Android listview 性能和 addview android recyclerview和listview

转载

charlesc 2024-02-23 08:33:45

文章标签 android ide List 文章分类 Android 移动开发

ListView

ListView是Android界面开发中最常用的控件之一，几乎所有的程序都会用到它。但是ListView的性能比较差，而且扩展性也不是特别好，所以Android提供了一个更加强大的滚动控件——RecylerView。未来越来越多的程序会从ListView到RecyerView,所以，这里我仅仅介绍ListView最基本的用法

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">
  <ListView
      android:id="@+id/list_view"
      android:layout_width="match_parent"
      android:layout_height="match_parent"/>

</LinearLayout>

主程序

package com.example.listtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;


public class MainActivity extends AppCompatActivity {
    private String[] data={
      "Apple","Banana","Orange","Watermelon","Pear"
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //隐藏标题
        if(getSupportActionBar()!=null){
            getSupportActionBar().hide();
        }
        //核心：使用适配器
        ArrayAdapter<String> adapter=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
        ListView listView=findViewById(R.id.list_view);
        listView.setAdapter(adapter);
    }
}

效果

核心：
由于数组中的数据无法直接传递给ListView，所以我们想要借助适配器，Android中有很多适配器实现类，其中最好的是ArrayAdapter。通过泛型来指定数据的数据类型。
这里是一种ArrayAdapter的构造函数的重载，传入的三个数据依次为当前上下文，ListView子项布局的id，以及要适配的数据
其中，ListView的子项布局id使用了一个Android内置的布局文件，里面有一个TextView，可用于简单地显示一段文本。

扩展–定制ListView界面

Frult类

package com.example.listtest;

public class Fruit {
    private String name;
    private int imageId;
    public Fruit(String name,int imageId){
        this.name=name;
        this.imageId=imageId;
    }

    public int getImageId() {
        return imageId;
    }

    public String getName() {
        return name;
    }
}

定制的界面

<?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"
    android:orientation="horizontal">
    <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"
        android:layout_marginLeft="10dp"/>
</LinearLayout>

适配器

package com.example.listtest;

import android.content.Context;
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 FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;
    //构造方法
    public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects){
        super(context,textViewResourceId,objects);
        resourceId=textViewResourceId;//将自定义样式存起来，作为全局变量
    }

//getView()方法在每个子项被滚动到屏幕内的时候会被调用
    @Override
    public View getView(int position, View convertView, ViewGroup parent){
        Fruit fruit=getItem(position);//获取当前的Fruit类
        View view;
        ViewHolder viewHolder;
        if(convertView==null){//如果为空，将之前加载好的布局进行缓存
            view=LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
            viewHolder=new ViewHolder();
            viewHolder.fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
            viewHolder.fruitName=(TextView)view.findViewById(R.id.fruit_name);
            view.setTag(viewHolder);//存起来
        }else{
            view=convertView;
            viewHolder=(ViewHolder)view.getTag();//拿出来
        }
        //false表示只让我们在父布局中声明的layout属性生效，但不会为这个View添加父布局



        viewHolder.fruitImage.setImageResource(fruit.getImageId());
        viewHolder.fruitName.setText(fruit.getName());
        return view;
    }
    public class ViewHolder{//ViewHolder类用于对获得的fruitImage和fruitName进行缓存
        ImageView fruitImage;
        TextView fruitName;
    }
}

主程序

package com.example.listtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

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);
        //隐藏标题
        if(getSupportActionBar()!=null){
            getSupportActionBar().hide();
        }

        initFruits();
        ListView listView=(ListView)findViewById(R.id.list_view);
        //初始化适配器，声明当前上下文，定制的样式和数据
        FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        //将适配器的值传给listView
        listView.setAdapter(adapter);
        //为listview里面的Item添加点击事件
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Fruit fruit=fruitList.get(position);
                Toast.makeText(MainActivity.this,fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
    }
    //构造数据方法
    public void initFruits(){
        for(int i=0;i<5;i++){
            Fruit apple=new Fruit("Apple",R.drawable.apple_pic);
            fruitList.add(apple);
            Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
            fruitList.add(banana);
            Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
            fruitList.add(orange);
            Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
            fruitList.add(watermelon);
            Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
            fruitList.add(pear);
            Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
            fruitList.add(grape);
            Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
            fruitList.add(strawberry);
            Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
            fruitList.add(cherry);
            Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
            fruitList.add(mango);
        }
    }
}

效果

RecyclerView

利用RecyclerView实现与上面ListView相同的界面
其中，Fruit.java，fruit_item与上面完全相同
FruitAdapter.java

package com.example.recyclerviewtest;

import android.support.v7.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

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;
        //ViewHolder的构造函数
        public ViewHolder(View view){
            super(view);
            fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
            fruitName=(TextView)view.findViewById(R.id.fruit_name);
        }
    }



    public FruitAdapter(List<Fruit> fruitList){//适配器的构造函数
        mFruitList=fruitList;
    }

    @Override
    public ViewHolder onCreateViewHolder(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(ViewHolder holder,int position){
        Fruit fruit=mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
    @Override
    public int getItemCount(){
        return mFruitList.size();
    }
}

MainAcitvity.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 android.widget.LinearLayout;

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);
        if(getSupportActionBar()!=null){
            getSupportActionBar().hide();
        }

        initFruits();
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycler_view);
        //layoutManager用于指定RecyclerView的布局方式，这里指定了线性布局(LinearLayoutManager),实现和ListView类似的效果
        LinearLayoutManager layoutManager=new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter=new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }
    public void initFruits(){
        for(int i=0;i<5;i++){
            Fruit apple=new Fruit("Apple",R.drawable.apple_pic);
            fruitList.add(apple);
            Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
            fruitList.add(banana);
            Fruit orange = new Fruit("Orange", R.drawable.orange_pic);
            fruitList.add(orange);
            Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
            fruitList.add(watermelon);
            Fruit pear = new Fruit("Pear", R.drawable.pear_pic);
            fruitList.add(pear);
            Fruit grape = new Fruit("Grape", R.drawable.grape_pic);
            fruitList.add(grape);
            Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
            fruitList.add(strawberry);
            Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
            fruitList.add(cherry);
            Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
            fruitList.add(mango);
        }
    }
}

本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。