Android值Drawable系列：   
一起来说说那些你不知道的Drawable：http://blog.csdn.net/mr_dsw/article/details/50998681
Android实践之Drawable的使用：http://blog.csdn.net/mr_dsw/article/details/50999818
开源项目circular-progress-button源码解析：http://blog.csdn.net/mr_dsw/article/details/51253844

在这几篇文章中，我们介绍了Drawable系列的基本成员以及基本的使用，这次我们以circular-progress-button开源项目为案例进行分析，这个开源项目里涉及到Drawable的使用，所以是一个不错分析案例。

一、项目概述     
这个项目实现了一套精美的按钮过渡效果：


是不是很靓丽。我们打开项目工程，查看这个项目工程的结构：


其中：
1.CircularProgressButton类：是我们实现的自定义控件，该控件继承Button实现。
2.CircularAnimatedDrawable类：实现弧长变化效果的Drawable。
3.CircularProgressDrawable类：实现圆形进度的Drawable。
4.MorphingAnimation类：里面封装属性动画实现Button不同效果之间的切换。
5.StateManager：控件状态管理类
6.StrokeGradientDrawable：渐变的Drawable管理类

下面我们就分别研究下所实现的原理。

二、具体类实现技术研究：
1、CircularProgressDrawable类

    public class CircularProgressDrawable extends Drawable {
    
        private float mSweepAngle;
        private float mStartAngle;
        private int mSize;
        private int mStrokeWidth;
        private int mStrokeColor;
    
        public CircularProgressDrawable(int size, int strokeWidth, int strokeColor) {
            mSize = size;
            mStrokeWidth = strokeWidth;
            mStrokeColor = strokeColor;
            mStartAngle = -90;
            mSweepAngle = 0;
        }
    
        public void setSweepAngle(float sweepAngle) {
            mSweepAngle = sweepAngle;
        }
    
        public int getSize() {
            return mSize;
        }
    
        @Override
        public void draw(Canvas canvas) {
            final Rect bounds = getBounds();
    
            if (mPath == null) {
                mPath = new Path();
            }
            mPath.reset();
            mPath.addArc(getRect(), mStartAngle, mSweepAngle);
            mPath.offset(bounds.left, bounds.top);
            canvas.drawPath(mPath, createPaint());
        }
    
        @Override
        public void setAlpha(int alpha) {
    
        }
    
        @Override
        public void setColorFilter(ColorFilter cf) {
        }
    
        @Override
        public int getOpacity() {
            return 1;
        }
    
        private RectF mRectF;
        private Paint mPaint;
        private Path mPath;
    
        private RectF getRect() {
            if (mRectF == null) {
                int index = mStrokeWidth / 2;
                mRectF = new RectF(index, index, getSize() - index, getSize() - index);
            }
            return mRectF;
        }
    
        private Paint createPaint() {
            if (mPaint == null) {
                mPaint = new Paint();
                mPaint.setAntiAlias(true);
                mPaint.setStyle(Paint.Style.STROKE);
                mPaint.setStrokeWidth(mStrokeWidth);
                mPaint.setColor(mStrokeColor);
            }
    
            return mPaint;
        }
    }

这是一个绘制圆形的自定义Drawable。首先通过CircularProgressDrawable构造方法我们指定圆形的描边宽度和描边颜色，同时初始化圆弧绘制的起始角度为-90和绘制角度0。我们通过setSweepAngle(float sweepAngle)方法设置圆弧绘制的角度，通过createPaint()初始化我们的画笔mPaint对象，通过getRect()方法指定绘制圆弧所在的矩形范围（通过size和描边确定）。最后我们在draw()方法中进行圆弧的绘制。这样，我们就实现了一个圆形进度的Drawable对象的开发。

