Android入门之ListView

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这篇文章我想来记录一下自己学习android开发中关于ListView布局的介绍以及使用，方便自己以后的翻阅和学习。

1. ListView简介

ListView 算得上是Android中最常用的控件之一了，几乎所有的应用程序都能够见到它的身影。其实简单来说，就是我们Android手机中见到的滚动列表(也有可能通过RecyclerView实现，下一篇文章可能进行介绍)，向查看QQ聊天等翻看列表都是在使用这个控件。

2. ListView使用过程

1)在Activity的布局xml中加入ListView；

2)准备数据

3)构建适配器

4)将适配器添加到ListView中

3. Adapter

在Android开发中的Adapter，可以简单地分为ArrayAdapter，BaseAdapter，CursorAdapter，HeaderViewListAdapter，ResourceCursorAdapter，SimpleAdapter，SimpleCursorAdapter，SimpleCursorAdapter，WrapperListAdapter，下面的内容分别以ArrayAdapter、SimpleAdapter和自定义ArrayAdapter进行呈现

4. 添加ListView布局

xxActivity的布局文件activity_xx.xml如下

<?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="wrap_content" /></LinearLayout>

对，很简单，这里我把ListView的ID设置为list_view，将宽度和高度都设置为match_parent，让ListView占满整个布局空间

5. StringListViewActivity

5.1 代码

这是一个简单的ListView的Activity，在这个Activity里面需要准备ListView展示的数据，可以是来自数据库等任何地方，这里的数据我就直接简单构造，然后适配器是ArrayAdapter，并指定它的泛型为String，在其构造器中依次传入当前上下文、ListView子项布局的id，以及要适配的数据。

import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.ArrayAdapter;import android.widget.ListView;public class StringListViewActivity extends AppCompatActivity {    private String[] data = {"Apple", "Balana", "Orange", "Watermelon", "pear"            , "Grape", "Pineapple", "Strawberry", "Cherry", "Mango", "Pineapple", "Strawbery"            , "Cherry", "Mango"};    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_stringlistview);        //构造适配器，android.R.layout.simple_list_item_1是Android内置的布局文件，其实就是一个TextView        ArrayAdapter<String> adapter = new ArrayAdapter<String>(StringListView.this, android.R.layout.simple_list_item_1, data);        ListView listView = (ListView) findViewById(R.id.list_view);        //装载适配器        listView.setAdapter(adapter);    }}

5.2 效果

6. SimpleListViewActivity

6.1 代码

这是一个带标题的ListView列表，使用simpleAdapter需要注意的需要使用Map<String, Object> item来保存列表中每一项的显示的title与text，构建Adapter时将map中的数据传入，列表就会被适配器自动构建。

import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.widget.ArrayAdapter;import android.widget.ListView;import android.widget.SimpleAdapter;import java.util.*;public class SimpleListViewActivity extends AppCompatActivity {    private String[] data = {"Apple", "Balana", "Orange", "Watermelon", "pear"            , "Grape", "Pineapple", "Strawberry", "Cherry", "Mango", "Pineapple", "Strawbery"            , "Cherry", "Mango"};    private String[] creation = {"created in China", "create in America", "create in England", "create in Russia"};    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_stringlistview);        //构造数据        ArrayList<Map<String,Object>> mData= new ArrayList<Map<String,Object>>();;            for(int i =0; i < data.length; i++) {                Map<String,Object> item = new HashMap<String,Object>();                item.put("fruit", data[i]);                item.put("creation", creation[i%4]);                mData.add(item);            }        //构造适配器，android.R.layout.simple_list_item_2是Android内置的布局文件，可以是多个TextView        SimpleAdapter adapter = new SimpleAdapter(this,mData,android.R.layout.simple_list_item_2,                new String[]{"fruit","creation"},new int[]{android.R.id.text1,android.R.id.text2});        ListView listView = (ListView) findViewById(R.id.list_view);        //装载适配器        listView.setAdapter(adapter);    }}

6.2 效果

7. 自定义ListView界面

7.1 代码

构建ListView的适配类

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 int getImageId(){        return imageId;    }}

为ListView的子项指定一个自定义的布局fruit_item.xml ，前两个例子都是用android中内置的布局

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

自定义适配器FruitAdapter，继承自ArrayAdapter，将其泛型设置为Fruit

import android.content.Context;import android.support.annotation.NonNull;import android.support.annotation.Nullable;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;/** * Created by apple on 2017/5/1. */public class FruitAdapter extends ArrayAdapter<Fruit>{    private int resourceId;    public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects){      super(context,textViewResourceId, objects);        resourceId = textViewResourceId;    }    //在每个子项被滚动到屏幕内被调用    @NonNull    @Override    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {//        Fruit fruit = getItem(position);//        View view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);//        ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);//        TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);//        fruitImage.setImageResource(fruit.getImageId());//        fruitName.setText(fruit.getName());//        return view;//        提高效率        Fruit fruit = getItem(position);        View view;        ViewHolder viewHolder;        if( convertView == null ){           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);        }else {            view = convertView;            viewHolder = (ViewHolder) view.getTag();        }        viewHolder.fruitImage.setImageResource(fruit.getImageId());        viewHolder.fruitName.setText(fruit.getName());        return view;    }    class ViewHolder {        ImageView fruitImage;        TextView fruitName;    }}

MainActivity中的代码，同时为每个ListView子项添加了点击事件

import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.AdapterView;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<Fruit>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // 初始化水果数据        initFruits();        //构建适配器        FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);        ListView listView = (ListView) findViewById(R.id.list_view);        //装载适配器        listView.setAdapter(adapter);        //注册点击按钮        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();            }        });    }    private void initFruits() {        for (int i = 0; i < 2; 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);        }    }}

7.2 效果

8. 参考书籍

《第一行代码——Android》郭霖

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