xamarin C# 安卓实现 ListView 放大缩小
翻译自java示例https://raw.githubusercontent.com/Xjasz/AndroidZoomableViewGroup/master/ZoomListView.java
using Android.App;
using Android.Widget;
using Android.OS;
using Android.Views;
using System.Collections.Generic;
using Android.Net;
using Android.Graphics;
using System.Net;
using Android.Content;
using Android.Util;
using Java.Lang; namespace App1
{
[Activity(Label = "App1", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle); // Set our view from the "main" layout resource
SetContentView (Resource.Layout.Main); var listView1 = FindViewById<ListView>(Resource.Id.listView1);
var rows = new List<RowItem>();
rows.Add(new RowItem { URL = "http://192.168.0.50:8001/OMS/tempimage/c152fd1f-ef44-42a6-96fb-3b4894ab8004636499813730162442.gif" });
rows.Add(new RowItem { URL = "http://192.168.0.50:8001/OMS/tempimage/9e8a1d81-7211-4c1f-bc5c-b7193c12a92c636499813730162442.gif" });
rows.Add(new RowItem { URL = "http://192.168.0.50:8001/OMS/tempimage/6f0eca83-7b5e-4e9e-999c-3ef88e277117636499813730162442.gif" });
listView1.Adapter = new ListViewRowAdapter(this, rows);
}
} public class MyListView : ListView
{
private MyListViewParameter ParameterInfo = new MyListViewParameter();
private ScaleGestureDetector ScaleDetector { get; set; } public MyListView(Context context)
:base(context)
{
this.ScaleDetector = new ScaleGestureDetector(context, new ScaleListener(ParameterInfo, this));
}
public MyListView(Context context, IAttributeSet attrs)
:base(context,attrs)
{
this.ScaleDetector = new ScaleGestureDetector(context, new ScaleListener(ParameterInfo, this));
}
public MyListView(Context context, IAttributeSet attrs, int defStyleAttr)
:base(context,attrs,defStyleAttr)
{
this.ScaleDetector = new ScaleGestureDetector(context, new ScaleListener(ParameterInfo, this));
}
public MyListView(Context context, IAttributeSet attrs, int defStyleAttr, int defStyleRes)
:base(context,attrs,defStyleAttr,defStyleRes)
{
this.ScaleDetector = new ScaleGestureDetector(context, new ScaleListener(ParameterInfo, this));
} protected override void OnMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
this.ParameterInfo.Width = MeasureSpec.GetSize(widthMeasureSpec);
this.ParameterInfo.Height = MeasureSpec.GetSize(heightMeasureSpec);
base.OnMeasure(widthMeasureSpec, heightMeasureSpec);
} public override bool OnTouchEvent(MotionEvent ev)
{
var result = base.OnTouchEvent(ev);
var action = ev.Action;
this.ScaleDetector.OnTouchEvent(ev);
switch (action)
{
case MotionEventActions.Down:
{
float x = ev.GetX();
float y = ev.GetY(); this.ParameterInfo.LastTouchX = x;
this.ParameterInfo.LastTouchY = y; this.ParameterInfo.ActivePointerId = ev.GetPointerId();
break;
} case MotionEventActions.Move:
{
int pointerIndex = ev.FindPointerIndex(this.ParameterInfo.ActivePointerId);
float x = ev.GetX(pointerIndex);
float y = ev.GetY(pointerIndex);
float dx = x - this.ParameterInfo.LastTouchX;
float dy = y - this.ParameterInfo.LastTouchY; this.ParameterInfo.PosX += dx;
this.ParameterInfo.PosY += dy; if (this.ParameterInfo.PosX > 0.0f)
this.ParameterInfo.PosX = 0.0f;
else if (this.ParameterInfo.PosX < this.ParameterInfo.MaxWidth)
this.ParameterInfo.PosX = this.ParameterInfo.MaxWidth; if (this.ParameterInfo.PosY > 0.0f)
this.ParameterInfo.PosY = 0.0f;
else if (this.ParameterInfo.PosY < this.ParameterInfo.MaxHeight)
this.ParameterInfo.PosY = this.ParameterInfo.MaxHeight; this.ParameterInfo.LastTouchX = x;
this.ParameterInfo.LastTouchY = y; this.Invalidate();
break;
} case MotionEventActions.Up:
{
this.ParameterInfo.ActivePointerId = this.ParameterInfo.INVALID_POINTER_ID;
break;
} case MotionEventActions.Cancel:
{
this.ParameterInfo.ActivePointerId = this.ParameterInfo.INVALID_POINTER_ID;
break;