2、CircularAnimatedDrawable类

    public class CircularAnimatedDrawable extends Drawable implements Animatable {

        private static final Interpolator ANGLE_INTERPOLATOR = new LinearInterpolator();
        private static final Interpolator SWEEP_INTERPOLATOR = new DecelerateInterpolator();
        private static final int ANGLE_ANIMATOR_DURATION = 2000;
        private static final int SWEEP_ANIMATOR_DURATION = 600;
        public static final int MIN_SWEEP_ANGLE = 30;
        private final RectF fBounds = new RectF();
    
        private ObjectAnimator mObjectAnimatorSweep;
        private ObjectAnimator mObjectAnimatorAngle;
        private boolean mModeAppearing;
        private Paint mPaint;
        private float mCurrentGlobalAngleOffset;
        private float mCurrentGlobalAngle;
        private float mCurrentSweepAngle;
        private float mBorderWidth;
        private boolean mRunning;
    
        public CircularAnimatedDrawable(int color, float borderWidth) {
            mBorderWidth = borderWidth;
    
            mPaint = new Paint();
            mPaint.setAntiAlias(true);
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setStrokeWidth(borderWidth);
            mPaint.setColor(color);
    
            setupAnimations();
        }
    
        @Override
        public void draw(Canvas canvas) {
            float startAngle = mCurrentGlobalAngle - mCurrentGlobalAngleOffset;
            float sweepAngle = mCurrentSweepAngle;
            if (!mModeAppearing) {
                startAngle = startAngle + sweepAngle;
                sweepAngle = 360 - sweepAngle - MIN_SWEEP_ANGLE;
            } else {
                sweepAngle += MIN_SWEEP_ANGLE;
            }
            canvas.drawArc(fBounds, startAngle, sweepAngle, false, mPaint);
        }
    
        @Override
        public void setAlpha(int alpha) {
            mPaint.setAlpha(alpha);
        }
    
        @Override
        public void setColorFilter(ColorFilter cf) {
            mPaint.setColorFilter(cf);
        }
    
        @Override
        public int getOpacity() {
            return PixelFormat.TRANSPARENT;
        }
    
        private void toggleAppearingMode() {
            mModeAppearing = !mModeAppearing;
            if (mModeAppearing) {
                mCurrentGlobalAngleOffset = (mCurrentGlobalAngleOffset + MIN_SWEEP_ANGLE * 2) % 360;
            }
        }
    
        @Override
        protected void onBoundsChange(Rect bounds) {
            super.onBoundsChange(bounds);
            fBounds.left = bounds.left + mBorderWidth / 2f + .5f;
            fBounds.right = bounds.right - mBorderWidth / 2f - .5f;
            fBounds.top = bounds.top + mBorderWidth / 2f + .5f;
            fBounds.bottom = bounds.bottom - mBorderWidth / 2f - .5f;
        }
    
        private Property<CircularAnimatedDrawable, Float> mAngleProperty  =
                new Property<CircularAnimatedDrawable, Float>(Float.class, "angle") {
            @Override
            public Float get(CircularAnimatedDrawable object) {
                return object.getCurrentGlobalAngle();
            }
    
            @Override
            public void set(CircularAnimatedDrawable object, Float value) {
                object.setCurrentGlobalAngle(value);
            }
        };
    
        private Property<CircularAnimatedDrawable, Float> mSweepProperty
                = new Property<CircularAnimatedDrawable, Float>(Float.class, "arc") {
            @Override
            public Float get(CircularAnimatedDrawable object) {
                return object.getCurrentSweepAngle();
            }
    
            @Override
            public void set(CircularAnimatedDrawable object, Float value) {
                object.setCurrentSweepAngle(value);
            }
        };
    
        private void setupAnimations() {
            mObjectAnimatorAngle = ObjectAnimator.ofFloat(this, mAngleProperty, 360f);
            mObjectAnimatorAngle.setInterpolator(ANGLE_INTERPOLATOR);
            mObjectAnimatorAngle.setDuration(ANGLE_ANIMATOR_DURATION);
            mObjectAnimatorAngle.setRepeatMode(ValueAnimator.RESTART);
            mObjectAnimatorAngle.setRepeatCount(ValueAnimator.INFINITE);
    
            mObjectAnimatorSweep = ObjectAnimator.ofFloat(this, mSweepProperty, 360f - MIN_SWEEP_ANGLE * 2);
            mObjectAnimatorSweep.setInterpolator(SWEEP_INTERPOLATOR);
            mObjectAnimatorSweep.setDuration(SWEEP_ANIMATOR_DURATION);
            mObjectAnimatorSweep.setRepeatMode(ValueAnimator.RESTART);
            mObjectAnimatorSweep.setRepeatCount(ValueAnimator.INFINITE);
            mObjectAnimatorSweep.addListener(new Animator.AnimatorListener() {
                @Override
                public void onAnimationStart(Animator animation) {
    
