当前位置：首页 > 资讯 > 技术文档

Android RecyclerView实现多种item布局的方法

时间：2021-03-07 15:28 编辑：来源：阅读：
扫一扫，手机访问

摘要：Android RecyclerView实现多种item布局的方法

在项目中列表是基本都会用到的，然而在显示列表时，我们需要的数据可能需要不止一种item显示，对于复杂的数据就需要多种item，以不同的样式显示出来，这样效果是很棒的，我们先看一下效果 [img]http://files.jb51.net/file_images/article/201712/201712060934566.jpg[/img] [img]http://files.jb51.net/file_images/article/201712/201712060934567.jpg[/img] 我们可以看到，这个RecyclerView中有多种item显示出来，那么具体怎么实现呢，其实在RecyclerView中，我们可以重写方法getItemViewType()，这个方法会传进一个参数position表示当前是第几个Item，然后我们可以通过position拿到当前的Item对象，然后判断这个item对象需要那种视图，返回一个int类型的视图标志，然后在onCreatViewHolder方法中给引入布局，这样就能够实现多种item显示了，讲了这么多我们看一下具体的例子

@Override 
public int getItemViewType(int position) { 
  if(list.size() == 0){ 
    return EMPTY_VIEW; 
  } else if(list.get(position) == null){ 
    return PROGRESS_VIEW; 
  } else if(list.get(position).getType().equals(News.IMAGE_NEWS)){ 
    return IMAGE_VIEW; 
  } else { 
    return super.getItemViewType(position); 
  } 
}

首先我们重写了getItemViewType这个方法，在这个方法中根据position对item对象做了一些判断，如果存储item对象的集合大小为空，返回空view标识（这里为1），如果item对象为null，返回进度条标识，这个主要是用于实现下拉加载更多，如果item对象类型属于图片类型，就返回图片类型对应的Item，这个就是效果图中的第一个Item类型，否则就是其它类型，也就是效果图中的另一种item布局，然后我们在onCreatViewHolder中具体的为每一种类型引入其布局

@Override 
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
  View view; 
  if(viewType == PROGRESS_VIEW){ 
    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.progressbar_item, parent, false); 
    return new ProgressViewHolder(view); 
  } else if(viewType == EMPTY_VIEW){ 
    return null; 
  } else if(viewType == IMAGE_VIEW){ 
    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.image_news_item, parent, false); 
    return new ImageViewHolder(view); 
  } else { 
    view = LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item, parent, false); 
    return new NewsViewHolder(view); 
  } 
}

上面的代码就是具体为每种viewType引入其对应的布局，这样就基本实现了多种item布局，但是仅仅是这些还不够，因为我们还要对每种item设置数据，所以还要对每种item写一个VIewHolder来为item显示数据

class NewsViewHolder extends RecyclerView.ViewHolder{  
  @BindView(R.id.news_title)TextView title; 
  @BindView(R.id.news_digest)TextView digest; 
  @BindView(R.id.news_time)TextView time; 
  @BindView(R.id.news_src)ImageView image;  
  public NewsViewHolder(View itemView) { 
    super(itemView); 
    ButterKnife.bind(this, itemView); 
  } 
} 
 
class ImageViewHolder extends RecyclerView.ViewHolder{  
  @BindView(R.id.news_title) TextView title; 
  @BindView(R.id.image_left) ImageView imageLeft; 
  @BindView(R.id.image_right) ImageView imageRight; 
  @BindView(R.id.image_middle) ImageView imageMiddle; 
  @BindView(R.id.news_time) TextView time;  
  public ImageViewHolder(View itemView) { 
    super(itemView); 
    ButterKnife.bind(this, itemView); 
  } 
} 
 
class ProgressViewHolder extends RecyclerView.ViewHolder {  
  @BindView(R.id.progressBar) ProgressBar progressBar; 
  @BindView(R.id.textView) TextView textView;  
  public ProgressViewHolder(View itemView) { 
    super(itemView); 
    ButterKnife.bind(this, itemView); 
  } 
}

上面就是item对应的几个ViewHolder，判断viewHolder属于那种对象，然后在onBindViewHolder中根据对应的ViewHolder对其控件设置数据并显示

