自定义pickerview实现倒计时

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一句话：倒计时网上也有框架。但是能写的还是用自定比较好。
刚开始我是想自己写的，但是透明度和滑动以及字体之间的比例把握不好，所以…………..。相信随着知识的增加有一天肯定能够自己写的！
首先我说一下这个类是我在网上找的，然后我把里面的注释写了一下，方便各位二次开发；
效果图分两种：
1：isFrom = 1 时：
这里写图片描述
2：isFrom = 2 时：

先看下核心类：
package com.app.test.pickerviewproject;import android.content.Context;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.Paint.Align;import android.graphics.Paint.FontMetricsInt;import android.graphics.Paint.Style;import android.os.Build;import android.os.Handler;import android.os.Message;import android.support.annotation.RequiresApi;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import java.util.ArrayList;import java.util.List;import java.util.Timer;import java.util.TimerTask;/** * Created by liumengqiang on 17/6/28. */public class PickerView extends View{    public static final String TAG = "PickerView";    public static final int TIMER = 1;//界面显示三个text    public static final int BIRTH = 2;//界面显示一个text    private int isFrom = 1;    /**     * text之间间距和minTextSize之比     */    public static final float MARGIN_ALPHA = 2.8f;    /**     * 自动回滚到中间的速度     */    public static final float SPEED = 2;    private List<String> mDataList;    /**     * 选中的位置，这个位置是mDataList的中心位置，一直不变     */    private int mCurrentSelected;    private Paint mPaint;    private float mMaxTextSize = 80;    private float mMinTextSize = 40;    private float mMaxTextAlpha = 255;    private float mMinTextAlpha = 120;    private int mColorText = 0x333333;    private int mViewHeight;    private int mViewWidth;    private float mLastDownY;    /**     * 滑动的距离     */    private float mMoveLen = 0;    private boolean isInit = false;    private onSelectListener mSelectListener;    private Timer timer;    private MyTimerTask mTask;    private boolean isRun = false;    private int firstBoolean  = 0;    Handler updateHandler = new Handler()    {        @Override        public void handleMessage(Message msg)        {                if (Math.abs(mMoveLen) < SPEED)            {                mMoveLen = 0;                if (mTask != null)                {                    mTask.cancel();                    mTask = null;                    performSelect();                }            } else                // 这里mMoveLen / Math.abs(mMoveLen)是为了保有mMoveLen的正负号，以实现上滚或下滚                mMoveLen = mMoveLen - mMoveLen / Math.abs(mMoveLen) * SPEED;            invalidate();        }    };    public PickerView(Context context)    {        super(context);        init();    }    public void setFrom(int from){        this.isFrom = from;    }    public PickerView(Context context, AttributeSet attrs)    {        super(context, attrs);        init();    }    /**     * 获得选中的text     * @param listener     */    public void setOnSelectListener(onSelectListener listener)    {            mSelectListener = listener;    }    private void performSelect()    {        if (mSelectListener != null)            mSelectListener.onSelect(mDataList.get(mCurrentSelected));    }    /**     * 给滚轮设置数据     * @param datas     */    public void setData(List<String> datas)    {        mDataList = datas;        mCurrentSelected = datas.size() / 2;        invalidate();    }    /**     * 设置是否能够滑动     * @param run ：false 能滑动 ? true 不能滑动     */    public void setRun(Boolean run){        this.isRun = run;    }    /**     * 选择选中的item的index     *     * @param selected     */    public void setSelected(int selected)    {        mCurrentSelected = selected;        int distance = mDataList.size() / 2 - mCurrentSelected;        if (distance < 0)            for (int i = 0; i < -distance; i++)            {                moveHeadToTail();                mCurrentSelected--;            }        else if (distance > 0)            for (int i = 0; i < distance; i++)            {                moveTailToHead();                mCurrentSelected++;            }        invalidate();    }    /**     * 选择选中的内容     *     * @param mSelectItem     */    public void setSelected(String mSelectItem)    {        for (int i = 0; i < mDataList.size(); i++)            if (mDataList.get(i).equals(mSelectItem))            {                setSelected(i);                break;            }    }    /**     * 从后往前滑动，比如 1-2-3-4     */    private void moveHeadToTail()    {        String head = mDataList.get(0);        mDataList.remove(0);        mDataList.add(head);    }    /**     * 从前往后滑动，也就是倒着滑动，比如4-3-2-1；     */    public void moveTailToHead()    {//        LogUtils.Debug_E(PickerView.class,mDataList.size()+".");        String tail = mDataList.get(mDataList.size() - 1);        mDataList.remove(mDataList.size() - 1);        mDataList.add(0, tail);    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)    {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        mViewHeight = getMeasuredHeight();        mViewWidth = getMeasuredWidth();        // 按照View的高度计算字体大小        mMaxTextSize = mViewHeight / 4.0f;        mMinTextSize = mMaxTextSize / 2f;        isInit = true;        invalidate();    }    private void init()    {        timer = new Timer();        mDataList = new ArrayList<String>();        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mPaint.setStyle(Style.FILL);        mPaint.setTextAlign(Align.CENTER);        mPaint.setColor(mColorText);    }    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)    @Override    protected void onDraw(Canvas canvas)    {        super.onDraw(canvas);        // 根据index绘制view        if (isInit)            drawData(canvas);    }    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)    private void drawData(Canvas canvas)    {        // 先绘制选中的text再往上往下绘制其余的text        float scale = parabola(mViewHeight / 4.0f, mMoveLen);        float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;        mPaint.setTextSize(size);        mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));        // text居中绘制，注意baseline的计算才能达到居中，y值是text中心坐标        float x = (float) (mViewWidth / 2.0);        float y = (float) (mViewHeight / 2.0 + mMoveLen);        FontMetricsInt fmi = mPaint.getFontMetricsInt();        float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));        canvas.drawText(mDataList.get(mCurrentSelected), x, baseline, mPaint);        // 绘制上方data        if(isFrom == TIMER){        for (int i = 1; (mCurrentSelected - i) >= 0; i++)        {            drawOtherText(canvas, i, -1);        }        // 绘制下方data        for (int i = 1; (mCurrentSelected + i) < mDataList.size(); i++)        {            drawOtherText(canvas, i, 1);        }        }    }    /**     * @param canvas     * @param position     *            距离mCurrentSelected的差值     * @param type     *            1表示向下绘制，-1表示向上绘制     */    private void drawOtherText(Canvas canvas, int position, int type)    {        float d = (float) (MARGIN_ALPHA * mMinTextSize * position + type                * mMoveLen);        float scale = parabola(mViewHeight / 4.0f, d);        float size = (mMaxTextSize - mMinTextSize) * scale + mMinTextSize;        mPaint.setTextSize(size);        mPaint.setAlpha((int) ((mMaxTextAlpha - mMinTextAlpha) * scale + mMinTextAlpha));        float y = (float) (mViewHeight / 2.0 + type * d);        FontMetricsInt fmi = mPaint.getFontMetricsInt();        float baseline = (float) (y - (fmi.bottom / 2.0 + fmi.top / 2.0));        canvas.drawText(mDataList.get(mCurrentSelected + type * position),                (float) (mViewWidth / 2.0), baseline, mPaint);    }    /**     * 抛物线     *     * @param zero     *            零点坐标     * @param x     *            偏移量     * @return scale     */    private float parabola(float zero, float x)    {        float f = (float) (1 - Math.pow(x / zero, 2));        return f < 0 ? 0 : f;    }    @Override    public boolean onTouchEvent(MotionEvent event)    {//        LogUtils.Debug_E(PickerView.class,"eee"+isRun);        if(isRun){            return true;        }else        switch (event.getActionMasked())        {            case MotionEvent.ACTION_DOWN:                doDown(event);                break;            case MotionEvent.ACTION_MOVE:                doMove(event);                break;            case MotionEvent.ACTION_UP:                doUp(event);                break;        }        return true;    }    private void doDown(MotionEvent event)    {        if (mTask != null)        {            mTask.cancel();            mTask = null;        }        mLastDownY = event.getY();    }    private void doMove(MotionEvent event)    {        mMoveLen += (event.getY() - mLastDownY);        if (mMoveLen > MARGIN_ALPHA * mMinTextSize / 2)        {            // 往下滑超过离开距离            moveTailToHead();            mMoveLen = mMoveLen - MARGIN_ALPHA * mMinTextSize;        } else if (mMoveLen < -MARGIN_ALPHA * mMinTextSize / 2)        {            // 往上滑超过离开距离            moveHeadToTail();            mMoveLen = mMoveLen + MARGIN_ALPHA * mMinTextSize;        }        mLastDownY = event.getY();        invalidate();    }    private void doUp(MotionEvent event)    {        // 抬起手后mCurrentSelected的位置由当前位置move到中间选中位置        if (Math.abs(mMoveLen) < 0.0001)        {            mMoveLen = 0;            return;        }        if (mTask != null)        {            mTask.cancel();            mTask = null;        }        mTask = new MyTimerTask(updateHandler);        timer.schedule(mTask, 0, 10);    }    class MyTimerTask extends TimerTask    {        Handler handler;        public MyTimerTask(Handler handler)        {            this.handler = handler;        }        @Override        public void run()        {            handler.sendMessage(handler.obtainMessage());        }    }    public interface onSelectListener    {        void onSelect(String text);    }}
最后附上倒计时源码：
http://download.csdn.net/detail/lmq121210/9882983
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