ListView的优化

用convertView优化ListView

package com.example.zhangmeng.myliestview;

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 {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ListView lv=(ListView)findViewById(R.id.lv);
        MyAdapter adapter=new MyAdapter();
        lv.setAdapter(adapter);
    }

    class MyAdapter extends BaseAdapter{

        @Override
        public int getCount() {
            return 100;
        }

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

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            TextView tv=null;
            if(convertView==null){
                tv=new TextView(MainActivity.this);
            }
            else{
                tv=(TextView) convertView;
            }

            tv.setText("Hello"+(position+1));
            return tv;
        }
    }
}