Android简单的ViewPager指示器

Posted 2020-07-26 冷不冷

平常写项目在写介绍页,或者一些简单的轮播图的时候,总会需要搭配指示器来标明当前在什么位置.写法也比较多,刚好自己需要用到,以前用的一些方法,用起来需要配置好多东西,有些大材小用,所以来简单的实现一个.效果图如下:

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一、简单分析与代码实现

因为比较简单,所以就简单的分析一下:
1)每一个指示器项有两种状态,普通状态和选中状态,所以需要准备两种状态的图片.
2)指示器的个数和ViewPager的页数要保持一致.可以引用ViewPager对象,来获取ViewPager的页数.从而创建指示器.
3)指示器要跟随ViewPager的移动来动态的改变状态.同样可以引用ViewPager对象,对ViewPager进行监听,处理指示器的状态改变.

有了思路,就来具体实现一下,提出一些自定义属性,在attr文件中定义:

 <?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"/>
    <declare-styleable name="IndicatorView">
        <attr name="normalDrawable"/>
        <attr name="selectDrawable"/>
        <attr name="indicatorInterval"/>
        <attr name="normalColor"/>
        <attr name="selectColor"/>
        <attr name="indicatorRadius"/>
    </declare-styleable>
</resources>

新建一个IndicatorView继承自LinearLayout即可,因为需要对ViewPager进行监听,所以实现一下ViewPager的监听.定义变量并获取自定义属性:

/**
 * 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;

    /**
     * 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);
        ta.recycle();
        // 初始化
        init();
    }

这里因为监听了ViewPager,所以需要对外提供回调方法,将ViewPager的监听方法暴露出去,方便其他地方对ViewPager对象进行监听.

再来看一下init方法:

    /**
     * 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();
    }

    /**
     * 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;
    }

在init方法中对自定义属性做了相关处理,如果没有设置指示器的图片,就建立两种状态下的圆形指示器图片.

接着看一下对于ViewPager对象的引用及处理:

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

    @Override
    public void onPageSelected(int position) {
        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);
        }
    }

获取ViewPager对象,并通过对ViewPager对象的监听去设置指示器的状态.获取ViewPager对象提供两种方法,方便设置指示器默认显示的位置.

最后看一下指示器的创建:

    /**
     * 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);
    }

    /**
     * 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;
    }

在绘制过程中,去创建指示器,并设置相关属性和默认选中指示器的位置.

---

二、完整代码及使用

不是特别复杂,注释也比较全,看一下完整代码:

activity_main.xml:

<?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:layout_marginTop="20dp"
        idv:indicatorInterval="10dp"
        android:gravity="center_horizontal"
        idv:normalDrawable="@mipmap/oval_indicator_grey"
        idv:selectDrawable="@mipmap/oval_indicator_green">
    </com.example.junweiliu.simpleindicatorview.IndicatorView>

</RelativeLayout>

banner_item.xml:

<?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>

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;

    /**
     * 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);
        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();
    }

    /**
     * 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) {
        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);
        }
    }

}

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<>();


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

    @Override
    public int getCount() {
        return pictureList.size();
    }

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

    @Override
    public Object instantiateItem(ViewGroup container, final int position) {
        View view = LayoutInflater.from(mContext).inflate(R.layout.banner_item, container, false);
        ImageView imageView = (ImageView) view.findViewById(R.id.iv_banner_item);
        imageView.setImageResource(pictureList.get(position));
        container.addView(view);
        return view;
    }

    @Override
    public void finishUpdate(ViewGroup container) {
    }

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

MainActivity:

package com.example.junweiliu.simpleindicatorview;

import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

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

public class MainActivity extends AppCompatActivity {
    /**
     * 轮播图
     */
    private ViewPager mViewPager;
    /**
     * 指示器
     */
    private IndicatorView mIndicatorView;
    /**
     * 适配器
     */
    private BannerPagerAdapter mBannerPagerAdapter;

    private List<Integer> pictureList = new ArrayList<>();

    @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(mViewPager);
        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) {

            }
        });
    }
}

关于无限循环和自动播放的内容可以参考

无限循环和自动播放的实现