design.pcs != 0) { 
     holder.btPcsCount.setText(Integer.toString(design.pcs)); 
    } 

    holder.ivDelete.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      openDialog(design); 
     } 
    }); 
    //other ClickListeners. 
    }else{ 
     //handle the empty layout Add button click listener 
    } 

} 

希望有幫助

Answer 3

@Override 
public int getItemViewType(int position) { 
     if ((designList.isEmpty() || designList == null || designList.size() == 0) { 
        return R.layout.empty_cart; 
     } 
     return R.layout.checkout_single_design; 
} 

@Override 
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
     if (viewType == R.layout.empty_cart) { 
      return new EmptyViewHolder(layoutInflater.inflate(viewType, parent, false)); 
     } else { 
      return new ViewHolder(layoutInflater.inflate(viewType, parent, false)); 
     } 
    }