偷看ViewPager下一页动画

PagerPeepAnimation.java

/**
 * 偷看ViewPager下一页动画
 */
public class PagerPeepAnimation extends Animation {

    private ViewPager viewPager;
    private AnimationListener wrapperAnimationListener;
    private int peepWidth;

    public PagerPeepAnimation(final ViewPager viewPager) {
        this.viewPager = viewPager;
        this.peepWidth = (int) ((10 * viewPager.getResources().getDisplayMetrics().density) + 0.5);
        super.setAnimationListener(new AnimationListener() {
            @Override
            public void onAnimationStart(Animation animation) {
                viewPager.beginFakeDrag();
                if (wrapperAnimationListener != null) {
                    wrapperAnimationListener.onAnimationStart(animation);
                }
            }

            @Override
            public void onAnimationRepeat(Animation animation) {
                if (wrapperAnimationListener != null) {
                    wrapperAnimationListener.onAnimationRepeat(animation);
                }
            }

            @Override
            public void onAnimationEnd(Animation animation) {
                if (viewPager.isFakeDragging()) {
                    viewPager.endFakeDrag();
                }
                if (wrapperAnimationListener != null) {
                    wrapperAnimationListener.onAnimationEnd(animation);
                }
            }
        });
    }

    @SuppressWarnings("unused")
    public void setPeepWidth(int peepWidth) {
        this.peepWidth = peepWidth;
    }

    @Override
    public void setAnimationListener(AnimationListener listener) {
        this.wrapperAnimationListener = listener;
    }

    @Override
    public void initialize(int width, int height, int parentWidth, int parentHeight) {
        super.initialize(width, height, parentWidth, parentHeight);
        setDuration(500);
        setInterpolator(new LinearInterpolator());
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        if (viewPager == null || !viewPager.isFakeDragging()) {
            return;
        }

        float preResult = (float) ((Math.atan(10 * (interpolatedTime - 0.5)) + Math.PI / 2f) * 2f / Math.PI);
        if (preResult <= 1) {
            viewPager.fakeDragBy(-peepWidth * preResult);
        } else {
            viewPager.fakeDragBy(peepWidth * (preResult - 2));
        }
    }
}