android 计时器 View (就像进度条一样)在 Canvas 中更新颜色

Question

我的应用程序，当我进入一个 Activity 时，我会显示一个计时器 View (看起来像一个进度条)，它根据来自服务器的计时器值运行。在开始时(例如 40 秒)计时器将为绿色，在中间(例如 25 秒)变为黄色，最后变为红色(例如 10 秒)，以下是我正在使用的代码

public class TimerView extends View 
{
    private LinearInterpolator mInterpolator;
    private Transformation mTransformation;
    private AlphaAnimation mAnimation;

    int orange = Color.rgb(255, 153, 0);
    private int green = Color.rgb(107, 155, 21);
    private int red = Color.rgb(194, 21, 30);
    private int yellow = Color.rgb(225, 170, 0);

    private RectF rect;
    private Integer mTimerVal = 0;
    private Paint tmrPaint;
    private Paint txtPaint;
    private float mDensity = 1.0f;

    public TimerView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    private void init() {
        mDensity = getResources().getDisplayMetrics().density;

        txtPaint = new Paint();
        tmrPaint = new Paint();
        tmrPaint.setAntiAlias(true);

        txtPaint.setColor(Color.WHITE);
        txtPaint.setTextSize(15.0f * mDensity);
        txtPaint.setAntiAlias(true);

        if (!isInEditMode()) {
            txtPaint.setTypeface(Typefaces.get(getContext(), "OpenSans-CondBold.ttf"));
        }
        rect = new RectF(0, 8 * mDensity, 0, 22 * mDensity);
        mInterpolator = new LinearInterpolator();
        // Timer Animation
        mTransformation = new Transformation();
        mAnimation = new AlphaAnimation(1.0f, 0.0f);
        mAnimation.setRepeatMode(AlphaAnimation.RESTART);
        mAnimation.setRepeatCount(0);
        mAnimation.setDuration(0);
        mAnimation.setInterpolator(mInterpolator);
        mAnimation.setStartTime(Animation.START_ON_FIRST_FRAME);
        mAnimation.cancel();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        // System.out.println("onLayout: " + left + " top: " + top + " r: " +
        // right + " b: " + bottom);
        super.onLayout(changed, left, top, right, bottom);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // System.out.println("onLayout onMeasure: " + widthMeasureSpec + " x "
        // + heightMeasureSpec);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onDraw(Canvas canvas) 
    {
        long time = getDrawingTime();
        mAnimation.getTransformation(time, mTransformation);
        float scale = mTransformation.getAlpha();

        int rem = (int) Math.floor(mTimerVal * scale);
        if (rem > 0) 
        {
            if (rem < 5) 
            {
                tmrPaint.setColor(red);
            }
            else if (rem <= 10) 
            {
                tmrPaint.setColor(yellow);
            }
            else 
            {
                tmrPaint.setColor(green);
            }

            rect.right = this.getWidth() - mDensity * 8;
            rect.left = (1 - scale) * (this.getWidth());

            canvas.drawRoundRect(rect, 4 * mDensity, 4 * mDensity, tmrPaint);
            canvas.drawText(String.format("%d", rem), 13 * mDensity, 20 * mDensity, txtPaint);
        }
        if (scale > 0.0f) {
            postInvalidateDelayed(40);
        }

        super.onDraw(canvas);
    }

    public void setTimer(TimerTag timer) {
        if (timer.getTimerValue() > 0) {
            mAnimation.reset();
            mTimerVal = timer.getTimerValue();
            mAnimation.setDuration(timer.getTimerValue() * 1000);
            mAnimation.start();
            postInvalidate();
        }

    }
}

现在我的问题是当我进入 Activity 时，如果服务器响应低于 25 和高于 10，我的计时器显示黄色，但它从末尾开始，我希望它从中间或其他位置开始 View ，我无法更改 Canvas 中的起点，任何建议.....

Answer 1

由于矩形坐标(尤其是左上坐标)是根据当前的 alpha 值计算的，因此 AlphaAnimation 的起始 alpha 值应该基于已经过去的时间。

例如如果定时器设置为 30 秒并且用户在第 10 秒进入 Activity ，则动画需要播放 20 秒。所以起始 alpha 值应该是 20/30，即 0.67f。 AlphaAnimation 应该如下实例化:

mAnimation = new AlphaAnimation(0.67f, 0.0f);