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) { supe