Android 自带描边颜色渐变炫酷进度条

上图是我在PhotoShop中做出的进度条效果图，这张图充分阐释了本篇自定义进度条的精髓！

在Android中实现该进度条的原理：(和ps中作图原理一样,理解ps中的图层便懂得了如何在android中实现该进度条)

1. 画第一个圆角矩形作为进度条的最底层(描边层)

2. 画第二个圆角矩形作为进度条的第二层(背景层)盖在描边层之上

3. 画第三个圆角矩形作为进度条的最外层(进度层)盖在背景层之上

4. 描边层和背景层颜色可用纯色,进度层为了炫酷可用渐变色

这是实现该自带描边颜色渐变进度条的原理,也是在PS中实现该效果的步骤,同样适用于在Android中用代码来实现。

原理明白之后,代码就变得非常简单了：

public class ColorGradientProgressBar extends View {    /**     * 渐变颜色组     */    private int[] GRADIENT_COLORS = {Color.parseColor("#85D0E8"), Color.parseColor("#138CCF")};    /**     * 最大进度     */    private float max = 100;    /**     * 当前进度     */    private float progress;    /**     * 画笔     */    private Paint mPaint;    /**     * 外描边的宽度     */    private float BORDER_STROCK;    /**     * 进度条进度矩形与控件边界的距离,≥BORDER_STROCK     */    private float PROGRESS_STROCK;    //进度条的宽高    private int mWidth, mHeight;    /**     * 画进度条的矩形     */    private RectF mRectF;    public ColorGradientProgressBar(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initView();    }    public ColorGradientProgressBar(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public ColorGradientProgressBar(Context context) {        this(context, null);    }    private void initView() {        mPaint = new Paint();        mPaint.setAntiAlias(true);        mRectF = new RectF();        BORDER_STROCK = getResources().getDimension(R.dimen.x3);        PROGRESS_STROCK = getResources().getDimension(R.dimen.x5);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        int round = mHeight / 2;//弧度为高度的一半        mRectF.set(0, 0, mWidth, mHeight);//第一层矩形(描边层)        mPaint.setColor(Color.parseColor("#A3D8E8"));//第一层矩形颜色(进度条描边的颜色)        canvas.drawRoundRect(mRectF, round, round, mPaint);//画第一层圆角矩形        mPaint.setColor(Color.parseColor("#474C4E"));//第二层矩形颜色(背景层颜色)        mRectF.set(BORDER_STROCK, BORDER_STROCK, mWidth - BORDER_STROCK, mHeight - BORDER_STROCK);//第二层矩形(背景层)        canvas.drawRoundRect(mRectF, round, round, mPaint);//画背景层圆角矩形(盖在描边层之上)        if (progress == 0)//进度为 0不画进度            return;        float section = progress / max;        //第三层矩形(进度层)        mRectF.set(PROGRESS_STROCK, PROGRESS_STROCK, (mWidth - PROGRESS_STROCK) * section, mHeight - PROGRESS_STROCK);        //创建线性颜色渐变器        LinearGradient shader = new LinearGradient(PROGRESS_STROCK, PROGRESS_STROCK,                (mWidth - PROGRESS_STROCK) * section, mHeight - PROGRESS_STROCK, GRADIENT_COLORS, null, Shader.TileMode.MIRROR);        mPaint.setShader(shader);//第三层矩形颜色(进度渐变色)        canvas.drawRoundRect(mRectF, round, round, mPaint);//画第三层(进度层)圆角矩形(盖在背景层之上)        mPaint.setShader(null);//清除之前传递的shader    }    /***     * 设置最大进度     *     * @param maxCount     */    public void setMax(float maxCount) {        this.max = maxCount;    }    /***     * 设置当前进度     *     * @param currentCount     */    public void setProgress(float currentCount) {        this.progress = currentCount > max ? max : currentCount;        invalidate();    }    public float getMax() {        return max;    }    /**     * 测量得到进度条的宽高     */    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);        int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);        int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);        int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);        if (widthSpecMode == MeasureSpec.EXACTLY || widthSpecMode == MeasureSpec.AT_MOST) {            mWidth = widthSpecSize;        } else {            mWidth = 0;        }        if (heightSpecMode == MeasureSpec.AT_MOST || heightSpecMode == MeasureSpec.UNSPECIFIED) {            mHeight = (int) getResources().getDimension(R.dimen.x20);        } else {            mHeight = heightSpecSize;        }        setMeasuredDimension(mWidth, mHeight);    }}

代码很简单,注释也很清楚,效果如下：

代码中使用了dimens适配,详情请看Android 屏幕适配之dimens适配

Demo源码下载

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