使用PageViewer和LayoutPagerAdapter时的内存管理

我有一个欢迎活动，使用ViewPager和自定义LayoutPagerAdapter。问题是布局包含相当大的图像，将它们保存在内存中并不是理想的。

这就是为什么当OnDestroyItem被调用时，我回收它们的原因。

当我做回收时，它会破坏应用程序，基本上关闭虚拟机。

下面是LayoutPagerAdapter的代码。

public class LayoutPagerAdapter : PagerAdapter
    {
        Context m_context;
        readonly int[] m_slideLayoutResourceIds;
        public LayoutPagerAdapter(Context context, int[] slideLayoutResourceIds)
        {
            m_context = context;
            m_slideLayoutResourceIds = slideLayoutResourceIds;
        }
        public override Java.Lang.Object InstantiateItem(ViewGroup container, int position)
        {
            var inflater = LayoutInflater.From(m_context);
            var view = inflater.Inflate(m_slideLayoutResourceIds[position], container, false);
            container.AddView(view);
            return view;
        }
        public override void DestroyItem(ViewGroup container, int position, Java.Lang.Object objectValue)
        {
            var bitmapDrawable = (BitmapDrawable)((View)objectValue).FindViewById<ImageView>(Resource.Id.welcomeBackgroundImage).Drawable;
            bitmapDrawable.Bitmap.Recycle();
            container.RemoveView((View)objectValue);
        }
        #region implemented abstract members of PagerAdapter
        public override bool IsViewFromObject(View view, Java.Lang.Object objectValue)
        {
            return view == objectValue;
        }
        public override int Count
        {
            get
            {
                return m_slideLayoutResourceIds.Length;
            }
        }
        #endregion
    }

这一行进行得很好，但由于不允许我回滚并出于某种原因关闭了VM，从而破坏了应用程序。

var bitmapDrawable = (BitmapDrawable)((View)objectValue).FindViewById<ImageView>(Resource.Id.welcomeBackgroundImage).Drawable;
                bitmapDrawable.Bitmap.Recycle();

这里是完整的活动代码。

[Activity(MainLauncher = true, Label = "")]         
    public class WelcomeActivity : Activity
    {
        ViewPager m_welcomeViewPager;
        LayoutPagerAdapter m_layoutPagerAdapter;
        TextView m_welcomeSkipButton;
        CirclePageIndicator m_circlePageIndicator;
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Welcome);
            m_circlePageIndicator = FindViewById<CirclePageIndicator>(Resource.Id.welcomeCirclePageIndicator);
            m_welcomeSkipButton = FindViewById<TextView>(Resource.Id.welcomeSkipButton);
            m_welcomeViewPager = FindViewById<ViewPager>(Resource.Id.welcomeViewPager);
            m_layoutPagerAdapter = new LayoutPagerAdapter(this, 
                new []
                { 
                    Resource.Layout.welcome_slide_1, 
                    Resource.Layout.welcome_slide_2,
                    Resource.Layout.welcome_slide_3,
                    Resource.Layout.welcome_slide_4,
                    Resource.Layout.welcome_slide_5,
                    Resource.Layout.welcome_slide_6
                });
            m_welcomeViewPager.Adapter = m_layoutPagerAdapter;
            m_circlePageIndicator.SetViewPager(m_welcomeViewPager);
            m_circlePageIndicator.SetCurrentItem(0);
        }
        protected override void OnResume()
        {
            base.OnResume();
            m_welcomeSkipButton.Click += WelcomeSkipButtonClick;
        }
        void WelcomeSkipButtonClick(object sender, System.EventArgs e)
        {
            // TODO
        }
        protected override void OnPause()
        {
            base.OnPause();
            m_welcomeSkipButton.Click -= WelcomeSkipButtonClick;
        }
        protected override void OnDestroy()
        {
            base.OnDestroy();
            if (m_circlePageIndicator != null)
            {
                m_circlePageIndicator.Dispose();
                m_circlePageIndicator = null;
            }
            if (m_layoutPagerAdapter != null)
            {
                m_layoutPagerAdapter.Dispose();
                m_layoutPagerAdapter = null;
            }
            if (m_welcomeSkipButton != null)
            {
                m_welcomeSkipButton.Dispose();
                m_welcomeSkipButton = null;
            }
            if (m_welcomeViewPager != null)
            {
                m_welcomeViewPager.Dispose();
                m_welcomeViewPager = null;
            }
        }
    }

这是应用程序在滚动布局时的输出，然后VM关闭。

[dalvikvm-heap] Grow heap (frag case) to 24.469MB for 2810896-byte allocation
[dalvikvm-heap] Grow heap (frag case) to 30.500MB for 6324496-byte allocation
[dalvikvm-heap] Grow heap (frag case) to 24.487MB for 2810896-byte allocation
[dalvikvm-heap] Grow heap (frag case) to 30.517MB for 6324496-byte allocation
[dalvikvm-heap] Grow heap (frag case) to 25.001MB for 2810896-byte allocation
[dalvikvm-heap] Grow heap (frag case) to 31.032MB for 6324496-byte allocation
[AndroidRuntime] Shutting down VM

我希望应用程序简单地重新实例化布局，当我尝试回滚。为什么回收会阻止它呢?