Android乐学成语之自定义Adapter

一、首先对Adapter概念深刻的了解

  首先看看他的继承图

 

• BaseAdapter：抽象类，实际开发中我们会继承这个类并且重写相关方法，用得最多的一个Adapter！
• ArrayAdapter：支持泛型操作，最简单的一个Adapter，只能展现一行文字~
• SimpleAdapter：同样具有良好扩展性的一个Adapter，可以自定义多种效果！
• SimpleCursorAdapter：用于显示简单文本类型的listView，一般在数据库那里会用到，不过有点过时， 不推荐使用！

      在这里拿ListView控件给大家讲解！

二、实例部分

    下面让我们实现一个这样的页面

    

主页布局：

<?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:background="@drawable/bg_ling"
    android:orientation="vertical" >
    <ListView
        android:id="@+id/lvAnimalList"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layoutAnimation="@anim/anim_layout_listview"
        android:listSelector="#00000000"
        >    
    </ListView>

</LinearLayout>

子布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" 
    android:padding="10dp"
    >
    <TextView
        android:id="@+id/tvName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:gravity="center"
        android:text="@string/animal_name"
        android:textAppearance="?android:attr/textAppearanceLarge"
        >    
    </TextView>
    <ImageButton 
        android:id="@+id/btnSave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@null"
        android:layout_alignParentRight="true"
        android:layout_alignTop="@+id/tvName"
        android:src="@drawable/btnsave"
        />

</RelativeLayout>

 代码的实现：

package com.bzu.qilu.adapter;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.bzu.qilu.R;
import com.bzu.qilu.entity.Fable;


/**
 * 寓言类适配器
 * @author 刘齐鲁
 * date 2016-5-31
 */
public class FableAdapter extends ArrayAdapter<Fable> {
       private int resourceld;
       private Context context;
       public FableAdapter(Context context,int resource,List<Fable>objects){
           super(context,resource,objects);
           this.context =context;
           resourceld = resource;
       }
       public View getView(int position,View convertView,ViewGroup parent){
           final  Fable fable=  getItem(position);//获取当前项的Animal实例
             View view ;
             ViewHolder viewHolder;
        
           if(convertView == null){
               view = LayoutInflater.from(getContext()).inflate(resourceld, null);
               viewHolder = new ViewHolder();
              
               viewHolder.tvName=(TextView)view.findViewById(R.id.tvName);
              
               viewHolder.btnSave=(ImageButton)view.findViewById(R.id.btnSave);
               ViewHolder.btnSave.setFocusable(false);
               ViewHolder.btnSave.setFocusableInTouchMode(false);
               viewHolder.btnSave.setOnClickListener(new OnClickListener() {
                
                @Override
                public void onClick(View arg0) {
                    
                    Toast.makeText(context, "你要收藏"+fable.getName()+"吗", Toast.LENGTH_SHORT).show();
                    
                }
                
            });
               
               view.setTag(viewHolder);//将ViewHolder存储在View中
              
           }else{
               view = convertView;
               viewHolder =(ViewHolder) view.getTag();//重新获取ViewHolder
           }
          
           viewHolder.tvName.setText(fable.getName());
           return view;
       }
       static class ViewHolder{
           static ImageView btnSave;
           TextView tvName;
         
           }
}

我们新增了一个内部类ViewHolder,用于对控件的实例进行缓存。当convertView为空的时候，创建一个ViewHolder对象，并将控件的实例都存放在ViewHolder里，然后调用View的setTag()方法，将ViewHolder对象存储在View中。当convertView不为空的时候则调用View的getTag()方法，把ViewHolder重新取出。这样所有的控件的实例都缓存在了ViewHolder里，就没有必要每次都通过findViewById()方法来获取控件实例了。

Activity代码：

package com.bzu.qilu.activity;

import java.util.ArrayList;
import java.util.List;

import com.bzu.qilu.R;
import com.bzu.qilu.adapter.CategoryAdapter;
import com.bzu.qilu.entity.Category;

import android.app.Activity;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;


/**
 * 成语类别显示界面
 * @author 刘齐鲁
 * date 2016-5-16
 */
public class StudyActivity extends Activity {
   private List<Category>categoryList;
   private String [] category_names;
   private int [] category_images;
   protected void onCreate(Bundle savedInstanceState){
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_study);
       initCategories();//初始化类别
       CategoryAdapter adapter =new CategoryAdapter(this, R.layout.category_item, categoryList);
       ListView listView =(ListView) findViewById(R.id.lvCategories);
       listView.setAdapter(adapter);
       listView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int position,
                long id) {
            // TODO Auto-generated method stub
            switch (position) {
            case 0:
            {
            Intent intent = new Intent(StudyActivity.this,StudyAnimalActivity.class);
           startActivity(intent);
           break;
            }
            case 1:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudyNatureActivity.class);
               startActivity(intent1);
               break;
            }
            case 2:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudyPersonActivity.class);
               startActivity(intent1);
               break;
            }
            case 3:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudySeasonActivity.class);
               startActivity(intent1);
               break;
            }
            case 4:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudyNumberActivity.class);
               startActivity(intent1);
               break;
            }
            case 5:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudyFableActivity.class);
               startActivity(intent1);
               break;
            }
            case 6:
            {    
                Intent intent1 = new Intent(StudyActivity.this,StudyOtherActivity.class);
               startActivity(intent1);
               break;
            }
            default:
                break;
            }
        }
    });
   }
   private void initCategories(){
       categoryList = new ArrayList<Category>();
       Resources resources =getResources();
       category_names=resources.getStringArray(R.array.category);
       category_images= new int []{R.drawable.category_animal,R.drawable.category_nature,
               R.drawable.category_human,R.drawable.category_season,R.drawable.category_number,R.drawable.category_fable,R.drawable.category_other};
         for(int i=0;i<category_names.length;i++){
             categoryList.add(new Category(category_names[i],category_images[i]));
       }
   }
 
}

以上就是那个页面的全部代码。