Listview 多布局优化

来源：互联网发布：jquery form to json 编辑：程序博客网时间：2024/05/24 01:43

listvew 多布局复用

* 重写 getItemViewType，目的：告诉listview当前条目是哪一种类型*
* 重写 getViewTypeCount，目的：告诉listview总共有几种类型*
在调用getview方法之前系统会自动调用getItemViewType方法，目的：判断该类型的布局是否有缓存过，如果有会在getview的conrview参数给予提供

Adapter

package com.example.doubuju_listview;import android.util.Log;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.TextView;import java.util.List;/** * Created by admin on 2016/8/17. */public class MyAdater extends BaseAdapter {    List<Context1> contextlist;    MainActivity mainActivity;    private  String tag="MyAdapter";    public MyAdater(MainActivity mainActivity, List<Context1> contextlist) {        this.mainActivity = mainActivity;        this.contextlist=contextlist;    }    @Override    public int getCount() {        return contextlist.size();    }    @Override    public Object getItem(int position) {        return null;    }    @Override    public long getItemId(int position) {        return 0;    }    //告诉listview当前条目是哪一种类型    @Override    public int getItemViewType(int position) {        return contextlist.get(position).type;    }    //告诉listview总共有几种类型    @Override    public int getViewTypeCount() {        return 3;    }    /*    *    * 新增细节 1.在getview方法之前会调用getItemViewType方法判断此类型的item布局是否以前出现过，    *            如果出现过getview方法中convertview参数为某个类型的item布局，否则此参数为空    *          2.listview中缓存getviewTypeCount()方法的返回值必须大于getItemViewType最大的返回值。    *          否则报indexoutofExeception    * */    @Override    public View getView(int position, View convertView, ViewGroup parent) {        Context1 context1 = contextlist.get(position);        int type = context1.type;        LeftViewHolder leftViewHolder=null;        CenterViewHolder centerViewHolder=null;        RightViewHolder rightViewHolder=null;        switch (type){            case 0:                if (convertView == null) {                    //实例化条目                  View  inflate = View.inflate(mainActivity, R.layout.item_left, null);                   TextView lefttext = (TextView) inflate.findViewById(R.id.item_left);                    convertView=inflate;                    //存储条目中的各种控件实例                    leftViewHolder  = new LeftViewHolder();                    leftViewHolder.textView=lefttext;                    inflate.setTag(leftViewHolder);                    Log.i(tag,"新建类型:"+type);                }else{                    leftViewHolder = (LeftViewHolder) convertView.getTag();                    Log.i(tag,"复用类型:"+type);                }                //给控件赋值                leftViewHolder.textView.setText(context1.context1);                break;            case 1:                if (convertView== null) {                    //实例化条目                    View  inflate = View.inflate(mainActivity, R.layout.item_center, null);                    TextView lefttext = (TextView) inflate.findViewById(R.id.item_center);                    //存条目布局实例                    convertView=inflate;                    //存储条目中的各种控件实例                    centerViewHolder  = new CenterViewHolder();                    centerViewHolder.textView=lefttext;                    inflate.setTag(centerViewHolder);                    Log.i(tag,"新建类型:"+type);                }else{                    centerViewHolder = (CenterViewHolder) convertView.getTag();                    Log.i(tag,"复用类型:"+type);                }                centerViewHolder.textView.setText(context1.context1);                break;            case 2:                if (convertView== null) {                    //实例化条目                    View  inflate = View.inflate(mainActivity, R.layout.item_right, null);                    TextView lefttext = (TextView) inflate.findViewById(R.id.item_right);                    //存条目布局实例                    convertView=inflate;                    //存储条目中的各种控件实例                    rightViewHolder  = new RightViewHolder();                    rightViewHolder.textView=lefttext;                    inflate.setTag(rightViewHolder);                    Log.i(tag,"新建类型:"+type);                }else{                    Log.i(tag,"复用类型:"+type);                    rightViewHolder = (RightViewHolder) convertView.getTag();                }                rightViewHolder.textView.setText(context1.context1);                break;            default:                break;        }        return convertView;    }    public class LeftViewHolder{        public TextView textView;    }    public class CenterViewHolder{        public TextView textView;    }    public class RightViewHolder{        public TextView textView;    }}

布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent">    <TextView        android:id="@+id/item_left"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="左边"/></LinearLayout>---------------------------------------------------<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:gravity="center_horizontal">    <TextView        android:id="@+id/item_center"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="中间"/></LinearLayout>-------------------------------------------------------<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:gravity="right">    <TextView        android:id="@+id/item_right"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="右边"/></LinearLayout>

activity

package com.example.doubuju_listview;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private ListView mian_lv;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mian_lv = (ListView) findViewById(R.id.main_lv);        List<Context1> contextlist = new ArrayList<Context1>();        //模拟数据        for (int i=0;i<200;i++){            Context1 context1 = new Context1();            context1.context1=i+"";            context1.type=i%3;            Log.i("log",i%3+"");            contextlist.add(i,context1);        }        mian_lv.setAdapter(new MyAdater(this,contextlist));    }}

Bean

package com.example.doubuju_listview;/** * Created by admin on 2016/8/17. */public class Context1 {    public int type=0;    public String context1=null;}

listview中缓存getviewTypeCount()方法的返回值必须大于getItemViewType最大的返回值。否则报indexoutofExeception

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