【Android】13.0 UI开发（四）——列表控件RecyclerView的横向布局排列实现

1.0 新建项目，由于ListView的局限性，RecyclerView是一种很好取代ListView的控件，可以灵活实现多种布局。

2.0 新建项目RecyclerviewTest，目录如下：

3.0 这里需要在app/build.gradle中配置，导入依赖包：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.android.support:recyclerview-v7:28.0.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

红色标签这行加入，后面的版本号和support:appcompat一致即可。

4.0 将之前项目中的构造类复制过来，省去重复编写代码的时间。

Province.java

package com.example.recyclerviewtest;

public class Province {
    private String name;
    public Province(String name){
        this.name = name;
    }

    public String getName() {
        return name;
    }
}

ProvinceAdapter.java，这里代码进行了修改，并在代码中做以说明：

package com.example.recyclerviewtest;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

public class ProvinceAdapter extends RecyclerView.Adapter<ProvinceAdapter.ViewHolder> {
    private List<Province> mProvinceList;
    private int resourceId;

//    定义一个内部类ViewHolder,该类继承自RecyclerView.ViewHolder。
//    需要传入一个View参数，通常是RecyclerView子项最外层布局
    static class ViewHolder extends RecyclerView.ViewHolder {
        //        ImageView provinceImage;
        TextView provinceName;

        public ViewHolder(View view) {
            super(view);
            provinceName = (TextView) view.findViewById(R.id.province_name);
        }
    }

//    该构造函数作用是将数据源赋值给一个全局变量mProvinceList
    public ProvinceAdapter(List<Province> provinceList) {
        mProvinceList = provinceList;
    }

//  由于ProvinceAdapter是继承自RecyclerView.Adapter，
//  所以需要重写三个方法：
// onCreateViewHolder() ：创建ViewHolder实例，将局部加载进来
//  onBindViewHolder() ：对RecyclerView子项数据进行赋值
//  getItemCount()

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.province_item,
                viewGroup,
                false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position
    ) {
        Province province = mProvinceList.get(position);
        holder.provinceName.setText(province.getName());
    }

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

5.0 在activity_main.xml布局文件中，写入RecyclerView布局，因为RecyclerView不是SDK内置布局，所以需要把全称写进去

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

6.0 province_item.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="100dp"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/province_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="18dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:gravity="center_horizontal"
        android:layout_marginTop="10dp"/>
</android.support.constraint.ConstraintLayout>

7.0 MainActivity.java

package com.example.recyclerviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private List<Province> provincelist = new ArrayList<>();
    private String[] data = {
            "广西壮族自治区", "内蒙古自治区", "宁夏回族自治区", "西藏藏族自治区", "新疆维吾尔自治区", "香港特别行政区", "澳门特别行政区",
            "北京市", "天津市", "上海市", "重庆市", "吉林省", "辽宁省", "黑龙江省",
            "河北省", "河南省", "安徽省", "甘肃省", "山东省",
            "湖南省", "湖北省", "江苏省", "浙江省", "江西省",
            "云南省", "广西省", "贵州省", "海南省", "台湾省",};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initProvince();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);

//        调用下面这行代码可以实现布局横向排列
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

//        GridLayoutManager 实现网格布局
//        StaggeredGridLayoutManager 实现瀑布流布局

//        和ListView不同的地方在于，ListView的布局排列是由自身去管理
//        而RecyclerView则将这个工作交给LayoutManager，它制定了一套可扩展的布局排列接口
//        子类只要按照接口的规范来实现，就能定制出不同排列方式的布局了
        recyclerView.setLayoutManager(layoutManager);
        ProvinceAdapter adapter = new ProvinceAdapter(provincelist);
        recyclerView.setAdapter(adapter);
    }

    public void initProvince() {
        for (String dataone : data) {
            Province province = new Province(dataone);
            provincelist.add(province);
        }
    }
}

8.0 运行效果如下：