Android无限循环与自动播放ViewPager的简单实现(广告栏)

Posted 2022-12-03 冷不冷

之前写过一个简单的ViewPager指示器,但是只能够展示指定数量的内容,没有实现无限循环和自动播放功能,今天来完整的把这几个功能写一下吧.当然还是用到之前写的简单的ViewPager指示器,并做一些小修改,来配合无限循环和自动播放.

可参考之前写过的Android简单的ViewPager指示器

效果图如下:

一、简单分析

首先考虑一下无限循环怎么实现,按照之前写的,只是指定了数据源的内容,ViewPager创建了数据源长度的子项个数,可滑动范围比较小.这样就导致拉到最后一页时,无法继续滑动,或者处于第一页的时候,无法向前滑动等情况,所以在设置ViewPager子项数量时,不能设置为数据源的个数.要设置一个比较大的值,才能使ViewPager的可滑动范围比较大,然后通过动态的修改ViewPager的位置,来实现无限循环的效果.

接着考虑一下自动播放如何实现,自动播放,需要一个播放频率,每隔一段时间,去播放一次(也就是向后边滑动一页),这个用定时器Timer配合TimerTask就可以完成,每隔一定时间去执行一次.播放用Handler来做,在TimerTask中,发送一个消息,然后Handler接收到这个消息后,去做播放操作.当然方法有很多.

---

二、具体实现

通过分析,先来写一下适配器,定义一个比较大的数来规定ViewPager的项数:

    /**
     * 默认轮播个数
     */
    public static final int FAKE_BANNER_SIZE = 10000;

    @Override
    public int getCount() 
        return FAKE_BANNER_SIZE;
    

这样,ViewPager的滑动范围就不会受到限制,不过位置发生变化后,绑定数据时要对位置进行处理,不然会出现数据获取不到或者获取错误的问题,处理位置

    @Override
    public Object instantiateItem(ViewGroup container, int position) 
        View view = LayoutInflater.from(mContext).inflate(R.layout.banner_item, container, false);
        ImageView imageView = (ImageView) view.findViewById(R.id.iv_banner_item);
        // 获取当前显示位置
        position %= pictureList.size();
        imageView.setImageResource(pictureList.get(position));
        container.addView(view);
        return view;
    

对position进行取余操作,这样就可以获取到符合数据源取值范围的位置,从而得到想要获取展示的数据.

搞定了适配器,再来看一下之前写的简单指示器,如何做一下修改呢.
首先新加入一个变量,来控制是否用于无限循环的ViewPager

    /**
     * 是否是循环
     */
    private boolean isCirculate;

    public IndicatorView(Context context, AttributeSet attrs, int defStyleAttr) 
        super(context, attrs, defStyleAttr);
        // 获取自定义属性
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.IndicatorView);

        ...

        isCirculate = ta.getBoolean(R.styleable.IndicatorView_isCirculate, true);
        ta.recycle();
        // 初始化
        init();

    

接着对外提供一个新的设置ViewPager的方法,因为之前获取创建指示器个数的方法是获取ViewPager适配器中子项的个数,适配器已经做了修改,显然这个方法已经不再适用.想一下,指示器个数其实和数据源的个数是一致的,所以提供一个新的方法

    /**
     * 设置vp
     *
     * @param childViewCount 需要显示指示器的个数
     * @param viewpager      vp
     */
    public void setViewPager(int childViewCount, ViewPager viewpager) 
        if (null == viewpager) 
            return;
        
        if (null == viewpager.getAdapter()) 
            throw new IllegalStateException("ViewPager does not have adapter.");
        
        this.mViewPager = viewpager;
        this.mViewPager.addOnPageChangeListener(this);
        this.childViewCount = childViewCount;
        removeAllViews();
        invalidate();
    

然后在修改指示器显示时,对位置也需要进行处理,方式同适配器中的处理相同

    @Override
    public void onPageSelected(int position) 
        // 处理位置变化,防止指示器显示错误
        if (isCirculate && 0 != childViewCount) 
            position %= childViewCount;
        
        setIndicatorState(position);
        if (null != mListener) 
            mListener.onPageSelected(position);
        
    

