Android自定义控件仿iOS滑块SwitchButton

public class SwitchButton extends View implements View.OnTouchListener {
 private Bitmap bg_on, bg_off, slipper_btn;
 /**
 * 按下时的x和当前的x
 */
 private float downX, nowX;
 /**
 * 记录用户是否在滑动
 */
 private boolean onSlip = false;
 /**
 * 当前的状态
 */
 private boolean nowStatus = false;
 /**
 * 监听接口
 */
 private OnChangedListener listener;
 /**
 * 一个滑动的距离临界值，判断是滑动还是点击
 * getScaledTouchSlop()：
 * Distance in pixels a touch can wander before we think the user is scrolling
 * */
 private int mTouchSlop=new ViewConfiguration().getScaledTouchSlop();
 
 public SwitchButton(Context context) {
 super(context);
 init();
 }
 public SwitchButton(Context context, AttributeSet attrs) {
 super(context, attrs);
 init();
 }
 public void init(){
 //载入图片资源
 bg_on = BitmapFactory.decodeResource(getResources(), R.mipmap.switch_on_on);
 bg_off = BitmapFactory.decodeResource(getResources(), R.mipmap.switch_off_off);
 slipper_btn = BitmapFactory.decodeResource(getResources(), R.mipmap.switch_ball_ball);
 setOnTouchListener(this);
 }
 protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 Matrix matrix = new Matrix();
 Paint paint = new Paint();
 float x = 0;
 //根据nowX设置背景，开或者关状态
 if (nowX < (bg_on.getWidth()/2)){
 canvas.drawBitmap(bg_off, matrix, paint);//画出关闭时的背景
 }else{
 canvas.drawBitmap(bg_on, matrix, paint);//画出打开时的背景
 }
 if (onSlip) {//是否是在滑动状态,
 if(nowX >= bg_on.getWidth())//是否划出指定范围,不能让滑块跑到外头,必须做这个判断
 x = bg_on.getWidth() - slipper_btn.getWidth()/2;//减去滑块1/2的长度
 else
 x = nowX - slipper_btn.getWidth()/2;
 }else {
 if(nowStatus){//根据当前的状态设置滑块的x值
 x = bg_on.getWidth() - slipper_btn.getWidth();
 }else{
 x = 0;
 }
 }
 //对滑块滑动进行异常处理，不能让滑块出界
 if (x < 0 ){
 x = 0;
 }
 else if(x > bg_on.getWidth() - slipper_btn.getWidth()){
 x = bg_on.getWidth() - slipper_btn.getWidth();
 }
 //画出滑块
 canvas.drawBitmap(slipper_btn, x, 0, paint);
 }
 
 @Override
 public boolean onTouch(View v, MotionEvent event) {
 switch(event.getAction()){
 case MotionEvent.ACTION_DOWN:{
 if (event.getX() > bg_off.getWidth() || event.getY() > bg_off.getHeight()){
 return false;
 }else{
 onSlip = true;
 downX = event.getX();
 nowX = downX;
 }
 break;
 }
 case MotionEvent.ACTION_MOVE:{
 nowX = event.getX();
 break;
 }
 case MotionEvent.ACTION_UP:{
 DebugLog.e("mTouchSlop:"+mTouchSlop);
 onSlip = false;
 nowX = event.getX();
 float float_distance=nowX - downX;
 int int_disatnce=(int)float_distance;
 DebugLog.e("int_disatnce:"+int_disatnce);
 /**
 * 滑动距离太短，认定是点击事件
 */
 if(Math.abs(int_disatnce)= (bg_on.getWidth()/2)){
 nowStatus = true;
 nowX = bg_on.getWidth() - slipper_btn.getWidth();
 }else{
 nowStatus = false;
 nowX = 0;
 }
 }
 if(listener != null){
 listener.OnChanged(SwitchButton.this, nowStatus);
 }
 break;
 }
 }
 //刷新界面
 invalidate();
 return true;
 }
 /**
 * 为WiperSwitch设置一个监听，供外部调用的方法
 * @param listener
 */
 public void setOnChangedListener(OnChangedListener listener){
 this.listener = listener;
 }
 /**
 * 设置滑动开关的初始状态，供外部调用
 * @param checked
 */
 public void setChecked(boolean checked){
 if(checked){
 nowX = bg_off.getWidth();
 }else{
 nowX = 0;
 }
 nowStatus = checked;
 }
 public boolean isChecked() {
 return nowStatus;
 }
 /**
 * 回调接口
 *
 */
 public interface OnChangedListener {
 public void OnChanged(SwitchButton wiperSwitch, boolean checkState);
 }
}