ViewPager单页显示3个item

原文地址：https://github.com/hongyangAndroid/MagicViewPager/wiki

MagicViewPager

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>