这样ViewPager无限循环的问题基本就搞定了.下面来做下自动播放的
部分.打算通过定时器配合Handle来完成.很简单.直接贴下代码
在Activity中

    /**
     * 轮播图自动轮播消息
     */
    public static final int AUTOBANNER_CODE = 0X1001;
    /**
     * 当前轮播图位置
     */
    private int mBannerPosition;
    /**
     * 自动轮播计时器
     */
    private Timer timer = new Timer();
    /**
     * 自动轮播任务
     */
    private BannerTimerTask mBannerTimerTask;
    /**
     * 用户当前是否点击轮播图
     */
    private boolean mIsUserTouched = false;
    /**
     * 轮播图Handler
     */
    Handler bannerHandler = new Handler(new Handler.Callback() 
        @Override
        public boolean handleMessage(Message msg) 
            // 当用户点击时,不进行轮播
            if (!mIsUserTouched) 
                // 获取当前的位置
                mBannerPosition = mViewPager.getCurrentItem();
                // 更换轮播图
                mBannerPosition = (mBannerPosition + 1) % mBannerPagerAdapter.FAKE_BANNER_SIZE;
                mViewPager.setCurrentItem(mBannerPosition);
            
            return true;
        
    );

    /**
     * 开始轮播
     */
    private void startBannerTimer() 
        if (timer == null) 
            timer = new Timer();
        
        if (mBannerTimerTask != null) 
            mBannerTimerTask.cancel();
        
        mBannerTimerTask = new BannerTimerTask(bannerHandler);
        if (timer != null && mBannerTimerTask != null) 
            // 循环5秒执行
            timer.schedule(mBannerTimerTask, 5000, 5000);
        
    

    public class BannerTimerTask extends TimerTask 
    /**
     * handler
     */
    Handler handler;

    public BannerTimerTask(Handler handler) 
        super();
        this.handler = handler;
    

    @Override
    public void run() 
               handler.sendEmptyMessage(MainActivity.AUTOBANNER_CODE);
    

创建一个定时器,每隔5秒钟发送一个消息,Handle接收到消息后,改变ViewPager的位置.不难理解.

这样效果就达到了,一个简单的广告栏效果也就实现了.当然还可以再进一步去做一些封装和优化,这里就不做了,最重要的其实就是把位置搞清楚,其他的问题并不难.

---

三、完整代码

IndicatorView:

package com.example.junweiliu.simpleindicatorview;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ImageView;
import android.widget.LinearLayout;

/**
 * 轮播图圆形指示器
 * Created by junweiliu on 16/6/15.
 */
public class IndicatorView extends LinearLayout implements ViewPager.OnPageChangeListener 
    /**
     * 需要创建的指示器个数
     */
    private int childViewCount = 0;
    /**
     * 设置圆点间margin
     */
    private int mInterval;
    /**
     * 当前选中的位置
     */
    private int mCurrentPostion = 0;
    /**
     * 普通显示的图片
     */
    private Bitmap normalBp;
    /**
     * 选中时显示的图片
     */
    private Bitmap selectBp;
    /**
     * 设置的轮播图Vp
     */
    private ViewPager mViewPager;
    /**
     * 指示器单项宽度
     */
    private int mWidth;
    /**
     * 指示器单项高度
     */
    private int mHeight;
    /**
     * 圆点半径
     */
    private int mRadius;
    /**
     * 普通状态圆点颜色
     */
    private int normalColor;
    /**
     * 选中状态圆点颜色
     */
    private int selectColor;
    /**
     * 是否是循环
     */
    private boolean isCirculate;


    /**
     * 对外提供ViewPager的回调接口
     */
    interface OnPageChangeListener 

        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels);

        public void onPageSelected(int position);

        public void onPageScrollStateChanged(int state);

    

    /**
     * 回调接口
     */
    private OnPageChangeListener mListener;

    /**
     * 设置回调
     *
     * @param listener
     */
    public void setOnPageChangeListener(OnPageChangeListener listener) 
        this.mListener = listener;
    

    public IndicatorView(Context context) 
        this(context, null);
    

    public IndicatorView(Context context, AttributeSet attrs) 
        this(context, attrs, 0);
    

    public IndicatorView(Context context, AttributeSet attrs, int defStyleAttr) 
        super(context, attrs, defStyleAttr);
        // 获取自定义属性
        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.IndicatorView);
        normalBp = drawableToBitamp(ta.getDrawable(R.styleable.IndicatorView_normalDrawable));
        selectBp = drawableToBitamp(ta.getDrawable(R.styleable.IndicatorView_selectDrawable));
        mInterval = ta.getDimensionPixelOffset(R.styleable.IndicatorView_indicatorInterval, 6);
        normalColor = ta.getColor(R.styleable.IndicatorView_normalColor, Color.GRAY);
        selectColor = ta.getColor(R.styleable.IndicatorView_selectColor, Color.RED);
        mRadius = ta.getInteger(R.styleable.IndicatorView_indicatorRadius, 6);
        isCirculate = ta.getBoolean(R.styleable.IndicatorView_isCirculate, true);
        ta.recycle();
        // 初始化
        init();

