显示和隐藏ImageView

Question

我有一个基于本教程的项目,其中用户旋转一个轮子,一个数字的值int days根据轮子的当前位置而改变,现在我想ImageView circle根据这个数字的值显示或隐藏另一个图像,但是它抛出NullPointerException

这是我的onTouch事,抱歉我的英语不好

@Override
public boolean onTouch(View v, MotionEvent event) {

    switch (event.getAction()) {

        case MotionEvent.ACTION_DOWN:
            // reset the touched quadrants
            for (int i = 0; i < quadrantTouched.length; i++) {
                quadrantTouched[i] = false;
            }
            allowRotating = false;
            startAngle = getAngle(event.getX(), event.getY());
            break;

        case MotionEvent.ACTION_MOVE:
            double currentAngle = getAngle(event.getX(), event.getY());
            rotateDialer((float) (startAngle - currentAngle));
            startAngle = currentAngle;
            days = ((int) currentAngle / 12) + 1;
            String test = Integer.toString(days);
            tvnumber.setText(test);

            switch (days) {
                case 1:
                    circle.setVisibility(View.INVISIBLE);
                    break;
                case 3:
                    circle.setVisibility(View.VISIBLE);
                    break;
            }
            break;

        case MotionEvent.ACTION_UP:
            allowRotating = false;
            break;
    }
}

我的logcat

Answer 1

您需要初始化circle视图,最有可能使用该findViewById()方法