viewPager小圆点

package com.example.administrator.myinfo;

import android.graphics.Color;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity {
    private ViewPager viewPager;
    private List<View> viewList = new ArrayList<>();
    private Indicator indicator;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = (ViewPager) findViewById(R.id.viewPager);
        indicator = (Indicator) findViewById(R.id.indicator);
        initData();


    }

    private void initData() {
        for (int i = 0; i < 8; i++) {
            View view = getLayoutInflater().inflate(R.layout.pager_item, null);
            ImageView ivPager = (ImageView) view.findViewById(R.id.ivPager);
            ivPager.setImageResource(R.drawable.banner01);
            viewList.add(view);
        }

        viewPager.setAdapter(new MyPagerAd());

        viewPager.addOnPageChangeListener(new MyPagerListner());
    }

    class MyPagerAd extends PagerAdapter {
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            position %= viewList.size();
            View view = viewList.get(position);
            container.addView(view);
            return view;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {

            position %= viewList.size();
            container.removeView(viewList.get(position));
        }

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

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

    class MyPagerListner implements ViewPager.OnPageChangeListener {
        /*
      positionOffset  便宜百分比
      positionOffsetPixels偏移量
         */
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            position %= viewList.size();
            indicator.setOffset(position, positionOffset,viewList.size());

        }

        @Override
        public void onPageSelected(int position) {

        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    }
}

package com.example.administrator.myinfo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by Administrator on 2016/12/8.
 */

public class Indicator extends View {
    /*
    前景色的小圆
     */
    private Paint forePaint;
    /*
   背景色的小圆
    */
    private Paint bgpPaint;
    private int number;//数量
    private int bedIus=20;//小圆的大小
    private float offset;    //移动的偏移量


    public void setOffset(int position, float positionOffset,int number) {
        offset = position * 3 * bedIus + positionOffset * 3 * bedIus;
        this.number=number;
        invalidate();//需要从新绘制
    }



    public Indicator(Context context, AttributeSet attrs) {
        super(context, attrs);
        initPaint();//初始化画笔
    }

    private void initPaint() {
        forePaint = new Paint();
        forePaint.setAntiAlias(true);
        forePaint.setStyle(Paint.Style.FILL);
        forePaint.setColor(Color.RED);
        forePaint.setStrokeWidth(2);

        bgpPaint = new Paint();
        bgpPaint.setAntiAlias(true);
        bgpPaint.setStyle(Paint.Style.STROKE);
        bgpPaint.setColor(Color.WHITE);
        bgpPaint.setStrokeWidth(2);
    }

    /*
    绘制试图
     */
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        for (int i = 0; i < number; i++) {
            canvas.drawCircle(60 + i * bedIus * 3, 60, bedIus, bgpPaint);
        }
        canvas.drawCircle(60 + offset, 60, bedIus, forePaint);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.administrator.myinfo.MainActivity">
    <com.example.administrator.myinfo.Indicator
        android:id="@+id/indicator"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/viewPager"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_marginRight="98dp"
        android:layout_marginEnd="98dp" />
    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="200dp">
    </android.support.v4.view.ViewPager>



</RelativeLayout>