android - 在 api 级别 8 中替代 setAlpha

Question

我正在开发一个可以在 Froyo 和 JellyBean 上运行的应用程序。我有一个扩展 PageTransformer 的类，如下所示:

import android.support.v4.view.ViewPager.PageTransformer;
import android.view.View;

public class ZoomOutPageTransformer implements PageTransformer {
    private static float MIN_SCALE = 0.85f;
    private static float MIN_ALPHA = 0.5f;

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();
        int pageHeight = view.getHeight();

        if (position < -1) { 
            view.setAlpha(0);

        } else if (position <= 1) { 
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            float vertMargin = pageHeight * (1 - scaleFactor) / 2;
            float horzMargin = pageWidth * (1 - scaleFactor) / 2;
            if (position < 0) {
                view.setTranslationX(horzMargin - vertMargin / 2);
            } else {
                view.setTranslationX(-horzMargin + vertMargin / 2);
            }


            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);


            view.setAlpha(MIN_ALPHA +
                    (scaleFactor - MIN_SCALE) /
                    (1 - MIN_SCALE) * (1 - MIN_ALPHA));

        } else { 
            view.setAlpha(0);
        }
    }
}

问题是，在这个类中编写的方法是在 API level 11 中添加的，而我的 sdk 版本最低为 API level 8。以下是 API 级别 11 中添加的方法:

1. setAlpha()
2. setTranslationX()
3. setScaleX()
4. setScaleY()

有什么办法可以解决这个问题？

Answer 1

所以，这里有一些解决方案:

---

setAlphaAnimation ... API 级别 1

AlphaAnimation alpha = new AlphaAnimation(0.7F, 0.7F);
alpha.setDuration(0); // Make animation instant
alpha.setFillAfter(true); // Tell it to persist after the animation ends
view.startAnimation(alpha);

---

setAlpha INT -> 从 API LEVEL 1 -> 在 16 中弃用

Drawable background = localLinLayout.getBackground();
background.setAlpha(180); //255 is max (visible)

---

setAlpha FLOAT -> API 级别 11+ ->

---

setImageAlpha -> API LEVEL 16+(仅用于 ImageViews)