Android Studio初学者实例：RecyclerView学习--模仿今日头条

本案例来自于学校的一个简单的课程实验

先看效果图，可以显然的看到，一些item是不同的布局，而其他布局就是简单的布局嵌套

看一下xml代码：

 XML代码中部分重复样式写入到了style文件中

看一下加入style.xm的代码，这个文件是存放在value文件夹下，存放样式、主题等。

看一下Activity的Java代码

使用数组存放标题、内容、时间、图片等数据（因为现在还只是死数据）

setDate（单词拼错了！） 该函数，就是将数据填充到NewsList（一个泛型List）中

然后就是new一个自己声明的一个自定义适配器，使用Listview的setAdapter方法设置其适配器

public class MainActivity40 extends AppCompatActivity {
private  String[] titles={"各地餐企齐行动，杜绝餐饮浪费","花菜有人焯水，有人直接炒，都错了，看饭店大厨如何做","睡觉时，双脚突然蹬一下，有踩空感，像从高楼坠落，是咋回事？","实拍外卖小哥砸开小吃店的卷帘门救火，灭火后淡定决定继续送外卖",
        "还没成熟就被迫提前采摘，8毛一斤却没人要，果农无奈，不摘不行","大会、大展、大赛一起来，北京电竞“好嗨哟”"};
private String[] names={"央视新闻客户端","味美食记","民富康健康","生活小记","禾木报告","燕鸣"};
private String[] comments={"1234评","14214评","534评","134评","1353评","876评"};
private String[]times={"刚刚","6小时前","8小时前","2小时前","刚刚","4小时前"};
private  int[] icons1={R.drawable.food,R.drawable.takeout,R.drawable.e_sports};
private int[] icons2={R.drawable.sleep1,R.drawable.sleep2,R.drawable.sleep3,R.drawable.fruit1,R.drawable.fruit2,R.drawable.fruit3};
private int[] types={1,1,2,1,2,1};
private RecyclerView mRecyclerView;
private myAdapter myAdapter;
private List NewsList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main40);
        setDate();
        mRecyclerView=findViewById(R.id.rv_list);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        myAdapter=new myAdapter(MainActivity40.this,NewsList);
        mRecyclerView.setAdapter(myAdapter);
    }

    private void setDate(){
            NewsList=new ArrayList();
            NewsBean bean;
        for (int i = 0; i < titles.length; i++) {
            bean=new NewsBean();
            bean.setId(i+1);
            bean.setTitle(titles[i]);
            bean.setName(names[i]);
            bean.setComment(comments[i]);
            bean.setTime(times[i]);
            bean.setType(types[i]);
            switch (i){
                case 0:
                    List imgList0=new ArrayList<>();
                    bean.setImgList(imgList0);
                    break;
                case 1:
                    List imgList1=new ArrayList<>();
                    imgList1.add(icons1[i-1]);
                    bean.setImgList(imgList1);
                    break;
                case 2:
                    List imgList2=new ArrayList<>();
                    imgList2.add(icons2[i-2]);
                    imgList2.add(icons2[i-1]);
                    imgList2.add(icons2[i]);
                    bean.setImgList(imgList2);
                    break;
                case 3:
                    List imgList3=new ArrayList<>();
                    imgList3.add(icons1[i-2]);
                    bean.setImgList(imgList3);
                    break;
                case 4:
                    List imgList4=new ArrayList<>();
                    imgList4.add(icons2[i-1]);
                    imgList4.add(icons2[i]);
                    imgList4.add(icons2[i+1]);
                    bean.setImgList(imgList4);
                    break;
                case 5:
                    List imgList5=new ArrayList<>();
                    imgList5.add(icons1[i-3]);
                    bean.setImgList(imgList5);

                    break;
            }
            NewsList.add(bean);

        }
    }

}

其中涉及到了适配器，话不多说，上适配器代码，适配器是连接数据与Listview的一个“桥梁”

RecyclerView与ListView的适配器其实共同特征有很多。

在自定义的适配器中，首先是一个构造方法，来获取当前上下文以及数据列表

class myAdapter extends RecyclerView.Adapter{
    private Context mContext;
    private List NewsList;
    public myAdapter(Context context, List list){
        this.mContext=context;
        this.NewsList=list;
    }

