【移动应用开发技术】RecyclerView怎么在Android中使用

【移动应用开发技术】RecyclerView怎么在Android中使用

RecyclerView怎么在Android中使用？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。首先ListView与RecyclerView两者非常相似，两者提供view都是依赖适配器。只不过就是5.0版本推出RecyclerView后，Google将adapter和viewHolder做了一系列的优化和封装。不像之前为了复用Listview里面的converView，要类似在getView里面实现下列的代码：上面代码看起来挺眼熟吧~二、对比RecyclerView，google进行的优化在RecyclerView依赖的适配器中，无论是适配器还是ViewHolder，从源码我们可以看出，都存在RecyclerView的匿名内部类。相对于Listview，RecyclerView内置了多级缓存、RecyclerViewPool（从线程的角度，可以理解成类似线程池的东西，即多个RecyclerView可以公用一个view）、ViewHolder(已经实现了复用，相对于Listview的BaseAdapter中getView方法需要开发者自己引入复用问题方便很多)等等。这里我们简单说下两个方法：public

ViewHolder

onCreateViewHolder(ViewGroup

parent,

int

viewType)public

void

onBindViewHolder(ViewHolder

holder,

int

position)在以前的BaseAdapter中,所有视图加载、数据绑定以及复用，都需要我们直接在getView里面进行操作。onCreateViewHolder负责视图加载并且内部完成复用，onBindViewHolder负责数据绑定并且内部完成一系列的缓存机制。这里满足了视图层与逻辑层的分离，典型的mvp模式。三、RecyclerView的头部与尾部实现RecyclerView不像ListView拥有addHeaderView()与addFooterView()的方法简单添加头部尾部即可，而且RecyclerView也没有像ListView的列表点击监听方法（setItemOnclickListener），这里我也不明白为什么官方会取消了这些独有的属性，不过我们依然可以在onBindViewHolder方法中进行事件绑定！具体头部与尾部实现方法，这里有个诀窍，这里先看一个方法：public

int

getItemViewType(int

position)getItemViewType方法是在执行onCreateViewHolder(ViewGroupparent,intviewType)前回调用viewType，目的是为了根据viewType不同创建不同的视图。我们可以通过在onCreateViewHolder创建视图的时候，对viewType进行判断，如果添加了头部，在position=0的时候回调头部的viewType给onCreateViewHolder，从而创建头部。尾部创建方法于此类同，直接看下代码，适配器的实现：package

cn.wsy.recyclerdemo;

import

android.content.Context;

import

android.support.v7.widget.GridLayoutManager;

import

android.support.v7.widget.RecyclerView;

import

android.view.LayoutInflater;

import

android.view.View;

import

android.view.ViewGroup;

import

android.widget.TextView;

import

java.util.ArrayList;

import

java.util.List;

/**

*

Created

by

wsy

on

2016/8/4.

*/

public

class

MyAdapter

extends

RecyclerView.Adapter<MyAdapter.MyHolder>

{

private

RecyclerView

mRecyclerView;

private

List<String>

data

=

new

ArrayList<>();

private

Context

mContext;

private

View

VIEW_FOOTER;

private

View

VIEW_HEADER;

//Type

private

int

TYPE_NORMAL

=

1000;

private

int

TYPE_HEADER

=

1001;

private

int

TYPE_FOOTER

=

1002;

public

MyAdapter(List<String>

data,

Context

mContext)

{

this.data

=

data;

this.mContext

=

mContext;

}

@Override

public

MyAdapter.MyHolder

onCreateViewHolder(ViewGroup

parent,

int

viewType)

{

if

(viewType

==

TYPE_FOOTER)

{

return

new

MyHolder(VIEW_FOOTER);

}

else

if

(viewType

==

TYPE_HEADER)

{

return

new

MyHolder(VIEW_HEADER);

}

else

{

return

new

MyHolder(getLayout(R.layout.item_list_layout));

}

}

@Override

public

void

onBindViewHolder(MyHolder

holder,

int

position)

{

if

(!isHeaderView(position)

&&

!isFooterView(position))

{

if

(haveHeaderView())

position--;

TextView

content

=

(TextView)

holder.itemView.findViewById(R.id.item_content);

TextView

time

=

(TextView)

holder.itemView.findViewById(R.id.item_time);

content.setText(data.get(position));

time.setText("2016-1-1");

}

}

@Override

public

int

getItemCount()

{

int

count

=

(data

==

null

?

