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：

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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<string> dataset;
public DataAdapter(Context context, List<string> 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<ImageView>(Resource.Id.image);
Text = itemView.FindViewById<TextView>(Resource.Id.text);
}
}
}
}

（8）打开Main.axml文件，构建RecyclerView。代码如下：

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<?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:background="#FFFFFF">
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>

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

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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<RecyclerView>(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

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

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