Android RecyclerView實現多種item布局的方法

2019-10-22 18:21:14

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在項目中列表是基本都會用到的，然而在顯示列表時，我們需要的數據可能需要不止一種item顯示，對于復雜的數據就需要多種item，以不同的樣式顯示出來，這樣效果是很棒的，我們先看一下效果

RecyclerView,item布局,RecyclerView實現item布局

我們可以看到，這個RecyclerView中有多種item顯示出來，那么具體怎么實現呢，其實在RecyclerView中，我們可以重寫方法getItemViewType()，這個方法會傳進一個參數position表示當前是第幾個Item，然后我們可以通過position拿到當前的Item對象，然后判斷這個item對象需要那種視圖，返回一個int類型的視圖標志，然后在onCreatViewHolder方法中給引入布局，這樣就能夠實現多種item顯示了，講了這么多我們看一下具體的例子

@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);   } }

首先我們重寫了getItemViewType這個方法，在這個方法中根據position對item對象做了一些判斷，如果存儲item對象的集合大小為空，返回空view標識（這里為1），如果item對象為null，返回進度條標識，這個主要是用于實現下拉加載更多，如果item對象類型屬于圖片類型，就返回圖片類型對應的Item，這個就是效果圖中的第一個Item類型，否則就是其它類型，也就是效果圖中的另一種item布局，然后我們在onCreatViewHolder中具體的為每一種類型引入其布局

@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);   } }

上面的代碼就是具體為每種viewType引入其對應的布局，這樣就基本實現了多種item布局，但是僅僅是這些還不夠，因為我們還要對每種item設置數據，所以還要對每種item寫一個VIewHolder來為item顯示數據

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對應的幾個ViewHolder，判斷viewHolder屬于那種對象，然后在onBindViewHolder中根據對應的ViewHolder對其控件設置數據并顯示

@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加載圖片      */     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);    } }

整個過程基本就是這樣，這種方式在項目中經常會用到，我們就可以這樣去處理，下拉加載更多就可以這樣實現，在加載完數據后再往對象集合中傳入null，然后判斷如果出現null就加載progressBar布局，再加上Google官方的SwipeRefreshLayout，下拉刷新，上拉加載就搞定了，其實很容易，而且也有點Material Design 的感覺~~~~~~

看下Adapter的全部代碼

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加載圖片        */       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);     }   } }

項目地址：https://github.com/xiyouZmt/E-Read

最后說一下為什么為什么用RecyclerView取代ListView。

用過ListView的都知道，在ListView中若要復用視圖緩存，就要在getView()方法中手動判斷convertView是否為空，若不為空則復用視圖緩存，若為空則重新加載視圖，而RecyclerView相當于對ListView的Adapter進行了再次封裝，把ListView手動判斷是否有緩存的代碼封裝到RecyclerView內部，使這部分邏輯不可見，我們只需要通過getItemCount()方法告訴RecyclerView有多少項數據，然后在onCreateViewHolder()中加載item布局實例化ViewHolder，然后在onBindViewHolder()中完成數據的綁定即可。

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VEVB武林網。

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