用Scroller绘制简易滚动选择视图

/**  * 数字滚动显示视图  * Created by yudongbo on 2017/9/25.  */ public class NumberScrollView extends View {
      private Paint centerPaint;     private Paint otherPaint;     private Scroller mScroller;     private int topY;     private int centerY;     private int bottomY;     private String topValue = "0";     private String centerValue = "1";     private String bottomValue = "2";     private String newValue = "3";     private int scrollUnit;     private int scrollFlag;     public NumberScrollView(Context context) {
          this(context, null);     }     public NumberScrollView(Context context, AttributeSet attrs) {
          this(context, attrs, 0);     }     public NumberScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
          super(context, attrs, defStyleAttr);         init();     }     private void init() {
          centerPaint = new Paint(Paint.ANTI_ALIAS_FLAG);         otherPaint = new Paint(Paint.ANTI_ALIAS_FLAG);         centerPaint.setTextSize(DensityUtils.sp2px(getContext(), 24));         centerPaint.setColor(0xffffffff);         otherPaint.setTextSize(DensityUtils.sp2px(getContext(), 24));         otherPaint.setColor(0x4dffffff);         mScroller = new Scroller(getContext(), new LinearInterpolator());     }     /**      * 设置当前选择状态      *      * @param isSelect true:选中, false:未选中      */     public void setSelect(boolean isSelect) {
          if (isSelect) {
              otherPaint.setColor(0xffffffff);         } else {
              otherPaint.setColor(0x4dffffff);         }     }     /**      * 计算滚动距离      */     @Override     public void computeScroll() {
          super.computeScroll();         if (mScroller.computeScrollOffset()) {
              invalidate();         } else {
              if (scrollFlag == 1) {
                  scrollFlag = 0;                 setValue(centerValue, bottomValue, newValue);             } else if (scrollFlag == 2) {
                  scrollFlag = 0;                 setValue(newValue, topValue, centerValue);             }         }     }     @Override     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
          super.onMeasure(widthMeasureSpec, heightMeasureSpec);         Paint.FontMetricsInt otherMetri = otherPaint.getFontMetricsInt();         int fontHeight = otherMetri.bottom - otherMetri.top;         int space = (getHeight() - 3 * fontHeight) / 2;         scrollUnit = fontHeight + space;         topY = fontHeight - 10;         centerY = getMeasuredHeight() / 2 + fontHeight / 2 - 10;         bottomY = getMeasuredHeight() - 10;     }     /**      * 设置当前值      * @param topValue 上值      * @param centerValue 中间值      * @param bottomValue 下值      */     public void setValue(String topValue, String centerValue, String bottomValue) {
          Log.d(getClass().getSimpleName(), "topValue:" + topValue + ", centerValue:" + centerValue + ", bottomValue:" + bottomValue);         this.topValue = topValue;         this.centerValue = centerValue;         this.bottomValue = bottomValue;         postInvalidate();     }     /**      * 设置颜色      * @param centerColor      * @param otherColor      */     public void setColor(int centerColor, int otherColor) {
          centerPaint.setColor(centerColor);         otherPaint.setColor(otherColor);     }     /**      * 设置字体大小      * @param textSize      */     public void setTextSize(int textSize) {
          centerPaint.setTextSize(textSize);         otherPaint.setTextSize(textSize);     }     /**      * 获取中间值      * @return      */     public String getCenterValue() {
          return centerValue;     }     /**      * 获取上面值      * @return      */     public String getTopValue() {
          return topValue;     }     /**      * 获取下面值      * @return      */     public String getBottomValue() {
          return bottomValue;     }     /**      * 从下面插入值      * @param newValue      */     public void scrollNext(String newValue) {
          if(!mScroller.isFinished()) {
              return;         }         scrollFlag = 1;         this.newValue = newValue;         mScroller.startScroll(0, 0, 0, -scrollUnit, 80);         invalidate();     }     /**      * 从上面插入值      * @param newValue      */     public void scrollPreview(String newValue) {
          if(!mScroller.isFinished()) {
              return;         }         scrollFlag = 2;         this.newValue = newValue;         mScroller.startScroll(0, 0, 0, scrollUnit, 80);         invalidate();     }     @Override     protected void onDraw(Canvas canvas) {
          int scrollY = mScroller.getCurrY();         int x = (int) (getMeasuredWidth() / 2 - centerPaint.measureText(centerValue) / 2);         if (scrollFlag == 0) {
              canvas.drawText(topValue, x, topY, otherPaint);             canvas.drawText(centerValue, x, centerY, centerPaint);             canvas.drawText(bottomValue, x, bottomY, otherPaint);         } else {
              canvas.drawText(topValue, x, topY + scrollY, otherPaint);             canvas.drawText(centerValue, x, centerY + scrollY, centerPaint);             canvas.drawText(bottomValue, x, bottomY + scrollY, otherPaint);         }         if (scrollFlag == 1) {
              canvas.drawText(newValue, x, bottomY + scrollUnit + scrollY, otherPaint);         } else if (scrollFlag == 2) {
              canvas.drawText(newValue, x, topY - scrollUnit + scrollY, otherPaint);         }     } }