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Made BottomSheets better respect gesture velocity.
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@nickbutcher
nickbutcher committed Sep 23, 2016
1 parent 3b10c99 commit 69fefeb
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Showing 2 changed files with 49 additions and 31 deletions.
71 changes: 40 additions & 31 deletions app/src/main/java/io/plaidapp/ui/widget/BottomSheet.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.TimeInterpolator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.support.v4.view.MotionEventCompat;
Expand All @@ -36,7 +37,6 @@
import java.util.concurrent.CopyOnWriteArrayList;

import io.plaidapp.util.AnimUtils;
import io.plaidapp.util.MathUtils;
import io.plaidapp.util.ViewOffsetHelper;

/**
Expand All @@ -50,12 +50,8 @@
public class BottomSheet extends FrameLayout {

// constants
private static final long DEFAULT_SETTLE_DURATION = 300L; // ms
private static final long MIN_SETTLE_DURATION = 50L; // ms

// config
private static final int MIN_SETTLE_VELOCITY = 6000; // px/s
private final int MIN_FLING_VELOCITY;
private final int MAX_FLING_VELOCITY;

// child views & helpers
private View sheet;
Expand Down Expand Up @@ -85,7 +81,6 @@ public BottomSheet(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
final ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
MIN_FLING_VELOCITY = viewConfiguration.getScaledMinimumFlingVelocity();
MAX_FLING_VELOCITY = viewConfiguration.getScaledMaximumFlingVelocity();
}

/**
Expand All @@ -110,11 +105,11 @@ public void unregisterCallback(Callbacks callback) {
}

public void dismiss() {
animateSettle(dismissOffset);
animateSettle(dismissOffset, 0);
}

public void expand() {
animateSettle(0);
animateSettle(0, 0);
}

public boolean isExpanded() {
Expand Down Expand Up @@ -213,10 +208,10 @@ public void onStopNestedScroll(View child) {
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
if (velocityY <= -MIN_FLING_VELOCITY /* flinging downward */
&& !target.canScrollVertically(-1)) { /* nested scrolling child can't scroll up */
animateSettle(dismissOffset, computeSettleDuration(velocityY, true));
animateSettle(dismissOffset, velocityY);
return true;
} else if (velocityY > 0 && !isExpanded()) {
animateSettle(0, computeSettleDuration(velocityY, false));
animateSettle(0, velocityY);
}
return false;
}
Expand All @@ -231,15 +226,11 @@ private boolean isDraggableViewUnder(int x, int y) {
return getVisibility() == VISIBLE && sheetDragHelper.isViewUnder(this, x, y);
}

private void animateSettle(int targetOffset) {
animateSettle(targetOffset, DEFAULT_SETTLE_DURATION);
}

private void animateSettle(int targetOffset, long duration) {
animateSettle(sheetOffsetHelper.getTopAndBottomOffset(), targetOffset, duration);
private void animateSettle(int targetOffset, float initialVelocity) {
animateSettle(sheetOffsetHelper.getTopAndBottomOffset(), targetOffset, initialVelocity);
}

private void animateSettle(int initialOffset, final int targetOffset, long duration) {
private void animateSettle(int initialOffset, final int targetOffset, float initialVelocity) {
if (settling) return;
if (sheetOffsetHelper.getTopAndBottomOffset() == targetOffset) {
if (targetOffset >= dismissOffset) {
Expand All @@ -249,17 +240,19 @@ private void animateSettle(int initialOffset, final int targetOffset, long durat
}

settling = true;
final boolean dismissing = targetOffset == dismissOffset;
final long duration = computeSettleDuration(initialVelocity, dismissing);
final ObjectAnimator settleAnim = ObjectAnimator.ofInt(sheetOffsetHelper,
ViewOffsetHelper.OFFSET_Y,
initialOffset,
targetOffset);
settleAnim.setDuration(duration);
settleAnim.setInterpolator(AnimUtils.getFastOutSlowInInterpolator(getContext()));
settleAnim.setInterpolator(getSettleInterpolator(dismissing, initialVelocity));
settleAnim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
dispatchPositionChangedCallback();
if (targetOffset == dismissOffset) {
if (dismissing) {
dispatchDismissCallback();
}
settling = false;
Expand All @@ -278,20 +271,36 @@ public void onAnimationUpdate(ValueAnimator animation) {
settleAnim.start();
}

