當麻許的超技八

<?xml version="1.0" encoding="utf-8"?>

<GridView xmlns:android="http://schemas.android.com/apk/res/android"

    android:id="@+id/gridview"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:numColumns="2"

    android:verticalSpacing="2dp"

    android:horizontalSpacing="2dp"

    android:scrollbarStyle="insideOverlay"

    android:verticalScrollbarPosition="right"

    android:scrollbars="vertical" />

class ListDataAdapter : BaseAdapter<UserInfo>

   {

       /// <summary>

       /// 所有UserInof 的資料

       /// </summary>

       List<UserInfo> items;

       Activity context;

       //暫存圖片下載的任務

       ConcurrentDictionary<string, Task<byte[]>> faceCache = new ConcurrentDictionary<string, Task<byte[]>>();

       public ListDataAdapter(Activity context, List<UserInfo> items)

           : base()

       {

           this.context = context;

           this.items = items;

       }

       public override long GetItemId(int position)

       {

           return position;

       }

       public override UserInfo this[int position]

       {

           get { return items[position]; }

       }

       public override int Count

       {

           get { return items.Count; }

       }

       /// <summary>

       /// 系統會呼叫 並且render.

       /// </summary>

       /// <param name="position"></param>

       /// <param name="convertView"></param>

       /// <param name="parent"></param>

       /// <returns></returns>

       public override View GetView(int position, View convertView, ViewGroup parent)

       {

           var view = convertView;

           if (view == null)

           {

               //listitem1

               view = context.LayoutInflater.Inflate(Resource.Layout.listitem1, null);

           }

           Display display = context.WindowManager.DefaultDisplay;

           Point size = new Point();

           display.GetSize(size);

           RelativeLayout.LayoutParams parms = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MatchParent, (size.X - 10) / 2); //Width, Height

           view.LayoutParameters = parms;

           var item = items[position];

           var img = view.FindViewById<ImageView>(Resource.Id.img);

           var name = view.FindViewById<TextView>(Resource.Id.textView1);

           name.Text = item.Name;

           FetchImage(item.Thumb, view);

           return view;

       }

       void FetchImage(string url, Android.Views.View view)

       {

           var data = faceCache.GetOrAdd(url, u => Task.Run(() =>

           {

               var client = new WebClient();

               try

               {

                   return client.DownloadData(u);

               }

               catch

               {

                   return null;

               }

           }));

           if (data.IsCompleted && data.Result != null)

           {

               var imgUser = view.FindViewById<ImageView>(Resource.Id.img);

               var bmp = BitmapFactory.DecodeByteArray(data.Result, 0, data.Result.Length);

               bmp = ResizeBitmap(bmp);

               imgUser.SetImageBitmap(bmp);

               //imgUser.SetImageDrawable(new VignetteDrawable(bmp, withEffect: false));

               GC.Collect();

           }

           else

           {

               data.ContinueWith(t =>

               {

                   if (t.Result != null)

                   {

                       var bmp = BitmapFactory.DecodeByteArray(data.Result, 0, data.Result.Length);

                       bmp = ResizeBitmap(bmp);

                       context.RunOnUiThread(() =>

                       {

                           var avatar = view.FindViewById<ImageView>(Resource.Id.img);

                           avatar.SetImageBitmap(bmp);

                       });

                   }

               });

               GC.Collect();

           }

       }

       //縮圖

       Bitmap ResizeBitmap(Bitmap inputBitmap)

       {

           var size = (int)TypedValue.ApplyDimension(ComplexUnitType.Px, 500, context.Resources.DisplayMetrics);

           return Bitmap.CreateScaledBitmap(inputBitmap, size, size, true);

       }

       /// <summary>

       /// 因為圖片是網址，所以將其圖片download回來後轉為bitmap

       /// Get IamgeBitmap form url.

       /// code reference : http://forums.xamarin.com/discussion/4323/image-from-url-in-imageview

       /// </summary>

       /// <param name="url"></param>

       /// <returns></returns>

       private Bitmap GetImageBitmapFromUrl(string url)

       {

           Bitmap imageBitmap = null;

           using (var webClient = new WebClient())

           {

               var imageBytes = webClient.DownloadData(url);

               if (imageBytes != null && imageBytes.Length > 0)

               {

                   imageBitmap = BitmapFactory.DecodeByteArray(imageBytes, 0, imageBytes.Length);

               }

           }

           return imageBitmap;

       }

   }