1.自定义View，继承View类

自定义View 实现主要继承View，并实现View的一些方法。

public class SwitchControlView extends View implements OnTouchListener {
    private Bitmap bg_on, bg_off, slipper_btn;
    private float downX, nowX;

    private boolean onSlip = false;

    private boolean nowStatus = false;

    private OnChangedListener listener;

    public SwitchControlView(Context context) {
        super(context);
        init();
    }

    public SwitchControlView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public void init() {
        bg_on = BitmapFactory.decodeResource(getResources(), R.drawable.on_btn);
        bg_off = BitmapFactory.decodeResource(getResources(),
                R.drawable.off_btn);
        slipper_btn = BitmapFactory.decodeResource(getResources(),
                R.drawable.white_btn);
        setOnTouchListener(this);
    }

    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Matrix matrix = new Matrix();
        Paint paint = new Paint();
        float x = 0;
        if (bg_on != null && bg_off != null) {
            if (nowX < (bg_on.getWidth() / 2)) {
                canvas.drawBitmap(bg_off, matrix, paint);
            } else {
                canvas.drawBitmap(bg_on, matrix, paint);
            }
        }

        if (onSlip) {
            if (nowX >= bg_on.getWidth())
                x = bg_on.getWidth() - slipper_btn.getWidth() / 2;
            else
                x = nowX - slipper_btn.getWidth() / 2;
        } else {
            if (nowStatus) {
                x = bg_on.getWidth() - slipper_btn.getWidth();
            } else {
                x = 0;
            }
        }

        if (x < 0) {
            x = 0;
        } else if (x > bg_on.getWidth() - slipper_btn.getWidth()) {
            x = bg_on.getWidth() - slipper_btn.getWidth();
        }

        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: {
            onSlip = false;
            if (event.getX() >= (bg_on.getWidth() / 2)) {
                nowStatus = true;
                nowX = bg_on.getWidth() - slipper_btn.getWidth();
            } else {
                nowStatus = false;
                nowX = 0;
            }

            if (listener != null) {
                listener.OnChanged(SwitchControlView.this, nowStatus);
            }
            break;
        }
        }
        invalidate();
        return true;
    }

    public void setOnChangedListener(OnChangedListener listener) {
        this.listener = listener;
    }

    public void setChecked(boolean checked) {
        if (checked) {
            nowX = bg_off.getWidth();
        } else {
            nowX = 0;
        }
        nowStatus = checked;
    }

    public interface OnChangedListener {
        public void OnChanged(SwitchControlView wiperSwitch, boolean checkState);
    }

}