android实现多图片放大缩小的切换

　　前天在网上看到了http://v.qq.com/vplus/56c7ec6c231bdbafd198c58fb86eb4dc　作者仿ＱＱ的代码，看了一下感觉很受启发。正好，单位在做引导页的时候，要用到类似的东西，只不过是放大缩小的样子。好了，下面我们来看一下代码。
　　

package com.example.cg.scaleimageview.Customs;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.drawable.Drawable;import android.os.Handler;import android.os.Message;import android.util.AttributeSet;import android.widget.ImageView;import com.example.cg.scaleimageview.R;/** * 自定义控件，根据传入的图片组，对图片进行从小到大的显示 * 作者：cg * 时间：2017/4/24 0024 上午 10:30 */public class ScaleImageView extends ImageView {    private Drawable mDrawable;    private Handler mHandler;    private int[] imgSrc = new int[]{R.mipmap.mm1};    private boolean isEnlarge = true;    private float scaleNum = 1.0f;                              //图片初始放大的倍数    private float scaleMaxNum = 1.2f;                           //图片最大会被放大多少，默认是1.2倍    private float scaleValue = 0.002f;                          //图片每次放大缩小的倍数    private int num = 1;                                        //当前显示到第几个图    public ScaleImageView(Context context) {        this(context,null);    }    public ScaleImageView(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public ScaleImageView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        TypedArray array = context.getTheme().obtainStyledAttributes(attrs,R.styleable.ScaleImageView,defStyleAttr,0);        int n = array.getIndexCount();        for(int i=0;i<n;i++)        {            int arr = array.getIndex(i);            switch (arr)            {                case R.styleable.ScaleImageView_isEnlarge:                    isEnlarge = array.getBoolean(arr,true);                    break;                case R.styleable.ScaleImageView_scaleMaxNum:                    scaleMaxNum = array.getFloat(arr,1.2f);                    break;                case R.styleable.ScaleImageView_scaleValue:                    scaleValue = array.getFloat(arr,0.002f);                    break;            }        }        array.recycle();        if(!isEnlarge)        {            scaleNum = scaleMaxNum;        }        //初始化第一个图        mDrawable=getDrawable();        mHandler=new ScaleImageView.MoveHandler();        mHandler.sendEmptyMessageDelayed(1, 220L);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        canvas.scale(scaleNum,scaleNum,getMeasuredWidth()/2,getMeasuredHeight()/2);        mDrawable.draw(canvas);    }    @Override    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {        super.onLayout(changed, left, top, right, bottom);        if(isEnlarge) {            mDrawable.setBounds(0, 0, getMeasuredWidth(), getMeasuredHeight());        }else{            int mCanvasWBgSize = Math.round(getMeasuredWidth() * scaleMaxNum);            int mCanvashBgSize = Math.round(getMeasuredHeight() * scaleMaxNum);            int leftRight = (mCanvasWBgSize - getMeasuredWidth())/2;            int topBottom = (mCanvashBgSize - getMeasuredHeight())/2;            mDrawable.setBounds(-leftRight,-topBottom,getMeasuredWidth() + leftRight,getMeasuredHeight() + topBottom);        }    }    private class MoveHandler extends Handler{        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            /**             * 此处进行判断，如果小于最大倍数，就不断放大，如果大于了最大或等于最大倍数，就进行换图             */            if(isEnlarge) {                if (scaleNum < scaleMaxNum) {                    scaleNum += scaleValue;                    invalidate();                    mHandler.sendEmptyMessageDelayed(1, 22);                } else {                    scaleNum = 1.0f;                    setImageResource(imgSrc[num % 3]);                    mDrawable = getDrawable();                    num++;                    invalidate();                    mHandler.sendEmptyMessageDelayed(1, 22);                }            }else{                if(scaleNum >= 0.9) {                    scaleNum -= 0.002;                    invalidate();                    mHandler.sendEmptyMessageDelayed(1, 22);                }else {                    scaleNum = scaleMaxNum;                    //如果图片只有一个，哪就循环此图片，不用更新                    if(imgSrc.length!=1) {                        setImageResource(imgSrc[num % 3]);                        mDrawable = getDrawable();                        num++;                    }                    invalidate();                    mHandler.sendEmptyMessageDelayed(1, 22);                }            }        }    }    /**     * 加载图片列表     * @param images   图片列表     */    public void setImages(int[] images)    {        this.imgSrc = images;        invalidate();    }}

代码中我加了详细的注解。都不难理解。
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