ViewPager

效果：

image.png

布局中viewPager必须设置android:clipChildren="false",同时它的父控件也必须设置，且viewpager需要设置与左边及右边的间隔:android:layout_marginLeft、android:layout_marginRight
·布局如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:clipChildren="false"
    android:layout_height="match_parent">


    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:clipChildren="false"
        android:background="@android:color/white"
        android:layout_marginLeft="80dp"
        android:layout_marginRight="80dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

java中
设置缩放及透明效果主要在ScaleTransformer中，其中Viewpager需要设置page的间隔及预加载页数

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ui_pager);
        ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
        pager.setPageMargin(8);
        pager.setOffscreenPageLimit(5);
        pager.setPageTransformer(false,new ScaleTransformer());
        pager.setAdapter(new MyAdapter(pager));
    }

     class MyAdapter extends PagerAdapter{

         ViewPager mViewPager;

         public MyAdapter(ViewPager viewPager){
            mViewPager = viewPager;
         }

        @Override
        public int getCount() {
            return 5;
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view==object;
        }

        @Override
        public Object instantiateItem(ViewGroup container, final int position) {
            ImageView imageView = new ImageView(PagerActivity.this);
            imageView.setImageResource(R.drawable.a);
            imageView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    mViewPager.setCurrentItem(position);
                    Toast.makeText(PagerActivity.this,"position:"+position,Toast.LENGTH_SHORT).show();
                }
            });
            container.addView(imageView);
            return imageView;
        }

         @Override
         public void destroyItem(ViewGroup container, int position, Object object) {
             container.removeView((View) object);
         }
     }

public class ScaleTransformer extends AlphaTransformer{

    private float MIN_ALPHA = 0.5f;
    private float MIN_SCALE = 0.70f;
    /**
     * position取值特点：
     * 假设页面从0～1，则：
     * 第一个页面position变化为[0,-1]
     * 第二个页面position变化为[1,0]
     */
    @Override
    public void transformPage(View page, float position) {
        //缩放效果
        if (position < -1 || position > 1) {
            page.setAlpha(MIN_ALPHA);
            page.setScaleX(MIN_SCALE);
            page.setScaleY(MIN_SCALE);
        } else if (position <= 1) { // [-1,1]
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            if (position < 0) {
                float scaleX = 1 + 0.3f * position;
                page.setScaleX(scaleX);
                page.setScaleY(scaleX);
            } else {
                float scaleX = 1 - 0.3f * position;
                page.setScaleX(scaleX);
                page.setScaleY(scaleX);
            }
            page.setAlpha(MIN_ALPHA + (scaleFactor - MIN_SCALE) / (1 - MIN_SCALE) * (1 - MIN_ALPHA));
        }
    }
}