/**
* Provides the appropriate interpolator for the settle animation depending upon:
* – If dismissing then exit at full speed i.e. linearly
* – If have initial velocity then respect it (i.e. start linearly) otherwise accelerate into
* the animation.
*/
private TimeInterpolator getSettleInterpolator(boolean dismissing, float initialVelocity) {
if (initialVelocity == 0 && dismissing) {
return AnimUtils.getFastOutLinearInInterpolator(getContext());
} else if (initialVelocity == 0 && !dismissing) {
return AnimUtils.getFastOutSlowInInterpolator(getContext());
} else if (dismissing) {
return AnimUtils.getLinearInterpolator();
} else {
return AnimUtils.getLinearOutSlowInInterpolator(getContext());
}
}

/**
* Calculate the duration of the settle animation based on the gesture velocity
* and how far it has to go.
*/
private long computeSettleDuration(final float velocity, final boolean dismissing) {
final float settleDistance = dismissing ?
sheetBottom - sheet.getTop() : sheet.getTop() - sheetExpandedTop;
final float clampedVelocity =
MathUtils.constrain(MIN_FLING_VELOCITY, MAX_FLING_VELOCITY, Math.abs(velocity));
final float distanceFraction = settleDistance / (sheetBottom - sheetExpandedTop);
final float velocityFraction = clampedVelocity / MAX_FLING_VELOCITY;
final long duration = MIN_SETTLE_DURATION +
(long) (distanceFraction * (1f - velocityFraction) * DEFAULT_SETTLE_DURATION);
return duration;
// enforce a min velocity to prevent too slow settling
final float clampedVelocity = Math.max(MIN_SETTLE_VELOCITY, Math.abs(velocity));
final int settleDistance = dismissing
? sheetBottom - sheet.getTop()
: sheet.getTop() - sheetExpandedTop;
// velocity is in px/s but we want duration in ms thus * 1000
return (long) (settleDistance * 1000 / clampedVelocity);
}

private final ViewDragHelper.Callback dragHelperCallbacks = new ViewDragHelper.Callback() {
Expand Down Expand Up @@ -327,7 +336,7 @@ public void onViewPositionChanged(View child, int left, int top, int dx, int dy)
public void onViewReleased(View releasedChild, float velocityX, float velocityY) {
// dismiss on downward fling, otherwise settle back to expanded position
final boolean dismiss = velocityY >= MIN_FLING_VELOCITY;
animateSettle(dismiss ? dismissOffset : 0, computeSettleDuration(velocityY, dismiss));
animateSettle(dismiss ? dismissOffset : 0, velocityY);
}

};
Expand Down Expand Up @@ -360,7 +369,7 @@ private void applySheetInitialHeightOffset(boolean animateChange, int previousOf
if (sheet.getTop() < minimumGap) {
final int offset = minimumGap - sheet.getTop();
if (animateChange) {
animateSettle(previousOffset, offset, DEFAULT_SETTLE_DURATION);
animateSettle(previousOffset, offset, 0);
} else {
sheetOffsetHelper.setTopAndBottomOffset(offset);
}
Expand Down
9 changes: 9 additions & 0 deletions app/src/main/java/io/plaidapp/util/AnimUtils.java
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
import android.util.Property;
import android.view.animation.AnimationUtils;
import android.view.animation.Interpolator;
import android.view.animation.LinearInterpolator;

import java.util.ArrayList;

Expand All @@ -37,6 +38,7 @@ private AnimUtils() { }
private static Interpolator fastOutSlowIn;
private static Interpolator fastOutLinearIn;
private static Interpolator linearOutSlowIn;
private static Interpolator linear;

public static Interpolator getFastOutSlowInInterpolator(Context context) {
if (fastOutSlowIn == null) {
Expand All @@ -62,6 +64,13 @@ public static Interpolator getLinearOutSlowInInterpolator(Context context) {
return linearOutSlowIn;
}

public static Interpolator getLinearInterpolator() {
if (linear == null) {
linear = new LinearInterpolator();
}
return linear;
}

/**
* Linear interpolate between a and b with parameter t.
*/
Expand Down

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