Android连载3-定制ListView的界面、性能优化以及绑定点击事件

2021-12-10 09:54:22

一、订制ListView的界面

1.先建立一个Fruit水果类

package com.example.listviewtest;

?

?

public class Fruit {

  private String name;

 

  private int imageId;

 

  public Fruit(String name,int imageId) {

    this.name=name;

    this.imageId = imageId;

  }

  public String getName() {

    return name;

  }

  public int getImageId() {

    return imageId;

   

  }

}

2.然后建立一个展示水果的LayOut文件

<?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" >

   

<ImageView

    android:id="@+id/fruit_image"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content" />

?

<TextView

    android:id="@+id/fruit_name"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:layout_gravity="center"

    android:layout_marginLeft="10dip" />

   

</LinearLayout>

然后新建一个FruitAdapter适配器，来继承ArrayAdapter

package com.example.listviewtest;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

import android.widget.TextView;

import android.content.Context;

import java.util.List;

?

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

?

?

public class FruitAdapter extends ArrayAdapter<Fruit> {

  

  private int resourceId;

 

  public FruitAdapter(Context context,int textViewResourceId,List<Fruit> objects) {

    super(context,textViewResourceId,objects);

    resourceId = textViewResourceId;

  }

 

  @Override

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

    Fruit fruit = getItem(position);//获取当前项的Fruit实例

    View view = LayoutInflater.from(getContext()).inflate(resourceId,null);

    ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);

    TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);

    fruitImage.setImageResource(fruit.getImageId());

    fruitName.setText(fruit.getName());

    return view;

   

  }

}

最后我们完善我们的主程序

package com.example.listviewtest;

?

import java.util.List;

?

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.ArrayAdapter;

import android.widget.ListView;

import java.util.*;

//import java.lang.ArrayAdapter;

?

public class MainActivity extends Activity {

 

  private List<Fruit> fruitList = new ArrayList<Fruit>();

 

//  private String[] data = {"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry"};

 

  @Override

  protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

   

    initFruits();//初始化水果数据

    FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);

   

//    ArrayAdapter<String> adapter = new ArrayAdapter<String>(

//        MainActivity.this,android.R.layout.simple_list_item_1,data);

    ListView listView = (ListView) findViewById(R.id.list_view);

    listView.setAdapter(adapter);

   

  }

  private void initFruits() {

    Fruit apple = new Fruit("Apple",R.drawable.apple_pic);

    fruitList.add(apple);

    Fruit banana = new Fruit("Banana",R.drawable.banana_pic);

    fruitList.add(banana);

    Fruit orange =new Fruit("Orange",R.drawable.orange_pic);

    fruitList.add(orange);

       

  }

}

这样运行我们的代码，得到如下的结果

二、提升ListView的运行效率

1.我们通过下面的注释内容可以看出，这一段代码的重构，可以将画面的流畅程度提升，以及缓存一个View?Holder对象就可以大幅度提升运行速度。

package com.example.listviewtest;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

import android.widget.TextView;

import android.content.Context;

import java.util.List;

?

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

?

?

public class FruitAdapter extends ArrayAdapter<Fruit> {

 

 

 

  private int resourceId;

 

  public FruitAdapter(Context context,int textViewResourceId,List<Fruit> objects) {

    super(context,textViewResourceId,objects);

    resourceId = textViewResourceId;

  }

 

  @Override

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

    Fruit fruit = getItem(position);//获取当前项的Fruit实例

//    View view = LayoutInflater.from(getContext()).inflate(resourceId,null);

    //上面我们注释掉一个View实例，我们下一行先初始化一个View实例

    View view;

    ViewHolder viewHolder;

    if(convertView == null) {//如果这个View不存在的话，我们就直接建一个View

      view = LayoutInflater.from(getContext()).inflate(resourceId,null);

      viewHolder = new ViewHolder();

      viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);

      viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);

      view.setTag(viewHolder);//将ViewHolder存储在View中

     

    }else {

      view = convertView;//如果View已经存在了，那么我们就复用已经存在了的View,这样就可以避免再次重新生成View,节省了运行时间

      viewHolder = (ViewHolder) view.getTag();//调用getTag方法，把ViewHolder重新取出。

    }

    //这里我们建立了一个内部类，用来存储已经生成了的fruitImage和fruieName的实例，就省的每次都需要通过findViewById的方法，来去内存中查找目标实例

    viewHolder.fruitImage.setImageResource(fruit.getImageId());

    viewHolder.fruitName.setText(fruit.getName());

?

//    ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);

//    TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);

//    fruitImage.setImageResource(fruit.getImageId());

//    fruitName.setText(fruit.getName());

    return view;

   

  }

  class ViewHolder{

    ImageView fruitImage;

   

    TextView fruitName;

  }

}

三、ListView的点击事件

如果只列出了几条内容，我们不能通过点击?List来来获取我们想要知道的信息，那将是毫无意义的。

接下来就在MainActivity?中来注册我们的点击事件。

package com.example.listviewtest;

?

import java.util.List;

?

import android.app.Activity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ArrayAdapter;

import android.widget.ListView;

import android.widget.Toast;

?

import java.util.*;

//import java.lang.ArrayAdapter;

?

public class MainActivity extends Activity {

 

  private List<Fruit> fruitList = new ArrayList<Fruit>();

 

//  private String[] data = {"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry"};

 

  @Override

  protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

   

    initFruits();//初始化水果数据

    FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);

   

//    ArrayAdapter<String> adapter = new ArrayAdapter<String>(

//        MainActivity.this,android.R.layout.simple_list_item_1,data);

    ListView listView = (ListView) findViewById(R.id.list_view);

    listView.setAdapter(adapter);

   

    //接下来就来注册点击事件

    listView.setOnItemClickListener(new OnItemClickListener() {

      @Override

      public void onItemClick(AdapterView<?> parent,View view,int position,long id) {

        Fruit fruit = fruitList.get(position);

        Toast.makeText(MainActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();

      }

    });

   

  }

  private void initFruits() {

    Fruit apple = new Fruit("Apple",R.drawable.apple_pic);

    fruitList.add(apple);

    Fruit banana = new Fruit("Banana",R.drawable.banana_pic);

    fruitList.add(banana);

    Fruit orange =new Fruit("Orange",R.drawable.orange_pic);

    fruitList.add(orange);

       

  }

}

四、源码：

1.项目地址

https://github.com/ruigege66/Android/tree/master/ListViewTest

2.CSDN：https://blog.csdn.net/weixin_44630050

3.博客园：https://www.cnblogs.com/ruigege0000/

4.欢迎关注微信公众号：傅里叶变换，个人公众号，仅用于学习交流，后台回复”礼包“，获取大数据学习资料

Android连载3-定制ListView的界面、性能优化以及绑定点击事件

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