    

    /**
     * 初始化数据
     */
    private void init() 
        // 处理自定义属性
        if (null == normalBp) 
            normalBp = makeIndicatorBp(normalColor);
        
        if (null == selectBp) 
            selectBp = makeIndicatorBp(selectColor);
        
        mWidth = normalBp.getWidth();
        mHeight = normalBp.getWidth();
    

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) 
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
        int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
        // 如果是wrap_content设置为图片宽高,否则设置为父容器宽高
        setMeasuredDimension((widthMode == MeasureSpec.EXACTLY) ? sizeWidth : (mWidth + mInterval) * childViewCount
                , (heightMode == MeasureSpec.EXACTLY) ? sizeHeight
                        : mHeight);
    

    /**
     * 重绘
     *
     * @param canvas
     */
    @Override
    protected void dispatchDraw(Canvas canvas) 
        // 创建指示器圆点
        if (getChildCount() < childViewCount && getChildCount() == 0) 
            for (int i = 0; i < childViewCount; i++) 
                addView(makeIndicatorItem());
            
            // 设置默认选中指示器
            setIndicatorState(mCurrentPostion);
        
        super.dispatchDraw(canvas);
    


    /**
     * 设置Vp
     *
     * @param viewpager
     */
    public void setViewPager(ViewPager viewpager) 
        if (null == viewpager) 
            return;
        
        if (null == viewpager.getAdapter()) 
            throw new IllegalStateException("ViewPager does not have adapter.");
        

        this.mViewPager = viewpager;
        this.mViewPager.addOnPageChangeListener(this);
        this.childViewCount = viewpager.getAdapter().getCount();
        invalidate();
    

    /**
     * 设置Vp
     *
     * @param viewpager
     * @param currposition 当前选中的位置
     */
    public void setViewPager(ViewPager viewpager, int currposition) 
        if (null == viewpager) 
            return;
        
        if (null == viewpager.getAdapter()) 
            throw new IllegalStateException("ViewPager does not have adapter.");
        
        this.mViewPager = viewpager;
        this.mViewPager.addOnPageChangeListener(this);
        this.childViewCount = viewpager.getAdapter().getCount();
        this.mCurrentPostion = currposition;
        invalidate();
    

    /**
     * 设置vp
     *
     * @param childViewCount 需要显示指示器的个数
     * @param viewpager      vp
     */
    public void setViewPager(int childViewCount, ViewPager viewpager) 
        if (null == viewpager) 
            return;
        
        if (null == viewpager.getAdapter()) 
            throw new IllegalStateException("ViewPager does not have adapter.");
        
        this.mViewPager = viewpager;
        this.mViewPager.addOnPageChangeListener(this);
        this.childViewCount = childViewCount;
        removeAllViews();
        invalidate();
    

    /**
     * 创建指示器
     *
     * @return
     */
    private View makeIndicatorItem() 
        ImageView iv = new ImageView(getContext());
        LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
        lp.width = normalBp.getWidth();
        lp.height = normalBp.getHeight();
        lp.rightMargin = mInterval;
        iv.setImageBitmap(normalBp);
        iv.setLayoutParams(lp);
        return iv;
    


    /**
     * 创建圆点指示器图片
     *
     * @param color 创建不同颜色的指示器项
     * @return
     */
    private Bitmap makeIndicatorBp(int color) 
        Bitmap normalBp = Bitmap.createBitmap(mRadius * 2, mRadius * 2,
                Bitmap.Config.ARGB_8888);
        Paint paint = new Paint();
        paint.setAntiAlias(true);
        paint.setColor(color);
        Canvas canvas = new Canvas(normalBp);
        canvas.drawCircle(mRadius, mRadius, mRadius, paint);
        return normalBp;
    


    /**
     * drawable转bitmap
     *
     * @param drawable
     * @return
     */
    private Bitmap drawableToBitamp(Drawable drawable) 
        if (null == drawable) 
            return null;
        
        if (drawable instanceof BitmapDrawable) 
            BitmapDrawable bd = (BitmapDrawable) drawable;
            return bd.getBitmap();
        
