Android适配器以及作用,Android RecyclerView 通用适配器的实现

分析

我们需要在RecyclerViewAdapter内部维持一个数据集合的引用

需要实现Item的点击事件，包括短按和长按，并需要向外部提供设置监听器的方法

这个适配器必须通用，所以应该是泛型的，并且ViewHolder也是通用的，可以采用SparseArray维持View的所有集合

在RecyclerViewAdapter内部需要实现数据的绑定(抽象方法，延迟到子类实现)，监听器的绑定

编写监听器

分为短按事件和长按事件

短按监听器

package cn.edu.zafu.base.adapter.listener;

import android.view.View;

/**

* Created by lizhangqu on 2015/6/3.

public interface OnItemClickListener {

void onClick(View view, T item);

}

长按监听器

package cn.edu.zafu.base.adapter.listener;

import android.view.View;

/**

* Created by lizhangqu on 2015/6/3.

public interface OnItemLongClickListener {

void onLongClick(View view, T item);

}

编写通用适配器

设置监听器

package cn.edu.zafu.base.adapter;

import android.support.v7.widget.RecyclerView;

import android.util.SparseArray;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ImageView;

import android.widget.TextView;

import java.util.List;

import cn.edu.zafu.base.adapter.listener.OnItemClickListener;

import cn.edu.zafu.base.adapter.listener.OnItemLongClickListener;

/**

* this is a BaseAdapter for RecyclerView

* author lizhangqu

* version 1.0

* date 2015/6/3.

public abstract class BaseRecyclerViewAdapter extends RecyclerView.Adapter {

/**

* click listener

protected OnItemClickListener mOnItemClickListener;

/**

* long click listener

protected OnItemLongClickListener mOnItemLongClickListener;

/**

* set a long click listener

* @param onItemLongClickListener

public void setOnItemLongClickListener(OnItemLongClickListener onItemLongClickListener) {

mOnItemLongClickListener = onItemLongClickListener;

}

/**

* set a click listener

* @param onItemClickListener

public void setOnItemClickListener(OnItemClickListener onItemClickListener) {

mOnItemClickListener = onItemClickListener;

}

编写构造方法，将数据集合进行赋值

/**

* data

protected List mList;

/**

* @param list the datas to attach the adapter

public BaseRecyclerViewAdapter(List list) {

mList = list;

}

实现几个必要的方法，比如获得Item以及覆写getItemCount方法

/**

* get a item by index

* @param position

* @return

protected T getItem(int position) {

return mList.get(position);

}

@Override

public int getItemCount() {

return mList.size();

}

实现将布局文件映射成View的方法

/**

* inflate a view by viewgroup ,id ,etc

* @param viewGroup

* @param layoutId

* @return

protected View inflateItemView(ViewGroup viewGroup, int layoutId) {

return inflateItemView(viewGroup, layoutId, false);

}

/**

* inflate a view by viewgroup ,id ,etc

* @param viewGroup

* @param layoutId

* @param attach

* @return

protected View inflateItemView(ViewGroup viewGroup, int layoutId, boolean attach) {

return LayoutInflater.from(viewGroup.getContext()).inflate(layoutId, viewGroup, attach);

}

实现onBindViewHolder方法，这一步很重要，将具体实现抽取到两个方法中去实现，bindDataToItemView是一个抽象方法，延迟到子类实现，bindItemViewClickListener方法设置监听器

/**

* a final function to avoid you override

* use template design pattern

* @param vh

* @param position

@Override

public final void onBindViewHolder(VH vh, int position) {

final T item = getItem(position);

bindDataToItemView(vh, item);

bindItemViewClickListener(vh, item);

}

/**

* bind data to itemview

* @param vh viewholder

* @param item item

protected abstract void bindDataToItemView(VH vh, T item);

/**

* bind click listner to itemview

* @param vh viewholder

* @param item item

protected final void bindItemViewClickListener(VH vh, final T item) {

if (mOnItemClickListener != null) {

vh.itemView.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View view) {

mOnItemClickListener.onClick(view, item);

}

});

}

if (mOnItemLongClickListener != null) {

vh.itemView.setOnLongClickListener(new View.OnLongClickListener() {

@Override

public boolean onLongClick(View v) {

mOnItemLongClickListener.onLongClick(v, item);

return true;

}

});

}

实现通用ViewHolder，内部使用SparseArray维持View对象

public static class SparseArrayViewHolder extends RecyclerView.ViewHolder {

private final SparseArray views;

public SparseArrayViewHolder(View itemView) {

super(itemView);

views = new SparseArray();

}

public T getView(int id) {

View view = views.get(id);

if (view == null) {

view = itemView.findViewById(id);

views.put(id, view);

}

return (T) view;

}

内部实现了一个泛型的getView方法，其作用就是将View缓存至SparseArray中去

实现通用ViewHolder的一些属性设置方法，采用链式调用，返回this对象

public SparseArrayViewHolder setText(int viewId, String value) {

TextView view = getView(viewId);

view.setText(value);