                }
    
                @Override
                public void onAnimationEnd(Animator animation) {
    
                }
    
                @Override
                public void onAnimationCancel(Animator animation) {
    
                }
    
                @Override
                public void onAnimationRepeat(Animator animation) {
                    toggleAppearingMode();
                }
            });
        }
    
        @Override
        public void start() {
            if (isRunning()) {
                return;
            }
            mRunning = true;
            mObjectAnimatorAngle.start();
            mObjectAnimatorSweep.start();
            invalidateSelf();
        }
    
        @Override
        public void stop() {
            if (!isRunning()) {
                return;
            }
            mRunning = false;
            mObjectAnimatorAngle.cancel();
            mObjectAnimatorSweep.cancel();
            invalidateSelf();
        }
    
        @Override
        public boolean isRunning() {
            return mRunning;
        }
    
        public void setCurrentGlobalAngle(float currentGlobalAngle) {
            mCurrentGlobalAngle = currentGlobalAngle;
            invalidateSelf();
        }
    
        public float getCurrentGlobalAngle() {
            return mCurrentGlobalAngle;
        }
    
        public void setCurrentSweepAngle(float currentSweepAngle) {
            mCurrentSweepAngle = currentSweepAngle;
            invalidateSelf();
        }
    
        public float getCurrentSweepAngle() {
            return mCurrentSweepAngle;
        }
    
    }

从类的声明上来看，CircularAnimatedDrawable类与CircularProgressDrawable的不同之处在于CircularAnimatedDrawable实现了Animatable接口。我们都知道这个Animatable接口就是为了支持Drawable实现动画的，所以这个CircularAnimatedDrawable肯定会有动画效果，即旋转的弧形效果。
首先我们从该类的成员变量分析，首先是定义的一些基本常量如：圆弧角度变化的加速器、持续时间、最小旋转角度等。同时也定义了一些常用的变量，比如：圆弧角度的变化对应的Animator、当前的角度(mCurrentGlobalAngle)、圆弧旋转角度(mCurrentSweepAngle)、角度偏移量(mCurrentGlobalAngleOffset)、圆弧宽度等。主题思路就是我们通过属性动画对圆弧的角度进行变化，然后进行绘制，形成动态的圆弧效果。在这里，我们需要着重较少下Property类型的两个成员变量mAngleProperty、mSweepProperty，它封装了我们的角度和旋转角度，我们就是通过Property类进行封装类的属性，然后进行属性动画变换（属性动画一般要求属性具有get、set方法）。
成员变量基本介绍完毕，这里我们回头去看构造函数，着重注意方法setupAnimations()，这个方法用于初始化属性动画类，指定相关的属性。这里注意一点，我们通过Property封装CircularAnimatedDrawable对象，然后进行设置角度，实现角度的改变，达到效果。最后在draw方法中进行绘制。这里的一个难点就是实现这个效果的一套角度的逻辑处理，需要仔细研究下。

3、CircularProgressButton类     
这个类就是我们的核心控件类，我们通过该类实现效果。在我们实际开发中，我们通过selector文件给Button设置不同状态下的样式。同样，这个的实现原理也是通过状态进行判断，针对不同状态之间的切换配以动画的处理，所以显得无比的靓丽。

public class CircularProgressButton extends Button {
    //Button的状态值
    public static final int IDLE_STATE_PROGRESS = 0;
    public static final int ERROR_STATE_PROGRESS = -1;
    public static final int SUCCESS_STATE_PROGRESS = 100;
    public static final int INDETERMINATE_STATE_PROGRESS = 50;

    private StrokeGradientDrawable background;
    //切换的两个Drawable
    private CircularAnimatedDrawable mAnimatedDrawable;
    private CircularProgressDrawable mProgressDrawable;
    //定义不同状态下的字体颜色ColorStateList
    private ColorStateList mIdleColorState;
    private ColorStateList mCompleteColorState;
    private ColorStateList mErrorColorState;
    //Button对应的不同状态的Drawable
    private StateListDrawable mIdleStateDrawable;
    private StateListDrawable mCompleteStateDrawable;
    private StateListDrawable mErrorStateDrawable;
    //状态管理器
    private StateManager mStateManager;
    private State mState;    //状态
    private String mIdleText;    //Idle状态下的文字
    private String mCompleteText;    //Complete时的文字
    private String mErrorText;        //Error时的文字
    private String mProgressText;    //进度条文字

    private int mColorProgress;
    private int mColorIndicator;
    private int mColorIndicatorBackground;
    private int mIconComplete;
    private int mIconError;
    private int mStrokeWidth;
    private int mPaddingProgress;
    private float mCornerRadius;
    private boolean mIndeterminateProgressMode;
    private boolean mConfigurationChanged;
    //枚举类型的状态
    private enum State {
        PROGRESS, IDLE, COMPLETE, ERROR
    }

    private int mMaxProgress;
    private int mProgress;

    private boolean mMorphingInProgress;

    public CircularProgressButton(Context context) {
        super(context);
        init(context, null);
    }

