RecyclerView是一种更强大的滚动控件,相比ListView,他不需要使用一些技巧提高运行效率,还能实现横向滚动等优点。
-
依赖库
因为Google 2018 IO 大会推出了 Android新的扩展库 AndroidX,用于替换原来的 Android扩展库,将原来的android.*
替换成androidx.*
;只有包名和Maven工件名受到影响,原来的类名,方法名和字段名不会更改,详情看我的上一篇博客Android到Androidx的变迁
在Android 9及之前需要添加以下内容
implementation 'com.android.support:recyclerview-v7:24.2.1'
在Android 10 需要添加
implementation 'androidx.recyclerview:recyclerview:1.1.0'
- 基本用法
新建一个Fruit类
package com.syc.androidlearning.listViewDemo;
public class Fruit {
private String name;
private int imageId;
public Fruit(String name, int imageId) {
this.name = name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getImageId() {
return imageId;
}
public void setImageId(int imageId) {
this.imageId = imageId;
}
}
修改activity_mian.xml布局文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
layout中新建fruit_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/fruit_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<TextView
android:id="@+id/fruit_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical" />
</LinearLayout>
接下来需要为RecyclerView准备一个适配器,新建FruitAdapter类,继承自RecyclerView.Adapter,并将泛型指定为FruitAdapter.ViewHolder。其中,viewholder为fruitadapter中定义的一个内部类。
package com.syc.androidlearning.recyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.syc.androidlearning.R;
import com.syc.androidlearning.listViewDemo.Fruit;
import java.util.List;
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
private List<Fruit> mFruitList;
static class ViewHolder extends RecyclerView.ViewHolder{
ImageView fruitImage;
TextView fruitName;
public ViewHolder(@NonNull View itemView) {
super(itemView);
fruitImage = itemView.findViewById(R.id.fruit_image);
fruitName = itemView.findViewById(R.id.fruit_name);
}
}
public FruitAdapter(List<Fruit> mFruitList) {
this.mFruitList = mFruitList;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item,parent,false);
ViewHolder holder = new ViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Fruit fruit = mFruitList.get(position);
holder.fruitName.setText(fruit.getName());
holder.fruitImage.setImageResource(fruit.getImageId());
}
@Override
public int getItemCount() {
return mFruitList.size();
}
}
最后,修改MainActivity中的代码
package com.syc.androidlearning;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import com.syc.androidlearning.listViewDemo.Fruit;
import com.syc.androidlearning.recyclerView.FruitAdapter;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private List<Fruit> fruitList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruits();
RecyclerView recyclerView = findViewById(R.id.recycler_view);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
FruitAdapter fruitAdapter = new FruitAdapter(fruitList);
recyclerView.setAdapter(fruitAdapter);
}
private void initFruits() {
for (int i = 1; i < 10; ++i) {
Fruit apple = new Fruit("apple", R.drawable.ic_launcher_background);
fruitList.add(apple);
}
}
}