    @NonNull
    @NotNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull @NotNull ViewGroup parent, int viewType) {
        View itemView=null;
        RecyclerView.ViewHolder holder=null;
        if(viewType==1){
            itemView= LayoutInflater.from(mContext).inflate(R.layout.list_item_one,parent,false);
            holder=new ViewHolder1(itemView);
        }else  if(viewType==2){
            itemView= LayoutInflater.from(mContext).inflate(R.layout.list_item_two,parent,false);
            holder=new ViewHolder2(itemView);
        }
        return holder;
    }

    @Override
    public int getItemViewType(int position) {
        return  NewsList.get(position).getType();
    }

    @Override
    public void onBindViewHolder(@NonNull @NotNull RecyclerView.ViewHolder holder, int position) {
        NewsBean bean=NewsList.get(position);
        if(holder instanceof ViewHolder1){
            if(position==0){
                ((ViewHolder1)holder).iv_top.setVisibility(View.VISIBLE);
                ((ViewHolder1)holder).iv_img.setVisibility(View.GONE);
            }else {
                ((ViewHolder1)holder).iv_top.setVisibility(View.GONE);
                ((ViewHolder1)holder).iv_img.setVisibility(View.VISIBLE);
            }
            ((ViewHolder1)holder).title.setText(bean.getTitle());
            ((ViewHolder1)holder).name.setText(bean.getName());
            ((ViewHolder1)holder).comment.setText(bean.getComment());
            ((ViewHolder1)holder).time.setText(bean.getTime());
            if (bean.getImgList().size()==0)return;
            ((ViewHolder1)holder).iv_img.setImageResource(bean.getImgList().get(0));
        }else  if(holder instanceof ViewHolder2){
            ((ViewHolder2) holder).title.setText(bean.getTitle());
            ((ViewHolder2) holder).name.setText(bean.getName());
            ((ViewHolder2) holder).comment.setText(bean.getComment());
            ((ViewHolder2) holder).time.setText(bean.getTime());
            ((ViewHolder2) holder).iv_img1.setImageResource(bean.getImgList().get(0));
            ((ViewHolder2) holder).iv_img2.setImageResource(bean.getImgList().get(1));
            ((ViewHolder2) holder).iv_img3.setImageResource(bean.getImgList().get(2));

        }
    }

    @Override
    public int getItemCount() {
        return NewsList.size();
    }

    class  ViewHolder1 extends RecyclerView.ViewHolder {
        ImageView iv_top,iv_img;
        TextView title,name,comment,time;
        public ViewHolder1(@NonNull @NotNull View itemView) {
            super(itemView);
            iv_top=itemView.findViewById(R.id.iv_top);
            iv_img=itemView.findViewById(R.id.iv_img);
            title=itemView.findViewById(R.id.tv_title);
            name=itemView.findViewById(R.id.tv_name);
            comment=itemView.findViewById(R.id.tv_comment);
            time=itemView.findViewById(R.id.tv_time);


        }
    }
    class  ViewHolder2 extends RecyclerView.ViewHolder {
        ImageView iv_img1,iv_img2,iv_img3;
        TextView title,name,comment,time;
        public ViewHolder2(@NonNull @NotNull View itemView) {
            super(itemView);
            iv_img1=itemView.findViewById(R.id.iv_img1);
            iv_img2=itemView.findViewById(R.id.iv_img2);
            iv_img3=itemView.findViewById(R.id.iv_img3);

            title=itemView.findViewById(R.id.tv_title);
            name=itemView.findViewById(R.id.tv_name);
            comment=itemView.findViewById(R.id.tv_comment);
            time=itemView.findViewById(R.id.tv_time);


        }
    }

}

代码解说将会在后续补充

5-3   现在补充一下 list_item_one.xml与list_item_two.xml，这两个布局文件是Listview中两个item

补充一下NewBean  其实就是个实体类啦  其中get、set方法以及构造方法可以快速生成

import java.util.List;

public class NewsBean {
    private  int id;
    private String title;
    private List imgList;
    private String name;
    private String comment;
    private String time;
    private int type;

    public NewsBean() {
    }

    public NewsBean(int id, String title, List imgList, String name, String comment, String time, int type) {
        this.id = id;
        this.title = title;
        this.imgList = imgList;
        this.name = name;
        this.comment = comment;
        this.time = time;
        this.type = type;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List getImgList() {
        return imgList;
    }

    public void setImgList(List imgList) {
        this.imgList = imgList;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getComment() {
        return comment;
    }

    public void setComment(String comment) {
        this.comment = comment;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public int getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }
}

6-26补充一下使用的顶部布局

在res/layout下创建title_bar.xml