} case MotionEventActions.PointerUp:
{
int pointerIndex = ((int)action & (int)MotionEventActions.PointerIndexMask) >> (int)MotionEventActions.PointerIndexShift;
int pointerId = ev.GetPointerId(pointerIndex);
if (pointerId == this.ParameterInfo.ActivePointerId)
{
int newPointerIndex = pointerIndex == ? : ;
this.ParameterInfo.LastTouchX = ev.GetX(newPointerIndex);
this.ParameterInfo.LastTouchY = ev.GetY(newPointerIndex);
this.ParameterInfo.ActivePointerId = ev.GetPointerId(newPointerIndex);
}
break;
}
} return true;
} protected override void OnDraw(Canvas canvas)
{
base.OnDraw(canvas);
canvas.Save(SaveFlags.Matrix);
canvas.Translate(this.ParameterInfo.PosX, this.ParameterInfo.PosY);
canvas.Scale(this.ParameterInfo.ScaleFactor, this.ParameterInfo.ScaleFactor);
canvas.Restore(); } protected override void DispatchDraw(Canvas canvas)
{
canvas.Save(SaveFlags.Matrix);
if (this.ParameterInfo.ScaleFactor == 1.0f)
{
this.ParameterInfo.PosX = 0.0f;
this.ParameterInfo.PosY = 0.0f;
}
canvas.Translate(this.ParameterInfo.PosX, this.ParameterInfo.PosY);
canvas.Scale(this.ParameterInfo.ScaleFactor, this.ParameterInfo.ScaleFactor);
base.DispatchDraw(canvas);
canvas.Restore();
this.Invalidate();
} public class MyListViewParameter
{
public MyListViewParameter()
{
this.INVALID_POINTER_ID = -;
this.ActivePointerId = -;
this.ScaleFactor = 1.0f;
this.MaxWidth = 0.0f;
this.MaxHeight = 0.0f;
} public int INVALID_POINTER_ID { get; private set; }
public int ActivePointerId { get; set; }
public float ScaleFactor { get; set; }
public float MaxWidth { get; set; }
public float MaxHeight { get; set; }
public float LastTouchX { get; set; }
public float LastTouchY { get; set; }
public float PosX { get; set; }
public float PosY { get; set; }
public float Width { get; set; }
public float Height { get; set; }
} private class ScaleListener : ScaleGestureDetector.SimpleOnScaleGestureListener
{
private MyListViewParameter ParameterInfo { get; set; }
private ListView MyListView { get; set; } public ScaleListener(MyListViewParameter pi,ListView lv)
{
this.ParameterInfo = pi;
this.MyListView = lv;
} public override bool OnScale(ScaleGestureDetector detector)
{
this.ParameterInfo.ScaleFactor *= detector.ScaleFactor;
this.ParameterInfo.ScaleFactor = Math.Max(1.0f, Math.Min(this.ParameterInfo.ScaleFactor, 3.0f));
this.ParameterInfo.MaxWidth = this.ParameterInfo.Width - (this.ParameterInfo.Width * this.ParameterInfo.ScaleFactor);
this.ParameterInfo.MaxHeight = this.ParameterInfo.Height - (this.ParameterInfo.Height * this.ParameterInfo.ScaleFactor);
this.MyListView.Invalidate();
return true;
}
}
} public class RowItem
{
public string URL { get; set; }
} public class ListViewRowAdapter : BaseAdapter<RowItem>
{
List<RowItem> items;
Activity context;
public ListViewRowAdapter(Activity context, List<RowItem> items)
: base()
{
this.context = context;
this.items = items;
}
public override long GetItemId(int position)
{
return position;
}
public override RowItem this[int position]
{
get { return items[position]; }
}
public override int Count
{
get { return items.Count; }
} /// <summary>
/// 下载图片
/// </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 > )
{
imageBitmap = BitmapFactory.DecodeByteArray(imageBytes, , imageBytes.Length);
}
} return imageBitmap;
}
public override View GetView(int position, View convertView, ViewGroup parent)
{
var item = items[position];
View view = convertView;
if (view == null) // no view to re-use, create new
view = context.LayoutInflater.Inflate(Resource.Layout.ListViewRow, null);
var url = Uri.Parse(item.URL);
view.FindViewById<ImageView>(Resource.Id.Image1).SetImageBitmap(GetImageBitmapFromUrl(item.URL));
return view;
}
}
}
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