ListView优化与问题解决-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_37127054/article/details/72972986

优化的实现步骤：

1. 判断convertView对象是否为null，如果为null，那么通过LayoutInflater对象进行初始化并且将convertView对象作为返回值返回值

此步骤实现了减少被返回的View对象的初始化次数

2. 创建一个类（通常此类名为ViewHolder），在该类中定义n条属性，

定义的属性取决于item的布局文件中有多少控件

3.在getView方法中声明一个ViewHolder对象，在convertView为null的时候，进行初始化，并初始化holder中所有的控件属性，

4. 初始化完成之后通过convertView的setTag方法将holder对象整体的存储起来

第2,3,4步骤的目的是减少item中控件的初始化次数

5.当convertView不为null时，通过getTag方法取出之前存储的ViewHolder对象

6. 通过holder调用属性设置控件的显示内容即可

优化的代码：

package com.example.administrator.myapplication;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
 
public class ItemTag {
    public ImageView imageView;
    public TextView textView;
    public Button button;
}

package com.example.administrator.myapplication;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private  String[] titles={"狗狗","大象","猫咪","烧鸡","黑牛"};
    private int[] images={R.drawable.dog,R.drawable.elephant,R.drawable.cat,R.drawable.chicken,R.drawable.cow};
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.lv_main_list);
        listView.setAdapter(new Mydapter());
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Toast.makeText(MainActivity.this,"跳转到"+titles[position%titles.length]+"页面",Toast.LENGTH_SHORT).show();
            }
        });

    }
    class Mydapter extends BaseAdapter{
        @Override
        public int getCount() {
            return 1000;
        }
        @Override
        public Object getItem(int position) {
            return titles[position%titles.length];
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            if(convertView==null){
                convertView=getLayoutInflater().inflate(R.layout.item_listview,null);
                ItemTag itemTag=new ItemTag();
                itemTag.imageView= (ImageView) convertView.findViewById(R.id.iv_images_images);
                itemTag.textView= (TextView) convertView.findViewById(R.id.tv_textview_text);
                itemTag.button= (Button) convertView.findViewById(R.id.bt_button_button);
                convertView.setTag(itemTag);
            }
            ItemTag itemTag= (ItemTag) convertView.getTag();
            itemTag.imageView.setImageResource(images[position% titles.length]);
            itemTag.textView.setText(titles[position%titles.length]+position);
            itemTag.button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(MainActivity.this,"正在下载"+titles[position%titles.length],Toast.LENGTH_SHORT).show();
                }
            });

            return convertView;
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >
    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/lv_main_list"
        ></ListView>

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:descendantFocusability="blocksDescendants"
    >
    <ImageView
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:id="@+id/iv_images_images"
        android:src="@drawable/bird"
        />
    <TextView
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:id="@+id/tv_textview_text"
        android:text="XX"
        android:textSize="30sp"
        />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="下载"
         android:id="@+id/bt_button_button"
        />

</LinearLayout>