Xamarin.Android之引导页的简单制作

0x01 前言

 　　对于现在大部分的APP，第一次打开刚安装或更新安装的APP都会有几个引导界面，通常这几个引导页是告诉用户

APP有些什么功能或者修改了什么bug、新增了什么功能等等等。

　　下面就用Xamarin.Android来简单实现一下。主要用到的是ViewPager，当然也就离不开Xamarin.Android.Support.v4

如果遇到不能编译的问题，可以参考Xamarin.Android之简单的抽屉布局的出错处理方案。

 0x02 页面布局编写

新建一个Android项目

添加几个简单的布局页面。

首先是添加个启动页面，splash.axml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
    <LinearLayout
        android:id="@+id/ll"
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="24.0dip"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true">
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/dot" />
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/dot" />
        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:clickable="true"
            android:padding="15.0dip"
            android:src="@drawable/dot" />
    </LinearLayout>
</RelativeLayout>

引导页，用了一个ViewPager，下面的线性布局是用来存放的三个点就是当前所在的引导页面。

用到的ImageView有个src指向drawable下面的dot.xml。内容如下：

<?xml version="1.0" encoding="utf-8" ?>
<selector
  xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_enabled="true" android:drawable="@drawable/dark_dot" />
  <item android:state_enabled="false" android:drawable="@drawable/white_dot" />
</selector>

然后是3个引导页的具体内容。

guide_first.axml

<?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:orientation="vertical">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="guide---first"
        android:textSize="30sp" />
</LinearLayout>

guide_second.axml

<?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:orientation="vertical">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="guide--second"
        android:textSize="30sp" />
</LinearLayout>

guide_third.axml

<?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:orientation="vertical">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="250dp"
        android:gravity="center"
        android:text="guide--third"
        android:textSize="30sp" />
    <Button
        android:id="@+id/startBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="begin now"
        android:layout_gravity="center"
        android:layout_marginBottom="55dp" />
</LinearLayout>

这里没有用图片来展示，就简单的用了文字，没有设计师设计，so....随意一点。

最后是Main.axml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:layout_gravity="center_vertical"
        android:text="the main page"
        android:textSize="30sp" />
</LinearLayout>

0x03 Activity的编写

首先SplashActivity

using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
using Android.Widget;
namespace GuideDemo
{
    [Activity(Label = "GuideDemo", MainLauncher = true, Icon = "@drawable/icon")]
    public class SplashActivity : Activity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.splash);
            //version's infomation
            var version = PackageManager.GetPackageInfo(this.PackageName, PackageInfoFlags.MatchAll).VersionName;
            var tvVersion = FindViewById<TextView>(Resource.Id.tv_version);
            tvVersion.Text = "Version " + version;
            //get infomation from shared preferences
            var sp = GetSharedPreferences("app_setting", FileCreationMode.Private);
            new Handler().PostDelayed(() =>
            {
                Intent intent;
                //first or not
                if (sp.GetString("version", "") != version)
                {
                    intent = new Intent(this, typeof(GuideActivity));
                }
                else
                {
                    intent = new Intent(this, typeof(MainActivity));
                }                
                StartActivity(intent);
                this.Finish();
            }, 1000);
        }
    }
}

把是否是第一次开启信息存放到sharepreferences，我这里主要是通过版本号来控制。

然后是GuideActivity

using Android.App;
using Android.Content;
using Android.Content.PM;
using Android.OS;
using Android.Support.V4.View;
using Android.Views;
using Android.Widget;
using System;
using System.Collections.Generic;
using static Android.Support.V4.View.ViewPager;
namespace GuideDemo
{
    [Activity(Label = "GuideActivity")]
    public class GuideActivity : Activity
    {     
        private ViewPager viewPager;
     
        private List<View> views;
     
        private View view1, view2, view3;
     
        private Button btnStart;
            
        private ImageView[] dots;
        
        private int currentIndex;
        private LinearLayout ll;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.activity_guide);
            viewPager = FindViewById<ViewPager>(Resource.Id.viewpager);
            //the layout
            LayoutInflater mLi = LayoutInflater.From(this);
            view1 = mLi.Inflate(Resource.Layout.guide_first, null);
            view2 = mLi.Inflate(Resource.Layout.guide_second, null);
            view3 = mLi.Inflate(Resource.Layout.guide_third, null);
            views = new List<View>();
            views.Add(view1);
            views.Add(view2);
            views.Add(view3);
            
            //the adapter
            viewPager.Adapter = new ViewPagerAdapter(views);
            //page selected
            viewPager.PageSelected += PageSelected;
            ll = FindViewById<LinearLayout>(Resource.Id.ll);
            //the dot infomation
            dots = new ImageView[3];
            for (int i = 0; i < views.Count; i++)
            {
                dots[i] = (ImageView)ll.GetChildAt(i);
                dots[i].Enabled = false;                
            }
            dots[0].Enabled = true;
            //the button
            btnStart = view3.FindViewById<Button>(Resource.Id.startBtn);
            btnStart.Click += Start;
        }
        /// <summary>
        /// page selected
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void PageSelected(object sender, PageSelectedEventArgs e)
        {
            ll = FindViewById<LinearLayout>(Resource.Id.ll);
            for (int i = 0; i < views.Count; i++)
            {
                dots[i] = (ImageView)ll.GetChildAt(i);
                dots[i].Enabled = false;
            }
            dots[e.Position].Enabled = true;
        }
        /// <summary>
        /// start the main page
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Start(object sender, EventArgs e)
        {
            //get infomation from shared preferences
            var sp = GetSharedPreferences("app_setting", FileCreationMode.Private);
            //the editor
            var editor = sp.Edit();
            //update
            editor.PutString("version", PackageManager.GetPackageInfo(this.PackageName, PackageInfoFlags.MatchAll).VersionName).Commit() ;
            StartActivity(typeof(MainActivity));
            this.Finish();
        }
    }
}

主要是ViewPager处理、页面切换点的处理以及begin now 按钮的点击事件。

其中有个ViewPagerAdapter要自己实现

using Android.Support.V4.View;
using Android.Views;
using System.Collections.Generic;
namespace GuideDemo
{
    internal class ViewPagerAdapter : PagerAdapter
    {
        private List<View> views;
        public ViewPagerAdapter(List<View> views)
        {
            this.views = views;
        }
        public override int Count
        {
            get
            {
                if (views != null)
                {
                    return views.Count;
                }
                else
                { 
                    return 0;
                }
            }
        }
        public override bool IsViewFromObject(View view, Java.Lang.Object objectValue)
        {
            return view== objectValue;
        }
        public override void DestroyItem(ViewGroup container, int position, Java.Lang.Object objectValue)
        {
            container.RemoveView(views[position]);
        }
        public override Java.Lang.Object InstantiateItem(ViewGroup container, int position)
        {
            container.AddView(views[position], 0);
            return views[position];
        }
    }
}

最后是MainActivity

using Android.App;
using Android.OS;
namespace GuideDemo
{
    [Activity(Label = "GuideDemo")]
    public class MainActivity : Activity
    {        
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            
            SetContentView(Resource.Layout.Main);         
        }
    }
}

到这里就OK了，下面就来看看效果。

0x04 效果图