Android自定義開關按鈕源碼解析

@SuppressLint("ResourceAsColor")
private void initParame(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ToggleColorY, defStyleAttr, 0);
    mOpenBGColor = typedArray.getColor(R.styleable.ToggleColorY_tby_open_bg, getResources().getColor(R.color.tby_orange));
    mCloseBGColor = typedArray.getColor(R.styleable.ToggleColorY_tby_close_bg, getResources().getColor(R.color.tby_gray));
    mTouchColor = typedArray.getColor(R.styleable.ToggleColorY_tby_touch, getResources().getColor(R.color.tby_read));
    mIsOpen = typedArray.getBoolean(R.styleable.ToggleColorY_tby_state, false);
    typedArray.recycle();
}

//    Paint.Style.FILL設置隻繪制圖形內容
//    Paint.Style.STROKE設置隻繪制圖形的邊
//    Paint.Style.FILL_AND_STROKE設置都繪制
private void initPaint() {
    //開關 開背景
    mOpenBGPaint = new Paint();
    mOpenBGPaint.setAntiAlias(true);
    mOpenBGPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    mOpenBGPaint.setColor(mOpenBGColor);
    //開關 關背景
    mCloseBGPaint = new Paint();
    mCloseBGPaint.setAntiAlias(true);
    mCloseBGPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    mCloseBGPaint.setColor(mCloseBGColor);
    //Touch 圓形
    mTouchPaint = new Paint();
    mTouchPaint.setAntiAlias(true);
    mTouchPaint.setStyle(Paint.Style.FILL_AND_STROKE);
    mTouchPaint.setColor(mTouchColor);
    
    //開 RectF
    mRectFOpen = new RectF();
    //關 RectF
    mRectFClose = new RectF();
}

@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
    super.onLayout(changed, left, top, right, bottom);
    mWidth = getWidth();
    mHeight = getHeight();
    initView();
}
private void initView() {
    mRectFClose.set(0, 0, mWidth, mHeight);
    mRectFOpen.set(0, 0, mWidth, mHeight);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //開關初始狀態
    if (mIsOpen) {
        canvas.drawRoundRect(mRectFOpen, mHeight / 2, mHeight / 2, mOpenBGPaint);//開
    } else {
        canvas.drawRoundRect(mRectFClose, mHeight / 2, mHeight / 2, mCloseBGPaint);//關
    }
    firstDraw();
    //繪制滑動按鈕
    canvas.drawCircle(mSlidingDistance, mHeight / 2, mHeight / 2, mTouchPaint);
}
/**
 * 根據開關初始狀態設置滑動按鈕位置
 */
private void firstDraw() {
    if (!mIsFirst) {
        if (mIsOpen) {
            mSlidingDistance = mWidth - mHeight / 2;
        } else {
            mSlidingDistance = mHeight / 2;
        }
        mIsFirst = !mIsFirst;
    }
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            //mLastX 是記錄手指按下的點X坐標值
            //mStartX 表示的是當前滑動的起始點X坐標值
            mLastX = mStartX = event.getX();
            //2種情況
            //1, Down->Up,若是這個順序,手指抬起時候,按照點擊邏輯切換開關
            //2, Down->Move->Up,若是這個順序, 手指抬起時候, 就按照滑動邏輯切換開關
            mIsEnableClick = true;
            break;
        case MotionEvent.ACTION_MOVE:
            float mEndX = event.getX();
            //滑動起始坐標與滑動後坐標值相減,得到手指移動距離
            float distanceX = mEndX - mStartX;
            //對手指移動距離進行累加,這個距離是圓心X軸坐標
            mSlidingDistance += distanceX;
            //判斷左右兩個臨界值,不能超出左右側邊值
            if (mSlidingDistance < mHeight / 2) {
                mSlidingDistance = mHeight / 2;
            }
            if (mSlidingDistance >= mWidth - mHeight / 2) {
                mSlidingDistance = mWidth - mHeight / 2;
            }
            //重繪,到這一步,圓就隨手指開始移動瞭
            invalidate();
            //手指按下坐標與滑動最後坐標差值
            float mMinDistanceX = Math.abs(mEndX - mLastX);
            //判斷差值
            //1,如果差值大於8, 則認為是滑動, 如果用戶松開按鈕則按照滑動條件判斷
            //1,如果差值小於8, 則認為是點擊, 如果用戶此時松開按鈕則按照點擊條件判斷
            if (mMinDistanceX > 8) {
                mIsEnableClick = false;
            } else {
                mIsEnableClick = true;
            }
            //更新滑動X軸起始坐標,為下一次Move事件滑動做準備
            mStartX = event.getX();
            break;
        case MotionEvent.ACTION_UP:
            if (!mIsEnableClick) {
                //當判定為滑動時, 首先判斷這次滑動累加的距離, 如果大於一半則開關取反
                if (mSlidingDistance >= mWidth / 2) {
                    mIsOpen = true;
                } else {
                    mIsOpen = false;
                }
                //設置好開關Flag,執行替換背景
                drawToggle();
            } else {
                mIsOpen = !mIsOpen;
                drawToggle();
            }
            break;
    }
    return true;
}
/**
 * 按鈕重繪
 */
public void drawToggle() {
    if (mIsOpen) {
        //開
        mSlidingDistance = mWidth - mHeight / 2;
    } else {
        //關
        mSlidingDistance = mHeight / 2;
    }
    if (onClick != null) {
        onClick.click(mIsOpen);
    }
    invalidate();
}