Android开发之ViewPager实现轮播图（轮播广告）效果的自定义View

最近开发中需要做一个类似京东首页那样的广告轮播效果，于是采用ViewPager自己自定义了一个轮播图效果的View。

主要原理就是利用定时任务器定时切换ViewPager的页面。

效果图如下：

主页面布局实现如下：

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v4.view.ViewPager
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:padding="5dp"
        android:gravity="center"
        android:orientation="horizontal">

        <View
            android:id="@+id/v_dot1"
            android:layout_width="8dp"
            android:layout_height="8dp"
            android:background="@drawable/dot_black" />

        <View
            android:id="@+id/v_dot2"
            android:layout_width="8dp"
            android:layout_height="8dp"
            android:layout_marginLeft="5dp"
            android:background="@drawable/dot_white" />

        <View
            android:id="@+id/v_dot3"
            android:layout_width="8dp"
            android:layout_height="8dp"
            android:layout_marginLeft="5dp"
            android:background="@drawable/dot_white" />

        <View
            android:id="@+id/v_dot4"
            android:layout_width="8dp"
            android:layout_height="8dp"
            android:layout_marginLeft="5dp"
            android:background="@drawable/dot_white" />

        <View
            android:id="@+id/v_dot5"
            android:layout_width="8dp"
            android:layout_height="8dp"
            android:layout_marginLeft="5dp"
            android:background="@drawable/dot_white" />

    </LinearLayout>
</RelativeLayout>

轮播效果视图类代码实现如下：

package com.czm.customview;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.os.Handler;
import android.os.Message;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v4.view.ViewPager.OnPageChangeListener;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.ImageView.ScaleType;

/**
 * ViewPager实现的轮播图广告自定义视图，如京东首页的广告轮播图效果；
 * 既支持自动轮播页面也支持手势滑动切换页面
 * @author caizhiming
 *
 */

public class SlideShowView extends FrameLayout {

    //轮播图图片数量
    private final static int IMAGE_COUNT = 5;
    //自动轮播的时间间隔
    private final static int TIME_INTERVAL = 5;
    //自动轮播启用开关
    private final static boolean isAutoPlay = true; 

    //自定义轮播图的资源ID
    private int[] imagesResIds;
    //放轮播图片的ImageView 的list
    private List<ImageView> imageViewsList;
    //放圆点的View的list
    private List<View> dotViewsList;

    private ViewPager viewPager;
    //当前轮播页
    private int currentItem  = 0;
    //定时任务
    private ScheduledExecutorService scheduledExecutorService;
    //Handler
    private Handler handler = new Handler(){

        @Override
        public void handleMessage(Message msg) {
            // TODO Auto-generated method stub
            super.handleMessage(msg);
            viewPager.setCurrentItem(currentItem);
        }

    };

    public SlideShowView(Context context) {
        this(context,null);
        // TODO Auto-generated constructor stub
    }
    public SlideShowView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
        // TODO Auto-generated constructor stub
    }
    public SlideShowView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
        initData();
        initUI(context);
        if(isAutoPlay){
            startPlay();
        }

    }
    /**
     * 开始轮播图切换
     */
    private void startPlay(){
        scheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
        scheduledExecutorService.scheduleAtFixedRate(new SlideShowTask(), 1, 4, TimeUnit.SECONDS);
    }
    /**
     * 停止轮播图切换
     */
    private void stopPlay(){
        scheduledExecutorService.shutdown();
    }
    /**
     * 初始化相关Data
     */
    private void initData(){
        imagesResIds = new int[]{
                R.drawable.pic1,
                R.drawable.pic2,
                R.drawable.pic3,
                R.drawable.pic4,
                R.drawable.pic5,

        };
        imageViewsList = new ArrayList<ImageView>();
        dotViewsList = new ArrayList<View>();

