BaseAdapter的使用与优化

 //逗比式............................................
        //加载布局文件
        //将xml文件转化为view，获取到view
//由于我们只需要将XML转化为View，并不涉及到具体的布局，所以第二个参数通常设置为null
//        View view = inflater.inflate(R.layout.item_buju,null);
//        // 实例化控件
//        ImageView imageView = (ImageView) view.findViewById(R.id.img);
//        TextView   text_title = (TextView) view.findViewById(R.id.title1);
//        TextView  text_context = (TextView) view.findViewById(R.id.context1);
//        //给view中对应的每一个控件赋值
//        imageView.setImageResource(data.get(position).itemImageID);
//        text_title.setText(data.get(position).itemTitle_ID);
//        text_context.setText(data.get(position).itemContext_ID);
//        return view;
        //逗比式...........................................

//普通式..........................................
        //注册view中对应的每一个控件
//        if(convertView == null){
//             convertView = inflater.inflate(R.layout.item_buju,null);
//        }
//        ImageView imageView = (ImageView) convertView.findViewById(R.id.img);
//        TextView   text_title = (TextView) convertView.findViewById(R.id.title1);
//        TextView  text_context = (TextView) convertView.findViewById(R.id.context1);
//        //给view中对应的每一个控件赋值
//        imageView.setImageResource(data.get(position).itemImageID);
//        text_title.setText(data.get(position).itemTitle_ID);
//        text_context.setText(data.get(position).itemContext_ID);
//        return convertView;
        //普通式..........................................

 //文艺式..........................................
        //避免重复创建 如果存在缓存池中就不用创建
        ViewHolder viewHolder;
        if(convertView == null){
            viewHolder = new ViewHolder();
            convertView = inflater.inflate(R.layout.item_buju,null);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.img);
            viewHolder.title     = (TextView) convertView.findViewById(R.id.title1);
            viewHolder.context   = (TextView) convertView.findViewById(R.id.context1);
            convertView.setTag(viewHolder);
        }
        else{
            viewHolder = (ViewHolder) convertView.getTag();
        }

        //给view中对应的每一个控件赋值
        viewHolder.imageView.setImageResource(data.get(position).itemImageID);
        viewHolder.title.setText(data.get(position).itemTitle_ID);
        viewHolder.context.setText(data.get(position).itemContext_ID);
        return convertView;
        //文艺式..........................................

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private List<MyItem> data;
    private Myadapter myadapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化
        init();
    }
    private void init() {
        listView = (ListView) findViewById(R.id.listview);
        //实例化 数据源
        data = new ArrayList<>();
        //加载到data List<MyItem>
        for(int i = 0;i  < 200 ; i++){
            data.add(new MyItem(android.R.drawable.sym_def_app_icon,"我是标题！"+i,"我是内容" + i));
        }
        //实例化适配器 Myadapter
        myadapter =new Myadapter(data,MainActivity.this);
        //加载适配器
        listView.setAdapter(myadapter);
    }
}

public class Myadapter extends BaseAdapter{
    private List<MyItem> data;
    private LayoutInflater  inflater;

    public Myadapter(List<MyItem> data, Context context) {
        this.data = data;

        //获取上下文
        this.inflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return data.size();
    }

    @Override
    public Object getItem(int position) {
        return data.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //逗比式............................................
        //加载布局文件
        //将xml文件转化为view，获取到view
//        View view = inflater.inflate(R.layout.item_buju,null);
//        //注册view中对应的每一个控件
//        ImageView imageView = (ImageView) view.findViewById(R.id.img);
//        TextView   text_title = (TextView) view.findViewById(R.id.title1);
//        TextView  text_context = (TextView) view.findViewById(R.id.context1);
//        //给view中对应的每一个控件赋值
//        imageView.setImageResource(data.get(position).itemImageID);
//        text_title.setText(data.get(position).itemTitle_ID);
//        text_context.setText(data.get(position).itemContext_ID);
//        return view;
        //逗比式...........................................

        //普通式..........................................
        //注册view中对应的每一个控件
//        if(convertView == null){
//             convertView = inflater.inflate(R.layout.item_buju,null);
//        }
//        ImageView imageView = (ImageView) convertView.findViewById(R.id.img);
//        TextView   text_title = (TextView) convertView.findViewById(R.id.title1);
//        TextView  text_context = (TextView) convertView.findViewById(R.id.context1);
//        //给view中对应的每一个控件赋值
//        imageView.setImageResource(data.get(position).itemImageID);
//        text_title.setText(data.get(position).itemTitle_ID);
//        text_context.setText(data.get(position).itemContext_ID);
//        return convertView;
        //普通式..........................................

        //文艺式..........................................
        //避免重复创建 如果存在缓存池中就不用创建
        ViewHolder viewHolder;
        if(convertView == null){
            viewHolder = new ViewHolder();
            convertView = inflater.inflate(R.layout.item_buju,null);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.img);
            viewHolder.title     = (TextView) convertView.findViewById(R.id.title1);
            viewHolder.context   = (TextView) convertView.findViewById(R.id.context1);
            convertView.setTag(viewHolder);
        }
        else{
            viewHolder = (ViewHolder) convertView.getTag();
        }

        //给view中对应的每一个控件赋值
        viewHolder.imageView.setImageResource(data.get(position).itemImageID);
        viewHolder.title.setText(data.get(position).itemTitle_ID);
        viewHolder.context.setText(data.get(position).itemContext_ID);
        return convertView;
        //文艺式..........................................

    }
    //View的容器 用class来封装
    class ViewHolder{
        public ImageView imageView;
        public TextView title;
        public TextView context;
    }

}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/img"
        android:background="@android:drawable/sym_def_app_icon"
        android:layout_width="60dp"
        android:layout_height="60dp" />

    <TextView
        android:id="@+id/title1"
        android:text="Title"
        android:textSize="25sp"
        android:gravity="center"
        android:layout_toEndOf="@+id/img"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/context1"
        android:text="Context"
        android:textSize="20sp"
        android:gravity="center_vertical"
        android:layout_toEndOf="@+id/img"
        android:layout_below="@+id/title1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</RelativeLayout>

package com.example.administrator.ten_88;

/**
 * Created by Administrator on 2015/10/8 0008.
 */
public class MyItem {
    public int itemImageID;
    public String itemTitle_ID;
    public String itemContext_ID;

    public MyItem(int itemImageID, String itemTitle_ID, String itemContext_ID) {
        this.itemImageID = itemImageID;
        this.itemTitle_ID = itemTitle_ID;
        this.itemContext_ID = itemContext_ID;
    }
}