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Android Listview中显示不同的视图布局详解及实例代码

2019-12-12 03:47:15
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Android Listview中显示不同的视图布局

1. 使用场景

在重写ListView的BaseAdapter时,我们常常在getView()方法中复用convertView,以提高性能。convertView在Item为单一的同种类型布局时,能够回收并重用,但是多个Item布局类型不同时,convertView的回收和重用会出现问题。比如有些行为纯文本,有些行则是图文混排,这里纯文本行为一类布局,图文混排的行为第二类布局。单一类型的ListView很简单,下面着重介绍一下ListView包含多种类型视图布局的情形。

2.ListView包含不同Item的布局

我们需要做这些工作:

  1)重写 getViewTypeCount() 该方法返回多少个不同的布局
  2)重写 getItemViewType(int) 根据position返回相应的Item
  3)根据view item的类型,在getView中创建正确的convertView

3.案例

import java.util.ArrayList; import android.app.Activity; import android.content.Context; import android.os.Bundle; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.CheckBox; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.ListView; import android.widget.TextView; public class listViewTest extends Activity { /** Called when the activity is first created. */  ListView listView;   MyAdapter listAdapter;   ArrayList<String> listString;   @Override   public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.main);     listView = (ListView)this.findViewById(R.id.listview);     listString = new ArrayList<String>();     for(int i = 0 ; i < 100 ; i++)     {       listString.add(Integer.toString(i));     }     listAdapter = new MyAdapter(this);     listView.setAdapter(listAdapter);   }   class MyAdapter extends BaseAdapter{     Context mContext;     LinearLayout linearLayout = null;     LayoutInflater inflater;     TextView tex;     final int VIEW_TYPE = 3;     final int TYPE_1 = 0;     final int TYPE_2 = 1;     final int TYPE_3 = 2;     public MyAdapter(Context context) {       // TODO Auto-generated constructor stub       mContext = context;       inflater = LayoutInflater.from(mContext);     }     @Override     public int getCount() {       // TODO Auto-generated method stub       return listString.size();     }     //每个convert view都会调用此方法,获得当前所需要的view样式     @Override     public int getItemViewType(int position) {       // TODO Auto-generated method stub       int p = position%6;       if(p == 0)         return TYPE_1;       else if(p < 3)         return TYPE_2;       else if(p < 6)         return TYPE_3;       else        return TYPE_1;     }     @Override     public int getViewTypeCount() {       // TODO Auto-generated method stub       return 3;     }     @Override     public Object getItem(int arg0) {       // TODO Auto-generated method stub       return listString.get(arg0);     }     @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       viewHolder1 holder1 = null;       viewHolder2 holder2 = null;       viewHolder3 holder3 = null;       int type = getItemViewType(position);       //无convertView,需要new出各个控件       if(convertView == null)       {         Log.e("convertView = ", " NULL");         //按当前所需的样式,确定new的布局         switch(type)         {         case TYPE_1:           convertView = inflater.inflate(R.layout.listitem1, parent, false);           holder1 = new viewHolder1();           holder1.textView = (TextView)convertView.findViewById(R.id.textview1);           holder1.checkBox = (CheckBox)convertView.findViewById(R.id.checkbox);           Log.e("convertView = ", "NULL TYPE_1");           convertView.setTag(holder1);           break;         case TYPE_2:           convertView = inflater.inflate(R.layout.listitem2, parent, false);           holder2 = new viewHolder2();           holder2.textView = (TextView)convertView.findViewById(R.id.textview2);           Log.e("convertView = ", "NULL TYPE_2");           convertView.setTag(holder2);           break;         case TYPE_3:           convertView = inflater.inflate(R.layout.listitem3, parent, false);           holder3 = new viewHolder3();           holder3.textView = (TextView)convertView.findViewById(R.id.textview3);           holder3.imageView = (ImageView)convertView.findViewById(R.id.imageview);           Log.e("convertView = ", "NULL TYPE_3");           convertView.setTag(holder3);           break;         }       }else{         //有convertView,按样式,取得不用的布局         switch(type)         {         case TYPE_1:           holder1 = (viewHolder1) convertView.getTag();           Log.e("convertView !!!!!!= ", "NULL TYPE_1");           break;         case TYPE_2:           holder2 = (viewHolder2) convertView.getTag();           Log.e("convertView !!!!!!= ", "NULL TYPE_2");           break;         case TYPE_3:           holder3 = (viewHolder3) convertView.getTag();           Log.e("convertView !!!!!!= ", "NULL TYPE_3");           break;         }       }     //设置资源       switch(type)       {         case TYPE_1:           holder1.textView.setText(Integer.toString(position));           holder1.checkBox.setChecked(true);           break;         case TYPE_2:           holder2.textView.setText(Integer.toString(position));           break;         case TYPE_3:           holder3.textView.setText(Integer.toString(position));           holder3.imageView.setBackgroundResource(R.drawable.icon);           break;       }       return convertView;     }   }   //各个布局的控件资源   class viewHolder1{     CheckBox checkBox;     TextView textView;   }   class viewHolder2{     TextView textView;   }   class viewHolder3{     ImageView imageView;     TextView textView;   } }

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