/*
* Copyright 2015 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.
*/
package io.plaidapp.ui.widget;
import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.util.AttributeSet;
import android.view.View;
import android.widget.FrameLayout;
import java.util.ArrayList;
import java.util.List;
import io.plaidapp.R;
import io.plaidapp.util.AnimUtils;
import io.plaidapp.util.ColorUtils;
import io.plaidapp.util.ViewUtils;
/**
* A {@link FrameLayout} which responds to nested scrolls to create drag-dismissable layouts.
* Applies an elasticity factor to reduce movement as you approach the given dismiss distance.
* Optionally also scales down content during drag.
*/
public class ElasticDragDismissFrameLayout extends FrameLayout {
// configurable attribs
private float dragDismissDistance = Float.MAX_VALUE;
private float dragDismissFraction = -1f;
private float dragDismissScale = 1f;
private boolean shouldScale = false;
private float dragElacticity = 0.8f;
// state
private float totalDrag;
private boolean draggingDown = false;
private boolean draggingUp = false;
private List<ElasticDragDismissCallback> callbacks;
public ElasticDragDismissFrameLayout(Context context) {
this(context, null, 0, 0);
}
public ElasticDragDismissFrameLayout(Context context, AttributeSet attrs) {
this(context, attrs, 0, 0);
}
public ElasticDragDismissFrameLayout(Context context, AttributeSet attrs,
int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public ElasticDragDismissFrameLayout(Context context, AttributeSet attrs,
int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
final TypedArray a = getContext().obtainStyledAttributes(
attrs, R.styleable.ElasticDragDismissFrameLayout, 0, 0);
if (a.hasValue(R.styleable.ElasticDragDismissFrameLayout_dragDismissDistance)) {
dragDismissDistance = a.getDimensionPixelSize(R.styleable
.ElasticDragDismissFrameLayout_dragDismissDistance, 0);
} else if (a.hasValue(R.styleable.ElasticDragDismissFrameLayout_dragDismissFraction)) {
dragDismissFraction = a.getFloat(R.styleable
.ElasticDragDismissFrameLayout_dragDismissFraction, dragDismissFraction);
}
if (a.hasValue(R.styleable.ElasticDragDismissFrameLayout_dragDismissScale)) {
dragDismissScale = a.getFloat(R.styleable
.ElasticDragDismissFrameLayout_dragDismissScale, dragDismissScale);
shouldScale = dragDismissScale != 1f;
}
if (a.hasValue(R.styleable.ElasticDragDismissFrameLayout_dragElasticity)) {
dragElacticity = a.getFloat(R.styleable.ElasticDragDismissFrameLayout_dragElasticity,
dragElacticity);
}
a.recycle();
}
public static abstract class ElasticDragDismissCallback {
/**
* Called for each drag event.
*
* @param elasticOffset Indicating the drag offset with elasticity applied i.e. may
* exceed 1.
* @param elasticOffsetPixels The elastically scaled drag distance in pixels.
* @param rawOffset Value from [0, 1] indicating the raw drag offset i.e.
* without elasticity applied. A value of 1 indicates that the
* dismiss distance has been reached.
* @param rawOffsetPixels The raw distance the user has dragged
*/
void onDrag(float elasticOffset, float elasticOffsetPixels,
float rawOffset, float rawOffsetPixels) { }
/**
* Called when dragging is released and has exceeded the threshold dismiss distance.