@Override 
public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) { 
  holder.itemView.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View v) { 
      clickListener.onItemClick(v, position); 
    } 
  }); 
  if(holder instanceof NewsViewHolder){ 
    NewsViewHolder viewHolder = (NewsViewHolder)holder; 
    viewHolder.title.setText(list.get(position).getTitle()); 
    viewHolder.time.setText(list.get(position).getTime()); 
    /** 
     * Glide加载图片 
     */ 
    Glide.with(context).load(list.get(position).getImageUrl().get(0)) 
        .override(dpToPx(72), dpToPx(72)).centerCrop().into(viewHolder.image); 
    if(list.get(position).getType().equals(News.TEXT_NEWS)){ 
      viewHolder.digest.setText(list.get(position).getDigest()); 
    } else { 
      viewHolder.digest.setText(""); 
    } 
  } else if(holder instanceof ImageViewHolder){ 
    ImageViewHolder viewHolder = (ImageViewHolder)holder; 
    viewHolder.title.setText(list.get(position).getTitle()); 
    viewHolder.time.setText(list.get(position).getTime()); 
    setItemImage(viewHolder, list, position); 
  } else if(holder instanceof ProgressViewHolder){ 
    ProgressViewHolder viewHolder = (ProgressViewHolder)holder; 
    viewHolder.progressBar.setIndeterminate(true); 
 
  } 
}

整个过程基本就是这样，这种方式在项目中经常会用到，我们就可以这样去处理，下拉加载更多就可以这样实现，在加载完数据后再往对象集合中传入null，然后判断如果出现null就加载progressBar布局，再加上Google官方的SwipeRefreshLayout，下拉刷新，上拉加载就搞定了，其实很容易，而且也有点Material Design 的感觉~~~~~~ 看下Adapter的全部代码

package com.zmt.e_read.Adapter;  
import android.content.Context; 
import android.support.v7.widget.RecyclerView; 
import android.util.DisplayMetrics; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ImageView; 
import android.widget.TextView;  
import com.bumptech.glide.Glide; 
import com.zmt.e_read.Module.News; 
import com.zmt.e_read.Module.OnItemClickListener; 
import com.zmt.e_read.R; 
import com.zmt.e_read.Utils.ProgressViewHolder; 
import java.util.Collection; 
import java.util.Collections; 
import java.util.List; 
import butterknife.BindView; 
import butterknife.ButterKnife;  
/** 
 * Created by Dangelo on 2016/9/27. 
 */ 
public class NewsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> { 
  private final int EMPTY_VIEW = 1; 
  private final int PROGRESS_VIEW = 2; 
  private final int IMAGE_VIEW = 3; 
  private Context context; 
  private List<News> list; 
  private OnItemClickListener clickListener; 
 
  public NewsAdapter(Context context, List<News> list, OnItemClickListener clickListener) { 
    this.context = context; 
    this.list = list; 
    this.clickListener = clickListener; 
  } 
 
  public void addOnItemClickListener(OnItemClickListener clickListener){ 
    this.clickListener = clickListener; 
  } 
 
  @Override 
  public int getItemViewType(int position) { 
    if(list.size() == 0){ 
      return EMPTY_VIEW; 
    } else if(list.get(position) == null){ 
      return PROGRESS_VIEW; 
    } else if(list.get(position).getType().equals(News.IMAGE_NEWS)){ 
      return IMAGE_VIEW; 
    } else { 
      return super.getItemViewType(position); 
    } 
  } 
 
  @Override 
  public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { 
    View view; 
    if(viewType == PROGRESS_VIEW){ 
      view = LayoutInflater.from(parent.getContext()).inflate(R.layout.progressbar_item, parent, false); 
      return new ProgressViewHolder(view); 
    } else if(viewType == EMPTY_VIEW){ 
      return null; 
    } else if(viewType == IMAGE_VIEW){ 
      view = LayoutInflater.from(parent.getContext()).inflate(R.layout.image_news_item, parent, false); 
      return new ImageViewHolder(view); 
    } else { 
      view = LayoutInflater.from(parent.getContext()).inflate(R.layout.news_item, parent, false); 
      return new NewsViewHolder(view); 
    } 
  } 
 
  @Override 
  public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) { 
    holder.itemView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
        clickListener.onItemClick(v, position); 
      } 
    }); 
    if(holder instanceof NewsViewHolder){ 
      NewsViewHolder viewHolder = (NewsViewHolder)holder; 
      viewHolder.title.setText(list.get(position).getTitle()); 
      viewHolder.time.setText(list.get(position).getTime()); 
      /** 
       * Glide加载图片 
       */ 
      Glide.with(context).load(list.get(position).getImageUrl().get(0)) 
          .override(dpToPx(72), dpToPx(72)).centerCrop().into(viewHolder.image); 
      if(list.get(position).getType().equals(News.TEXT_NEWS)){ 
        viewHolder.digest.setText(list.get(position).getDigest()); 
      } else { 
        viewHolder.digest.setText(""); 
      } 
    } else if(holder instanceof ImageViewHolder){ 
      ImageViewHolder viewHolder = (ImageViewHolder)holder; 
      viewHolder.title.setText(list.get(position).getTitle()); 
      viewHolder.time.setText(list.get(position).getTime()); 
      setItemImage(viewHolder, list, position); 
    } else if(holder instanceof ProgressViewHolder){ 
      ProgressViewHolder viewHolder = (ProgressViewHolder)holder; 
      viewHolder.progressBar.setIndeterminate(true); 
 
