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Improve logic when flinging up.

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Makes sure that we don't accelerate even more if the movement is
already fast enough. Around 3000dp/s, we switch to a linear curve.

Change-Id: I9a1cdb1a0a65ed7a8ddf00683c08e83c13bf20f7
This commit is contained in:
Jorim Jaggi
2014-05-21 17:14:18 +02:00
parent 1d480695df
commit efbd7e3bb8
1 changed files with 26 additions and 5 deletions
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31
packages/SystemUI/src/com/android/systemui/statusbar/FlingAnimationUtils.java
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@@ -28,33 +28,35 @@ import android.view.animation.PathInterpolator;
public class FlingAnimationUtils {
private static final float LINEAR_OUT_SLOW_IN_X2 = 0.35f;
private static final float LINEAR_OUT_FASTER_IN_Y2 = 0.7f;
private static final float LINEAR_OUT_FASTER_IN_Y2_MIN = 0.7f;
private static final float LINEAR_OUT_FASTER_IN_Y2_MAX = 1f;
private static final float MIN_VELOCITY_DP_PER_SECOND = 250;
private static final float HIGH_VELOCITY_DP_PER_SECOND = 3000;
/**
* Crazy math. http://en.wikipedia.org/wiki/B%C3%A9zier_curve
*/
private static final float LINEAR_OUT_SLOW_IN_START_GRADIENT = 1.0f / LINEAR_OUT_SLOW_IN_X2;
private static final float LINEAR_OUT_FASTER_IN_START_GRADIENT = LINEAR_OUT_FASTER_IN_Y2;
private Interpolator mLinearOutSlowIn;
private Interpolator mFastOutSlowIn;
private Interpolator mFastOutLinearIn;
private Interpolator mLinearOutFasterIn;
private float mMinVelocityPxPerSecond;
private float mMaxLengthSeconds;
private float mHighVelocityPxPerSecond;
public FlingAnimationUtils(Context ctx, float maxLengthSeconds) {
mMaxLengthSeconds = maxLengthSeconds;
mLinearOutSlowIn = new PathInterpolator(0, 0, LINEAR_OUT_SLOW_IN_X2, 1);
mLinearOutFasterIn = new PathInterpolator(0, 0, 1, LINEAR_OUT_FASTER_IN_Y2);
mFastOutSlowIn
= AnimationUtils.loadInterpolator(ctx, android.R.interpolator.fast_out_slow_in);
mFastOutLinearIn
= AnimationUtils.loadInterpolator(ctx, android.R.interpolator.fast_out_linear_in);
mMinVelocityPxPerSecond
= MIN_VELOCITY_DP_PER_SECOND * ctx.getResources().getDisplayMetrics().density;
mHighVelocityPxPerSecond
= HIGH_VELOCITY_DP_PER_SECOND * ctx.getResources().getDisplayMetrics().density;
}
/**
@@ -126,7 +128,12 @@ public class FlingAnimationUtils {
* Math.pow(Math.abs(endValue - currValue) / maxDistance, 0.5f));
float diff = Math.abs(endValue - currValue);
float velAbs = Math.abs(velocity);
float durationSeconds = LINEAR_OUT_FASTER_IN_START_GRADIENT * diff / velAbs;
float y2 = calculateLinearOutFasterInY2(velAbs);
// The gradient at the start of the curve is just y2.
float startGradient = y2;
Interpolator mLinearOutFasterIn = new PathInterpolator(0, 0, 1, y2);
float durationSeconds = startGradient * diff / velAbs;
if (durationSeconds <= maxLengthSeconds) {
animator.setInterpolator(mLinearOutFasterIn);
} else if (velAbs >= mMinVelocityPxPerSecond) {
@@ -148,6 +155,20 @@ public class FlingAnimationUtils {
animator.setDuration((long) (durationSeconds * 1000));
}
/**
* Calculates the y2 control point for a linear-out-faster-in path interpolator depending on the
* velocity. The faster the velocity, the more "linear" the interpolator gets.
*
* @param velocity the velocity of the gesture.
* @return the y2 control point for a cubic bezier path interpolator
*/
private float calculateLinearOutFasterInY2(float velocity) {
float t = (velocity - mMinVelocityPxPerSecond)
/ (mHighVelocityPxPerSecond - mMinVelocityPxPerSecond);
t = Math.max(0, Math.min(1, t));
return (1 - t) * LINEAR_OUT_FASTER_IN_Y2_MIN + t * LINEAR_OUT_FASTER_IN_Y2_MAX;
}
/**
* @return the minimum velocity a gesture needs to have to be considered a fling
*/