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Made BottomSheets respect fling gestures.
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@nickbutcher
nickbutcher committed Feb 10, 2016
1 parent b533387 commit b003931
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Showing 3 changed files with 100 additions and 33 deletions.
100 changes: 75 additions & 25 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 @@ -22,6 +22,8 @@
import android.animation.ValueAnimator;
import android.content.Context;
import android.content.res.TypedArray;
import android.support.annotation.IntDef;
import android.support.annotation.Nullable;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ViewDragHelper;
Expand All @@ -31,13 +33,17 @@
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.animation.LinearInterpolator;
import android.widget.FrameLayout;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.ArrayList;
import java.util.List;

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

/**
Expand All @@ -55,22 +61,34 @@
public class BottomSheet extends FrameLayout {

// configurable attributes
private int dismissDistance = Integer.MAX_VALUE;
private boolean hasScrollingChild = false;
private int scrollingChildId = -1;

// constants
private static final long MIN_DISMISS_DURATION = 50L; // ms
private static final long DEFAULT_DISMISS_DURATION = 200L; // ms
private static final int SETTLE_EXPAND = 0;
private static final int SETTLE_DISMISS = 1;
private static final int SETTLE_FLING_DISMISS = 2;

@Retention(RetentionPolicy.SOURCE)
@IntDef({ SETTLE_EXPAND, SETTLE_DISMISS, SETTLE_FLING_DISMISS})
public @interface SettleType { }

// config
private final int MIN_FLING_VELOCITY;
private final int MAX_FLING_VELOCITY;

// child views & helpers
private View sheet;
private View scrollingChild;
private @Nullable View scrollingChild;
private ViewDragHelper sheetDragHelper;
private ViewOffsetHelper sheetOffsetHelper;

// state
private final int FLING_VELOCITY;
private List<Callbacks> callbacks;
private int sheetExpandedTop;
private int sheetBottom;
private int nestedScrollInitialTop;
private boolean settling;
private boolean isNestedScrolling = false;
private boolean initialHeightChecked = false;
Expand All @@ -85,7 +103,10 @@ public BottomSheet(Context context, AttributeSet attrs) {

public BottomSheet(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
FLING_VELOCITY = ViewConfiguration.get(context).getScaledMinimumFlingVelocity();
final ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
MIN_FLING_VELOCITY = viewConfiguration.getScaledMinimumFlingVelocity();
MAX_FLING_VELOCITY = viewConfiguration.getScaledMaximumFlingVelocity();

final TypedArray a =
getContext().obtainStyledAttributes(attrs, R.styleable.BottomSheet, 0, 0);

Expand All @@ -94,10 +115,6 @@ public BottomSheet(Context context, AttributeSet attrs, int defStyle) {
scrollingChildId = a.getResourceId(R.styleable.BottomSheet_scrollingChild,
scrollingChildId);
}
if (a.hasValue(R.styleable.BottomSheet_dragDismissDistance)) {
dismissDistance = a.getDimensionPixelSize(
R.styleable.BottomSheet_dragDismissDistance, dismissDistance);
}
a.recycle();
}

Expand All @@ -123,11 +140,11 @@ public void unregisterCallback(Callbacks callback) {
}

public void dismiss() {
animateSettle(true);
animateSettle(SETTLE_DISMISS);
}

public void expand() {
animateSettle(false);
animateSettle(SETTLE_EXPAND);
}

public boolean isExpanded() {
Expand Down Expand Up @@ -211,7 +228,6 @@ public void computeScroll() {
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
if ((nestedScrollAxes & View.SCROLL_AXIS_VERTICAL) != 0) {
isNestedScrolling = true;
nestedScrollInitialTop = sheet.getTop();
return true;
}
return false;
Expand Down Expand Up @@ -246,13 +262,19 @@ public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
@Override
public void onStopNestedScroll(View child) {
isNestedScrolling = false;
final int distanceDragged = sheet.getTop() - nestedScrollInitialTop;
nestedScrollInitialTop = 0;
if (distanceDragged == 0) return;
if (!settling) { // fling might have occurred
animateSettle(SETTLE_EXPAND);
}
}

