Android ViewPager未跳转到半屏幕

我试图实现的是，用户将打开查看页面的第一页，并且查看页面将像弹簧一样反弹到第二页的一半，然后反弹到第一页，表明有更多页面可滚动。在我的代码中，它只显示下半页。它工作得很好。但是反弹的动画不起作用

private int animFactor;
private ValueAnimator animator = new ValueAnimator();
AnimatorSet set = new AnimatorSet();
// private Animation animation1=  new TranslateAnimation()

private void animateViewPager(final ViewPager pager, final int offset, final int delay) {

    if (!animator.isRunning()) {
        animator.removeAllUpdateListeners();
        animator.removeAllListeners();
        //Set animation
        animator.setIntValues(0, -offset);
        animator.setDuration(delay);
        animator.setRepeatCount(1);
        animator.setRepeatMode(ValueAnimator.RESTART);
        animator.setInterpolator(new BounceInterpolator());
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            public void onAnimationUpdate(ValueAnimator animation) {
                Integer value = animFactor * (Integer) animation.getAnimatedValue();
                if (!pager.isFakeDragging()) {
                    pager.beginFakeDrag();
                }
                pager.fakeDragBy(value);
            }
        });
        animator.addListener(new AnimatorListenerAdapter() {

            @Override
            public void onAnimationStart(Animator animation) {
                animFactor = 1;
            }

            @Override
            public void onAnimationEnd(Animator animation) {
                pager.endFakeDrag();
            }

            @Override
            public void onAnimationRepeat(Animator animation) {
                animFactor = -1;
            }
        });
        set.play(animator);
        set.start();
    }
}

并使用这种方式调用此方法

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);

    if (hasFocus) {
        Handler handler = new Handler();

        final Runnable r = new Runnable() {
            public void run() {
                if (articleDetailPager.getCurrentItem() >= 0) {
                    Context context = ArticleDetailActivity.this;
                    String filename = "Init";
                    SharedPreferences stats;
                    stats = context.getSharedPreferences(filename, 0);
                    int appOpen = stats.getInt("appOpen", 0);

                    if (appOpen == 0) {
                        animateViewPager(articleDetailPager, 20, 300);

                        appOpen += 1;
                        SharedPreferences.Editor editor = stats.edit();
                        editor.putInt("appOpen", appOpen);
                        editor.commit();
                    }
                }

            }
        };

        handler.postDelayed(r, 1000);

    }
}

---

我得到了一个解决方案，我们可以用动画课来做这个。

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);

    if (hasFocus) {
        Handler handler = new Handler();

        final Runnable r = new Runnable() {
            public void run() {
                if (articleDetailPager.getCurrentItem() >= 0) {
                    Context context = ArticleDetailActivity.this;
                    String filename = "Init";
                    SharedPreferences stats;
                    stats = context.getSharedPreferences(filename, 0);
                    int appOpen = stats.getInt("appOpen", 0);

                    if (appOpen == 0) {
                        animateViewPager(articleDetailPager, 20, 300);

                        appOpen += 1;
                        SharedPreferences.Editor editor = stats.edit();
                        editor.putInt("appOpen", appOpen);
                        editor.commit();
                    }
                }

            }
        };

        handler.postDelayed(r, 1000);

    }
}