android ListView常用知识总结

先来看下项目主要内容：

ListView中填充数据：

1. 重现添加数据后置顶，具体阐明了决解方案，如下：
   

   

   
   

2. 刷新适配器后没有响应的错误现象，具体阐明了决解方案，如下：

   

   

   
   

   
   

3. 正确示范一：

   /**
   * 正确示范一（正确运用，修改原始对象对应引用也改变）
   *
   * @author johnny
   *
   */
   public class ThreeListViewActivity extends Activity {
   private ListView mContentLv;
   private OneAdapter adapter;
   private ArrayList> arrayList= new ArrayList>();
   @Override
   protected void onCreate(Bundle savedInstanceState) {
   // TODO Auto-generated method stub
   super .onCreate(savedInstanceState);
   setContentView(R.layout.activity_listview);
   
   mContentLv = (ListView) findViewById(R.id.lv_content);
   adapter= new OneAdapter( this ,arrayList);
   mContentLv.setAdapter(adapter);
   
   initData();
   
   ToastUtils.show(getApplicationContext(), "6秒后延迟添加，刷新adapter" );
   
   //开启异步线程
   setData();
   
   }
   private void setData() {
   new Thread( new Runnable() {
   @Override
   public void run() {
   // TODO Auto-generated method stub
   try {
   //做一些耗时的操作后添加数据，之后刷新adapter
   Thread.sleep( 6000 );
   } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   }
   //可能这个时候才重网络上获取到了新数据，，现在开始添加数据
   HashMap hashMap;
   for ( int i = 0 ; i < 5 ; i++) {
   hashMap = new HashMap();
   if (i % 4 == 0 ) {
   hashMap.put( "name" , "大海" );
   hashMap.put( "address" , "上海" );
   } else if (i % 4 == 1 ) {
   hashMap.put( "name" , "老马" );
   hashMap.put( "address" , "深圳" );
   } else if (i % 4 == 2 ) {
   hashMap.put( "name" , "小三" );
   hashMap.put( "address" , "东莞" );
   } else if (i % 4 == 3 ) {
   hashMap.put( "name" , "老哥" );
   hashMap.put( "address" , "北京" );
   }
   arrayList.add(hashMap);
   }
   handler.sendEmptyMessage( 1 );
   }
   }).start();
   }
   Handler handler = new Handler(){
   public void handleMessage(android.os.Message msg) {
   adapter.notifyDataSetChanged(); //没有重现设置adapter，只做了刷新数据，listview不会到顶。
   ToastUtils.show(getApplicationContext(), "adapter共有" +adapter.getAllList().size()+ "个数据，activity共有" +arrayList.size()+ "个数据，刷新结束！" );
   };
   };
   private void initData() {
   HashMap hashMap;
   for ( int i = 0 ; i < 15 ; i++) {
   hashMap = new HashMap();
   if (i % 4 == 0 ) {
   hashMap.put( "name" , "小明" );
   hashMap.put( "address" , "上海" );
   } else if (i % 4 == 1 ) {
   hashMap.put( "name" , "老马" );
   hashMap.put( "address" , "深圳" );
   } else if (i % 4 == 2 ) {
   hashMap.put( "name" , "小三" );
   hashMap.put( "address" , "东莞" );
   } else if (i % 4 == 3 ) {
   hashMap.put( "name" , "老哥" );
   hashMap.put( "address" , "北京" );
   }
   arrayList.add(hashMap);
   }
   }
   }

   
   

   正确示范二：

   /**
   * 正确示范二（正确运用，Activity里面对象不用作Adapter原始对象，只做数据的备份。
   * 这也是本人比较喜欢的写法，原因：很多时候我们会不经意间改变Activity里面的数据源后导致ListView的改变，
   * 导致出错后排除错误难解<正确示范一，当然也有好处，比如：改变Activity数据后，不需要再做多余的Adapter数据的更改，方便>）
   *
   * @注意 这里只是数据添加方案本人赞成写法，具体完整结合adapter请移步个人推荐一或二<有错误示范，才能慢慢完善改变，错误何尝不是一种成长>
   * @author johnny
   *
   */
   public class FourListViewActivity extends Activity {
   private ListView mContentLv;
   private OneAdapter adapter;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
   // TODO Auto-generated method stub
   super .onCreate(savedInstanceState);
   setContentView(R.layout.activity_listview);
   
   mContentLv = (ListView) findViewById(R.id.lv_content);
   adapter= new OneAdapter( this );
   mContentLv.setAdapter(adapter);
   
   initData();
   
   ToastUtils.show(getApplicationContext(), "6秒后延迟添加，刷新adapter" );
   
   //开启异步线程
   setData();
   