        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();
        Bitmap bitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        drawable.setBounds(0, 0, w, h);
        drawable.draw(canvas);
        return bitmap;
    

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) 
        if (null != mListener) 
            mListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
        
    

    @Override
    public void onPageSelected(int position) 
        if (isCirculate && 0 != childViewCount) 
            position %= childViewCount;
        
        setIndicatorState(position);
        if (null != mListener) 
            mListener.onPageSelected(position);
        
    

    @Override
    public void onPageScrollStateChanged(int state) 
        if (null != mListener) 
            mListener.onPageScrollStateChanged(state);
        
    

    /**
     * 设置指示器的状态
     *
     * @param position
     */
    public void setIndicatorState(int position) 
        for (int i = 0; i < getChildCount(); i++) 
            if (i == position)
                ((ImageView) getChildAt(i)).setImageBitmap(selectBp);
            else
                ((ImageView) getChildAt(i)).setImageBitmap(normalBp);
        
    

适配器BannerPagerAdapter

package com.example.junweiliu.simpleindicatorview;

import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

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

/**
 * Created by junweiliu on 16/6/14.
 * VP适配器
 */
public class BannerPagerAdapter extends PagerAdapter 
    /**
     * 上下文
     */
    private Context mContext;
    /**
     * 图像列表
     */
    private List<Integer> pictureList = new ArrayList<>();
    /**
     * 默认轮播个数
     */
    public static final int FAKE_BANNER_SIZE = 10000;

    public BannerPagerAdapter(Context context, List<Integer> pictureList) 
        this.mContext = context;
        this.pictureList = pictureList;
    

    @Override
    public int getCount() 
        return FAKE_BANNER_SIZE;
    

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

    @Override
    public Object instantiateItem(ViewGroup container, int position) 
        View view = LayoutInflater.from(mContext).inflate(R.layout.banner_item, container, false);
        ImageView imageView = (ImageView) view.findViewById(R.id.iv_banner_item);
        // 获取当前显示位置
        position %= pictureList.size();
        imageView.setImageResource(pictureList.get(position));
        container.addView(view);
        return view;
    


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

MainActivity

package com.example.junweiliu.simpleindicatorview;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.view.View;

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

public class MainActivity extends AppCompatActivity 
    /**
     * 轮播图
     */
    private ViewPager mViewPager;
    /**
     * 指示器
     */
    private IndicatorView mIndicatorView;
    /**
     * 适配器
     */
    private BannerPagerAdapter mBannerPagerAdapter;
    /**
     * 图片资源
     */
    private List<Integer> pictureList = new ArrayList<>();
    /**
     * 轮播图自动轮播消息
     */
    public static final int AUTOBANNER_CODE = 0X1001;
    /**
     * 当前轮播图位置
     */
    private int mBannerPosition;
    /**
     * 自动轮播计时器
     */
    private Timer timer = new Timer();
    /**
     * 自动轮播任务
     */
    private BannerTimerTask mBannerTimerTask;
    /**
     * 用户当前是否点击轮播图
     */
    private boolean mIsUserTouched = false;
    /**
     * 轮播图Handler
     */
    Handler bannerHandler = new Handler(new Handler.Callback() 
        @Override
        public boolean handleMessage(Message msg) 
            // 当用户点击时,不进行轮播
            if (!mIsUserTouched) 
                // 获取当前的位置
                mBannerPosition = mViewPager.getCurrentItem();
                // 更换轮播图
                mBannerPosition = (mBannerPosition + 1) % mBannerPagerAdapter.FAKE_BANNER_SIZE;
                mViewPager.setCurrentItem(mBannerPosition);
            
            return true;
        
    );


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

    /**
     * 初始化数据
     */
    private void initDatas() 
        pictureList.add(R.drawable.pic_one);
        pictureList.add(R.drawable.pic_two);
        pictureList.add(R.drawable.pic_three);
        pictureList.add(R.drawable.pic_one);
        pictureList.add(R.drawable.pic_two);
        pictureList.add(R.drawable.pic_three);
    