0

:

data.size());

if

(VIEW_FOOTER

!=

null)

{

count++;

}

if

(VIEW_HEADER

!=

null)

{

count++;

}

return

count;

}

@Override

public

int

getItemViewType(int

position)

{

if

(isHeaderView(position))

{

return

TYPE_HEADER;

}

else

if

(isFooterView(position))

{

return

TYPE_FOOTER;

}

else

{

return

TYPE_NORMAL;

}

}

@Override

public

void

onAttachedToRecyclerView(RecyclerView

recyclerView)

{

try

{

if

(mRecyclerView

==

null

&&

mRecyclerView

!=

recyclerView)

{

mRecyclerView

=

recyclerView;

}

ifGridLayoutManager();

}

catch

(Exception

e)

{

e.printStackTrace();

}

}

private

View

getLayout(int

layoutId)

{

return

LayoutInflater.from(mContext).inflate(layoutId,

null);

}

public

void

addHeaderView(View

headerView)

{

if

(haveHeaderView())

{

throw

new

IllegalStateException("hearview

has

already

exists!");

}

else

{

//避免出现宽度自适应

ViewGroup.LayoutParams

params

=

new

ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,

ViewGroup.LayoutParams.WRAP_CONTENT);

headerView.setLayoutParams(params);

VIEW_HEADER

=

headerView;

ifGridLayoutManager();

notifyItemInserted(0);

}

}

public

void

addFooterView(View

footerView)

{

if

(haveFooterView())

{

throw

new

IllegalStateException("footerView

has

already

exists!");

}

else

{

ViewGroup.LayoutParams

params

=

new

ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,

ViewGroup.LayoutParams.WRAP_CONTENT);

footerView.setLayoutParams(params);

VIEW_FOOTER

=

footerView;

ifGridLayoutManager();

notifyItemInserted(getItemCount()

-

1);

}

}

private

void

ifGridLayoutManager()

{

if

(mRecyclerView

==

null)

return;

final

RecyclerView.LayoutManager

layoutManager

=

mRecyclerView.getLayoutManager();

if

(layoutManager

instanceof

GridLayoutManager)

{

final

GridLayoutManager.SpanSizeLookup

originalSpanSizeLookup

=

((GridLayoutManager)

layoutManager).getSpanSizeLookup();

((GridLayoutManager)

layoutManager).setSpanSizeLookup(new

GridLayoutManager.SpanSizeLookup()

{

@Override

public

int

getSpanSize(int

position)

{

return

(isHeaderView(position)

||

isFooterView(position))

?

((GridLayoutManager)

layoutManager).getSpanCount()

:

1;

}

});

}

}

private

boolean

haveHeaderView()

{

return

VIEW_HEADER

!=

null;

}

public

boolean

haveFooterView()

{

return

VIEW_FOOTER

!=

null;

}

private

boolean

isHeaderView(int

position)

{

return

haveHeaderView()

&&

position

==

0;

}

private

boolean

isFooterView(int

position)

{

return

haveFooterView()

&&

position

==

getItemCount()

-

1;

}

public

static

class

MyHolder

extends

RecyclerView.ViewHolder

{

public

MyHolder(View

itemView)

{

super(itemView);

}

}

}四、实现方法简单的初始化RecycerView，以及设置适配器，如下：

private

void

initRecyc()

{

//

mRecyclerView.setLayoutManager(new

GridLayoutManager(this,2));

mRecyclerView.setLayoutManager(new

LinearLayoutManager(this));

adapter

=

new

MyAdapter(data,

this);

mRecyclerView.setAdapter(adapter);

adapter.addFooterView(LayoutInflater.from(this).inflate(R.layout.item_footer_layout,null));

adapter.addHeaderView(LayoutInflater.from(this).inflate(R.layout.item_header_layout,null));

}五、注意的问题笔者在添加头部尾部的时候，发现在配置RecyclerView，如果模式是配置GridLayoutManager的时候，发现头部会跑到第一格，也就是不是自己想要独立一行的效果，这里