XamarinAndroid组件教程RecylerView适配器设置动画示例

【示例1-3】下面将在RecylerView的子元素进行滚动时，使用适配器动画。具体的操作步骤如下：

（1）创建一个名为RecylerViewAnimatorsAdapter的项目。

（2）将RecyclerViewAnimators.dll、Square.OkHttp.dll、Square.OkIO.dll、Square.Picasso.dll、Xamarin.Android.Arch.Core.Common.dll、Xamarin.Android.Arch.Lifecycle.Common.dll、Xamarin.Android.Arch.Lifecycle.Runtime.dll、Xamarin.Android.Support.Animated.Vector.Drawable.dll、Xamarin.Android.Support.Annotations.dll、Xamarin.Android.Support.Compat.dll、Xamarin.Android.Support.Core.UI.dll、Xamarin.Android.Support.Core.Utils.dll、Xamarin.Android.Support.Fragment.dll、Xamarin.Android.Support.Media.Compat.dll、Xamarin.Android.Support.v4.dll、Xamarin.Android.Support.v7.AppCompat.dll、Xamarin.Android.Support.v7.RecyclerView.dll和Xamarin.Android.Support.Vector.Drawable.dll库添加到RecylerViewAnimatorsAdapter项目的引用中。

（3）添加图片chip.jpg到RecylerViewAnimatorsAdapter项目的Resources下方的drawable文件夹中。

（4）创建一个xml文件，命名为layout_list_item。

（5）打开layout_list_item.cs文件，构建RecylerView的子元素。代码与RecylerViewAnimatorsItemAnimator项目一样。只不过需要将TextView的颜色设置为黑色。

（6）创建一个适配器文件，命名为DataAdapter。

（7）打开DataAdapter.cs文件，添加以下代码：

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 Square.Picasso;

using Android.Support.V7.Widget;

namespace RecylerViewAnimatorsAdapter

{

 class DataAdapter : RecyclerView.Adapter

 {

 Context context;

 List dataset;

 public DataAdapter(Context context, List dataset)

 {

 this.context = context;

 this.dataset = dataset;

 }

 //子元素的个数

 public override int ItemCount

 {

 get

 {

 return dataset.Count;

 }

 }

 //返回一个自定义的ViewHolder

 public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)

 {

 var v = LayoutInflater.From(context).Inflate(Resource.Layout.layout_list_item, parent, false);

 return new ViewHolder(v);

 }

 //填充onCreateViewHolder()方法返回的ViewHolder中的控件

 public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)

 {

 var h = (ViewHolder)holder;

 Picasso.With(context).Load(Resource.Drawable.image).Into(h.Image);

 h.Text.Text = dataset[position];

 }

 private class ViewHolder : RecyclerView.ViewHolder

 {

 public ImageView Image { get; private set; }

 public TextView Text { get; private set; }

 public ViewHolder(View itemView)

 : base(itemView)

 {

 Image = itemView.FindViewById(Resource.Id.image);

 Text = itemView.FindViewById(Resource.Id.text);

 }

 }

 }

}

（8）打开Main.axml文件，构建RecyclerView。代码如下：

 android:orientation="vertical"

 android:layout_width="match_parent"

 android:layout_height="match_parent"

 android:background="#FFFFFF">

 android:id="@+id/list"

 android:layout_width="match_parent"

 android:layout_height="match_parent"/>

（9）打开MainActivity.cs文件，在RecylerView滚动时使用适配器动画。代码如下：

using Android.App;

using Android.Widget;

using Android.OS;

using Android.Support.V7.Widget;

using System.Linq;

using RecyclerViewAnimators.Adapters;

using Android.Views.Animations;

namespace RecylerViewAnimatorsAdapter

{

 [Activity(Label = "RecylerViewAnimatorsAdapter", MainLauncher = true, Icon = "@mipmap/icon")]

 public class MainActivity : Activity

 {

 static readonly string[] data = {

 "Apple", "Ball", "Camera", "Day", "Egg", "Foo", "Google", "Hello", "Iron", "Japan", "Coke",

 "Dog", "Cat", "Yahoo", "Sony", "Canon", "Fujitsu", "USA", "Nexus", "LINE", "Haskell", "C++",

 "Java", "Go", "Swift", "Objective-c", "Ruby", "PHP", "Bash", "ksh", "C", "Groovy", "Kotlin",

 "Chip", "Japan", "U.S.A", "San Francisco", "Paris", "Tokyo", "Silicon Valley", "London",

 "Spain", "China", "Taiwan", "Asia", "New York", "France", "Kyoto", "Android", "Google", "C#",

 "iPhone", "iPad", "iPod", "Wasabeef", "Xamarin", "South Africa", "Cape Town", "Microsoft"

 };

 protected override void OnCreate(Bundle savedInstanceState)

 {

 base.OnCreate(savedInstanceState);

 SetContentView(Resource.Layout.Main);

 var recyclerView = FindViewById(Resource.Id.list);

 recyclerView.SetLayoutManager(new LinearLayoutManager(this));

 var adapter = new DataAdapter(this, data.ToList());

 var alphaAdapter = new AlphaInAnimationAdapter(adapter); //创建适配器动画

 var scaleAdapter = new ScaleInAnimationAdapter(alphaAdapter); //创建复合适配器动画

 scaleAdapter.SetFirstOnly(false); //不是显示一次动画效果

 scaleAdapter.SetInterpolator(new OvershootInterpolator()); //设置插值器

 recyclerView.SetAdapter(scaleAdapter);  //设置适配器

 }

 }

}

运行程序后，初始状态如图1.3所示。当滚动子元素后，会看到动画效果。

图1.3  初始状态