Improvements to ScaleGestureDetector

import android.content.Context;

import android.util.DisplayMetrics;

import android.util.FloatMath;

/**

 * Detects transformation gestures involving more than one pointer ("multitouch")

     * A convenience class to extend when you only want to listen for a subset

     * of scaling-related events. This implements all methods in

     * {@link OnScaleGestureListener} but does nothing.

     * {@link OnScaleGestureListener#onScale(ScaleGestureDetector)} and

     * {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)} return

     * {@link OnScaleGestureListener#onScale(ScaleGestureDetector)} returns

     * {@code false} so that a subclass can retrieve the accumulated scale

     * factor in an overridden onScaleEnd.

     * {@link OnScaleGestureListener#onScaleBegin(ScaleGestureDetector)} returns

     * {@code true}. 

     */

    public static class SimpleOnScaleGestureListener implements OnScaleGestureListener {

        public boolean onScale(ScaleGestureDetector detector) {

            return true;

            return false;

        }

        public boolean onScaleBegin(ScaleGestureDetector detector) {

        }

    }

    /**

     * This value is the threshold ratio between our previous combined pressure

     * and the current combined pressure. We will only fire an onScale event if

     * the computed ratio between the current and previous event pressures is

     * greater than this value. When pressure decreases rapidly between events

     * the position values can often be imprecise, as it usually indicates

     * that the user is in the process of lifting a pointer off of the device.

     * Its value was tuned experimentally.

     */

    private static final float PRESSURE_THRESHOLD = 0.67f;

    private Context mContext;

    private OnScaleGestureListener mListener;

    private final Context mContext;

    private final OnScaleGestureListener mListener;

    private boolean mGestureInProgress;

    private MotionEvent mPrevEvent;

    private float mPrevPressure;

    private long mTimeDelta;

    private float mEdgeSlop;

    private final float mEdgeSlop;

    private float mRightSlopEdge;

    private float mBottomSlopEdge;

    private boolean mSloppyGesture;

        if (mCurrLen == -1) {

            final float cvx = mCurrFingerDiffX;

            final float cvy = mCurrFingerDiffY;

            mCurrLen = (float)Math.sqrt(cvx*cvx + cvy*cvy);

            mCurrLen = FloatMath.sqrt(cvx*cvx + cvy*cvy);

        }

        return mCurrLen;

    }

        if (mPrevLen == -1) {

            final float pvx = mPrevFingerDiffX;

            final float pvy = mPrevFingerDiffY;

            mPrevLen = (float)Math.sqrt(pvx*pvx + pvy*pvy);

            mPrevLen = FloatMath.sqrt(pvx*pvx + pvy*pvy);

        }

        return mPrevLen;

    }