    } 
  } 
 
  public void setItemImage(ImageViewHolder viewHolder, List<News> list, int position){ 
    viewHolder.imageMiddle.setVisibility(View.VISIBLE); 
    viewHolder.imageRight.setVisibility(View.VISIBLE); 
    DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics(); 
    if(list.get(position).getImageUrl().size() == 1){ 
      Glide.with(context).load(list.get(position).getImageUrl().get(0)) 
          .override(displayMetrics.widthPixels - dpToPx(10), dpToPx(90)) 
          .centerCrop().into(viewHolder.imageLeft); 
      viewHolder.imageMiddle.setVisibility(View.GONE); 
      viewHolder.imageRight.setVisibility(View.GONE); 
    } else if(list.get(position).getImageUrl().size() == 2){ 
      int imageWidth = (displayMetrics.widthPixels - dpToPx(20)) / 2; 
      Glide.with(context).load(list.get(position).getImageUrl().get(0)) 
          .override(imageWidth, dpToPx(90)) 
          .centerCrop().into(viewHolder.imageLeft); 
      Glide.with(context).load(list.get(position).getImageUrl().get(1)) 
          .override(imageWidth, dpToPx(90)) 
          .centerCrop().into(viewHolder.imageMiddle); 
      viewHolder.imageRight.setVisibility(View.GONE); 
    } else if(list.get(position).getImageUrl().size() >= 3){ 
      int imageWidth = (displayMetrics.widthPixels - dpToPx(30)) / 3; 
      Glide.with(context).load(list.get(position).getImageUrl().get(0)) 
          .override(imageWidth, dpToPx(90)) 
          .centerCrop().into(viewHolder.imageLeft); 
      Glide.with(context).load(list.get(position).getImageUrl().get(1)) 
          .override(imageWidth, dpToPx(90)) 
          .centerCrop().into(viewHolder.imageMiddle); 
      Glide.with(context).load(list.get(position).getImageUrl().get(2)) 
          .override(imageWidth, dpToPx(90)) 
          .centerCrop().into(viewHolder.imageRight); 
    } 
  } 
 
  @Override 
  public int getItemCount() { 
    return list.size(); 
  } 
 
  public int dpToPx(float dp){ 
    float px = context.getResources().getDisplayMetrics().density; 
    return (int)(dp * px + 0.5f); 
  } 
 
  class NewsViewHolder extends RecyclerView.ViewHolder{ 
    @BindView(R.id.news_title)TextView title; 
    @BindView(R.id.news_digest)TextView digest; 
    @BindView(R.id.news_time)TextView time; 
    @BindView(R.id.news_src)ImageView image;  
    public NewsViewHolder(View itemView) { 
      super(itemView); 
      ButterKnife.bind(this, itemView); 
    } 
  } 
 
  class ImageViewHolder extends RecyclerView.ViewHolder{ 
     @BindView(R.id.news_title) TextView title; 
    @BindView(R.id.image_left) ImageView imageLeft; 
    @BindView(R.id.image_right) ImageView imageRight; 
    @BindView(R.id.image_middle) ImageView imageMiddle; 
    @BindView(R.id.news_time) TextView time;  
    public ImageViewHolder(View itemView) { 
      super(itemView); 
      ButterKnife.bind(this, itemView); 
    } 
  } 
     
  class ProgressViewHolder extends RecyclerView.ViewHolder { 
    @BindView(R.id.progressBar) ProgressBar progressBar; 
    @BindView(R.id.textView) TextView textView;  
    public ProgressViewHolder(View itemView) { 
      super(itemView); 
      ButterKnife.bind(this, itemView); 
    } 
  } 
}

项目地址：[url=https://github.com/xiyouZmt/E-Read]https://github.com/xiyouZmt/E-Read[/url] [b]最后说一下为什么为什么用RecyclerView取代ListView。[/b] 用过ListView的都知道，在ListView中若要复用视图缓存，就要在getView()方法中手动判断convertView是否为空，若不为空则复用视图缓存，若为空则重新加载视图，而RecyclerView相当于对ListView的Adapter进行了再次封装，把ListView手动判断是否有缓存的代码封装到RecyclerView内部，使这部分逻辑不可见，我们只需要通过getItemCount()方法告诉RecyclerView有多少项数据，然后在onCreateViewHolder()中加载item布局实例化ViewHolder，然后在onBindViewHolder()中完成数据的绑定即可。以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持编程素材网。

全部评论(0)

上一篇：android自定义开关控件-SlideSwitch的实例
下一篇：最简单的SD卡文件遍历Android程序

资讯排行榜
更多>>