ViewPager/PagerAdapter 在第一页显示所有浏览量

Question

发生了什么事
我的应用程序中的 ViewPager 显示了我在第一页上实例化的所有视图。例如，如果我实例化两个视图，两个视图都显示在第一页，第二页只是空白。

显示问题的图像
正如您在下面看到的，第一页包含两个页面，第二页是空的。

我不明白为什么会这样。长期以来一直在努力解决这个问题。我尝试不将视图添加到适配器，添加视图并提供索引，不是膨胀它而是在适配器中创建 ImageView 等

我错过了什么？如有任何帮助，我们将不胜感激！

代码
Activity

[Activity(Label = "Foto's", ScreenOrientation = ScreenOrientation.Portrait)]
public class PicturesActivity : BaseActivity
{
    private ImagePagerAdapter _imageAdapter;
    private List<string> _filePaths;
    private ViewPager _viewPager;

    private const int _maxPictures = 5;

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);
        SetContentView(Resource.Layout.Pictures);
        _viewPager = FindViewById<ViewPager>(Resource.Id.ViewPager);
    }

    protected override void OnStart()
    {
        base.OnStart();

        _imageAdapter = new ImagePagerAdapter(this, _filePaths);
        _viewPager.Adapter = _imageAdapter;
        _viewPager.SetCurrentItem(0, false);
    }
}

PagerAdapter

internal class ImagePagerAdapter : PagerAdapter
{
    Activity _activity;
    List<string> _filePaths;

    public ImagePagerAdapter(Activity activity, List<string> filePaths)
    {
        _activity = activity;
        _filePaths = filePaths;
    }

    public override Java.Lang.Object InstantiateItem(ViewGroup container, int position)
    {
        var view = _activity.LayoutInflater.Inflate(Resource.Layout.PicturePageItem, container, false);
        var imageView = view.FindViewById<ImageView>(Resource.Id.ImageView);
        var filePath = _filePaths[position];

        DisplayMetrics metrics = _activity.Resources.DisplayMetrics;
        using (var bitmap = BitmapHelper.GetResizedBitmap(filePath, new Size(metrics.WidthPixels, metrics.HeightPixels)))
            imageView.SetImageBitmap(bitmap);

        container.JavaCast<ViewPager>().AddView(view);
        return view;
    }

    public override void DestroyItem(ViewGroup container, int position, Java.Lang.Object @object)
    {
        var view = (LinearLayout)@object;
        var imageView = view.FindViewById<ImageView>(Resource.Id.ImageView);

        if (imageView != null && imageView.Drawable != null)
        {
            imageView.Drawable.Dispose();
            imageView.SetImageBitmap(null);
        }

        container.JavaCast<ViewPager>().RemoveView(view);
    }

    public override int Count
    {
        get { return _filePaths.Count; }
    }

    public override bool IsViewFromObject(View view, Java.Lang.Object @object)
    {
        return view is LinearLayout;
    }
}

图片布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <android.support.v4.view.ViewPager
        android:id="@+id/ViewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

PicturePageItem布局（适配器页面布局）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
        android:id="@+id/ImageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerInside" />
</LinearLayout>

Answer 1

我认为问题可能出在您的方法 IsViewFromObject().

调用此方法是为了将 View 与 Key Object 进行比较。您的版本始终返回 true，因此 ViewPager 认为您的所有视图都在同一页面上。

您应该像这样修改您的代码：

public override bool IsViewFromObject(View view, Java.Lang.Object @object)
{
    return (object)view == @object;
}

详情请见：

http://developer.android.com/reference/android/support/v4/view/PagerAdapter.html

ViewPager/PagerAdapter 在第一页显示所有浏览量

ViewPager/PagerAdapter shows all views on first page

c#

android

android-viewpager

xamarin.android

android-pageradapter