ViewPager 添加动画效果

Viewpager 添加动画效果
* 第一种动画效果 分别对应 各自的 DepthPageTransformer
* 第2中动画效果 分别对应 各自的 ZoomOutPageTransformer
*
* 以上两个动画的效果直接在 Android API文档下面直接复制的源码
* file:///D:/adt-64/sdk/docs/training/animation/screen-slide.html

---

主界面 Activity

package com.gaoo.viewpageranin;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageView;

import java.util.ArrayList;
import java.util.List;

/**
 * Viewpager 添加动画效果
 * 第一种动画效果 分别对应 各自的 DepthPageTransformer
 * 第2中动画效果 分别对应 各自的 ZoomOutPageTransformer
 *
 * 以上两个动画的效果直接在 Android API文档下面直接复制的源码 
 * file:///D:/adt-64/sdk/docs/training/animation/screen-slide.html
 */
public class MainActivity extends Activity {
    ViewPager id_viewpager;
    //图片资源
    private int[] mImgIds = new int[]{R.drawable.shuangta, R.drawable.shui, R.drawable.xiangbi};
    private List<ImageView> mImages = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        initView();


        //为 Viewpager 添加动画效果 (3.0 版本以上有用)

        //第一种动画效果 分别对应 各自的 DepthPageTransformer
        //id_viewpager.setPageTransformer(true,new DepthPageTransformer()); // 茂松叠加缩小显示动画效果

        //第2中动画效果 分别对应 各自的 ZoomOutPageTransformer
        id_viewpager.setPageTransformer(true,new ZoomOutPageTransformer()); // 平移缩放显示动画效果


        //VIewpager 设置adapter
        id_viewpager.setAdapter(new PagerAdapter() {
            @Override
            public int getCount() {
                return mImgIds.length;
            }

            @Override
            public Object instantiateItem(ViewGroup container, int position) {
                ImageView imageView = new ImageView(MainActivity.this);
                imageView.setImageResource(mImgIds[position]);
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);

                container.addView(imageView);

                mImages.add(imageView);

                return imageView;

            }

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

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

    private void initView() {
        id_viewpager = (ViewPager) findViewById(R.id.id_viewpager);
    }
}

---

以下两种不同的动画效果

DepthPageTransformer

package com.gaoo.viewpageranin;

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

public class DepthPageTransformer implements ViewPager.PageTransformer {
    private static float MIN_SCALE = 0.75f;

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

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

        } else if (position <= 0) { // [-1,0]
            // Use the default slide transition when moving to the left page
            view.setAlpha(1);
            view.setTranslationX(0);
            view.setScaleX(1);
            view.setScaleY(1);

        } else if (position <= 1) { // (0,1]
            // Fade the page out.
            view.setAlpha(1 - position);

            // Counteract the default slide transition
            view.setTranslationX(pageWidth * -position);

            // Scale the page down (between MIN_SCALE and 1)
            float scaleFactor = MIN_SCALE
                    + (1 - MIN_SCALE) * (1 - Math.abs(position));
            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);

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

---

ZoomOutPageTransformer

package com.gaoo.viewpageranin;

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

/**
 * ViewPager 缩小翻页动画效果
 */
public class ZoomOutPageTransformer implements ViewPager.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) { // [-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);
        }
    }
}