android 仿IOS开关

      Android中开关的控件有 Switch、ToggleButton这样，但是风格不太美观，不像IOS那样好看。好，既然IOS美观，我们就模仿他，毕竟要向优秀的人事物学习。此demo重在学习基础知识，样式如下：

 

网上也有实现这种效果的，但是大都滑动没中间消失的动画，或者是很复杂，今天用简单的绘图方式实现，重点就在onDraw里绘图。

/**
 * Created by gongdongdong on 2017/1/9.
 * ios开关效果
 */
public class SwitchButton extends View {
    private final Paint mPaint = new Paint();
    private static final double MBTNHEIGHT = 0.55;
    private static final int OFFSET = 3;
    private int mHeight;
    private float mAnimate = 0L;
    //此处命名不规范，目的和Android自带的switch有相同的用法
    private boolean checked = false;
    private float mScale;
    private int mSelectColor;
    private OnCheckedChangeListener mOnCheckedChangeListener;

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

    public SwitchButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.SwitchButton);
        mSelectColor = typedArray.getColor(R.styleable.SwitchButton_buttonColor, Color.parseColor("#2eaa57"));
        typedArray.recycle();
    }

    /**
     * @param widthMeasureSpec
     * @param heightMeasureSpec 高度是是宽度的0.55倍
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int width = MeasureSpec.getSize(widthMeasureSpec);
        mHeight = (int) (MBTNHEIGHT * width);
        setMeasuredDimension(width, mHeight);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAntiAlias(true);
        mPaint.setColor(mSelectColor);
        Rect rect = new Rect(0, 0, getWidth(), getHeight());
        RectF rectf = new RectF(rect);
        //绘制圆角矩形
        canvas.drawRoundRect(rectf, mHeight / 2, mHeight / 2, mPaint);

//以下save和restore很重要，确保动画在中间一层 ，如果大家不明白，可以去搜下用法

        canvas.save();
        mPaint.setColor(Color.parseColor("#e6e6e6"));
        mAnimate = mAnimate - 0.1f > 0 ? mAnimate - 0.1f : 0; // 动画标示 ，重绘10次，借鉴被人的动画
        mScale = (!checked ? 1 - mAnimate : mAnimate);
        canvas.scale(mScale, mScale, getWidth() - getHeight() / 2, rect.centerY());
        //绘制缩放的灰色圆角矩形
        canvas.drawRoundRect(rectf, mHeight / 2, mHeight / 2, mPaint);

        mPaint.setColor(Color.WHITE);
        Rect rect_inner = new Rect(OFFSET, OFFSET, getWidth() - OFFSET, getHeight() - OFFSET);
        RectF rect_f_inner = new RectF(rect_inner);
        //绘制缩放的白色圆角矩形，和上边的重叠实现灰色边框效果
        canvas.drawRoundRect(rect_f_inner, (mHeight - 8) / 2, (mHeight - 8) / 2, mPaint);
        canvas.restore();

        //中间圆形平移
        int sWidth = getWidth();
        int bTranslateX = sWidth - getHeight();
        final float translate = bTranslateX * (!checked ? mAnimate : 1 - mAnimate);
        canvas.translate(translate, 0);

        //以下两个圆带灰色边框
        mPaint.setColor(Color.parseColor("#e6e6e6"));
        canvas.drawCircle(getHeight() / 2, getHeight() / 2, getHeight() / 2 - OFFSET / 2, mPaint);

        mPaint.setColor(Color.WHITE);
        canvas.drawCircle(getHeight() / 2, getHeight() / 2, getHeight() / 2 - OFFSET, mPaint);

        if (mScale > 0) {
            mPaint.reset();
            invalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                return true;
            case MotionEvent.ACTION_MOVE:
                break;
            case MotionEvent.ACTION_UP:
                mAnimate = 1;
                checked = !checked;

             if(mOnCheckedChangeListener!=null){

                  mOnCheckedChangeListener.OnCheckedChanged(checked);

               }
                invalidate();
                break;
        }
        return super.onTouchEvent(event);
    }

    public boolean isChecked() {
        return checked;
    }

    public void setChecked(boolean checked) {
        this.checked = checked;
    }

    public OnCheckedChangeListener getmOnCheckedChangeListener() {
        return mOnCheckedChangeListener;
    }

    public void setmOnCheckedChangeListener(OnCheckedChangeListener mOnCheckedChangeListener) {
        this.mOnCheckedChangeListener = mOnCheckedChangeListener;
    }

    public  interface  OnCheckedChangeListener{
        void OnCheckedChanged(boolean isChecked);
    }

以上代码重在学习，大家有好的想法可以提出来。呵呵呵