android - 如何在 ViewPager 中为 ImageView 设置不同的动画

Question

https://github.com/anitaa1990/OnboardingSample 我想在 ViewPager 的 ImageView 上使用 ZoomOut 转换动画。只有 ImageView 应该有 ZoomOut 动画，ViewPager 的其他元素应该有默认动画。

Answer 1

在您的 Activity 中。 主要代码在ZoomOutPageTransformer看transformPage()方法。 (如果它回答你的问号作为答案。谢谢)

public class ScreenSlidePagerActivity extends FragmentActivity {
/**
 * The number of pages (wizard steps) to show in this demo.
 */
private static final int NUM_PAGES = 5;

/**
 * The pager widget, which handles animation and allows swiping horizontally to access previous
 * and next wizard steps.
 */
private ViewPager mPager;

/**
 * The pager adapter, which provides the pages to the view pager widget.
 */
private PagerAdapter mPagerAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_screen_slide);

    // Instantiate a ViewPager and a PagerAdapter.
    mPager = (ViewPager) findViewById(R.id.pager);
    mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
    mPager.setAdapter(mPagerAdapter);
    // watch and understand what this code does
    mPager.setPageTransformer(true, new ZoomOutPageTransformer());
}

@Override
public void onBackPressed() {
    if (mPager.getCurrentItem() == 0) {
        // If the user is currently looking at the first step, allow the system to handle the
        // Back button. This calls finish() on this activity and pops the back stack.
        super.onBackPressed();
    } else {
        // Otherwise, select the previous step.
        mPager.setCurrentItem(mPager.getCurrentItem() - 1);
    }
}

/**
 * A simple pager adapter that represents 5 ScreenSlidePageFragment objects, in
 * sequence.
 */
private class ScreenSlidePagerAdapter extends FragmentStatePagerAdapter {
    public ScreenSlidePagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        // return your fragment here
        return new ScreenSlidePageFragment();
    }

    @Override
    public int getCount() {
        return NUM_PAGES;
    }
}

这是你的 ZoomOutPager 类

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

public void transformPage(View CurentView, float position) {
    ImageView view = (ImageView)CurrentView.findViewById(// the id of the image view you would like)
    int pageWidth = view.getWidth();
    int pageHeight = view.getHeight();

    if (position < -1) { // [-Infinity,-1)
        // This page is way off-screen to the left.
        view.setAlpha(0);

    } else if (position <= 1) { // [-1,1]
        // Modify the default slide transition to shrink the page as well
        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);
        }

        // Scale the page down (between MIN_SCALE and 1)
        view.setScaleX(scaleFactor);
        view.setScaleY(scaleFactor);

        // Fade the page relative to its size.
        view.setAlpha(MIN_ALPHA +
                (scaleFactor - MIN_SCALE) /
                (1 - MIN_SCALE) * (1 - MIN_ALPHA));

    } else { // (1,+Infinity]
        // This page is way off-screen to the right.
        view.setAlpha(0);
    }
}

主要代码在ZoomOutPageTransformer看transformPage()方法