Android实现单页显示3个Item的ViewPager炫酷切换效果

mViewPager.setPageMargin(20);//设置page间间距，自行根据需求设置
mViewPager.setOffscreenPageLimit(3);//>=3
mViewPager.setAdapter...//写法不变

//setPageTransformer 决定动画效果
mViewPager.setPageTransformer(true, new RotateDownPageTransformer());

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import android.os.Bundle;
import android.os.Handler;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

import com.zhy.magicviewpager.transformer.ScaleInTransformer;

import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {

  private ViewPager mViewPager;
  private PagerAdapter mAdapter;
  private LinearLayout dotLayout;
  private Timer timer;
  private Handler mHandler = new Handler();

  private int prePosition = 0;

  int[] imgRes = {R.drawable.a, R.drawable.b, R.drawable.c, R.drawable.d,
      R.drawable.e, R.drawable.f, R.drawable.g, R.drawable.h, R.drawable.i};

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

    mViewPager = (ViewPager) findViewById(R.id.viewpager);
    dotLayout = (LinearLayout) findViewById(R.id.dotLayout);

    initDots();

    mViewPager.setPageMargin(20);
    mViewPager.setOffscreenPageLimit(3);
    mViewPager.setAdapter(mAdapter = new PagerAdapter() {
      @Override
      public Object instantiateItem(ViewGroup container, int position) {
        ImageView view = new ImageView(MainActivity.this);
        view.setScaleType(ImageView.ScaleType.FIT_XY);
        view.setImageResource(imgRes[position % imgRes.length]);
        container.addView(view);
        return view;
      }

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

      @Override
      public int getCount() {
        return Integer.MAX_VALUE;
      }

      @Override
      public boolean isViewFromObject(View view, Object o) {
        return view == o;
      }
    });
    mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
      @Override
      public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

      }

      @Override
      public void onPageSelected(int position) {
        dotLayout.getChildAt(prePosition).setEnabled(false);
        dotLayout.getChildAt(position % imgRes.length).setEnabled(true);
        prePosition = position % imgRes.length;
      }

      @Override
      public void onPageScrollStateChanged(int state) {

      }
    });
    mViewPager.setPageTransformer(true, new ScaleInTransformer());
    if (null != timer) {
      timer.cancel();
    }
    timer = new Timer();
    timer.schedule(new TimerTask() {
      @Override
      public void run() {
        mHandler.post(new Runnable() {
          @Override
          public void run() {
            mViewPager.setCurrentItem(mViewPager.getCurrentItem() + 1);
          }
        });
      }
    }, 0, 1000);

  }

  private void initDots() {
    if (null != dotLayout) {
      dotLayout.removeAllViews();
    }
    for (int i = 0; i 

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