2.5.1 ListView Item多布局的实现

本节引言:

本节是ListView这个小节的最后一节,给大家带来的是ListView多布局Item的实现, 何为ListView Item多布局,打个比方,QQ这种聊天列表:

假如他是用一个ListView做的,那么一个ListView上不就有两种不同的Item咯! 一左一右,嘿嘿,本节就来教大家如何实现ListView的多布局!

1.要点讲解:

重写getItemViewType()方法对应View是哪个类别,以及getViewTypeCount()方法iew返回 总共多少个类别!然后再getView那里调用getItemViewType获得对应类别,再加载对应的View!

2.代码实现:

这里的话直接用上一节的两个布局,然后另外写一个Adapter重写要点中的几个几个地方:

MutiLayoutAdapter.java

/**
 * Created by Jay on 2015/9/23 0023.
 */  public  class  MutiLayoutAdapter  extends  BaseAdapter{  //定义两个类别标志  private  static  final  int TYPE_BOOK =  0;  private  static  final  int TYPE_APP =  1;  private  Context mContext;  private  ArrayList<Object> mData =  null;  public  MutiLayoutAdapter(Context mContext,ArrayList<Object> mData)  {  this.mContext = mContext;  this.mData = mData;  }  @Override  public  int getCount()  {  return mData.size();  }  @Override  public  Object getItem(int position)  {  return mData.get(position);  }  @Override  public  long getItemId(int position)  {  return position;  }  //多布局的核心,通过这个判断类别  @Override  public  int getItemViewType(int position)  {  if  (mData.get(position)  instanceof  App)  {  return TYPE_APP;  }  else  if  (mData.get(position)  instanceof  Book)  {  return TYPE_BOOK;  }  else  {  return  super.getItemViewType(position);  }  }  //类别数目  @Override  public  int getViewTypeCount()  {  return  2;  }  @Override  public  View getView(int position,  View convertView,  ViewGroup parent)  {  int type = getItemViewType(position);  ViewHolder1 holder1 =  null;  ViewHolder2 holder2 =  null;  if(convertView ==  null){  switch  (type){  case TYPE_APP: holder1 =  new  ViewHolder1(); convertView =  LayoutInflater.from(mContext).inflate(R.layout.item_one, parent,  false); holder1.img_icon =  (ImageView) convertView.findViewById(R.id.img_icon); holder1.txt_aname =  (TextView) convertView.findViewById(R.id.txt_aname); convertView.setTag(R.id.Tag_APP,holder1);  break;  case TYPE_BOOK: holder2 =  new  ViewHolder2(); convertView =  LayoutInflater.from(mContext).inflate(R.layout.item_two, parent,  false); holder2.txt_bname =  (TextView) convertView.findViewById(R.id.txt_bname); holder2.txt_bauthor =  (TextView) convertView.findViewById(R.id.txt_bauthor); convertView.setTag(R.id.Tag_Book,holder2);  break;  }  }else{  switch  (type){  case TYPE_APP: holder1 =  (ViewHolder1) convertView.getTag(R.id.Tag_APP);  break;  case TYPE_BOOK: holder2 =  (ViewHolder2) convertView.getTag(R.id.Tag_Book);  break;  }  }  Object obj = mData.get(position);  //设置下控件的值  switch  (type){  case TYPE_APP:  App app =  (App) obj;  if(app !=  null){ holder1.img_icon.setImageResource(app.getaIcon()); holder1.txt_aname.setText(app.getaName());  }  break;  case TYPE_BOOK:  Book book =  (Book) obj;  if(book !=  null){ holder2.txt_bname.setText(book.getbName()); holder2.txt_bauthor.setText(book.getbAuthor());  }  break;  }  return convertView;  }  //两个不同的ViewHolder  private  static  class  ViewHolder1{  ImageView img_icon;  TextView txt_aname;  }  private  static  class  ViewHolder2{  TextView txt_bname;  TextView txt_bauthor;  }  }

这里有个地方要注意的,convertView.setTag(R.id.Tag_APP,holder1);我们平时都直接 setTag(Object)的,这个是setTag的重载方法,参数是一个唯一的key以及后面的一个对象! 唯一!!!我一开始直接把TYPE_BOOK作为第一个参数,然后就报下面这个错误:

The key must be an application-specific resource id 就是前面这个要唯一,定义一个final类型的int变量和硬编码一个值的方式都是行不通的 这里的做法是直接在strings.xml中添加:

<item  name="Tag_APP"  type="id"></item>  <item  name="Tag_Book"  type="id"></item>

当然你也可以在res/values/下另外创建一个ids.xml文件,把上面这段代码贴上去! 除了这个还有一个要注意的地方,就是这个区分类别的标志要从0开始算,不然会报下面 这样的错误:

MainActivity.java

public  class  MainActivity  extends  AppCompatActivity  {  private  static  final  int TYPE_BOOK =  0;  private  static  final  int TYPE_APP =  1;  private  ListView list_content;  private  ArrayList<Object> mData =  null;  private  MutiLayoutAdapter myAdapter =  null;  @Override  protected  void onCreate(Bundle savedInstanceState)  {  super.onCreate(savedInstanceState); setContentView(R.layout.activity_main);  //数据准备: mData =  new  ArrayList<Object>();  for(int i =  0;i <  20;i++){  switch  ((int)(Math.random()  *  2)){  case TYPE_BOOK: mData.add(new  Book("《第一行代码》","郭霖"));  break;  case TYPE_APP: mData.add(new  App(R.mipmap.iv_icon_baidu,"百度"));  break;  }  } list_content =  (ListView) findViewById(R.id.list_content); myAdapter =  new  MutiLayoutAdapter(MainActivity.this,mData); list_content.setAdapter(myAdapter);  }  }

上面随机生成0和1,0就往集合中添加一个Book的对象,1的话就添加一个App的对象!

3.代码下载:

ListViewDemo6.zip

本节小结:

好的,本节给大家讲解了ListView Item多布局的实现,就是两个方法的重写, 然后getView()做下判断,设置不同的布局而已~代码非常简单~

关于ListView的知识就告一段落吧,当然ListView的知识并不止这些, 异步加载,优化等等,这些我们都会在进阶部分进行学习~就说这么多,谢谢~

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