Android上實現IOS的switch button

import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Paint;import android.graphics.Rect;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import android.view.View.OnTouchListener;public class SlipButton extends View implements OnTouchListener {    private boolean mNowChecked = false;    private boolean mOnSlip = false;    private float mDownX, mNowX;    private Rect mBtnOn, mBtnOff;    private boolean isChgLsnOn = false;    private OnChangedListener mChgLsn;    private Bitmap mOnBg, mOffBg, mSlipBg;    public SlipButton(Context context) {        super(context);        init();    }    public SlipButton(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    private void init() {        mOnBg = BitmapFactory.decodeResource(getResources(), R.drawable.slip_bg_on);        mOffBg = BitmapFactory.decodeResource(getResources(), R.drawable.slip_bg_off);        mSlipBg = BitmapFactory.decodeResource(getResources(), R.drawable.slip_btn);        mBtnOn = new Rect(0, 0, mSlipBg.getWidth(), mSlipBg.getHeight());        mBtnOff = new Rect(mOffBg.getWidth() - mSlipBg.getWidth(), 0, mOffBg.getWidth(),                mSlipBg.getHeight());        setOnTouchListener(this);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        Matrix matrix = new Matrix();        Paint paint = new Paint();        float x;        {            if (!mNowChecked)                canvas.drawBitmap(mOffBg, matrix, paint);            else                canvas.drawBitmap(mOnBg, matrix, paint);            if (mOnSlip)            {                if (mNowX >= mOnBg.getWidth())                    x = mOnBg.getWidth() - mSlipBg.getWidth() / 2;                else                    x = mNowX - mSlipBg.getWidth() / 2;            } else {                if (mNowChecked)                    x = mBtnOff.left;                else                    x = mBtnOn.left;            }            if (x < 0)                x = 0;            else if (x > mOnBg.getWidth() - mSlipBg.getWidth())                x = mOnBg.getWidth() - mSlipBg.getWidth();            canvas.drawBitmap(mSlipBg, x, 0, paint);        }    }    @Override    public boolean onTouch(View v, MotionEvent event) {        switch (event.getAction())        {            case MotionEvent.ACTION_MOVE:                mNowX = event.getX();                break;            case MotionEvent.ACTION_DOWN:                if (event.getX() > mOnBg.getWidth() || event.getY() > mOnBg.getHeight())                    return false;                mDownX = event.getX();                mNowX = mDownX;                break;            case MotionEvent.ACTION_UP:                mOnSlip = false;                boolean LastChoose = mNowChecked;                if (!mNowChecked)                    mNowChecked = true;                else                    mNowChecked = false;                if (isChgLsnOn && (LastChoose != mNowChecked))                    mChgLsn.OnChanged(mNowChecked);                break;            default:        }        invalidate();        return true;    }    public void setChecked(boolean checked) {        if (mNowChecked != checked) {            mNowChecked = checked;            invalidate();        }    }    public void setOnChangedListener(OnChangedListener l) {        isChgLsnOn = true;        mChgLsn = l;    }    public interface OnChangedListener {        abstract void OnChanged(boolean CheckState);    }}