自定义View之垂直滚动TextView

public class VerticalScrollTextView extends View {
/**
* 滑动的两个字符串
*/
private String text1, text2;
/**
* 开始绘制textview的Y轴起点
*/
private float fromY;

/**
 * text1,text2滑动的时候的Y坐标
 */
private float y1, y2;

/**
 * 每次向上滑动 1px
 */
private int offsetY = 1;


/**
 * 一次滚动完成后，暂停2秒钟
 */
private final int pauseTime = 2000;

/**
 * 每一次小的滑动间隔时间
 */
private int scrollDelayTime;

private int height;

private List list;

/**
 * text1在list中的索引
 */
private int currIndex;
/**
 * 是否需要边框
 */
private boolean isBorder;

private Paint paint, redPaint;

private float textsize;

public VerticalScrollTextView(Context context) {
    super(context);
}

public VerticalScrollTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
    TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.VerticalScrollTextView);
    textsize=array.getDimensionPixelSize(R.styleable.VerticalScrollTextView_textsize,16);
    array.recycle();


    paint = new Paint();
    paint.setTextSize(textsize);
    paint.setColor(Color.GRAY);
    paint.setAntiAlias(true);

    redPaint = new Paint();
    redPaint.setTextSize(textsize);
    redPaint.setAntiAlias(true);
    redPaint.setColor(Color.RED);

}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    if (text1 == null || text2 == null) {
        return;
    }
    if (isBorder) {
        //画字符串,显示在空间x轴中间位置
        redPaint.setStyle(Paint.Style.FILL);
        canvas.drawText(text1, getWidth() / 2 - paint.measureText(text1) / 2, y1, redPaint);
        canvas.drawText(text2, getWidth() / 2 - paint.measureText(text2) / 2, y2, redPaint);

        redPaint.setStyle(Paint.Style.STROKE);
        redPaint.setStrokeWidth(2);
        RectF rectF = new RectF(1, 1, getWidth() - 1, getHeight() - 1);
        //设置画笔是空心的
        canvas.drawRoundRect(rectF, 15, 15, redPaint);

    } else {
        //画字符串,显示在空间x轴中间位置
        canvas.drawText(text1,0, y1, paint);
        canvas.drawText(text2,0, y2, paint);

// canvas.drawText(text1, getWidth() / 2 - paint.measureText(text1) / 2, y1, paint);
// canvas.drawText(text2, getWidth() / 2 - paint.measureText(text2) / 2, y2, paint);
}

}

public void setList(List list, Boolean isBorder) {
    this.list = list;
    this.isBorder = isBorder;
    start();
}

/**
 * 第一次操作
 */
private void start() {
    post(new Runnable() {
        @Override
        public void run() {
            height = getHeight();
            fromY = getHeight() / 2 + (paint.descent() - paint.ascent()) / 2 - paint.descent();
            //间隔时间=总时间/绘制次数
            scrollDelayTime = 1000 / (height / offsetY);
            next();
        }
    });
}

/**
 * 下一次大的滚动操作
 */
private void next() {
    int index1 = currIndex % list.size();
    text1 = list.get(index1);
    currIndex++;
    int index2 = currIndex % list.size();
    text2 = list.get(index2);

    //text1的Y坐标和超始点一样
    y1 = fromY;
    //text的Y坐标比text1的Y坐标大一个控件的高度
    y2 = y1 + height;

    scroll();
}

/**
 * 执行一次小的滑动
 */
private void scroll() {
    y1 = y1 - offsetY;
    y2 = y2 - offsetY;
    //重新绘制
    invalidate();

    //延时执行下一次小的滑动
    postDelayed(new Runnable() {
        @Override
        public void run() {
            //判断是否需要暂停
            if (y2 <= fromY) {
                pause();
            } else {
                scroll();
            }
        }
    }, scrollDelayTime);
}

/**
 * 暂停
 */
private void pause() {
    //延时执行下一次大的滑动
    postDelayed(new Runnable() {
        @Override
        public void run() {
            next();
        }
    }, pauseTime);

}

/**
 * 得到下标
 */
public int  getCurrentIndex(){

    return currIndex % list.size();
}

}