适配器的经典写法

有关ListView优化机制及滑动时数据错乱问题的讨论


class GridViewAdapter extends BaseAdapter{

        LayoutInflater inflater;
        List<PackageInfo> pkInfos;
        public GridViewAdapter(Context context,List<PackageInfo> packageInfos) {
            inflater = LayoutInflater.from(context);
            this.pkInfos = packageInfos;
        }
        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return pkInfos.size();
        }

        @Override
        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return pkInfos.get(position);
        }

        @Override
        public long getItemId(int position) {
            // TODO Auto-generated method stub
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub
        
                View view = inflater.inflate(R.layout.gv_item, null);
                TextView tv = (TextView)view.findViewById(R.id.gv_item_appname);
                ImageView iv = (ImageView)view.findViewById(R.id.gv_item_icon);
                tv.setText(pkInfos.get(position).applicationInfo.loadLabel(getPackageManager()));
                iv.setImageDrawable(pkInfos.get(position).applicationInfo.loadIcon(getPackageManager()));
                
            return view;
        }
        
    }

 1 class ListViewAdapter extends BaseAdapter{
 2 
 3         LayoutInflater inflater;
 4         List<PackageInfo> pkInfos;
 5         public ListViewAdapter(Context context,List<PackageInfo> packageInfos) {
 6             inflater = LayoutInflater.from(context);
 7             this.pkInfos = packageInfos;
 8         }
 9         @Override
10         public int getCount() {
11             // TODO Auto-generated method stub
12             return pkInfos.size();
13         }
14 
15         @Override
16         public Object getItem(int position) {
17             // TODO Auto-generated method stub
18             return pkInfos.get(position);
19         }
20 
21         @Override
22         public long getItemId(int position) {
23             // TODO Auto-generated method stub
24             return position;
25         }
26 
27         @Override
28         public View getView(int position, View convertView, ViewGroup parent) {
29             // TODO Auto-generated method stub
30         
31                 View view = inflater.inflate(R.layout.lv_item, null);
32                 TextView ntv = (TextView)view.findViewById(R.id.lv_item_appname);
33                 TextView ptv = (TextView)view.findViewById(R.id.lv_item_packagename);
34                 ImageView iv = (ImageView)view.findViewById(R.id.lv_icon);
35                 ntv.setText(pkInfos.get(position).packageName);
36                 ptv.setText(pkInfos.get(position).applicationInfo.loadLabel(getPackageManager()));
37                 iv.setImageDrawable(pkInfos.get(position).applicationInfo.loadIcon(getPackageManager()));
38                 
39             return view;
40         }
41         
42     }

尽量自己构建适配器，这样加载速度快，效率高。哪怕简单的也尽量不要使用SimpleAdapter

view holder的用法：

<?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="horizontal" >

    <TextView
        android:id="@+id/userinfo1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:layout_weight="4" />

    <TextView
        android:id="@+id/userinfo2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2" />

    <TextView
        android:id="@+id/userinfo3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="4" />

    <TextView
        android:id="@+id/userinfo4"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="3" />

    <TextView
        android:id="@+id/userinfo5"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginRight="10dp"
        android:layout_weight="3" />

</LinearLayout>
View Code
package com.example.health;

import java.util.List;

import com.example.health.util.LogUtil;
import com.example.health.util.User;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class UserListActivity extends Activity{
    
    private ListView userList;
    private MyApplication app;
    private static final String TAG = "UserListActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.userlist);
        app = (MyApplication) getApplication();
        LogUtil.i(TAG ,app.userList.get(0).toString());
        userList = (ListView) findViewById(R.id.data_list);
        userList.setAdapter(new UserListAdapter(this, app.userList));
    }
    
    class UserListAdapter extends BaseAdapter {
        private LayoutInflater mInflater;
        private Context mContext;
        private List<User> mDatas;

        public UserListAdapter(Context context, List<User> mDatas)
        {
            mInflater = LayoutInflater.from(context);
            this.mContext = context;
            this.mDatas = mDatas;
        }

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

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

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

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder = null;  
            if (convertView == null)  
            {  
                convertView = mInflater.inflate(R.layout.userlistitem, parent, false);  
                viewHolder = new ViewHolder();  
                viewHolder.mTextView1 = (TextView) convertView.findViewById(R.id.userinfo1);
                viewHolder.mTextView2 = (TextView) convertView.findViewById(R.id.userinfo2);
                viewHolder.mTextView3 = (TextView) convertView.findViewById(R.id.userinfo3);
                viewHolder.mTextView4 = (TextView) convertView.findViewById(R.id.userinfo4);
                viewHolder.mTextView5 = (TextView) convertView.findViewById(R.id.userinfo5);
                convertView.setTag(viewHolder);  
            } else  
            {  
                viewHolder = (ViewHolder) convertView.getTag();  
            }  
            
            viewHolder.mTextView1.setText(mDatas.get(position).getShenfennum());
            viewHolder.mTextView2.setText(mDatas.get(position).getName());
            viewHolder.mTextView3.setText(mDatas.get(position).getRegtime());
            viewHolder.mTextView4.setText(mDatas.get(position).getAddress());
            viewHolder.mTextView5.setText(mDatas.get(position).getBirthdate());
            return convertView;  
        }

        
        
        /*@Override
        public View getView(int position, View convertView, ViewGroup parent)
        {
            TextView mTextView1;
            TextView mTextView2;
            TextView mTextView3;
            TextView mTextView4;
            TextView mTextView5;    
            View view  = mInflater.inflate(R.layout.userlistitem, null);
            mTextView1 = (TextView) view.findViewById(R.id.userinfo1);
            mTextView2 = (TextView) view.findViewById(R.id.userinfo2);
            mTextView3 = (TextView) view.findViewById(R.id.userinfo3);
            mTextView4 = (TextView) view.findViewById(R.id.userinfo4);
            mTextView5 = (TextView) view.findViewById(R.id.userinfo5);
            mTextView1.setText(mDatas.get(position).getShenfennum());
            mTextView2.setText(mDatas.get(position).getName());
            mTextView3.setText(mDatas.get(position).getRegtime());
            mTextView4.setText(mDatas.get(position).getAddress());
            mTextView5.setText(mDatas.get(position).getBirthdate());
                    
            return view;
            
        }    */

    }
    
    private final class ViewHolder  
    {  
        TextView mTextView1;
        TextView mTextView2;
        TextView mTextView3;
        TextView mTextView4;
        TextView mTextView5;    
    } 

}
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原文地址：https://www.cnblogs.com/hixin/p/4123749.html