Android Question [Solved] Need help converting Java code to B4A

[IndieDev]

Hi,

Been working on code for a compass.
Got stuck at converting the code below to B4A.

This slows down rotation of the compass (Ease To functionality).

Would appreciate if anyone could help converting this or enlighten me on how to use this in #If Java.

    protected Runnable mCompassViewUpdater = new Runnable() {
        @Override
        public void run() {
            final float MAX_ROTATE_DEGREE = 1.0f;
            if (mPointer != null && !mStopDrawing) {
                if (mDirection != mTargetDirection) {
                    /** Calculate the short routine */
                    float to = mTargetDirection;
                    if (to - mDirection > 180) {
                        to -= 360;
                    } else if (to - mDirection < -180) {
                        to += 360;
                    }
                    /** Limit max speed to MAX_ROTATE_DEGREE */
                    float distance = to - mDirection;
                    if (Math.abs(distance) > MAX_ROTATE_DEGREE) {
                        distance = distance > 0 ? MAX_ROTATE_DEGREE : (-1.0f * MAX_ROTATE_DEGREE);
                    }
                    /** Slow down if the distance is short */
                    mDirection = normalizeDegree(mDirection
                            + ((to - mDirection)
                            * mInterpolator.getInterpolation(Math.abs(distance) > MAX_ROTATE_DEGREE ? 0.4f : 0.3f)));
                    mPointer.updateDirection(mDirection);
                }
            }
        }
    };

    private float normalizeDegree(float degrees) {
        return (degrees + 720) % 360;
    }

This is how I tried to use in #If Java code.

#If JAVA
    import android.view.animation.AccelerateInterpolator;
    import java.lang.Object;
    import java.util.concurrent.Callable;
   
    float mDirection;
    //float mTargetDirection;
    AccelerateInterpolator mInterpolator;
    boolean mStopDrawing;

    public float doRotate(float mTargetDirection) {
        BA.Log("mTargetDirection=" + mTargetDirection);
        final float MAX_ROTATE_DEGREE = 1.0f;
        if (!mStopDrawing) {
            if (mDirection != mTargetDirection) {
                /** Calculate the short routine */
                float to = mTargetDirection;
                if (to - mDirection > 180) {
                    to -= 360;
                } else if (to - mDirection < -180) {
                    to += 360;
                }
                /** Limit max speed to MAX_ROTATE_DEGREE */
                float distance = to - mDirection;
                if (Math.abs(distance) > MAX_ROTATE_DEGREE) {
                    distance = distance > 0 ? MAX_ROTATE_DEGREE : (-1.0f * MAX_ROTATE_DEGREE);
                }
                /** Slow down if the distance is short */
                mDirection = normalizeDegree(mDirection
                        + ((to - mDirection)
                        * mInterpolator.getInterpolation(Math.abs(distance) > MAX_ROTATE_DEGREE ? 0.4f : 0.3f)));
                //mPointer.updateDirection(mDirection);
            }
            BA.Log("mDirection=" + mDirection);
            return mDirection;
        }
        return 0.0f;
    }

    private float normalizeDegree(float degrees) {
        return (degrees + 720) % 360;
    }

#End If

Am calling the above #If Java code like this:

    Try
        Dim s As String =  NativeMe.RunMethod("doRotate", Array(Rot))
        Log("s=" & s)
    Catch
        Log("LastException=" & LastException)
    End Try

* The variable Rot has the float rotation value.

 

[IndieDev]

No, no.
The #If Java code is being called (in a kind of loop), but I am getting this error.

LastException=(NullPointerException) java.lang.NullPointerException: Attempt to invoke virtual method 'float android.view.animation.AccelerateInterpolator.getInterpolation(float)' on a null object reference

The Rotation float value is received in the doRotate function.

 

[Johan Schoeman]

Best you upload a small sample project that demonstrates the issue.

Why are you assigning the return value to a string when the inline java code returns a float?

 

[agraham]

You haven't created an AccelerateInterpolator instance

float factor = 1;
AccelerateInterpolator mInterpolator = new AccelerateInterpolator(factor);

factor

float: Degree to which the animation should be eased. Seting factor to 1.0f produces a y=x^2 parabola. Increasing factor above 1.0f exaggerates the ease-in effect (i.e., it starts even slower and ends evens faster)

https://developer.android.com/reference/android/view/animation/AccelerateInterpolator

 

[IndieDev]

Okay.

Please allow me a little time to try and revert.
Thank you.

 

[IndieDev]

You haven't created an AccelerateInterpolator instance

float factor = 1;
AccelerateInterpolator mInterpolator = new AccelerateInterpolator(factor);

https://developer.android.com/reference/android/view/animation/AccelerateInterpolator

I get this error now.

src\b4a\compass\main.java:1171: error: variable mInterpolator is already defined in class main
    AccelerateInterpolator mInterpolator = new AccelerateInterpolator(factor);
                           ^

Please allow me a liitle time to put together a quick sample program and upload.

 

[agraham]

You probably have blindly added my code and left your original declaration so you now have two declarations. Remove the original one.

 

[IndieDev]

You probably have blindly added my code and left your original declaration so you now have two declarations. Remove the original one.

Spot on!!

I actually had a declaration:

AccelerateInterpolator mInterpolator;

Now, the #If JAVA code is returning values.
Will update my code for the returned values and revert back.

Thank you.

 

[IndieDev]

@agraham

The code is working fine now!

Thanks a lot for your help.