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Android连载3-定制ListView的界面、性能优化以及绑定点击事件

2020年04月08日  | 移动技术网IT编程  | 我要评论

安徽旅游,面包大王吻戏,mxo魔法学院

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

 

 

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