自定义view练手，效果图如下：

实现功能    可设置圆环颜色和线宽及触摸后的颜色和线宽    可设置圆环内圈显示的文本内容及字体大小、颜色    可设置触摸点的图片    可设置触摸的有效范围源码github链接使用示例<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="circlebar.oden.com.circleseekbardemo.MainActivity">    <circlebar.oden.com.circleseekbar.CircleSeekbar        android:id="@+id/circle_seekbar"        android:layout_centerInParent="true"        android:layout_width="300dp"        android:layout_height="300dp" />    <TextView        android:id="@+id/tv_progress"        android:text="0%"        android:textColor="#FF383838"        android:textSize="18sp"        android:layout_centerInParent="true"        android:layout_width="wrap_content"        android:layout_height="wrap_content" /></RelativeLayout>public class MainActivity extends AppCompatActivity {     String TAG = "MainActivity";    CircleSeekbar circleSeekbar;    TextView tv_progress;    @Override    protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        circleSeekbar = (CircleSeekbar) findViewById(R.id.circle_seekbar);        tv_progress = (TextView) findViewById(R.id.tv_progress);        circleSeekbar.setOnSeekBarChangeListener(new CircleSeekbar.OnSeekBarChangeListener() {             @Override            public void onProgressChanged(CircleSeekbar circleSeekbar, int progress, boolean fromUser) {                 Log.d(TAG, "onProgressChanged progress: " + progress);                tv_progress.setText(progress + "%");            }        });    }}实现过程attrs中定义属性可设置的属性如下<?xml version="1.0" encoding="utf-8"?><resources>    <declare-styleable name="CircleSeekbar">        <attr name="circleColor" format="color" />        <attr name="progressColor" format="color" />        <attr name="textColor" format="color" />        <attr name="textSize" format="dimension" />        <attr name="progress" format="integer" />        <attr name="maxProgress" format="integer" />        <attr name="progressWidth" format="dimension" />        <attr name="circleWidth" format="dimension" />        <attr name="thumb" format="reference" />        <attr name="enabled" format="boolean" />        <attr name="touchInside" format="boolean" />    </declare-styleable></resources>获取属性及初始化画笔 private void init(Context context, AttributeSet attrs) {         float density = context.getResources().getDisplayMetrics().density;        int thumbHalfheight = 0;        int thumbHalfWidth = 0;        circleColor = getResources().getColor(R.color.circleseekbar_gray);        progressColor = getResources().getColor(R.color.circleseekbar_blue_light);        textColor = getResources().getColor(R.color.circleseekbar_text_color);        progressWidth = (int) (progressWidth * density);        circleWidth = (int) (circleWidth * density);        textSize = (int) (textSize * density);        padding = (int) (padding * density);        mThumb = getResources().getDrawable(R.drawable.seekbar_control_selector);        if (null != attrs) {             TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.CircleSeekbar);            circleColor = typedArray.getColor(R.styleable.CircleSeekbar_circleColor, circleColor);            progressColor = typedArray.getColor(R.styleable.CircleSeekbar_circleColor, progressColor);            textColor = typedArray.getColor(R.styleable.CircleSeekbar_textColor, textColor);            textSize = typedArray.getColor(R.styleable.CircleSeekbar_textSize, textSize);            circleWidth = (int) typedArray.getDimension(R.styleable.CircleSeekbar_circleWidth, circleWidth);            progressWidth = (int) typedArray.getDimension(R.styleable.CircleSeekbar_progressWidth, progressWidth);            mProgress = typedArray.getInteger(R.styleable.CircleSeekbar_progress, mProgress);            maxProgress = typedArray.getInteger(R.styleable.CircleSeekbar_maxProgress, maxProgress);            mTouchInside = typedArray.getBoolean(R.styleable.CircleSeekbar_touchInside, mTouchInside);            Drawable thumb = typedArray.getDrawable(R.styleable.CircleSeekbar_thumb);            