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

    public CircularProgressButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init(context, attrs);
    }
    //用于初始化相关的成员变量
    private void init(Context context, AttributeSet attributeSet) {
        mStrokeWidth = (int) getContext().getResources().getDimension(R.dimen.cpb_stroke_width);

        initAttributes(context, attributeSet);

        mMaxProgress = 100;
        mState = State.IDLE;
        mStateManager = new StateManager(this);

        setText(mIdleText);
        //状态初始化为Idle静止状态
        initIdleStateDrawable();
        setBackgroundCompat(mIdleStateDrawable);
    }
    //设置为Error状态
    private void initErrorStateDrawable() {
        int colorPressed = getPressedColor(mErrorColorState);

        StrokeGradientDrawable drawablePressed = createDrawable(colorPressed);
        mErrorStateDrawable = new StateListDrawable();
        //给ErrorStateDrawable添加状态。
        mErrorStateDrawable.addState(new int[]{android.R.attr.state_pressed}, drawablePressed.getGradientDrawable());
        mErrorStateDrawable.addState(StateSet.WILD_CARD, background.getGradientDrawable());
    }
    //初始化Complete状态的StateListDrawable
    private void initCompleteStateDrawable() {
        int colorPressed = getPressedColor(mCompleteColorState);

        StrokeGradientDrawable drawablePressed = createDrawable(colorPressed);
        mCompleteStateDrawable = new StateListDrawable();

        mCompleteStateDrawable.addState(new int[]{android.R.attr.state_pressed}, drawablePressed.getGradientDrawable());
        mCompleteStateDrawable.addState(StateSet.WILD_CARD, background.getGradientDrawable());
    }

    private void initIdleStateDrawable() {
        int colorNormal = getNormalColor(mIdleColorState);
        int colorPressed = getPressedColor(mIdleColorState);
        int colorFocused = getFocusedColor(mIdleColorState);
        int colorDisabled = getDisabledColor(mIdleColorState);
        if (background == null) {
            background = createDrawable(colorNormal);
        }

        StrokeGradientDrawable drawableDisabled = createDrawable(colorDisabled);
        StrokeGradientDrawable drawableFocused = createDrawable(colorFocused);
        StrokeGradientDrawable drawablePressed = createDrawable(colorPressed);
        mIdleStateDrawable = new StateListDrawable();

        mIdleStateDrawable.addState(new int[]{android.R.attr.state_pressed}, drawablePressed.getGradientDrawable());
        mIdleStateDrawable.addState(new int[]{android.R.attr.state_focused}, drawableFocused.getGradientDrawable());
        mIdleStateDrawable.addState(new int[]{-android.R.attr.state_enabled}, drawableDisabled.getGradientDrawable());
        mIdleStateDrawable.addState(StateSet.WILD_CARD, background.getGradientDrawable());
    }
    //获取正常状态下的ColorStateList
    private int getNormalColor(ColorStateList colorStateList) {
        return colorStateList.getColorForState(new int[]{android.R.attr.state_enabled}, 0);
    }

    private int getPressedColor(ColorStateList colorStateList) {
        return colorStateList.getColorForState(new int[]{android.R.attr.state_pressed}, 0);
    }

    private int getFocusedColor(ColorStateList colorStateList) {
        return colorStateList.getColorForState(new int[]{android.R.attr.state_focused}, 0);
    }

    private int getDisabledColor(ColorStateList colorStateList) {
        return colorStateList.getColorForState(new int[]{-android.R.attr.state_enabled}, 0);
    }

