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>

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

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。