Android基础06

ListView:展示大量数据，可以将屏幕外的数据划入屏幕内，主要任：将数据填充到布局，处理用户的选择点击等操作。

1. 添加ListView控件
2. 添加适配器
3. 将适配器添加到ListView

添加控件

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

添加适配器(第一个参数获得上下文，第二个参数添加一个简单的子项布局到适配器中，展示的数据）

ArrayAdapter<String> fruit = new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,data);

将适配器添加到ListView

listView = (ListView) findViewById(R.id.list_view);
listView.setAdapter(fruit);

以这种方式构造一种定制的ListView界面
set、get方法

package com.example.bbw.listviewdemo;

/**
 * Created by bbw on 2017/7/20.
 */

public class Fruit {
    private int imageId;

    public int getImageId() {
        return imageId;
    }

    public void setImageId(int imageId) {
        this.imageId = imageId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    private String name;

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

子项布局：

<?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">

    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:textSize="10sp" />

    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

自定义适配器：

package com.example.bbw.listviewdemo;

import android.content.Context;
import android.support.annotation.LayoutRes;
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 bbw on 2017/7/20.
 * 新的适配器
 */

public class FruitAdapter extends ArrayAdapter<Fruit>{

    private ImageView fruit_image;
    private TextView fruit_name;
    private int resourceId;
    public FruitAdapter(@NonNull Context context, @LayoutRes int resource, @NonNull List<Fruit> objects) {
        super(context, resource, objects);
        resourceId = resource;
    }

    @NonNull
    @Override
    //重写getView，返回的view作为listView的子项布局
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {

        View view;
        if (convertView == null){
            view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);//为子项加载传入的布局
        }else{
            view = convertView;
        }

        Fruit fruit = getItem(position);//获得当前位置的fruit对象
        fruit_image = view.findViewById(R.id.fruit_image);
        fruit_name = view.findViewById(R.id.fruit_name);
        fruit_image.setImageResource(fruit.getImageId());
        fruit_name.setText(fruit.getName());
        return view;
    }
}

初始化数据

private void initFruit() {

        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);
        }

添加适配器

 FruitAdapter fruit = new FruitAdapter(MainActivity.this,R.layout.fruit,fruitList);
        listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(fruit);