    }
    /**
     * 初始化Views等UI
     */
    private void initUI(Context context){
        LayoutInflater.from(context).inflate(R.layout.layout_slideshow, this, true);
        for(int imageID : imagesResIds){
            ImageView view =  new ImageView(context);
            view.setImageResource(imageID);
            view.setScaleType(ScaleType.FIT_XY);
            imageViewsList.add(view);
        }
        dotViewsList.add(findViewById(R.id.v_dot1));
        dotViewsList.add(findViewById(R.id.v_dot2));
        dotViewsList.add(findViewById(R.id.v_dot3));
        dotViewsList.add(findViewById(R.id.v_dot4));
        dotViewsList.add(findViewById(R.id.v_dot5));

        viewPager = (ViewPager) findViewById(R.id.viewPager);
        viewPager.setFocusable(true);

        viewPager.setAdapter(new MyPagerAdapter());
        viewPager.setOnPageChangeListener(new MyPageChangeListener());
    }

    /**
     * 填充ViewPager的页面适配器
     * @author caizhiming
     */
    private class MyPagerAdapter  extends PagerAdapter{

        @Override
        public void destroyItem(View container, int position, Object object) {
            // TODO Auto-generated method stub
            //((ViewPag.er)container).removeView((View)object);
            ((ViewPager)container).removeView(imageViewsList.get(position));
        }

        @Override
        public Object instantiateItem(View container, int position) {
            // TODO Auto-generated method stub
            ((ViewPager)container).addView(imageViewsList.get(position));
            return imageViewsList.get(position);
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return imageViewsList.size();
        }

        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            // TODO Auto-generated method stub
            return arg0 == arg1;
        }
        @Override
        public void restoreState(Parcelable arg0, ClassLoader arg1) {
            // TODO Auto-generated method stub

        }

        @Override
        public Parcelable saveState() {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        public void startUpdate(View arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void finishUpdate(View arg0) {
            // TODO Auto-generated method stub

        }

    }
    /**
     * ViewPager的监听器
     * 当ViewPager中页面的状态发生改变时调用
     * @author caizhiming
     */
    private class MyPageChangeListener implements OnPageChangeListener{

        boolean isAutoPlay = false;

        @Override
        public void onPageScrollStateChanged(int arg0) {
            // TODO Auto-generated method stub
            switch (arg0) {
            case 1:// 手势滑动，空闲中
                isAutoPlay = false;
                break;
            case 2:// 界面切换中
                isAutoPlay = true;
                break;
            case 0:// 滑动结束，即切换完毕或者加载完毕
                // 当前为最后一张，此时从右向左滑，则切换到第一张
                if (viewPager.getCurrentItem() == viewPager.getAdapter().getCount() - 1 && !isAutoPlay) {
                    viewPager.setCurrentItem(0);
                }
                // 当前为第一张，此时从左向右滑，则切换到最后一张
                else if (viewPager.getCurrentItem() == 0 && !isAutoPlay) {
                    viewPager.setCurrentItem(viewPager.getAdapter().getCount() - 1);
                }
                break;
        }
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onPageSelected(int pos) {
            // TODO Auto-generated method stub

            currentItem = pos;
            for(int i=0;i < dotViewsList.size();i++){
                if(i == pos){
                    ((View)dotViewsList.get(pos)).setBackgroundResource(R.drawable.dot_black);
                }else {
                    ((View)dotViewsList.get(i)).setBackgroundResource(R.drawable.dot_white);
                }
            }
        }

    }

    /**
     *执行轮播图切换任务
     *@author caizhiming
     */
    private class SlideShowTask implements Runnable{

        @Override
        public void run() {
            // TODO Auto-generated method stub
            synchronized (viewPager) {
                currentItem = (currentItem+1)%imageViewsList.size();
                handler.obtainMessage().sendToTarget();
            }
        }

    }
    /**
     * 销毁ImageView资源，回收内存
     * @author caizhiming
     */
    private void destoryBitmaps() {

        for (int i = 0; i < IMAGE_COUNT; i++) {
            ImageView imageView = imageViewsList.get(i);
            Drawable drawable = imageView.getDrawable();
            if (drawable != null) {
                //解除drawable对view的引用
                drawable.setCallback(null);
            }
        }
    }

}

如何引用上面自定义的轮播图效果视图View呢？其实很引用普通的View类似，实现如下：

<com.czm.customview.SlideShowView
                android:id="@+id/slideshowView"
                android:layout_width="335dp"
                android:layout_height="120dp"
                android:layout_centerHorizontal="true"
                />