    private StrokeGradientDrawable createDrawable(int color) {
        GradientDrawable drawable = (GradientDrawable) getResources().getDrawable(R.drawable.cpb_background).mutate();
        drawable.setColor(color);
        drawable.setCornerRadius(mCornerRadius);
        StrokeGradientDrawable strokeGradientDrawable = new StrokeGradientDrawable(drawable);
        strokeGradientDrawable.setStrokeColor(color);
        strokeGradientDrawable.setStrokeWidth(mStrokeWidth);

        return strokeGradientDrawable;
    }

    //关键点，重写drawableStateChanged方法，判断改变的状态，然后进行不同状态的切换
    @Override
    protected void drawableStateChanged() {
        if (mState == State.COMPLETE) {
            initCompleteStateDrawable();
            setBackgroundCompat(mCompleteStateDrawable);
        } else if (mState == State.IDLE) {
            initIdleStateDrawable();
            setBackgroundCompat(mIdleStateDrawable);
        } else if (mState == State.ERROR) {
            initErrorStateDrawable();
            setBackgroundCompat(mErrorStateDrawable);
        }

        if (mState != State.PROGRESS) {
            super.drawableStateChanged();
        }
    }

    private void initAttributes(Context context, AttributeSet attributeSet) {
        TypedArray attr = getTypedArray(context, attributeSet, R.styleable.CircularProgressButton);
        if (attr == null) {
            return;
        }

        try {

            mIdleText = attr.getString(R.styleable.CircularProgressButton_cpb_textIdle);
            mCompleteText = attr.getString(R.styleable.CircularProgressButton_cpb_textComplete);
            mErrorText = attr.getString(R.styleable.CircularProgressButton_cpb_textError);
            mProgressText = attr.getString(R.styleable.CircularProgressButton_cpb_textProgress);

            mIconComplete = attr.getResourceId(R.styleable.CircularProgressButton_cpb_iconComplete, 0);
            mIconError = attr.getResourceId(R.styleable.CircularProgressButton_cpb_iconError, 0);
            mCornerRadius = attr.getDimension(R.styleable.CircularProgressButton_cpb_cornerRadius, 0);
            mPaddingProgress = attr.getDimensionPixelSize(R.styleable.CircularProgressButton_cpb_paddingProgress, 0);

            int blue = getColor(R.color.cpb_blue);
            int white = getColor(R.color.cpb_white);
            int grey = getColor(R.color.cpb_grey);

            int idleStateSelector = attr.getResourceId(R.styleable.CircularProgressButton_cpb_selectorIdle,
                    R.color.cpb_idle_state_selector);
            mIdleColorState = getResources().getColorStateList(idleStateSelector);

            int completeStateSelector = attr.getResourceId(R.styleable.CircularProgressButton_cpb_selectorComplete,
                    R.color.cpb_complete_state_selector);
            mCompleteColorState = getResources().getColorStateList(completeStateSelector);

            int errorStateSelector = attr.getResourceId(R.styleable.CircularProgressButton_cpb_selectorError,
                    R.color.cpb_error_state_selector);
            mErrorColorState = getResources().getColorStateList(errorStateSelector);

            mColorProgress = attr.getColor(R.styleable.CircularProgressButton_cpb_colorProgress, white);
            mColorIndicator = attr.getColor(R.styleable.CircularProgressButton_cpb_colorIndicator, blue);
            mColorIndicatorBackground =
                    attr.getColor(R.styleable.CircularProgressButton_cpb_colorIndicatorBackground, grey);
        } finally {
            attr.recycle();
        }
    }

    protected int getColor(int id) {
        return getResources().getColor(id);
    }

    protected TypedArray getTypedArray(Context context, AttributeSet attributeSet, int[] attr) {
        return context.obtainStyledAttributes(attributeSet, attr, 0, 0);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        if (mProgress > 0 && mState == State.PROGRESS && !mMorphingInProgress) {
            if (mIndeterminateProgressMode) {//绘制可变弧长形式
                drawIndeterminateProgress(canvas);
            } else {//绘制纯进度条形式
                drawProgress(canvas);
            }
        }
    }

    private void drawIndeterminateProgress(Canvas canvas) {
        if (mAnimatedDrawable == null) {
            int offset = (getWidth() - getHeight()) / 2;
            mAnimatedDrawable = new CircularAnimatedDrawable(mColorIndicator, mStrokeWidth);
            int left = offset + mPaddingProgress;
            int right = getWidth() - offset - mPaddingProgress;
            int bottom = getHeight() - mPaddingProgress;
            int top = mPaddingProgress;
            mAnimatedDrawable.setBounds(left, top, right, bottom);
            mAnimatedDrawable.setCallback(this);
            mAnimatedDrawable.start();
        } else {
            mAnimatedDrawable.draw(canvas);
        }
    }

