android自定义渐变圆环进度条

先看下效果：

 

分析：比较常见于扫描结果、进度条等场景

利用canvas.drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint)绘制圆弧

Paint的一些属性定义粗细、颜色、样式等

LinearGradient实现颜色的线型渐变

同样的道理，可以画出长条进度条，扇图饼图等，感兴趣可以试下..

package com.liujing.progressviewdemo;

/***
 * 自定义圆弧进度条
 * 
 * @author liujing
 */
public class ProgressView extends View {

    //分段颜色 
    private static final int[] SECTION_COLORS = { Color.GREEN, Color.YELLOW,
            Color.RED };
    private static final String[] ALARM_LEVEL = { "安全", "低危", "中危", "高危" };
    private float maxCount;
    private float currentCount;
    private int score;
    private String crrentLevel;
    private Paint mPaint;
    private Paint mTextPaint;
    private int mWidth, mHeight;

    public ProgressView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context);
    }

    public ProgressView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ProgressView(Context context) {
        this(context, null);
    }

    private void init(Context context) {
        mPaint = new Paint();
        mTextPaint = new Paint();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        initPaint();
        RectF rectBlackBg = new RectF(20, 20, mWidth - 20, mHeight - 20);
        canvas.drawArc(rectBlackBg, 0, 360, false, mPaint);
        mPaint.setColor(Color.BLACK);
        canvas.drawText(score + "分", mWidth / 2, mHeight / 2, mTextPaint);
        mTextPaint.setTextSize(40);
        if (crrentLevel != null) {
            canvas.drawText(crrentLevel, mWidth / 2, mHeight / 2 + 50,
                    mTextPaint);
        }
        float section = currentCount / maxCount;
        if (section <= 1.0f / 3.0f) {
            if (section != 0.0f) {
                mPaint.setColor(SECTION_COLORS[0]);
            } else {
                mPaint.setColor(Color.TRANSPARENT);
            }
        } else {
            int count = (section <= 1.0f / 3.0f * 2) ? 2 : 3;
            int[] colors = new int[count];
            System.arraycopy(SECTION_COLORS, 0, colors, 0, count);
            float[] positions = new float[count];
            if (count == 2) {
                positions[0] = 0.0f;
                positions[1] = 1.0f - positions[0];
            } else {
                positions[0] = 0.0f;
                positions[1] = (maxCount / 3) / currentCount;
                positions[2] = 1.0f - positions[0] * 2;
            }
            positions[positions.length - 1] = 1.0f;
            LinearGradient shader = new LinearGradient(3, 3, (mWidth - 3)
                    * section, mHeight - 3, colors, null,
                    Shader.TileMode.MIRROR);
            mPaint.setShader(shader);
        }
        canvas.drawArc(rectBlackBg, 180, section * 360, false, mPaint);
    }

    private void initPaint() {
        mPaint.setAntiAlias(true);
        mPaint.setStrokeWidth((float) 40.0);
        mPaint.setStyle(Style.STROKE);
        mPaint.setStrokeCap(Cap.ROUND);
        mPaint.setColor(Color.TRANSPARENT);

        mTextPaint.setAntiAlias(true);
        mTextPaint.setStrokeWidth((float) 3.0);
        mTextPaint.setTextAlign(Paint.Align.CENTER);
        mTextPaint.setTextSize(50);
        mTextPaint.setColor(Color.BLACK);

    }

    private int dipToPx(int dip) {
        float scale = getContext().getResources().getDisplayMetrics().density;
        return (int) (dip * scale + 0.5f * (dip >= 0 ? 1 : -1));
    }

    public int getScore() {
        return score;
    }

    public String getCrrentLevel() {
        return crrentLevel;
    }

    public void setCrrentLevel(String crrentLevel) {
        this.crrentLevel = crrentLevel;
    }

    public float getMaxCount() {
        return maxCount;
    }

    public float getCurrentCount() {
        return currentCount;
    }

    public void setScore(int score) {
        this.score = score;
        if (score == 100) {
            this.crrentLevel = ALARM_LEVEL[0];
        } else if (score >= 70 && score < 100) {
            this.crrentLevel = ALARM_LEVEL[1];
        } else if (score >= 30 && score < 70) {
            this.crrentLevel = ALARM_LEVEL[2];
        } else {
            this.crrentLevel = ALARM_LEVEL[3];
        }
        invalidate();
    }

    /***
     * 设置最大的进度值
     * 
     * @param maxCount
     */
    public void setMaxCount(float maxCount) {
        this.maxCount = maxCount;
    }

    /***
     * 设置当前的进度值
     * 
     * @param currentCount
     */
    public void setCurrentCount(float currentCount) {
        this.currentCount = currentCount > maxCount ? maxCount : currentCount;
        invalidate();
    }

    @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 = dipToPx(15);
        } else {
            mHeight = heightSpecSize;
        }
        setMeasuredDimension(mWidth, mHeight);
    }

}

 Demo：https://files.cnblogs.com/files/liujingg/ProgressViewDemo.rar