if (thumb != null) {                 mThumb = thumb;            }            thumbHalfheight = (int) mThumb.getIntrinsicHeight() / 2;            thumbHalfWidth = (int) mThumb.getIntrinsicWidth() / 2;            mThumb.setBounds(-thumbHalfWidth, -thumbHalfheight, thumbHalfWidth,                    thumbHalfheight);            typedArray.recycle();        }        padding = thumbHalfheight + padding;        maxWidth = circleWidth > progressWidth ? circleWidth : progressWidth;        mProgress = (mProgress > maxProgress) ? maxProgress : mProgress;        mProgress = (mProgress < 0) ? 0 : mProgress;        circlePaint = new Paint();        circlePaint.setColor(circleColor);        circlePaint.setAntiAlias(true);        circlePaint.setStyle(Paint.Style.STROKE);        circlePaint.setStrokeWidth(circleWidth);        progressPaint = new Paint();        progressPaint.setColor(progressColor);        progressPaint.setAntiAlias(true);        progressPaint.setStyle(Paint.Style.STROKE);        progressPaint.setStrokeWidth(progressWidth);        paintDegree = new Paint();        paintDegree.setColor(textColor);        paintDegree.setAntiAlias(true);        paintDegree.setStyle(Paint.Style.FILL);        paintDegree.setStrokeWidth(1);        paintDegree.setTextSize(textSize);    }测量获取圆的中心坐标、半径、以及用来画弧的RectF@Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {         int height = getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec);        int width = getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec);        mWidth = Math.min(width, height);        centreX = mWidth / 2;        centreY = mWidth / 2;        float left = getPaddingLeft() + maxWidth / 2 + padding;        float top = getPaddingTop() + maxWidth / 2 + padding;        float right = mWidth - getPaddingRight() - maxWidth / 2 - padding;        float bottom = mWidth - getPaddingBottom() - maxWidth / 2 - padding;        diameter = mWidth - getPaddingLeft() - getPaddingRight() - maxWidth - padding * 2;        radius = diameter / 2;        mCircleRect.set(left, top, left + diameter, top + diameter);        updateThumbPosition(mCurAngle);        setTouchInSide(mTouchInside);        setMeasuredDimension(mWidth, mWidth);    }绘制view  @Override    protected void onDraw(Canvas canvas) {         canvas.drawColor(Color.RED);        canvas.drawCircle(mWidth / 2, mWidth / 2, radius, circlePaint);        canvas.drawArc(mCircleRect, -90, (float) mCurAngle, false, progressPaint);        drawText(canvas);        canvas.translate(mThumbXPos, mThumbYPos);        mThumb.draw(canvas);    }  private void drawText(Canvas canvas) {         float rotation = 360 / degreeText.length;        for (int i = 0; i < degreeText.length; i++) {             canvas.drawText(degreeText[i], centreX - paintDegree.measureText(degreeText[i]) / 2, 100/*字体的高度*/, paintDegree);            canvas.rotate(rotation, centreX, centreY);        }    }设置触摸事件 @Override    public boolean onTouchEvent(MotionEvent event) {         if (enable) {             this.getParent().requestDisallowInterceptTouchEvent(true);//通知父控件勿拦截本次触摸事件            switch (event.getAction()) {                 case MotionEvent.ACTION_DOWN:                    updateOnTouch(event);                    break;                case MotionEvent.ACTION_MOVE:                    updateOnTouch(event);                    break;                case MotionEvent.ACTION_UP:                    isFirstTouch = true;                    setPressed(false);                    this.getParent().requestDisallowInterceptTouchEvent(false);                    break;                case MotionEvent.ACTION_CANCEL:                    isFirstTouch = true;                    setPressed(false);                    this.getParent().requestDisallowInterceptTouchEvent(false);                    break;            }            return true;        }        return false;    }触摸事件中计算相应的角度及进度条的值 private void