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：http://files.cnblogs.com/files/liujingg/ProgressViewDemo.rar