[Android新手学习笔记23]-如何使用ListView展示列表数据

基本配置：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    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>

设置Adapter：

public class MainActivity extends AppCompatActivity {
    private String[] data = {
            "草莓",
            "梨",
            "芒果",
            "苹果",
            "西瓜",
            "香蕉",
            "樱桃",
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                MainActivity.this, android.R.layout.simple_list_item_1, data
        );
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
    }
}

自定义ListView：

1.数据类

定义一个Fruit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 this.name;
    }
    public int getImageId() {
        return this.imageId;
    }
}

2.自定义ListView布局

新建布局文件：fruit_item.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="60dp"
        android:layout_height="60dp" />
    <TextView
        android:id="@+id/fruit_name"
        android:textSize="30sp"
        android:gravity="center_vertical"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_marginLeft="10dp"
        android:layout_height="60dp" />
</LinearLayout>

3.Adapter

新建FruitAdapter类继承ArrayAdapter<Fruit>：

public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;
    public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }
    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit = getItem(position); // 获取当前项的Fruit实例
        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;
    }
}

4.使用

初始化数据，创建FruitAdapter，设置adapter：

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();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
    }
    private void initFruits() {
        Fruit strawberry = new Fruit("草莓", R.drawable.strawberry);
        fruitList.add(strawberry);
        Fruit pear = new Fruit("梨", R.drawable.pear);
        fruitList.add(pear);
        Fruit mango = new Fruit("芒果", R.drawable.mango);
        fruitList.add(mango);
        Fruit apple = new Fruit("苹果", R.drawable.apple);
        fruitList.add(apple);
        Fruit watermelon = new Fruit("西瓜", R.drawable.watermelon);
        fruitList.add(watermelon);
        Fruit banana = new Fruit("香蕉", R.drawable.banana);
        fruitList.add(banana);
        Fruit cherry = new Fruit("樱桃", R.drawable.cherry);
        fruitList.add(cherry);
    }
}

性能优化：

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit = getItem(position); // 获取当前项的Fruit实例
        View view;
        if (convertView == null) {
            view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);
        } else {
            view = convertView;
        }
        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;
    }

convertView参数，用于将之前加载好的布局进行缓存，这样不会再重复去加载布局。

新增一个内部类ViewHolder，用于对控件的实例进行缓存。就不用每次都通过findViewById()方法来获取实例了。

最终实现代码如下：

public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;
    public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }
    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit = getItem(position); // 获取当前项的Fruit实例
        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); // 将viewHolder存储在View中
        } else {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag(); // 重新获取viewHolder
        }
        viewHolder.fruitImage.setImageResource(fruit.getImageId());
        viewHolder.fruitName.setText(fruit.getName());
        return view;
    }
    class ViewHolder {
        ImageView fruitImage;
        TextView fruitName;
    }
}

增加ListView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();
     }
});