Android实现单页显示3个Item的ViewPager炫酷切换效果

单页显示3个Item的ViewPager炫酷切换效果，适用于Banner等。

效果图

Rotate Y

Rotate Down

Rotate Up

Alpha

ScaleIn

ScaleIn + Alpha + Rotate Down

使用

###（1）引入

compile `com.zhy:magic-viewpager:1.0.1`

###（2）示例

布局文件

<FrameLayout
  android:layout_width="match_parent"
  android:layout_height="160dp"
  android:clipChildren="false"
  android:layout_centerInParent="true"
  android:background="#aadc71ff"
  >
  <android.support.v4.view.ViewPager
    android:id="@+id/id_viewpager"
    android:layout_width="match_parent"
    android:layout_marginLeft="60dp"
    android:clipChildren="false"
    android:layout_marginRight="60dp"
    android:layout_height="120dp"
    android:layout_gravity="center"
    >
  </android.support.v4.view.ViewPager>

</FrameLayout>

注意外层android:layout_centerInParent="true".（貌似其实没什么影响）

编码

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());

##目前可选动画

AlphaPageTransformer
RotateDownPageTransformer
RotateUpPageTransformer
RotateYTransformer
NonPageTransformer
ScaleInTransformer

动画间可以自由组合，例如：

mViewPager.setPageTransformer(true,new RotateDownPageTransformer(new AlphaPageTransformer(new ScaleInTransformer())));

需求：

1.一个页面显示三个item

2.viewpager无限循环

3.定时滑动

4.长条形小点

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:background="#aadc71ff"
  android:clipChildren="false"
  tools:context="com.example.administrator.banner2.MainActivity">

  <android.support.v4.view.ViewPager
    android:id="@+id/viewpager"
    android:layout_width="match_parent"
    android:layout_height="150dp"
    android:layout_gravity="center"
    android:layout_marginBottom="10dp"
    android:layout_marginLeft="30dp"
    android:layout_marginRight="30dp"
    android:layout_marginTop="10dp"
    android:clipChildren="false"></android.support.v4.view.ViewPager>

  <LinearLayout
    android:id="@+id/dotLayout"
    android:layout_width="match_parent"
    android:layout_height="10dp"
    android:layout_gravity="bottom"
    android:layout_marginBottom="10dp"
    android:gravity="center"
    android:orientation="horizontal"></LinearLayout>

</FrameLayout>

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 < imgRes.length; i++) {
      ImageView dot = new ImageView(this);
      dot.setEnabled(false);
      dot.setImageResource(R.drawable.dot);
      LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
      params.leftMargin = 10;
      dot.setLayoutParams(params);
      dotLayout.addView(dot);
    }
    dotLayout.getChildAt(0).setEnabled(true);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_enabled="true">
    <shape android:shape="rectangle">
      <size android:width="15dp" android:height="3dp"></size>
      <corners android:radius="10dp" />
      <solid android:color="#ff0000" />
    </shape>
  </item>
  <item android:state_enabled="false">
    <shape android:shape="rectangle">
      <size android:width="15dp" android:height="3dp"></size>
      <corners android:radius="10dp" />
      <solid android:color="#ffffff" />
    </shape>
  </item>
</selector>

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