Xamarin开发Android UI笔记(二):图片切换ImageSwitcher
在移动应用开发过程中经常会使用到图片展示场景,例如利用多张图片说明一个产品的特点,此处就会使用到ImageSwithcher,当然也可以使用ViewFliper来实现,但使用ViewFliper的时候会资源释放的问题,需要手动进行操作,这点在以后的文章中讲述。
要使用ImageSwithcher,首先需要在界面文件中添加ImageSwithcher,然后在代码中为ImageSwithcher指定图片加载方法以及触控方法。如下为完成之后的界面:
下面讲述具体的实现方法:
界面Xml文件为:
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:minWidth="25px" android:minHeight="25px" android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/relativeLayout1" android:background="#ffececec"> <ImageView android:src="@drawable/ImgSlideLeft" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnFeatureLeft" android:layout_centerVertical="true" android:layout_alignParentLeft="true" /> <ImageSwitcher android:minWidth="25px" android:minHeight="25px" android:layout_width="1180px" android:layout_height="638px" android:id="@+id/SwitcherProductFeature" android:layout_centerInParent="true" /> <ImageView android:src="@drawable/ImgSlideRight" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btnFeatureRight" android:layout_centerVertical="true" android:layout_alignParentRight="true" /> </RelativeLayout>
实现代码为:
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; namespace MobileInsured.Activitys { [Activity (Label = "ProductFeatureActivity")] public class ProductFeatureActivity : ContentActivity,ViewSwitcher.IViewFactory,GestureDetector.IOnGestureListener { private GestureDetector gestureDetector = null; private ImageSwitcher imageSwitcher; private int[] imgs = new int[]{ Resource.Drawable.ImgProductFeature11, Resource.Drawable.ImgProductFeature12, Resource.Drawable.ImgProductFeature13 }; private int currentPosition; protected override void OnCreate (Bundle bundle) { base.OnCreate (bundle); // Create your application here SetContent (Resource.Layout.ProductFeature); gestureDetector = new GestureDetector(this); var productId = Intent.GetStringExtra ("ProductId"); SetTitle ("产品特色"); imageSwitcher = FindViewById<ImageSwitcher> (Resource.Id.SwitcherProductFeature); currentPosition = 0; imageSwitcher.SetFactory (this); imageSwitcher.SetImageResource (Resource.Drawable.ImgProductFeature11); } public View MakeView(){ ImageView img = new ImageView (this); img.SetBackgroundColor (Android.Graphics.Color.Transparent); img.SetScaleType (ImageView.ScaleType.Center); return img; } public override bool OnTouchEvent(MotionEvent e) { return gestureDetector.OnTouchEvent(e); } public bool OnFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if (e2.GetX() - e1.GetX() > 100) { currentPosition--; if (currentPosition < 0) currentPosition = imgs.Length - 1; imageSwitcher.SetInAnimation (this, Resource.Animation.LeftIn); imageSwitcher.SetOutAnimation (this, Resource.Animation.RightOut); imageSwitcher.SetImageResource (imgs [currentPosition]); } else if (e2.GetX() - e1.GetX() < -100) { currentPosition++; if (currentPosition > imgs.Length - 1) currentPosition = 0; imageSwitcher.SetInAnimation (this, Resource.Animation.RightIn); imageSwitcher.SetOutAnimation (this, Resource.Animation.LeftOut); imageSwitcher.SetImageResource (imgs [currentPosition]); } return true; } public bool OnDown(MotionEvent e) { return false; } public void OnLongPress(MotionEvent e) { } public bool OnScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { return false; } public void OnShowPress(MotionEvent e) { } public bool OnSingleTapUp(MotionEvent e) { return false; } } }
如上代码所示,主要的地方时为ImageSwithcher设定Factory,声明MakeView方法,并根据需要设定具体手势判断方法。
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