xamarin android viewpager的用法

• 通过手势滑动可以完成view的切换，一般是用来app的引导页或则实现图片轮播，类似网页上的banner轮播.
• Adnroid 3.0后引入的一个UI控件,在xamarin android 的开发中必须引入v4兼容包(ps这里有坑,菜鸟需要注意)
• 和ListView,GridView一样需要一个Adapter,将View和ViewPager进行绑定,而ViewPager则有一个特定的Adapter--PagerAdapter

  另外，Google官方是建议我们使用Fragment来填充ViewPager的，这样可以更加方便的生成每个Page，以及管理每个Page的生命周期！给我们提供了两个Fragment专用的Adapter：FragmentPageAdapter和FragmentStatePagerAdapter我们简要的来分析下这两个Adapter的区别：

  • FragmentPageAdapter：和PagerAdapter一样，只会缓存当前的Fragment以及左边一个，右边一个，即总共会缓存3个Fragment而已，假如有1，2，3，4四个页面：
    处于1页面：缓存1，2
    处于2页面：缓存1，2，3
    处于3页面：销毁1页面，缓存2，3，4
    处于4页面：销毁2页面，缓存3，4
    更多页面的情况，依次类推~
  • FragmentStatePagerAdapter：当Fragment对用户不见得时，整个Fragment会被销毁，只会保存Fragment的状态！而在页面需要重新显示的时候，会生成新的页面.

2.Xamarin android ViewPager的用法

1. GetCount:获得ViewPager中有多少个view
2. DestroyItem():移除一个位置的页面，适配器有责任从容器中删除这个视图,这是为了确保在FinishUpdate(ViewGroup)返回时视图能够被删除
3. InstantiateItem():①将给定位置的view添加到ViewGroup(容器)中,创建并显示出来②返回一个代表新增页面的Object(key),通常都是直接返回view本身就可以了,当然你也可以自定义自己的key,但是key和每个view要一一对应的关系
4. IsViewFromObject():判断instantiateItem(ViewGroup, int)函数所返回来的Key与一个页面视图是否是代表的同一个视图(即它俩是否是对应的，对应的表示同一个View),通常我们直接写return view == object

3.ViewPager的基础用法

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="#FFBA55"    android:gravity="center"    android:orientation="vertical">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="第一个Page"        android:textColor="#000000"        android:textSize="18sp"        android:textStyle="bold" /></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.support.v4.view.ViewPager        android:id="@+id/viewpager1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center" /></LinearLayout>

using System;using System.Collections.Generic;using System.Linq;using System.Text;using Android.App;using Android.Content;using Android.OS;using Android.Runtime;using Android.Views;using Android.Widget;using Android.Support.V4.View;using Java.Lang;namespace android_appcompat.Adapter{    public class MyPagerAdapter : PagerAdapter    {        public List<View> viewLists;        public MyPagerAdapter() { }        public MyPagerAdapter(List<View> viewLists) {                        this.viewLists = viewLists;        }        public override int Count        {            get            {                return viewLists.Count();            }        }        public override bool IsViewFromObject(View view, Java.Lang.Object objectValue)        {            return view == objectValue;        }        public override Java.Lang.Object InstantiateItem(ViewGroup container, int position)        {            container.AddView(viewLists[position]);            return viewLists[position];        }        public override void DestroyItem(ViewGroup container, int position, Java.Lang.Object objectValue)        {            container.RemoveView(viewLists[position]);        }    }}

4.xamarin android PagerTitleStrip的用法

PagerTitleStrip所在Activtiy的布局：activity_two.xml： 

<?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:layout_width="match_parent"        android:layout_height="48dp"        android:background="#ccff99"        android:gravity="center"        android:text="PagerTitleStrip效果演示"        android:textColor="#000000"        android:textSize="18sp" />    <android.support.v4.view.ViewPager        android:id="@+id/viewpager_two"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_gravity="center">        <android.support.v4.view.PagerTitleStrip //如果要实现效果图那样的效果，改成PageTabStrip就行了            android:id="@+id/pagetitle"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:layout_gravity="top" />    </android.support.v4.view.ViewPager></LinearLayout>

using System;using System.Collections.Generic;using System.Linq;using System.Text;using Android.App;using Android.Content;using Android.OS;using Android.Runtime;using Android.Views;using Android.Widget;using Android.Support.V4.View;using Java.Lang;namespace android_appcompat.Adapter{    public class MyPagerAdapter2:PagerAdapter    {        public List<View> viewLists;        public List<string> titleLists;        public override int Count        {            get{return viewLists.Count;}        }        public MyPagerAdapter2(){ }        public MyPagerAdapter2(List<View> viewLists,List<string> titleLists)        {            this.viewLists = viewLists;            this.titleLists = titleLists;          }        public override bool IsViewFromObject(View view, Java.Lang.Object objectValue)        {            return view == objectValue;        }        public override Java.Lang.Object InstantiateItem(ViewGroup container,int position)        {            container.AddView(viewLists[position]);            return viewLists[position];        }        public override  ICharSequence GetPageTitleFormatted(int position)        {            return CharSequence.ArrayFromStringArray(new string[] { titleLists[position] })[0];                   }        public  override void DestroyItem(ViewGroup container,int position,Java.Lang.Object objectValue)        {            container.RemoveView(viewLists[position]);        }    }}

using System;using System.Collections.Generic;using System.Linq;using System.Text;using Android.App;using Android.Content;using Android.OS;using Android.Runtime;using Android.Views;using Android.Widget;using android_appcompat.Adapter;using Android.Support.V4.View;using Java.Lang;namespace android_appcompat{    [Activity(Label = "Activity2", MainLauncher = true)]    public class Activity2 : Activity    {        private List<View> viewLists;        private List<string> titleList;        private MyPagerAdapter2 adapter;        private ViewPager viewPapgeTitle;          protected override void OnCreate(Bundle savedInstanceState)        {            base.OnCreate(savedInstanceState);            SetContentView(Resource.Layout.activity_two);            // Create your application here            viewPapgeTitle = FindViewById<ViewPager>(Resource.Id.viewpager_two);            viewLists = new List<View>();            LayoutInflater li = LayoutInflater;            viewLists.Add(li.Inflate(Resource.Layout.view_one,null,false));            viewLists.Add(li.Inflate(Resource.Layout.view_two, null, false));            viewLists.Add(li.Inflate(Resource.Layout.view_three, null, false));            titleList = new List<string>() {                "红褐色","黄色","白色"            };            adapter = new MyPagerAdapter2 (viewLists,titleList);            viewPapgeTitle.Adapter = adapter;        }    }}

ViewPager实现TabHost的效果：