android笔记 listview

public class MainActivity extends AppCompatActivity {    private List<Fruit> fruitList = new ArrayList<Fruit>();    //先定义一个list    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main); //设定在哪个view呈现        initFruits(); // 初始化水果数据       FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList);        //自定义适配器搭配listview使用 第一个参数:传给谁 第二个参数:谁传的 第三个参数要传啥        ListView listView = (ListView) findViewById(R.id.listview);        listView.setAdapter(adapter); // setAdapter专门用于传进去        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);    }}}

//先写一支class用来初始化 上面有用到

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;    }}

//自定义适配器

public class FruitAdapter extends ArrayAdapter<Fruit> {    private int resourceId;    public FruitAdapter(Context context, int textViewResourceId,                        List<Fruit> objects) {        super(context, textViewResourceId, objects);        resourceId = textViewResourceId;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        Fruit fruit = getItem(position); // Fruit位置        View view;        ViewHolder viewHolder;        if (convertView == null) {            view = LayoutInflater.from(getContext()).inflate(resourceId, parent, false);            viewHolder = new ViewHolder();//优化性能用的            viewHolder.fruitImage = (ImageView) view.findViewById (R.id.fruit_image);            viewHolder.fruitName = (TextView) view.findViewById (R.id.fruit_name);            view.setTag(viewHolder); //存View        } else {            view = convertView;            viewHolder = (ViewHolder) view.getTag(); //取ViewHolder        }        viewHolder.fruitImage.setImageResource(fruit.getImageId());        viewHolder.fruitName.setText(fruit.getName());        return view;    }    class ViewHolder {        ImageView fruitImage;        TextView fruitName;    }}

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