updateOnTouch(MotionEvent event) {         boolean ignoreTouch = ignoreTouch(event.getX(), event.getY());        if (ignoreTouch) {             return;        }        setPressed(true);        getTouchDegrees(event.getX(), event.getY());        mProgress = getProgressForAngle(mCurAngle);        updateProgress(mProgress, true);    }    //根据触摸点的坐标获取角度值    private double getTouchDegrees(float xPos, float yPos) {         float x = xPos - centreX;        float y = yPos - centreY;        // convert to arc Angle        double angle = Math.toDegrees(Math.atan2(y, x) + (Math.PI / 2));        if (angle < 0) {             angle = 360 + angle;        }        if (isOnlyScrollOneCircle) {             if (mCurAngle > 270 && angle < 90) {                 mCurAngle = 360;            } else if (mCurAngle < 90 && angle > 270) {                 mCurAngle = 0;            } else {                 mCurAngle = angle;            }        } else {             mCurAngle = angle;        }        if (isFirstTouch) {  //如果是滑动前第一次点击则总是移动到该度数            mCurAngle = angle;            isFirstTouch = false;        }        Log.d(TAG, "getTouchDegrees: " + angle);        return mCurAngle;    }    //根据触摸的角度值获取滑动条progree的值    private int getProgressForAngle(double angle) {         int touchProgress = (int) Math.round(maxProgress * angle / 360);        touchProgress = (touchProgress < 0) ? INVALID_PROGRESS_VALUE                : touchProgress;        touchProgress = (touchProgress > maxProgress) ? INVALID_PROGRESS_VALUE                : touchProgress;        return touchProgress;    }    //更新view    private void updateProgress(int progress, boolean fromUser) {         if (progress == INVALID_PROGRESS_VALUE) {             return;        }        progress = (progress > maxProgress) ? maxProgress : progress;        progress = (progress < 0) ? 0 : progress;        mProgress = progress;        if (onSeekBarChangeListener != null) {             onSeekBarChangeListener.onProgressChanged(this, progress, fromUser);        }        updateThumbPosition(mCurAngle);        invalidate();    }    //更新thum的坐标    private void updateThumbPosition(double angle) {         double cos = -Math.cos(Math.toRadians(angle));        if (angle < 180) {             mThumbXPos = (int) (getMeasuredWidth() / 2 + Math.sqrt(1 - cos * cos) * radius);        } else {             mThumbXPos = (int) (getMeasuredWidth() / 2 - Math.sqrt(1 - cos * cos) * radius);        }        mThumbYPos = (int) (centreX + radius * (float) cos);    }设置触摸的生效范围同时根据触摸状态同步改变thum的状态//设置触摸生效范围    public void setTouchInSide(boolean isEnabled) {         int thumbHalfheight = (int) mThumb.getIntrinsicHeight() / 2;        int thumbHalfWidth = (int) mThumb.getIntrinsicWidth() / 2;        mTouchInside = isEnabled;        if (mTouchInside) {             mTouchIgnoreRadius = (float) radius / 4;        } else {             // Don't use the exact radius makes interaction too tricky            mTouchIgnoreRadius = radius - Math.min(thumbHalfWidth, thumbHalfheight);        }    }    private boolean ignoreTouch(float xPos, float yPos) {         boolean ignore = false;        float x = xPos - centreX;        float y = yPos - centreY;        float touchRadius = (float) Math.sqrt(((x * x) + (y * y)));        if (touchRadius < mTouchIgnoreRadius) {             ignore = true;        }        return ignore;    }    //重写drawableStateChanged，同步改变thum的状态    @Override    protected void drawableStateChanged() {         super.drawableStateChanged();        if (mThumb != null && mThumb.isStateful()) {             int[] state = getDrawableState();            mThumb.setState(state);        }        invalidate();    }   设置监听器public interface OnSeekBarChangeListener {         void onProgressChanged(CircleSeekbar circleSeekbar, int progress, boolean fromUser);    }    public void setOnSeekBarChangeListener(OnSeekBarChangeListener onSeekBarChangeListener) {         this.onSeekBarChangeListener = onSeekBarChangeListener;    }