    private void drawProgress(Canvas canvas) {
        if (mProgressDrawable == null) {
            int offset = (getWidth() - getHeight()) / 2;
            int size = getHeight() - mPaddingProgress * 2;
            mProgressDrawable = new CircularProgressDrawable(size, mStrokeWidth, mColorIndicator);
            int left = offset + mPaddingProgress;
            mProgressDrawable.setBounds(left, mPaddingProgress, left, mPaddingProgress);
        }
        float sweepAngle = (360f / mMaxProgress) * mProgress;
        mProgressDrawable.setSweepAngle(sweepAngle);
        mProgressDrawable.draw(canvas);
    }

    public boolean isIndeterminateProgressMode() {
        return mIndeterminateProgressMode;
    }

    public void setIndeterminateProgressMode(boolean indeterminateProgressMode) {
        this.mIndeterminateProgressMode = indeterminateProgressMode;
    }

    @Override
    protected boolean verifyDrawable(Drawable who) {
        return who == mAnimatedDrawable || super.verifyDrawable(who);
    }

    private MorphingAnimation createMorphing() {
        mMorphingInProgress = true;

        MorphingAnimation animation = new MorphingAnimation(this, background);
        animation.setFromCornerRadius(mCornerRadius);
        animation.setToCornerRadius(mCornerRadius);

        animation.setFromWidth(getWidth());
        animation.setToWidth(getWidth());

        if (mConfigurationChanged) {
            animation.setDuration(MorphingAnimation.DURATION_INSTANT);
        } else {
            animation.setDuration(MorphingAnimation.DURATION_NORMAL);
        }

        mConfigurationChanged = false;

        return animation;
    }

    private MorphingAnimation createProgressMorphing(float fromCorner, float toCorner, int fromWidth, int toWidth) {
        mMorphingInProgress = true;

        MorphingAnimation animation = new MorphingAnimation(this, background);
        animation.setFromCornerRadius(fromCorner);
        animation.setToCornerRadius(toCorner);

        animation.setPadding(mPaddingProgress);

        animation.setFromWidth(fromWidth);
        animation.setToWidth(toWidth);

        if (mConfigurationChanged) {
            animation.setDuration(MorphingAnimation.DURATION_INSTANT);
        } else {
            animation.setDuration(MorphingAnimation.DURATION_NORMAL);
        }

        mConfigurationChanged = false;

        return animation;
    }
    //切换到进度条形式
    private void morphToProgress() {
        setWidth(getWidth());
        setText(mProgressText);

        MorphingAnimation animation = createProgressMorphing(mCornerRadius, getHeight(), getWidth(), getHeight());

        animation.setFromColor(getNormalColor(mIdleColorState));
        animation.setToColor(mColorProgress);

        animation.setFromStrokeColor(getNormalColor(mIdleColorState));
        animation.setToStrokeColor(mColorIndicatorBackground);

        animation.setListener(mProgressStateListener);

        animation.start();
    }

    private OnAnimationEndListener mProgressStateListener = new OnAnimationEndListener() {
        @Override
        public void onAnimationEnd() {
            mMorphingInProgress = false;
            mState = State.PROGRESS;

            mStateManager.checkState(CircularProgressButton.this);
        }
    };

    private void morphProgressToComplete() {
        MorphingAnimation animation = createProgressMorphing(getHeight(), mCornerRadius, getHeight(), getWidth());

        animation.setFromColor(mColorProgress);
        animation.setToColor(getNormalColor(mCompleteColorState));

        animation.setFromStrokeColor(mColorIndicator);
        animation.setToStrokeColor(getNormalColor(mCompleteColorState));

        animation.setListener(mCompleteStateListener);

        animation.start();

    }
    //idle状态切换为complete状态
    private void morphIdleToComplete() {
        MorphingAnimation animation = createMorphing();

        animation.setFromColor(getNormalColor(mIdleColorState));
        animation.setToColor(getNormalColor(mCompleteColorState));

        animation.setFromStrokeColor(getNormalColor(mIdleColorState));
        animation.setToStrokeColor(getNormalColor(mCompleteColorState));

        animation.setListener(mCompleteStateListener);

        animation.start();

