Android Exception ViewHolder 无法转换为另一个 Viewholder

Question

我尝试在我的列表视图上使用我的 FriendList 适配器，但是当我尝试滑动列表时，它出现了一个异常：

10-02 22:55:54.503 25872-25872/com.snapchat.team2.snapchat E/AndroidRuntime：致命异常：主要 进程：com.snapchat.team2.snapchat，PID：25872 java.lang.ClassCastException： com.snapchat.team2.snapchat.customAdapter.ChatFriendListAdapter$ViewHolder1 不能转换为 com.snapchat.team2.snapchat.customAdapter.ChatFriendListAdapter$ViewHolder2 在 com.snapchat.team2.snapchat.customAdapter.ChatFriendListAdapter.getView(ChatFriendListAdapter.java:82)

这些是我的代码

package com.snapchat.team2.snapchat.customAdapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import android.widget.TextView;

import com.snapchat.team2.snapchat.ListAdapterDataModel.Friend;
import com.snapchat.team2.snapchat.R;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


public class ChatFriendListAdapter extends BaseAdapter{

private List<Friend> ls;
private LayoutInflater inflater;
private final int ITEM_TYPE_1=1;
private final int ITEM_TYPE_2=2;
@Override
public int getCount() {
    return ls.size();
}

@Override
public Object getItem(int position) {
    return ls.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    Friend item = ls.get(position);
    int type = getItemViewType(position);

    ViewHolder1 holder1 = null;
    ViewHolder2 holder2 = null;

    if(convertView ==null){
        switch (type){
            case ITEM_TYPE_1:
                holder1 = new ViewHolder1();
                convertView = inflater .inflate(R.layout.chat_friend_list_item,null);
                holder1.t_initial_1=(TextView)convertView.findViewById(R.id.chat_friend_letter);
                holder1.t_name_1 = (TextView)convertView.findViewById(R.id.chat_friend_name);
                holder1.t_initial_1.setText(item.getInitial_letter());
                holder1.t_name_1.setText(item.getName());
                convertView.setTag(holder1);
                break;
            case ITEM_TYPE_2:
                holder2 = new ViewHolder2();
                convertView = inflater.inflate((R.layout.chat_frind_list_item_2),null);
                holder2.t_name_2 = (TextView)convertView.findViewById(R.id.chat_friend_name_2);
                holder2.t_name_2.setText(item.getName());
                convertView.setTag(holder2);
                break;
            default:
                break;
        }
    }
    else{
        switch (type){
            case ITEM_TYPE_1:
                holder1 = (ViewHolder1)convertView.getTag();
                holder1.t_initial_1.setText(item.getInitial_letter());
                holder1.t_name_1.setText(item.getName());
                break;
            case ITEM_TYPE_2:
                holder2 = (ViewHolder2)convertView.getTag();
                holder2.t_name_2.setText(item.getName());
                break;
            default:
                break;
        }
    }
    return  convertView;


}

public int getItemViewType(int position){
    return ls.get(position).getItem_type();
}

//constructor
public ChatFriendListAdapter(Context context,List<Friend> list){
    this.ls=list;
    //this.inflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.inflater =LayoutInflater.from(context);
}


class ViewHolder1{
    TextView t_initial_1;
    TextView t_name_1;
}
class ViewHolder2{
    TextView t_name_2;
}

}

为什么会发生这种情况。是Layout inflater的问题？

Answer 1

您需要像这样声明您的ViewHolder。

public class ViewHolder1 extends ViewHolder {

    private final TextView t_initial_1;
    private final TextView t_name_1;

    public ViewHolder1(View itemView) {
        super(itemView);

        // Find the views here
        t_initial_1 = (TextView) itemView.findViewById(R.id.t_initial_1);
        t_name_1 = (TextView) itemView.findViewById(R.id.t_name_1);
    }
}

为ViewHolder2做同样的事情

Answer 2

Activity中listview的选项比较多，如果你点击了一个选项，listview的长度大于屏幕的长度，点击另一个选项后会出错。因为现在convertview不为null但持有者为null，你可以这样做：

    switch(type){
        case ITEM_TYPE_1:
            if (holder1 == null) {
                holder1 = new ViewHolder1();
                convertView = inflater.inflate(R.layout.chat_friend_list_item, null);
                holder1.t_initial_1 = (TextView) convertView.findViewById(R.id.chat_friend_letter);
                holder1.t_name_1 = (TextView) convertView.findViewById(R.id.chat_friend_name);
                holder1.t_initial_1.setText(item.getInitial_letter());
                holder1.t_name_1.setText(item.getName());
                convertView.setTag(holder1);
            } else {
                holder1 = (ViewHolder1) convertView.getTag();
            }
            break;
        case ITEM_TYPE_2:
            if (holder2 == null) {
                holder2 = new ViewHolder2();
                convertView = inflater.inflate((R.layout.chat_frind_list_item_2), null);
                holder2.t_name_2 = (TextView) convertView.findViewById(R.id.chat_friend_name_2);
                holder2.t_name_2.setText(item.getName());
                convertView.setTag(holder2);
            } else {
                holder2 = (ViewHolder2) convertView.getTag();
            }
            break;
    }