我正在阅读有关旋转图像的教程（在我的情况下是轮子）
我需要角度，但每次我再次触摸轮子时，它都从 0 开始，但它必须从最后一个角度开始。
任何人都可以解释并告诉我如何做到这一点吗？
这是我的代码：
public class MainActivity extends Activity {
private static Bitmap imageOriginal, imageScaled;
private static Matrix matrix;
private ImageView dialer;
private int dialerHeight, dialerWidth;
private GestureDetector detector;
private boolean[] quadrantTouched;
private boolean allowRotating;
private double startAngle, currentAngle, current_Angle;
MotionEvent e;
boolean isClicked = false;
private SensorManager mSensorManager;
private ShakeEventListener mSensorListener;
@Override
public void onCreate(Bundle b) {
super.onCreate(b);
setContentView(R.layout.activity_soundboard);
this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
/*
* Dit regelt het roteren van het wiel.
*/
if (imageOriginal == null) {
imageOriginal = BitmapFactory.decodeResource(getResources(), R.drawable.wheelcircle);
}
// initialize the matrix only once
if (matrix == null) {
matrix = new Matrix();
} else {
// not needed, you can also post the matrix immediately to restore the old state
matrix.reset();
}
detector = new GestureDetector(this, new MyGestureDetector());
quadrantTouched = new boolean[] { false, false, false, false, false };
allowRotating = true;
dialer = (ImageView) findViewById(R.id.imageView);
dialer.setOnTouchListener(new MyOnTouchListener());
dialer.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
// method called more than once, but the values only need to be initialized one time
if (dialerHeight == 0 || dialerWidth == 0) {
dialerHeight = dialer.getHeight();
dialerWidth = dialer.getWidth();
// resize
Matrix resize = new Matrix();
resize.postScale((float)Math.min(dialerWidth, dialerHeight) / (float)imageOriginal.getWidth(), (float)Math.min(dialerWidth, dialerHeight) / (float)imageOriginal.getHeight());
imageScaled = Bitmap.createBitmap(imageOriginal, 0, 0, imageOriginal.getWidth(), imageOriginal.getHeight(), resize, false);
// translate to the image view's center
float translateX = dialerWidth / 2 - imageScaled.getWidth() / 2;
float translateY = dialerHeight / 2 - imageScaled.getHeight() / 2;
matrix.postTranslate(translateX, translateY);
dialer.setImageBitmap(imageScaled);
dialer.setImageMatrix(matrix);
}
}
});
}
private class MyOnTouchListener implements View.OnTouchListener {
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
for (int i = 0; i < quadrantTouched.length; i++) {
quadrantTouched[i] = false;
}
allowRotating = false;
startAngle = getAngle(event.getX(), event.getY());
break;
case MotionEvent.ACTION_MOVE:
currentAngle = getAngle(event.getX(), event.getY());
rotateDialer((float) (startAngle - currentAngle));
startAngle = currentAngle;
break;
case MotionEvent.ACTION_UP:
break;
}
quadrantTouched[getQuadrant(event.getX() - (dialerWidth / 2), dialerHeight - event.getY() - (dialerHeight / 2))] = true;
detector.onTouchEvent(event);
Log.e("Angle", currentAngle + "");
return true;
}
}
private class MyGestureDetector extends SimpleOnGestureListener {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
// get the quadrant of the start and the end of the fling
int q1 = getQuadrant(e1.getX() - (dialerWidth / 2), dialerHeight - e1.getY() - (dialerHeight / 2));
int q2 = getQuadrant(e2.getX() - (dialerWidth / 2), dialerHeight - e2.getY() - (dialerHeight / 2));
// the inversed rotations
if ((q1 == 2 && q2 == 2 && Math.abs(velocityX) < Math.abs(velocityY))
|| (q1 == 3 && q2 == 3)
|| (q1 == 1 && q2 == 3)
|| (q1 == 4 && q2 == 4 && Math.abs(velocityX) > Math.abs(velocityY))
|| ((q1 == 2 && q2 == 3) || (q1 == 3 && q2 == 2))
|| ((q1 == 3 && q2 == 4) || (q1 == 4 && q2 == 3))
|| (q1 == 2 && q2 == 4 && quadrantTouched[3])
|| (q1 == 4 && q2 == 2 && quadrantTouched[3])) {
dialer.post(new FlingRunnable(-1 * (velocityX + velocityY)));
} else {
// the normal rotation
dialer.post(new FlingRunnable(velocityX + velocityY));
}
return true;
}
}
private class FlingRunnable implements Runnable {
private float velocity;
public FlingRunnable(float velocity) {
this.velocity = velocity;
}
@Override
public void run() {
if (Math.abs(velocity) > 5 && allowRotating) {
rotateDialer(velocity / 75);
velocity /= 1.0666F;
// post this instance again
dialer.post(this);
}
}
}
private double getAngle(double xTouch, double yTouch) {
double x = xTouch - (dialerWidth / 2d);
double y = dialerHeight - yTouch - (dialerHeight / 2d);
switch (getQuadrant(x, y)) {
case 1:
return Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
case 2:
return 180 - Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
case 3:
return 180 + (-1 * Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI);
case 4:
return 360 + Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
default:
return 0;
}
}
/**
* @return The selected quadrant.
*/
private static int getQuadrant(double x, double y) {
if (x >= 0) {
return y >= 0 ? 1 : 4;
} else {
return y >= 0 ? 2 : 3;
}
}
private void rotateDialer(float degrees) {
matrix.postRotate(degrees, dialerWidth / 2, dialerHeight / 2);
dialer.setImageMatrix(matrix);
}
}