    /**
     * 初始化控件
     */
    private void initView() 
        mViewPager = (ViewPager) findViewById(R.id.vp_banner);
        mIndicatorView = (IndicatorView) findViewById(R.id.idv_banner);
        mBannerPagerAdapter = new BannerPagerAdapter(this, pictureList);
        mViewPager.setAdapter(mBannerPagerAdapter);
        mIndicatorView.setViewPager(pictureList.size(), mViewPager);
        // 设置默认起始位置,使开始可以向左边滑动
        mViewPager.setCurrentItem(pictureList.size() * 100);
        mIndicatorView.setOnPageChangeListener(new IndicatorView.OnPageChangeListener() 
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) 

            

            @Override
            public void onPageSelected(int position) 

            

            @Override
            public void onPageScrollStateChanged(int state) 

            
        );
        mViewPager.setOnTouchListener(new View.OnTouchListener() 

            @Override
            public boolean onTouch(View v, MotionEvent event) 
                int action = event.getAction();
                if (action == MotionEvent.ACTION_DOWN
                        || action == MotionEvent.ACTION_MOVE) 
                    mIsUserTouched = true;
                 else if (action == MotionEvent.ACTION_UP) 
                    mIsUserTouched = false;
                
                return false;
            
        );
        startBannerTimer();
    

    /**
     * 开始轮播
     */
    private void startBannerTimer() 
        if (timer == null) 
            timer = new Timer();
        
        if (mBannerTimerTask != null) 
            mBannerTimerTask.cancel();
        
        mBannerTimerTask = new BannerTimerTask(bannerHandler);
        if (timer != null && mBannerTimerTask != null) 
            // 循环5秒执行
            timer.schedule(mBannerTimerTask, 5000, 5000);
        
    


    /**
     * 销毁时,关闭任务,防止异常
     */
    @Override
    public void onDestroy() 
        super.onDestroy();
        if (null != mBannerTimerTask) 
            mBannerTimerTask.cancel();
            mBannerTimerTask = null;
        
    

BannerTimerTask

package com.example.junweiliu.simpleindicatorview;

import android.os.Handler;

import java.util.TimerTask;

/**
 * Created by junweiliu on 16/6/15.
 */
public class BannerTimerTask extends TimerTask 
    /**
     * handler
     */
    Handler handler;

    public BannerTimerTask(Handler handler) 
        super();
        this.handler = handler;
    

    @Override
    public void run() 
        handler.sendEmptyMessage(MainActivity.AUTOBANNER_CODE);
    

attr

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <!--IndicatorView相关-->
    <!--普通指示器图片-->
    <attr name="normalDrawable" format="reference"/>
    <!--选中指示器图片-->
    <attr name="selectDrawable" format="reference"/>
    <!--指示器间隔-->
    <attr name="indicatorInterval" format="dimension"/>
    <!--普通指示器颜色-->
    <attr name="normalColor" format="color"/>
    <!--选中指示器颜色-->
    <attr name="selectColor" format="color"/>
    <!--圆点弧度-->
    <attr name="indicatorRadius" format="integer"/>
    <!--是否是循环-->
    <attr name="isCirculate" format="boolean"/>
    <declare-styleable name="IndicatorView">
        <attr name="normalDrawable"/>
        <attr name="selectDrawable"/>
        <attr name="indicatorInterval"/>
        <attr name="normalColor"/>
        <attr name="selectColor"/>
        <attr name="indicatorRadius"/>
        <attr name="isCirculate"/>
    </declare-styleable>
</resources>

activity_main

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:idv="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="225dp"
    tools:context="com.example.junweiliu.simpleindicatorview.MainActivity">
    <!--轮播图-->
    <android.support.v4.view.ViewPager
        android:id="@+id/vp_banner"
        android:layout_width="match_parent"
        android:layout_height="225dp"
        >
    </android.support.v4.view.ViewPager>
    <!--指示器-->
    <com.example.junweiliu.simpleindicatorview.IndicatorView
        android:id="@+id/idv_banner"
        android:layout_width="match_parent"
        android:layout_height="10dp"
        android:layout_alignParentBottom="true"
        android:gravity="center_horizontal"
        android:layout_marginTop="20dp"
        idv:indicatorInterval="10dp"
        idv:isCirculate="true"
        idv:normalDrawable="@mipmap/oval_indicator_grey"
        idv:selectDrawable="@mipmap/oval_indicator_green">
    </com.example.junweiliu.simpleindicatorview.IndicatorView>

</RelativeLayout>

banner_item

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:orientation="vertical">

    <ImageView
        android:id="@+id/iv_banner_item"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitXY"
        />

</LinearLayout>

源码地址