我正在开发一款适用于Android的Mono应用程序。无法击败'内存不足'异常
我一直在努力解决过去几天内存不足的问题,并开始失去希望!
我有一个ListView显示200到600个项目的任何东西。这些项目由位图缩略图和一些文本组成。
我异步使用的AsyncTask位图解码,这里是代码:
public class BitmapWorkerTask : AsyncTask
{
private WeakReference imageViewReference;
public string thisURL = "";
private int sampleSize = 0;
private int reqHeight = 0;
private int reqWidht = 0;
public BitmapWorkerTask(ImageView imageView, int pSampleSize, int pReqWidth, int pReqHeight)
{
//_____________________________________________________________________
// Use a WeakReference to ensure the ImageView can be garbage collected
imageViewReference = new WeakReference(imageView);
reqHeight = pReqHeight;
reqWidht = pReqWidth;
sampleSize = pSampleSize;
}
protected override Java.Lang.Object DoInBackground(params Java.Lang.Object[] @params)
{
string strUrl = @params[0].ToString();
try
{
return DecodeSampleBitmapFromStream(strUrl, reqWidht, reqHeight);
}
catch (Exception ex)
{
return null;
}
}
protected override void OnPostExecute(Java.Lang.Object result)
{
base.OnPostExecute(result);
if (IsCancelled)
{
result = null;
Log.Debug("TT", "OnPostExecute - Task Cancelled");
}
else
{
Bitmap bmpResult = result as Bitmap;
if (imageViewReference != null && bmpResult != null)
{
ImageView view = imageViewReference.Target as ImageView;
if (view != null)
{
view.SetImageBitmap(bmpResult);
}
}
}
}
public static int CalculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight)
{
//_____________________________
// Raw height and width of image
int height = options.OutHeight;
int width = options.OutWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth)
{
if (width > height)
{
inSampleSize = (int)Math.Round((float)height/(float)reqHeight);
}
else
{
inSampleSize = (int)Math.Round((float)width/(float)reqWidth);
}
}
return inSampleSize;
}
public static Bitmap DecodeSampleBitmapFromStream(string URL, int reqWidth, int reqHeight)
{
URL url = new URL(URL);
try
{
//______________________________________________________________
// First decode with inJustDecodeBounds=true to check dimensions
BitmapFactory.Options options = new BitmapFactory.Options();
options.InJustDecodeBounds = true;
BitmapFactory.DecodeStream(url.OpenConnection().InputStream, null, options);
//______________________
// Calculate inSampleSize
options.InSampleSize = CalculateInSampleSize(options, reqWidth, reqHeight);
//____________________________________
// Decode bitmap with inSampleSize set
options.InJustDecodeBounds = false;
return BitmapFactory.DecodeStream(url.OpenConnection().InputStream, null, options);
}
catch (Exception ex)
{
return null;
}
finally
{
url.Dispose();
}
}
我开始使用这种方法的列表GetView()函数此的AsyncTask:
public void loadBitmap(string url, ImageView imageView)
{
if (Common.cancelPotentialWork(url, imageView))
{
BitmapWorkerTask task = new BitmapWorkerTask(imageView, 2, 80,80);
AsyncDrawable asyncDrawable = new AsyncDrawable(null, null, task);
imageView.SetImageDrawable(asyncDrawable);
task.Execute(url);
}
}
一切按预期工作一段时间,但如果我不断滚动浏览列表,我最终会开始获取OutOfMemoryException
秒,并且应用程序崩溃。我对Android列表工作原理的理解是,它在屏幕上移动时会处理ListItem
视图,但感觉好像没有发生!
当我滚动列表时,感觉像所有这些位图解码都是出于什么原因被存储在内存中?我在这里可能会丢失什么,阻止了这些位图被丢弃?我可以在哪里实施致电Bitmap.Recycle()
以确保位图清除?
我做了一个测试,我在每次调用GetView时都调用了GC.Collect,这似乎确保我的内存使用情况相当一致,但我知道这不应该被需要,它会影响滚动性能。
为什么当我通过我的列表滚动而没有调用GC.Collect()
上午我没有看到那些垃圾收集消息表明系统实际上正在做例行收集?
任何帮助表示赞赏,我失去了代码的意志!
如果你能击败他们... ...购买更多的内存。 :) – gdoron