第四课 Gallery的使用

直接上代码

1.Layout——Main.axml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:minWidth="25px"
    android:minHeight="25px">
    <TextView
        android:text="@string/Welcome"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/textView1" />
    <Gallery
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/gallery1" />
</LinearLayout>

2.Activity1.cs

using System;

using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Database;
using Android.Provider;

namespace GalleryViewDemo
{
    [Activity(Label = "Gallery View Sample", MainLauncher = true, Icon = "@drawable/icon")]
    public class GalleryViewSample : Activity
    {

        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);
            CreateGallery();

        }


        private void CreateGallery()
        {
            Gallery g = this.FindViewById<Gallery>(Resource.Id.gallery1);
            g.Adapter = new ImageAdapter(this);
        }
    }
}

3.ImageAdapter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.Database;
using Android.Provider;

namespace GalleryViewDemo
{
    public class ImageAdapter : BaseAdapter
    {
        Context _Context;
        ICursor _ImageCursor;
        protected ICursor ImageCursor
        {
            get
            {
                if (_ImageCursor == null)
                {
                    _ImageCursor = GetImageCursor();
                }
                return _ImageCursor;
            }
            set
            {
                _ImageCursor = value;
            }
        }
        public ImageAdapter(Context c)
        {
            _Context = c;
        }
        private ICursor GetImageCursor()
        {
            string[] Projection = { MediaStore.Images.Thumbnails.ImageId };
            var ImageCursor = ((Activity)_Context).ManagedQuery(MediaStore.Images.Thumbnails.ExternalContentUri,
                Projection, null, null, null);
            return ImageCursor;
        }
        public override int Count
        {
            get { return ImageCursor.Count; }
        }

        public override Java.Lang.Object GetItem(int position)
        {
            return position;
        }

        public override long GetItemId(int position)
        {
            ImageCursor.MoveToPosition(position);
            var ImageId = ImageCursor.GetString(0);
            return position;
        }

        public override View GetView(int position, View convertView, ViewGroup parent)
        {
            if (convertView == null)
            {
                ImageView ReturnView = new ImageView(_Context);
                ImageCursor.MoveToPosition(position);

                var ImageId = ImageCursor.GetString(0);
                ReturnView.SetImageURI(Android.Net.Uri.WithAppendedPath(MediaStore.Images.Thumbnails.ExternalContentUri, ImageId));
                ReturnView.SetScaleType(ImageView.ScaleType.CenterCrop);
                return ReturnView;
            }
            else
            {
                return(ImageView) convertView;
            }
        }
    }
}

在模拟器中,先下载了两幅图片,运行成功。

在手机上运行失败，尚不知道原因，求解。