Android核心技术-day03-03-ListView

<?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">

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

package com.gaozewen.listviewdemo;

import android.graphics.Color;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private ListView mLv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mLv = (ListView) findViewById(R.id.lv);
        mLv.setAdapter(new MyAdapter());
    }

    private class MyAdapter extends BaseAdapter {
        // 获取列表中一共有多少条记录
        @Override
        public int getCount() {
            return 1000000;
        }

        // 获取一条 item
        @Override
        public Object getItem(int position) {
            return null;
        }

        // 获取一条 item  id
        @Override
        public long getItemId(int position) {
            return 0;
        }

        // 返回一个 view 对象，这个 view 对象显示在指定位置
        @Override
        public View getView(int position, View convertView, ViewGroup viewGroup) {
            TextView tv;
            if (convertView == null){
                tv = new TextView(MainActivity.this);
                System.out.println("使用创建的view：" + position); // 一开始创建了 0-16 个
            }else {
                tv = (TextView) convertView;
                System.out.println("使用回收的view：" + position);
            }
            tv.setText("我是文本" + position);
            tv.setTextColor(Color.BLUE);
            tv.setTextSize(20);
            return tv;
        }
    }
}