android - Custom shape button

Question

I am trying to make each slice of the pie a button. The pie is a bunch of vector drawables in an image view. I don't necessarily need the actual pie slices to be clicked. I was thinking of using Path to draw a transparent shape and place it on top and make that the button, but from what I understand, drawables aren't clickable.

I read one blog post that apparently used paths to make a custom shaped image view, and I know image views are clickable, but it seems like with the implementation in the blog post the image views are still rectangular, but the bitmaps the blogger was using in the example were just trimmed to a custom shape inside the image view. This is the post I'm referring to: http://www.androidhub4you.com/2014/10/android-custom-shape-imageview-rounded.html

Please explain this to me like a five year old. I'm relatively new to programming. Were it not for Android Studio's automatic everything, I would not be here.

Thank you.

Answer 1

You can just using drawArc and drawCircle to draw a radial menu, and using distance between touch point and center point and angle to detect which slice is currently being click. I wrote a Sample for you:

public class RadioButtons extends View {

    //the number of slice
    private int mSlices = 6;

    //the angle of each slice
    private int degreeStep = 360 / mSlices;

    private int quarterDegreeMinus = -90;

    private float mOuterRadius;
    private float mInnerRadius;

    //using radius square to prevent square root calculation
    private float outerRadiusSquare;
    private float innerRadiusSquare;

    private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private RectF mSliceOval = new RectF();

    private static final double quarterCircle = Math.PI / 2;

    private float innerRadiusRatio = 0.3F;

    //color for your slice
    private int[] colors = new int[]{Color.GREEN, Color.GRAY, Color.BLUE, Color.CYAN, Color.DKGRAY, Color.RED};

    private int mCenterX;
    private int mCenterY;

    private OnSliceClickListener mOnSliceClickListener;
    private int mTouchSlop;

    private boolean mPressed;
    private float mLatestDownX;
    private float mLatestDownY;

    public interface OnSliceClickListener{
        void onSlickClick(int slicePosition);
    }

    public RadioButtons(Context context){
        this(context, null);
    }

    public RadioButtons(Context context, AttributeSet attrs){
        this(context, attrs, 0);
    }

    public RadioButtons(Context context, AttributeSet attrs, int defStyle){
        super(context, attrs, defStyle);

        ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
        mTouchSlop = viewConfiguration.getScaledTouchSlop();

        mPaint.setStrokeWidth(10);
    }

    public void setOnSliceClickListener(OnSliceClickListener onSliceClickListener){
        mOnSliceClickListener = onSliceClickListener;
    }

    @Override
    public void onSizeChanged(int w, int h, int oldw, int oldh){
        mCenterX = w / 2;
        mCenterY = h / 2;

        mOuterRadius = mCenterX > mCenterY ? mCenterY : mCenterX;
        mInnerRadius = mOuterRadius * innerRadiusRatio;

        outerRadiusSquare = mOuterRadius * mOuterRadius;
        innerRadiusSquare = mInnerRadius * mInnerRadius;

        mSliceOval.left = mCenterX - mOuterRadius;
        mSliceOval.right = mCenterX + mOuterRadius;
        mSliceOval.top = mCenterY - mOuterRadius;
        mSliceOval.bottom = mCenterY + mOuterRadius;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event){
        float currX = event.getX();
        float currY = event.getY();

        switch(event.getActionMasked()){
            case MotionEvent.ACTION_DOWN:
                mLatestDownX = currX;
                mLatestDownY = currY;

                mPressed = true;
                break;
            case MotionEvent.ACTION_MOVE:


                if(Math.abs(currX - mLatestDownX) > mTouchSlop || Math.abs(currY - mLatestDownY) > mTouchSlop) mPressed = false;
                break;
            case MotionEvent.ACTION_UP:

                if(mPressed){
                    int dx = (int) currX - mCenterX;
                    int dy = (int) currY - mCenterY;
                    int distanceSquare = dx * dx + dy * dy;

                    //if the distance between touchpoint and centerpoint is smaller than outerRadius and longer than innerRadius, then we're in the clickable area
                    if(distanceSquare > innerRadiusSquare && distanceSquare < outerRadiusSquare){

                        //get the angle to detect which slice is currently being click
                        double angle = Math.atan2(dy, dx);

                        if(angle >= -quarterCircle && angle < 0){
                            angle += quarterCircle;
                        }else if(angle >= -Math.PI && angle < -quarterCircle){
                            angle += Math.PI + Math.PI + quarterCircle;
                        }else if(angle >= 0 && angle < Math.PI){
                            angle += quarterCircle;
                        }

                        double rawSliceIndex = angle / (Math.PI * 2) * mSlices;

                        if(mOnSliceClickListener != null){
                            mOnSliceClickListener.onSlickClick((int) rawSliceIndex);
                        }

                    }
                }
                break;
        }

        return true;
    }

    @Override
    public void onDraw(Canvas canvas){
        int startAngle = quarterDegreeMinus;

        //draw slice
        for(int i = 0; i < mSlices; i++){
            mPaint.setStyle(Paint.Style.FILL);
            mPaint.setColor(colors[i % colors.length]);
            canvas.drawArc(mSliceOval, startAngle, degreeStep, true, mPaint);

            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(Color.WHITE);
            canvas.drawArc(mSliceOval, startAngle, degreeStep, true, mPaint);

            startAngle += degreeStep;
        }

        //draw center circle
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setColor(Color.BLACK);
        canvas.drawCircle(mCenterX, mCenterY, mInnerRadius, mPaint);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(Color.WHITE);
        canvas.drawCircle(mCenterX, mCenterY, mInnerRadius, mPaint);
    }
}