ListView的用法

-主界面布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

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

</LinearLayout>

-adapter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="40dp"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv_main_content"
        android:text="content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

-adapter,java写法:

class MyAdapter extends BaseAdapter {

    @Override
    public int getCount() {
        return 40;
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;
        if (convertView == null) {
            convertView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_adapter, parent, false);
            viewHolder = new ViewHolder(convertView);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        viewHolder.tv_main_content.setText("content"+position);
        return convertView;
    }

    class ViewHolder {
        final View itemView;
        final TextView tv_main_content;

        ViewHolder(View itemView) {
            this.itemView = itemView;
            tv_main_content = itemView.findViewById(R.id.tv_main_content);
        }
    }
}

-主界面写法:

class MainActivity : AppCompatActivity() {

    val listView by lazy { findViewById<ListView>(R.id.lv_main) }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        listView.adapter=MyAdapter()
    }
}

-adapter,kotlin写法:

class MyAdapter : BaseAdapter() {
    override fun getCount(): Int {
        return 40
    }

    override fun getItem(position: Int): Any {
        return position
    }

    override fun getItemId(position: Int): Long {
        return position.toLong()
    }

    override fun getView(
        position: Int,
        convertView: View,
        parent: ViewGroup
    ): View {
        var convertView = convertView
        var viewHolder: ViewHolder? = null
        if (convertView == null) {
            convertView = LayoutInflater.from(parent.context)
                .inflate(R.layout.item_adapter, parent, false)
            viewHolder = ViewHolder(convertView)
            convertView.tag = viewHolder
        } else {
            viewHolder = convertView.tag as ViewHolder
        }
        viewHolder.tv_main_content.text = "content$position"
        return convertView
    }

    internal inner class ViewHolder(val itemView: View) {
        val tv_main_content: TextView

        init {
            tv_main_content = itemView.findViewById(R.id.tv_main_content)
        }
    }
}