// check if we should perform a dismiss or settle back into place
final boolean dismiss = distanceDragged >= dismissDistance;
animateSettle(dismiss);
@Override
public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
if (velocityY <= -MIN_FLING_VELOCITY /* flinging downward */
&& !target.canScrollVertically(-1)) { /* at top of nested scrolling child */
animateSettle(SETTLE_FLING_DISMISS, computeDismissDuration(velocityY));
return true;
}
return false;
}

private void dispatchDismissCallback() {
Expand All @@ -275,25 +297,38 @@ private boolean isDraggableViewUnder(int x, int y) {
return getVisibility() == VISIBLE && sheetDragHelper.isViewUnder(this, x, y);
}

private void animateSettle(final boolean dismiss) {
private void animateSettle(final @SettleType int settleType) {
animateSettle(settleType, DEFAULT_DISMISS_DURATION);
}

private void animateSettle(final @SettleType int settleType, long duration) {
if (settling) return;

// animate the offset from expanded position
final int targetOffset = dismiss ? (sheetBottom - sheetExpandedTop) : 0;
final int targetOffset = settleType == SETTLE_EXPAND ? 0 : (sheetBottom - sheetExpandedTop);
if (sheetOffsetHelper.getTopAndBottomOffset() == targetOffset) return;

settling = true;
final ObjectAnimator settleAnim = ObjectAnimator.ofInt(sheetOffsetHelper,
ViewOffsetHelper.OFFSET_Y,
sheetOffsetHelper.getTopAndBottomOffset(),
targetOffset);
settleAnim.setDuration(200L);
settleAnim.setInterpolator(dismiss ? AnimUtils.getFastOutLinearInInterpolator(getContext())
: AnimUtils.getFastOutSlowInInterpolator(getContext()));
settleAnim.setDuration(duration);
switch (settleType) {
case SETTLE_EXPAND:
settleAnim.setInterpolator(AnimUtils.getFastOutSlowInInterpolator(getContext()));
break;
case SETTLE_DISMISS:
settleAnim.setInterpolator(AnimUtils.getFastOutLinearInInterpolator(getContext()));
break;
case SETTLE_FLING_DISMISS:
settleAnim.setInterpolator(new LinearInterpolator());
break;
}
settleAnim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
if (dismiss) {
if (settleType != SETTLE_EXPAND) {
dispatchDismissCallback();
}
settling = false;
Expand All @@ -311,6 +346,21 @@ public void onAnimationUpdate(ValueAnimator animation) {
settleAnim.start();
}

/**
* Calculate the duration of the dismiss animation based on the gesture velocity
* and how far it has to go.
*/
private long computeDismissDuration(float velocity) {
final float distance = sheetBottom - sheet.getTop();
final float clampedVelocity =
MathUtils.constrain(-MAX_FLING_VELOCITY, -MIN_FLING_VELOCITY, velocity);
final float distanceFraction = distance / (sheetBottom - sheetExpandedTop);
final float velocityFraction = clampedVelocity / -MAX_FLING_VELOCITY;
final long duration = MIN_DISMISS_DURATION +
(long) (distanceFraction * (1f - velocityFraction) * DEFAULT_DISMISS_DURATION);
return duration;
}

private ViewDragHelper.Callback dragHelperCallbacks = new ViewDragHelper.Callback() {

@Override
Expand Down Expand Up @@ -342,7 +392,7 @@ public void onViewPositionChanged(View child, int left, int top, int dx, int dy)

@Override
public void onViewReleased(View releasedChild, float velocityX, float velocityY) {
if (velocityY >= FLING_VELOCITY) {
if (velocityY >= MIN_FLING_VELOCITY) {
sheetDragHelper.settleCapturedViewAt(sheet.getLeft(), sheetBottom);
} else {
// settle back into position
Expand Down
24 changes: 24 additions & 0 deletions app/src/main/res/values/attrs_bottom_sheet.xml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2016 Google Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->

<resources>

<declare-styleable name="BottomSheet">
<attr name="scrollingChild" format="reference" />
</declare-styleable>

</resources>
9 changes: 1 addition & 8 deletions ...in/res/values/attrs_drag_dismissables.xml → ...trs_elastic_drag_dismiss_frame_layout.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -17,18 +17,11 @@

<resources>

<attr name="dragDismissDistance" format="dimension" />

<declare-styleable name="ElasticDragDismissFrameLayout">
<attr name="dragDismissDistance" />
<attr name="dragDismissDistance" format="dimension" />
<attr name="dragDismissFraction" format="float" />
<attr name="dragDismissScale" format="float" />
<attr name="dragElasticity" format="float" />
</declare-styleable>

<declare-styleable name="BottomSheet">
<attr name="scrollingChild" format="reference" />
<attr name="dragDismissDistance" />
</declare-styleable>

</resources>

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