    }

    private OnAnimationEndListener mCompleteStateListener = new OnAnimationEndListener() {
        @Override
        public void onAnimationEnd() {
            if (mIconComplete != 0) {
                setText(null);
                setIcon(mIconComplete);
            } else {
                setText(mCompleteText);
            }
            mMorphingInProgress = false;
            mState = State.COMPLETE;

            mStateManager.checkState(CircularProgressButton.this);
        }
    };

    private void morphCompleteToIdle() {
        MorphingAnimation animation = createMorphing();

        animation.setFromColor(getNormalColor(mCompleteColorState));
        animation.setToColor(getNormalColor(mIdleColorState));

        animation.setFromStrokeColor(getNormalColor(mCompleteColorState));
        animation.setToStrokeColor(getNormalColor(mIdleColorState));

        animation.setListener(mIdleStateListener);

        animation.start();

    }
    //error状态切换到idle状态
    private void morphErrorToIdle() {
        MorphingAnimation animation = createMorphing();

        animation.setFromColor(getNormalColor(mErrorColorState));
        animation.setToColor(getNormalColor(mIdleColorState));

        animation.setFromStrokeColor(getNormalColor(mErrorColorState));
        animation.setToStrokeColor(getNormalColor(mIdleColorState));

        animation.setListener(mIdleStateListener);

        animation.start();

    }

    private OnAnimationEndListener mIdleStateListener = new OnAnimationEndListener() {
        @Override
        public void onAnimationEnd() {
            removeIcon();
            setText(mIdleText);
            mMorphingInProgress = false;
            mState = State.IDLE;

            mStateManager.checkState(CircularProgressButton.this);
        }
    };
    //idle状态切换到error状态
    private void morphIdleToError() {
        MorphingAnimation animation = createMorphing();

        animation.setFromColor(getNormalColor(mIdleColorState));
        animation.setToColor(getNormalColor(mErrorColorState));

        animation.setFromStrokeColor(getNormalColor(mIdleColorState));
        animation.setToStrokeColor(getNormalColor(mErrorColorState));

        animation.setListener(mErrorStateListener);

        animation.start();

    }
    //进度条切换到error状态
    private void morphProgressToError() {
        MorphingAnimation animation = createProgressMorphing(getHeight(), mCornerRadius, getHeight(), getWidth());

        animation.setFromColor(mColorProgress);
        animation.setToColor(getNormalColor(mErrorColorState));

        animation.setFromStrokeColor(mColorIndicator);
        animation.setToStrokeColor(getNormalColor(mErrorColorState));
        animation.setListener(mErrorStateListener);

        animation.start();
    }

    private OnAnimationEndListener mErrorStateListener = new OnAnimationEndListener() {
        @Override
        public void onAnimationEnd() {
            if (mIconError != 0) {
                setText(null);
                setIcon(mIconError);
            } else {
                setText(mErrorText);
            }
            mMorphingInProgress = false;
            mState = State.ERROR;

            mStateManager.checkState(CircularProgressButton.this);
        }
    };

    private void morphProgressToIdle() {
        MorphingAnimation animation = createProgressMorphing(getHeight(), mCornerRadius, getHeight(), getWidth());

        animation.setFromColor(mColorProgress);
        animation.setToColor(getNormalColor(mIdleColorState));

        animation.setFromStrokeColor(mColorIndicator);
        animation.setToStrokeColor(getNormalColor(mIdleColorState));
        animation.setListener(new OnAnimationEndListener() {
            @Override
            public void onAnimationEnd() {
                removeIcon();
                setText(mIdleText);
                mMorphingInProgress = false;
                mState = State.IDLE;

                mStateManager.checkState(CircularProgressButton.this);
            }
        });

        animation.start();
    }

    private void setIcon(int icon) {
        Drawable drawable = getResources().getDrawable(icon);
        if (drawable != null) {
            int padding = (getWidth() / 2) - (drawable.getIntrinsicWidth() / 2);
            setCompoundDrawablesWithIntrinsicBounds(icon, 0, 0, 0);
            setPadding(padding, 0, 0, 0);
        }
    }

    protected void removeIcon() {
        setCompoundDrawablesWithIntrinsicBounds(0, 0, 0, 0);
        setPadding(0, 0, 0, 0);
    }

