先看效果
点击按钮时切换状态，也可以拖动切换。在滑动过程中，颜色透明度有渐变（本想做颜色渐变，但是对颜色计算不太懂，直接取平均值做出来很难看，故而采用透明度来调节效果）。
直接在代码里注释说明
public class SlideButton extends View {
private Paint paint = new Paint();
/**
* false 为关闭
*/
private boolean mCurrState = false; // 开关当前的状态, 默认为: 关闭
private int mCurrentX; // x轴的偏移量
private boolean mIsDragable = false; // 是否可拖拽
private boolean mIsSliding = false; // 是否正在滑动
private OnStateChangedListener mListener;
private String text;
private float density; // 屏幕密度
private RectF mRectBg; // 按钮背景框
private RectF mRectSlide; // 滑块框
private int mColorOn; // 打开的颜色
private int mColorOff; // 关闭的颜色
private float widthSlide; // 滑块的宽度
private int width; // 控件的宽度
private int height; //控件的高低，滑块的高度一样
private float radio; // 控件的圆角半径
public SlideButton(Context context, AttributeSet attrs) {
super(context, attrs);
density = context.getResources().getDisplayMetrics().density;
text = "开关";
mColorOn = Color.parseColor("#fe2a66");
mColorOff = Color.parseColor("#a6a6a6");
widthSlide = dip2px(30);
width = dip2px(44);
height = dip2px(24);
radio = height/2;
mRectBg = new RectF(0, 0, width, height);
mRectSlide = new RectF(0, 0, widthSlide, height);
}
/**
* 当测量当前控件的宽高时回调
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
// 设置开关的宽和高
setMeasuredDimension(width+2, height+2);
}
/**
* 绘制当前控件的方法
*/
@Override
protected void onDraw(Canvas canvas) {
float left = mCurrentX - (widthSlide / 2); // 滑块左偏移
if (left < 0) { // 处理参数
left = 0;
} else if (left > width - widthSlide) {
left = width - widthSlide;
}
float percent = left/(width-widthSlide);
paint.setAntiAlias(true);
// 把滑动开关的背景画到画布上
paint.setStyle(Style.FILL);
paint.setColor(Color.WHITE);
canvas.drawRoundRect(mRectBg, radio, radio, paint);
// 绘制渐变边框
paint.setStyle(Style.STROKE);
paint.setStrokeWidth(2f);
drawRoundRect(canvas, mRectBg, percent); // 绘制渐变
// 计算滑块位置
float textSize = height/2f;
int textX = (int) ((widthSlide-textSize*2)/2f);
int textY = (int) ((height+textSize-dip2px(2))/2f);
paint.setTextSize(textSize);
paint.setStyle(Style.FILL);
// 绘制滑块
paint.setStyle(Style.FILL);
mRectSlide.left = left;
mRectSlide.right = left + widthSlide;
drawRoundRect(canvas, mRectSlide, percent); // 绘制渐变
// 绘制问题
paint.setColor(Color.WHITE);
canvas.drawText(text, left + textX, textY, paint);
if (mIsSliding) { // 是否自动滑动
setClickable(false);
postDelayed(mAutoSlideTask, 10); // 保证滑动速度
} else {
setClickable(true);
}
super.onDraw(canvas);
}
private Runnable mAutoSlideTask = new Runnable() {
@Override
public void run() {
if (mCurrState) {
mCurrentX = mCurrentX + 3; // 不能太大，否则会有卡顿感
if (mCurrentX > width) {
mCurrentX = (int) width;
mIsSliding = false;
}
} else {
mCurrentX = mCurrentX - 3;
if (mCurrentX < 0) {
mCurrentX = 0;
mIsSliding = false;
}
}
invalidate();
}
};
/**
* 绘制渐变圆角矩形
* @param canvas
* @param rectF
* @param percent
*/
private void drawRoundRect(Canvas canvas, RectF rectF, float percent) {
int alpha = paint.getAlpha();
paint.setColor(mColorOn);
paint.setAlpha((int)(255*percent));
canvas.drawRoundRect(rectF, radio, radio, paint);
paint.setColor(mColorOff);
paint.setAlpha(255 - (int)(255*percent));
canvas.drawRoundRect(rectF, radio, radio, paint);
paint.setAlpha(alpha);// 还原
}
/**
* 当产生触摸时间时回调此方法
*/
@Override
public boolean onTouchEvent(MotionEvent event) {
if (mIsSliding) {
return true;
}
if (!mIsDragable) { // 不可拖拽时，点击就切换状态
if (event.getAction() == MotionEvent.ACTION_DOWN) {
mCurrState = !mCurrState;
if (mListener != null) {
mListener.onToggleStateChanged(mCurrState);
}
mIsSliding = true;
invalidate();
}
return true;
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN: // 按下
mCurrentX = (int) event.getX();
break;
case MotionEvent.ACTION_MOVE: // 移动
mCurrentX = (int) event.getX();
break;
case MotionEvent.ACTION_UP: // 擡起
// 判断当前滑动块, 偏向于哪一边, 如果滑动块的中心点小于背景的中心点, 设置为关闭状态
boolean state = mCurrentX > width / 2;; // 改变后的状态
// 调用用户的监听事件
if (state != mCurrState && mListener != null) {
mListener.onToggleStateChanged(state);
}
mCurrState = state;
mIsSliding = true;
break;
default:
break;
}
if (mCurrentX < 0) {
mCurrentX = 0;
} else if (mCurrentX > width) {
mCurrentX = (int) width;
}
invalidate(); // 刷新当前控件, 会引起onDraw方法的调用
return true;
}
/**
* 设置开关的状态
*
* @param b
*/
public void setToggleState(boolean state) {
mCurrState = state;
}
/**
* 设置是否可以拖拽，不可拖拽时点击就切换状态
* @param dragable
*/
public void setDragable(boolean dragable) {
mIsDragable = dragable;
}
/**
* 设置开关状态改变的监听事件
*
* @param listener
*/
public void setOnStateChangedListener(OnStateChangedListener listener) {
this.mListener = listener;
}
/**
* 获取当前是否打开
* @return
*/
public boolean isSwitchOn() {
return mCurrState;
}
private int dip2px(float dpValue) {
return (int) (dpValue * density + 0.5f);
}
/**
* @author andong 开关状态改变的监听事件
*/
public interface OnStateChangedListener {
/**
* 当开关的状态改变时回调此方法
*
* @param state 当前开关最新的状态
*/
void onToggleStateChanged(boolean state);
}
}
