Move viscous fluid interpolator to its own class (d75e2539) · Commits · e / os / android_frameworks_base

core/java/android/widget/Scroller.java

+45 −33

Original line number	Diff line number	Diff line
		@@ -61,6 +61,8 @@ import android.view.animation.Interpolator;
		* }</pre>
		*/
		public class Scroller {
		private final Interpolator mInterpolator;

		private int mMode;

		private int mStartX;
		@@ -81,7 +83,6 @@ public class Scroller {
		private float mDeltaX;
		private float mDeltaY;
		private boolean mFinished;
		private Interpolator mInterpolator;
		private boolean mFlywheel;

		private float mVelocity;
		@@ -142,18 +143,8 @@ public class Scroller {
		SPLINE_TIME[i] = coef * ((1.0f - y) * P1 + y * P2) + y * y * y;
		}
		SPLINE_POSITION[NB_SAMPLES] = SPLINE_TIME[NB_SAMPLES] = 1.0f;

		// This controls the viscous fluid effect (how much of it)
		sViscousFluidScale = 8.0f;
		// must be set to 1.0 (used in viscousFluid())
		sViscousFluidNormalize = 1.0f;
		sViscousFluidNormalize = 1.0f / viscousFluid(1.0f);

		}

		private static float sViscousFluidScale;
		private static float sViscousFluidNormalize;

		/**
		* Create a Scroller with the default duration and interpolator.
		*/
		@@ -178,7 +169,11 @@ public class Scroller {
		*/
		public Scroller(Context context, Interpolator interpolator, boolean flywheel) {
		mFinished = true;
		if (interpolator == null) {
		mInterpolator = new ViscousFluidInterpolator();
		} else {
		mInterpolator = interpolator;
		}
		mPpi = context.getResources().getDisplayMetrics().density * 160.0f;
		mDeceleration = computeDeceleration(ViewConfiguration.getScrollFriction());
		mFlywheel = flywheel;
		@@ -312,13 +307,7 @@ public class Scroller {
		if (timePassed < mDuration) {
		switch (mMode) {
		case SCROLL_MODE:
		float x = timePassed * mDurationReciprocal;

		if (mInterpolator == null)
		x = viscousFluid(x);
		else
		x = mInterpolator.getInterpolation(x);

		final float x = mInterpolator.getInterpolation(timePassed * mDurationReciprocal);
		mCurrX = mStartX + Math.round(x * mDeltaX);
		mCurrY = mStartY + Math.round(x * mDeltaY);
		break;
		@@ -499,20 +488,6 @@ public class Scroller {
		return mFlingFriction * mPhysicalCoeff * Math.exp(DECELERATION_RATE / decelMinusOne * l);
		}

		static float viscousFluid(float x)
		{
		x *= sViscousFluidScale;
		if (x < 1.0f) {
		x -= (1.0f - (float)Math.exp(-x));
		} else {
		float start = 0.36787944117f; // 1/e == exp(-1)
		x = 1.0f - (float)Math.exp(1.0f - x);
		x = start + x * (1.0f - start);
		}
		x *= sViscousFluidNormalize;
		return x;
		}

		/**
		* Stops the animation. Contrary to {@link #forceFinished(boolean)},
		* aborting the animating cause the scroller to move to the final x and y
		@@ -583,4 +558,41 @@ public class Scroller {
		return !mFinished && Math.signum(xvel) == Math.signum(mFinalX - mStartX) &&
		Math.signum(yvel) == Math.signum(mFinalY - mStartY);
		}

		private static class ViscousFluidInterpolator implements Interpolator {
		/** Controls the viscous fluid effect (how much of it). */
		private static final float VISCOUS_FLUID_SCALE = 8.0f;

		private static final float VISCOUS_FLUID_NORMALIZE;
		private static final float VISCOUS_FLUID_OFFSET;

		static {

		// must be set to 1.0 (used in viscousFluid())
		VISCOUS_FLUID_NORMALIZE = 1.0f / viscousFluid(1.0f);
		// account for very small floating-point error
		VISCOUS_FLUID_OFFSET = 1.0f - VISCOUS_FLUID_NORMALIZE * viscousFluid(1.0f);
		}

		private static float viscousFluid(float x) {
		x *= VISCOUS_FLUID_SCALE;
		if (x < 1.0f) {
		x -= (1.0f - (float)Math.exp(-x));
		} else {
		float start = 0.36787944117f; // 1/e == exp(-1)
		x = 1.0f - (float)Math.exp(1.0f - x);
		x = start + x * (1.0f - start);
		}
		return x;
		}

		@Override
		public float getInterpolation(float input) {
		final float interpolated = VISCOUS_FLUID_NORMALIZE * viscousFluid(input);
		if (input > 0) {
		return input + VISCOUS_FLUID_OFFSET;
		}
		return input;
		}
		}
		}