    /**
     * Set the View's background. Masks the API changes made in Jelly Bean.
     */
    @SuppressWarnings("deprecation")
    @SuppressLint("NewApi")
    public void setBackgroundCompat(Drawable drawable) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
            setBackground(drawable);
        } else {
            setBackgroundDrawable(drawable);
        }
    }

    public void setProgress(int progress) {
        mProgress = progress;

        if (mMorphingInProgress || getWidth() == 0) {
            return;
        }

        mStateManager.saveProgress(this);

        if (mProgress >= mMaxProgress) {
            if (mState == State.PROGRESS) {
                morphProgressToComplete();
            } else if (mState == State.IDLE) {
                morphIdleToComplete();
            }
        } else if (mProgress > IDLE_STATE_PROGRESS) {
            if (mState == State.IDLE) {
                morphToProgress();
            } else if (mState == State.PROGRESS) {
                invalidate();
            }
        } else if (mProgress == ERROR_STATE_PROGRESS) {
            if (mState == State.PROGRESS) {
                morphProgressToError();
            } else if (mState == State.IDLE) {
                morphIdleToError();
            }
        } else if (mProgress == IDLE_STATE_PROGRESS) {
            if (mState == State.COMPLETE) {
                morphCompleteToIdle();
            } else if (mState == State.PROGRESS) {
                morphProgressToIdle();
            } else if (mState == State.ERROR) {
                morphErrorToIdle();
            }
        }
    }

    public int getProgress() {
        return mProgress;
    }

    public void setBackgroundColor(int color) {
        background.getGradientDrawable().setColor(color);
    }

    public void setStrokeColor(int color) {
        background.setStrokeColor(color);
    }

    public String getIdleText() {
        return mIdleText;
    }

    public String getCompleteText() {
        return mCompleteText;
    }

    public String getErrorText() {
        return mErrorText;
    }

    public void setIdleText(String text) {
        mIdleText = text;
    }

    public void setCompleteText(String text) {
        mCompleteText = text;
    }

    public void setErrorText(String text) {
        mErrorText = text;
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        if (changed) {
            setProgress(mProgress);
        }
    }

    @Override
    public Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();
        SavedState savedState = new SavedState(superState);
        savedState.mProgress = mProgress;
        savedState.mIndeterminateProgressMode = mIndeterminateProgressMode;
        savedState.mConfigurationChanged = true;

        return savedState;
    }

    @Override
    public void onRestoreInstanceState(Parcelable state) {
        if (state instanceof SavedState) {
            SavedState savedState = (SavedState) state;
            mProgress = savedState.mProgress;
            mIndeterminateProgressMode = savedState.mIndeterminateProgressMode;
            mConfigurationChanged = savedState.mConfigurationChanged;
            super.onRestoreInstanceState(savedState.getSuperState());
            setProgress(mProgress);
        } else {
            super.onRestoreInstanceState(state);
        }
    }


    static class SavedState extends BaseSavedState {

        private boolean mIndeterminateProgressMode;
        private boolean mConfigurationChanged;
        private int mProgress;

        public SavedState(Parcelable parcel) {
            super(parcel);
        }

        private SavedState(Parcel in) {
            super(in);
            mProgress = in.readInt();
            mIndeterminateProgressMode = in.readInt() == 1;
            mConfigurationChanged = in.readInt() == 1;
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeInt(mProgress);
            out.writeInt(mIndeterminateProgressMode ? 1 : 0);
            out.writeInt(mConfigurationChanged ? 1 : 0);
        }

        public static final Creator<SavedState> CREATOR = new Creator<SavedState>() {

            @Override
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            @Override
            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }
}

上面就是源码，个别的细节知识点就不做讲解，只说说总体的思路，通过重写drawableStateChanged()方法监听Button的State状态改变，然后针对状态做我们指定的状态切换，这里就涉及到各个initXXXStateDrawable()方法，通过这些方法实现各个State状态对应的StateListDrawable对应及其他相关变量的初始化，然后在onLayout方法中通过setProgress()方法实现切换，这个方法中根据不同的progress判断，进行状态的切换，主要是执行一系列的morphToXX方法，在这个方法里，封装了一个MorphingAnimation对象，该对象内部通过封装的属性动画实现控件宽度长度的渐变，达到改变控件大小的效果。最后在更新控件，实现效果。


改变主要针对整体的思路，具体的实现细节还需进一步研究源码，特此记录下Drawable的不错案例。