自定义折叠工具栏平滑标题大小调整

android java xamarin android-collapsingtoolbarlayout

2022-09-03 15:35:09

我使用的是自定义折叠工具栏布局，它有一个标题和一个副标题。
我让标题在弯曲的路径上折叠和动画，但是标题的部分随着折叠而变小并不平滑。它以锯齿状的方式调整大小。
这是我负责移动和调整标题大小的行为：

public class ViewBehavior : CoordinatorLayout.Behavior
{
    private Context mContext;

    private int mStartMarginRight;
    private int mEndMargintRight;
    private int mMarginLeft;
    private int mStartMarginBottom;
    private bool isHide;
    private static float SCALE_MINIMUM = 0.5f;
    public ViewBehavior(Context context, IAttributeSet attrs)
    {
        mContext = context;
    }

    public override bool LayoutDependsOn(CoordinatorLayout parent, Java.Lang.Object child, View dependency)
    {
        return dependency is AppBarLayout;
    }

    public override bool OnDependentViewChanged(CoordinatorLayout parent, Java.Lang.Object child, View dependency)
    {
        ShouldInitProperties((child as HeaderView), dependency);

        int maxScroll = ((AppBarLayout)dependency).TotalScrollRange;
        float percentage = System.Math.Abs(dependency.GetY()) / (float)maxScroll;

        float childPosition = dependency.Height
                + dependency.GetY()
                - (child as View).Height
                - (getToolbarHeight() - (child as View).Height) * percentage / 2;


        childPosition = childPosition - mStartMarginBottom * (1f - percentage);

        CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams)(child as View).LayoutParameters;
        lp.RightMargin = (int)(100 * System.Math.Sin(percentage * System.Math.PI)) + mStartMarginRight / 2 + mEndMargintRight / 2;
        lp.LeftMargin = mMarginLeft;
        (child as View).LayoutParameters = lp;

        (child as View).SetY(childPosition);
        float x = (child as HeaderView).Title.TextSize;
        //Here is the algorithm for setting the text size
        (child as HeaderView).Title.SetTextSize(ComplexUnitType.Sp, 36 * (1 - percentage / 2));
        (child as HeaderView).SubTitle.SetTextSize(ComplexUnitType.Sp, 26 * (1 - percentage / 2));

        var toolbarTitleSize = (int)TypedValue.ApplyDimension(ComplexUnitType.Sp, 18, Application.Context.Resources.DisplayMetrics);
        var toolbarSubTitleSize = (int)TypedValue.ApplyDimension(ComplexUnitType.Sp, 16, Application.Context.Resources.DisplayMetrics);
        if ((child as HeaderView).Title.TextSize < toolbarTitleSize)
            (child as HeaderView).Title.SetTextSize(ComplexUnitType.Sp, 18);
        if ((child as HeaderView).SubTitle.TextSize < toolbarSubTitleSize)
            (child as HeaderView).SubTitle.SetTextSize(ComplexUnitType.Sp, 14);
        if (Build.VERSION.SdkInt < BuildVersionCodes.Lollipop)
        {
            if (isHide && percentage < 1)
            {
                (child as View).Visibility = ViewStates.Visible;
                isHide = false;
            }
            else if (!isHide && percentage == 1)
            {
                (child as View).Visibility = ViewStates.Gone;
                isHide = true;
            }
        }
        return true;
    }


    public void ShouldInitProperties(HeaderView child, View dependency)
    {

        if (mStartMarginRight == 0)
            mStartMarginRight = mContext.Resources.GetDimensionPixelOffset(Resource.Dimension.header_view_start_margin_right);

        if (mEndMargintRight == 0)
            mEndMargintRight = mContext.Resources.GetDimensionPixelOffset(Resource.Dimension.header_view_end_margin_right);

        if (mStartMarginBottom == 0)
            mStartMarginBottom = mContext.Resources.GetDimensionPixelOffset(Resource.Dimension.header_view_start_margin_bottom);

        if (mMarginLeft == 0)
            mMarginLeft = mContext.Resources.GetDimensionPixelOffset(Resource.Dimension.header_view_end_margin_left);

    }


    public int getToolbarHeight()
    {
        int result = 0;
        TypedValue tv = new TypedValue();
        if (mContext.Theme.ResolveAttribute(Android.Resource.Attribute.ActionBarSize, tv, true))
        {
            result = TypedValue.ComplexToDimensionPixelSize(tv.Data, mContext.Resources.DisplayMetrics);
        }
        return result;
    }
}

如何更改算法，使其以更平滑的方式调整大小？

编辑 - 视频：
https://youtu.be/j6LseSW6h1s

答案 1

正如其他人提到的，通过textSize在Android动画中不能很好地工作，因为它不够准确（它将十进制值四舍五入为整数）。

如果它满足了您的需求，您应该使用 / 属性执行动画，例如：scaleXscaleY

float scale = 1 - percentage * SCALE_MINIMUM;
(child as HeaderView).Title.SetScaleX(scale);
(child as HeaderView).Title.SetScaleY(scale);
(child as HeaderView).SubTitle.SetScaleX(scale);
(child as HeaderView).SubTitle.SetScaleY(scale);

答案 2

您遇到的问题是，即使您将比例计算为半值，它们也会成为 TextView 中的整数值。您应该在 TextView 的 Paint 类中同时启用LINEAR_TEXT_FLAG和SUBPIXEL_TEXT_FLAG标志，以实现平滑缩放和定位。

像这样：

yourTextView.Paint.SubpixelText = true;
yourTextView.Paint.LinearText = true;