Question

我想将这个java类转换为kotlin

package com.mkhaleghy.cinema.adapter;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.mkhaleghy.cinema.R;
import com.mkhaleghy.cinema.daylist.Movie;

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

public class RecyclerAdapter<T extends Element> extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {

public RecyclerAdapter(Context context) {

}

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    return null;
}

@Override
public int getItemViewType(int position) {
    return 0;
}

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

}

@Override
public int getItemCount() {
    return 10;
}

public class ViewHolder extends RecyclerView.ViewHolder {
    View itemView;

    public ViewHolder(View itemView) {
        super(itemView);
        this.itemView = itemView;
    }
}

}

哈哈，真是太简单了。我使用android studio kotlin工具转换它，结果是

class RecyclerAdapter<T : Element>(context: Context) : RecyclerView.Adapter<RecyclerAdapter.ViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return null
    }

    override fun getItemViewType(position: Int): Int {
        return 0
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
s
        return 10
    }

    inner class ViewHolder(internal var itemView: View) : RecyclerView.ViewHolder(itemView)

}

但我在RecyclerAdapter.ViewHolder上收到错误，上面写着“类RecyclerAdapter需要的一个类型参数” 谁能帮助我？

Answer 1

如果您有类似的通用类：

class Adapter<T : Element>

比你必须称之为：

: RecyclerView.Adapter<Adapter<Element>.ViewHolder>()

这就是问题所在。但是你应该怎么做？最简单的想法是在单独的文件（而不是内部类）中创建ViewHolder并实现一些绑定接口。但您也可以搜索其他解决方案。

请参阅此示例：https://medium.com/@mohanmanu/generic-adapter-with-kotlin-part-i-74e191d68b0f

Answer 2

删除＆lt;＆gt;你的问题将得到解决

class EmployeeAdapter(context: Context) : RecyclerView.Adapter<EmployeeAdapter.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ViewHolder {
    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}

override fun onBindViewHolder(holder: ViewHolder?, position: Int) {
    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}

override fun getItemCount(): Int {
    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
}




inner class ViewHolder(internal var itemView: View) : RecyclerView.ViewHolder(itemView)

}

子类和父类中的Kotlin泛型

2 个答案: