简易listview与adapter使用

item.xml

<?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"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:gravity="center"
        android:text="万能适配器测试"
        android:textSize="18sp" />
</LinearLayout>

listview加载数据

private void commonAdapterTest() {
    ListView listView = (ListView) findViewById(R.id.listview);
    List<String> datas = new ArrayList<>();
    for (int i = 0; i < 18; i++) {
        datas.add("万能适配器测试" + i);
    }

    listView.setAdapter(new CommonAdapter<String>(this, datas, R.layout.item) {

        @Override
        protected void convertView(View item, String s) {
            TextView textView = CommonViewHolder.get(item, R.id.textView);
            textView.setText(s);
        }
    });
}

两个工具类优化listview

public abstract class CommonAdapter<T> extends BaseAdapter {
    private Context context;
    private List<T> datas;
    private int layoutId;

    public CommonAdapter(Context context, List<T> datas, int layoutId) {
        this.context = context;
        this.datas = datas;
        this.layoutId = layoutId;
    }

    @Override
    public int getCount() {
        return datas == null ? 0 : datas.size();
    }

    @Override
    public T getItem(int position) {
        return datas.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            Log.d("listview", "---------LayoutInflater()-----------" + position);
            convertView = LayoutInflater.from(context).inflate(layoutId, null);
        }else{
        }
//        Log.d("listview", "---------getView()-----------" + position);
        T t = getItem(position);
        convertView(convertView, t);
        return convertView;
    }

    /**
     * 局部更新数据，调用一次getView()方法；Google推荐的做法
     *
     * @param listView 要更新的listview
     * @param position 要更新的位置
     */
    public void notifyDataSetChanged(ListView listView, int position) {
        /**第一个可见的位置**/
        int firstVisiblePosition = listView.getFirstVisiblePosition();
        /**最后一个可见的位置**/
        int lastVisiblePosition = listView.getLastVisiblePosition();

        /**在看见范围内才更新，不可见的滑动后自动会调用getView方法更新**/
        if (position >= firstVisiblePosition && position <= lastVisiblePosition) {
            /**获取指定位置view对象**/
            View view = listView.getChildAt(position - firstVisiblePosition);
            getView(position, view, listView);
        }

    }

    /**
     * 需要去实现的对item中的view的设置操作
     *
     * @param item
     * @param t
     */
    protected abstract void convertView(View item, T t);

}

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public class CommonViewHolder {
    /**
     * @param view 所有缓存View的根View
     * @param id   缓存View的唯一标识
     * @return
     */
    public static <T extends View> T get(View view, int id) {

        SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
        //如果根view没有用来缓存View的集合
        if (viewHolder == null) {
            viewHolder = new SparseArray<View>();
            view.setTag(viewHolder);//创建集合和根View关联
        }
        View chidlView = viewHolder.get(id);//获取根View储存在集合中的孩纸
        if (chidlView == null) {//如果没有改孩纸
            //找到该孩纸
            chidlView = view.findViewById(id);
            viewHolder.put(id, chidlView);//保存到集合
        }
        return (T) chidlView;
    }
}