*/
void onDragDismissed() { }
}
@Override
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
return (nestedScrollAxes & View.SCROLL_AXIS_VERTICAL) != 0;
}
@Override
public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
// if we're in a drag gesture and the user reverses up the we should take those events
if (draggingDown && dy > 0 || draggingUp && dy < 0) {
dragScale(dy);
consumed[1] = dy;
}
}
@Override
public void onNestedScroll(View target, int dxConsumed, int dyConsumed,
int dxUnconsumed, int dyUnconsumed) {
dragScale(dyUnconsumed);
}
@Override
public void onStopNestedScroll(View child) {
if (Math.abs(totalDrag) >= dragDismissDistance) {
dispatchDismissCallback();
} else { // settle back to natural position
animate()
.translationY(0f)
.scaleX(1f)
.scaleY(1f)
.setDuration(200L)
.setInterpolator(AnimUtils.getFastOutSlowInInterpolator(getContext()))
.setListener(null)
.start();
totalDrag = 0;
draggingDown = draggingUp = false;
dispatchDragCallback(0f, 0f, 0f, 0f);
}
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (dragDismissFraction > 0f) {
dragDismissDistance = h * dragDismissFraction;
}
}
public void addListener(ElasticDragDismissCallback listener) {
if (callbacks == null) {
callbacks = new ArrayList<>();
}
callbacks.add(listener);
}
public void removeListener(ElasticDragDismissCallback listener) {
if (callbacks != null && callbacks.size() > 0) {
callbacks.remove(listener);
}
}
private void dragScale(int scroll) {
if (scroll == 0) return;
totalDrag += scroll;
// track the direction & set the pivot point for scaling
// don't double track i.e. if start dragging down and then reverse, keep tracking as
// dragging down until they reach the 'natural' position
if (scroll < 0 && !draggingUp && !draggingDown) {
draggingDown = true;
if (shouldScale) setPivotY(getHeight());
} else if (scroll > 0 && !draggingDown && !draggingUp) {
draggingUp = true;
if (shouldScale) setPivotY(0f);
}
// how far have we dragged relative to the distance to perform a dismiss
// (0–1 where 1 = dismiss distance). Decreasing logarithmically as we approach the limit
float dragFraction = (float) Math.log10(1 + (Math.abs(totalDrag) / dragDismissDistance));
// calculate the desired translation given the drag fraction
float dragTo = dragFraction * dragDismissDistance * dragElacticity;
if (draggingUp) {
// as we use the absolute magnitude when calculating the drag fraction, need to
// re-apply the drag direction
dragTo *= -1;
}
setTranslationY(dragTo);
if (shouldScale) {
final float scale = 1 - ((1 - dragDismissScale) * dragFraction);
setScaleX(scale);
setScaleY(scale);
}
// if we've reversed direction and gone past the settle point then clear the flags to
// allow the list to get the scroll events & reset any transforms
if ((draggingDown && totalDrag >= 0)
|| (draggingUp && totalDrag <= 0)) {
totalDrag = dragTo = dragFraction = 0;
draggingDown = draggingUp = false;
setTranslationY(0f);
setScaleX(1f);
setScaleY(1f);
}
dispatchDragCallback(dragFraction, dragTo,
Math.min(1f, Math.abs(totalDrag) / dragDismissDistance), totalDrag);
}
private void dispatchDragCallback(float elasticOffset, float elasticOffsetPixels,
float rawOffset, float rawOffsetPixels) {
if (callbacks != null && !callbacks.isEmpty()) {
for (ElasticDragDismissCallback callback : callbacks) {
callback.onDrag(elasticOffset, elasticOffsetPixels,
rawOffset, rawOffsetPixels);
}
}
}
private void dispatchDismissCallback() {
if (callbacks != null && !callbacks.isEmpty()) {
for (ElasticDragDismissCallback callback : callbacks) {
callback.onDragDismissed();
}
}
}
/**
* An {@link ElasticDragDismissCallback} which fades system chrome (i.e. status bar and
* navigation bar) whilst elastic drags are performed and
* {@link Activity#finishAfterTransition() finishes} the activity when drag dismissed.
*/
public static class SystemChromeFader extends ElasticDragDismissCallback {
private final Activity activity;
private final int statusBarAlpha;
private final int navBarAlpha;
private final boolean fadeNavBar;
public SystemChromeFader(Activity activity) {
this.activity = activity;
statusBarAlpha = Color.alpha(activity.getWindow().getStatusBarColor());
navBarAlpha = Color.alpha(activity.getWindow().getNavigationBarColor());
fadeNavBar = ViewUtils.isNavBarOnBottom(activity);
}
@Override
public void onDrag(float elasticOffset, float elasticOffsetPixels,
float rawOffset, float rawOffsetPixels) {
if (elasticOffsetPixels > 0) {
// dragging downward, fade the status bar in proportion
activity.getWindow().setStatusBarColor(ColorUtils.modifyAlpha(activity.getWindow()
.getStatusBarColor(), (int) ((1f - rawOffset) * statusBarAlpha)));
} else if (elasticOffsetPixels == 0) {
// reset
activity.getWindow().setStatusBarColor(ColorUtils.modifyAlpha(
activity.getWindow().getStatusBarColor(), statusBarAlpha));
activity.getWindow().setNavigationBarColor(ColorUtils.modifyAlpha(
activity.getWindow().getNavigationBarColor(), navBarAlpha));
} else if (fadeNavBar) {
// dragging upward, fade the navigation bar in proportion
activity.getWindow().setNavigationBarColor(
ColorUtils.modifyAlpha(activity.getWindow().getNavigationBarColor(),
(int) ((1f - rawOffset) * navBarAlpha)));
}
}
public void onDragDismissed() {
activity.finishAfterTransition();
}
}
}