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
