我正在尝试创建一个应用程序来使用 Monotouch 和 Zxing 的 C# 端口读取 QR 码，但遇到了内存问题。当应用程序处理捕获的屏幕帧时，应用程序会收到内存警告，然后关闭。我删除了对 Zxing 的调用，以追踪内存问题的根源，并且只需循环捕获屏幕图像即可重现该问题。
这是代码：
using System;
using System.Drawing;
using System.Collections.Generic;
using System.Threading;
using MonoTouch.UIKit;
using MonoTouch.Foundation;
using MonoTouch.CoreGraphics;
using com.google.zxing;
using com.google.zxing.common;
using System.Collections;
using MonoTouch.AudioToolbox;
using iOS_Client.Utilities;
namespace iOS_Client.Controllers
{
public class CameraOverLayView : UIView
{
private Thread _thread;
private CameraViewController _parentViewController;
private Hashtable hints;
private static com.google.zxing.MultiFormatReader _multiFormatReader = null;
private static RectangleF picFrame = new RectangleF(0, 146, 320, 157);
private static UIImage _theScreenImage = null;
public CameraOverLayView(CameraViewController parentController) : base()
{
Initialize();
_parentViewController = parentController;
}
private void Initialize()
{
}
private bool Worker()
{
Result resultb = null;
if(DeviceHardware.Version == DeviceHardware.HardwareVersion.iPhone4
|| DeviceHardware.Version == DeviceHardware.HardwareVersion.iPhone4S)
{
picFrame = new RectangleF(0, 146*2, 320*2, 157*2);
}
if(hints==null)
{
var list = new ArrayList();
list.Add (com.google.zxing.BarcodeFormat.QR_CODE);
hints = new Hashtable();
hints.Add(com.google.zxing.DecodeHintType.POSSIBLE_FORMATS, list);
hints.Add (com.google.zxing.DecodeHintType.TRY_HARDER, true);
}
if(_multiFormatReader == null)
{
_multiFormatReader = new com.google.zxing.MultiFormatReader();
}
using (var screenImage = CGImage.ScreenImage.WithImageInRect(picFrame))
{
using (_theScreenImage = UIImage.FromImage(screenImage))
{
Bitmap srcbitmap = new System.Drawing.Bitmap(_theScreenImage);
LuminanceSource source = null;
BinaryBitmap bitmap = null;
try {
source = new RGBLuminanceSource(srcbitmap, screenImage.Width, screenImage.Height);
bitmap = new BinaryBitmap(new HybridBinarizer(source));
try {
_multiFormatReader.Hints = hints;
resultb = null;
//_multiFormatReader.decodeWithState(bitmap);
if(resultb != null && resultb.Text!=null)
{
InvokeOnMainThread( () => _parentViewController.BarCodeScanned(resultb));
}
}
catch (ReaderException re)
{
//continue;
}
} catch (Exception ex) {
Console.WriteLine(ex.Message);
}
finally {
if(bitmap!=null)
bitmap = null;
if(source!=null)
source = null;
if(srcbitmap!=null)
{
srcbitmap.Dispose();
srcbitmap = null;
}
}
}
}
return resultb != null;
}
public void StartWorker()
{
if(_thread==null)
{
_thread = new Thread(()=> {
bool result = false;
while (result == false)
{
result = Worker();
Thread.Sleep (67);
}
});
}
_thread.Start();
}
public void StopWorker()
{
if(_thread!=null)
{
_thread.Abort();
_thread = null;
}
//Just in case
_multiFormatReader = null;
hints = null;
}
protected override void Dispose(bool disposing)
{
StopWorker();
base.Dispose(disposing);
}
}
}
有趣的是我看了一下http://blog.reinforce-lab.com/2010/02/monotouchvideocapturinghowto.html http://blog.reinforce-lab.com/2010/02/monotouchvideocapturinghowto.html尝试看看其他人如何捕获和处理视频，此代码与我的代码相同，大约 40 秒后退出并出现内存警告。
希望 QR 码能在 40 秒内被扫描，但我不确定内存是否会被释放，因此在扫描许多代码后可能会出现问题。无论哪种方式，都应该可以连续捕获视频源而不会出现内存问题，对吗？
这有点违反直觉，但每次调用 ScreenImage 属性时都会创建一个新的 CGImage 实例，因此您还必须对该对象调用 Dispose：
using (var img = CGImage.ScreenImage) {
using (var screenImage = img.WithImageInRect(picFrame))
{
}
}
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