   }
   private void setData() {
   new Thread( new Runnable() {
   @Override
   public void run() {
   // TODO Auto-generated method stub
   try {
   //做一些耗时的操作后添加数据，之后刷新adapter
   Thread.sleep( 6000 );
   } catch (InterruptedException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
   }
   ArrayList> arrayList= new ArrayList>();
   //可能这个时候才重网络上获取到了新数据，，现在开始添加数据
   HashMap hashMap;
   for ( int i = 0 ; i < 5 ; i++) {
   hashMap = new HashMap();
   if (i % 4 == 0 ) {
   hashMap.put( "name" , "大海" );
   hashMap.put( "address" , "上海" );
   } else if (i % 4 == 1 ) {
   hashMap.put( "name" , "老马" );
   hashMap.put( "address" , "深圳" );
   } else if (i % 4 == 2 ) {
   hashMap.put( "name" , "小三" );
   hashMap.put( "address" , "东莞" );
   } else if (i % 4 == 3 ) {
   hashMap.put( "name" , "老哥" );
   hashMap.put( "address" , "北京" );
   }
   //这里添加的只是在临时数据存储的对象，adapter里面不属于同一个对象
   arrayList.add(hashMap);
   }
   //和正确范例一区别在于此，每次都需要把数据copy到adapter里面
   adapter.setAddList(arrayList);
   handler.sendEmptyMessage( 1 );
   }
   }).start();
   }
   Handler handler = new Handler(){
   public void handleMessage(android.os.Message msg) {
   adapter.notifyDataSetChanged(); //没有重现设置adapter，只做了刷新数据，ListView不会到顶。
   ToastUtils.show(getApplicationContext(), "adapter共有" +adapter.getAllList().size()+ "个数据。" );
   };
   };
   private void initData() {
   ArrayList> arrayList= new ArrayList>();
   HashMap hashMap;
   for ( int i = 0 ; i < 15 ; i++) {
   hashMap = new HashMap();
   if (i % 4 == 0 ) {
   hashMap.put( "name" , "小明" );
   hashMap.put( "address" , "上海" );
   } else if (i % 4 == 1 ) {
   hashMap.put( "name" , "老马" );
   hashMap.put( "address" , "深圳" );
   } else if (i % 4 == 2 ) {
   hashMap.put( "name" , "小三" );
   hashMap.put( "address" , "东莞" );
   } else if (i % 4 == 3 ) {
   hashMap.put( "name" , "老哥" );
   hashMap.put( "address" , "北京" );
   }
   arrayList.add(hashMap);
   }
   adapter.setAddList(arrayList);
   }
   }

   
   

   
   

   ListView 适配器推荐写法：

   • 
     

     @Override
     public View getView( int position, View convertView, ViewGroup parent) {
     // TODO Auto-generated method stub
     
     View v = convertView;
     //判断是否为null，这是每个要做复用的都要写的
     if (v == null ) {
     v = inflater.inflate(R.layout.lv_item, null );
     }
     
     //相比之下
     //写法太集中，没有细化
     /*if (null == convertView) {
     holder = new ViewHolder();
     convertView = inflater.inflate(R.layout.lv_item, null);
     holder.mNameTv = (TextView) convertView.findViewById(R.id.tv_name);
     holder.mAddressTv = (TextView) convertView.findViewById(R.id.tv_address);
     convertView.setTag(holder);
     } else {
     holder = (ViewHolder) convertView.getTag();
     }*/
     //简洁，把初始化控件放到了ViewHolder里面，是的getView方法更清晰简洁，只需要做数据的赋值和复杂的逻辑，没有混为一滩
     ViewHolder holder = (ViewHolder) v.getTag();
     if (holder == null ) {
     holder = new ViewHolder(v);
     v.setTag(holder);
     }
     HashMap hashMap = getItem(position);
     holder.mNameTv.setText(hashMap.get( "name" ));
     holder.mAddressTv.setText(hashMap.get( "address" ));
     
     return v;
     }

     
     

   
   

   方法二：
   

   • @Override
     public View getView( int position, View convertView, ViewGroup parent) {
     // TODO Auto-generated method stub
     
     View v = convertView;
     //判断是否为null，这是每个要做复用的都要写的
     if (v == null ) {
     v = inflater.inflate(R.layout.lv_item, null );
     }
     
     //简洁,方便,快速
     TextView mNameTv=ViewHolder.get(v, R.id.tv_name);
     TextView mAddressTv=ViewHolder.get(v, R.id.tv_address);
     HashMap hashMap = getItem(position);
     mNameTv.setText(hashMap.get( "name" ));
     mAddressTv.setText(hashMap.get( "address" ));
     
     return v;
     }

     
     

   • 
     

   
   

ListView中疑难杂症：

只做截图具体下载代码查看：不需要豆子

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ListView中常用知识总结