/*
* Copyright (C) 2014 The Android Open Source Project
*
* 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 com.android.systemui.recents.views;
import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.annotation.TargetApi;
import android.os.Build;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.animation.LinearInterpolator;
import com.android.systemui.recents.RecentsConfiguration;
/**
* This class facilitates swipe to dismiss. It defines an interface to be implemented by the
* by the class hosting the views that need to swiped, and, using this interface, handles touch
* events and translates / fades / animates the view as it is dismissed.
*/
public class SwipeHelper {
static final String TAG = "SwipeHelper";
private static final boolean SLOW_ANIMATIONS = false; // DEBUG;
private static final boolean CONSTRAIN_SWIPE = true;
private static final boolean FADE_OUT_DURING_SWIPE = true;
private static final boolean DISMISS_IF_SWIPED_FAR_ENOUGH = true;
public static final int X = 0;
public static final int Y = 1;
private static LinearInterpolator sLinearInterpolator = new LinearInterpolator();
private float SWIPE_ESCAPE_VELOCITY = 100f; // dp/sec
private int DEFAULT_ESCAPE_ANIMATION_DURATION = 75; // ms
private int MAX_ESCAPE_ANIMATION_DURATION = 150; // ms
private static final int SNAP_ANIM_LEN = SLOW_ANIMATIONS ? 1000 : 250; // ms
public static float ALPHA_FADE_START = 0.15f; // fraction of thumbnail width
// where fade starts
static final float ALPHA_FADE_END = 0.65f; // fraction of thumbnail width
// beyond which alpha->0
private float mMinAlpha = 0f;
private float mPagingTouchSlop;
Callback mCallback;
private int mSwipeDirection;
private VelocityTracker mVelocityTracker;
private float mInitialTouchPos;
private boolean mDragging;
private View mCurrView;
private boolean mCanCurrViewBeDimissed;
private float mDensityScale;
public boolean mAllowSwipeTowardsStart = true;
public boolean mAllowSwipeTowardsEnd = true;
private boolean mRtl;
public SwipeHelper(int swipeDirection, Callback callback, float densityScale,
float pagingTouchSlop) {
mCallback = callback;
mSwipeDirection = swipeDirection;
mVelocityTracker = VelocityTracker.obtain();
mDensityScale = densityScale;
mPagingTouchSlop = pagingTouchSlop;
}
public void setDensityScale(float densityScale) {
mDensityScale = densityScale;
}
public void setPagingTouchSlop(float pagingTouchSlop) {
mPagingTouchSlop = pagingTouchSlop;
}
public void cancelOngoingDrag() {
if (mDragging) {
if (mCurrView != null) {
mCallback.onDragCancelled(mCurrView);
setTranslation(mCurrView, 0);
mCallback.onSnapBackCompleted(mCurrView);
mCurrView = null;
}
mDragging = false;
}
}
public void resetTranslation(View v) {
setTranslation(v, 0);
}
private float getPos(MotionEvent ev) {
return mSwipeDirection == X ? ev.getX() : ev.getY();
}
private float getTranslation(View v) {
return mSwipeDirection == X ? v.getTranslationX() : v.getTranslationY();
}
private float getVelocity(VelocityTracker vt) {
return mSwipeDirection == X ? vt.getXVelocity() :
vt.getYVelocity();
}
private ObjectAnimator createTranslationAnimation(View v, float newPos) {
ObjectAnimator anim = ObjectAnimator.ofFloat(v,
mSwipeDirection == X ? View.TRANSLATION_X : View.TRANSLATION_Y, newPos);
return anim;
}
private float getPerpendicularVelocity(VelocityTracker vt) {
return mSwipeDirection == X ? vt.getYVelocity() :
vt.getXVelocity();
}
private void setTranslation(View v, float translate) {
if (mSwipeDirection == X) {
v.setTranslationX(translate);
} else {
v.setTranslationY(translate);
}
}
private float getSize(View v) {
final DisplayMetrics dm = v.getContext().getResources().getDisplayMetrics();
return mSwipeDirection == X ? dm.widthPixels : dm.heightPixels;
}
public void setMinAlpha(float minAlpha) {
mMinAlpha = minAlpha;
}
float getAlphaForOffset(View view) {
float viewSize = getSize(view);
final float fadeSize = ALPHA_FADE_END * viewSize;
float result = 1.0f;
float pos = getTranslation(view);
if (pos >= viewSize * ALPHA_FADE_START) {
result = 1.0f - (pos - viewSize * ALPHA_FADE_START) / fadeSize;
} else if (pos < viewSize * (1.0f - ALPHA_FADE_START)) {
result = 1.0f + (viewSize * ALPHA_FADE_START + pos) / fadeSize;
}
result = Math.min(result, 1.0f);
result = Math.max(result, 0f);
return Math.max(mMinAlpha, result);
}
/**
* Determines whether the given view has RTL layout.
*/
@TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
public static boolean isLayoutRtl(View view) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
return View.LAYOUT_DIRECTION_RTL == view.getLayoutDirection();
} else {
return false;
}
}
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN:
mDragging = false;
mCurrView = mCallback.getChildAtPosition(ev);
mVelocityTracker.clear();
if (mCurrView != null) {
mRtl = isLayoutRtl(mCurrView);
mCanCurrViewBeDimissed = mCallback.canChildBeDismissed(mCurrView);
mVelocityTracker.addMovement(ev);
mInitialTouchPos = getPos(ev);
} else {
mCanCurrViewBeDimissed = false;
}
break;
case MotionEvent.ACTION_MOVE:
if (mCurrView != null) {
mVelocityTracker.addMovement(ev);
float pos = getPos(ev);
float delta = pos - mInitialTouchPos;
if (Math.abs(delta) > mPagingTouchSlop) {
mCallback.onBeginDrag(mCurrView);
mDragging = true;
mInitialTouchPos = pos - getTranslation(mCurrView);
}
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
mDragging = false;
mCurrView = null;
break;
}
return mDragging;
}
/**
* @param view The view to be dismissed
* @param velocity The desired pixels/second speed at which the view should move
*/
private void dismissChild(final View view, float velocity) {
final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
float newPos;
if (velocity < 0
|| (velocity == 0 && getTranslation(view) < 0)
// if we use the Menu to dismiss an item in landscape, animate up
|| (velocity == 0 && getTranslation(view) == 0 && mSwipeDirection == Y)) {
newPos = -getSize(view);
} else {
newPos = getSize(view);
}
int duration = MAX_ESCAPE_ANIMATION_DURATION;
if (velocity != 0) {
duration = Math.min(duration,
(int) (Math.abs(newPos - getTranslation(view)) *
1000f / Math.abs(velocity)));
} else {
duration = DEFAULT_ESCAPE_ANIMATION_DURATION;
}
ValueAnimator anim = createTranslationAnimation(view, newPos);
anim.setInterpolator(sLinearInterpolator);
anim.setDuration(duration);
anim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mCallback.onChildDismissed(view);
if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
view.setAlpha(1.f);
}
}
});
anim.addUpdateListener(new AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
view.setAlpha(getAlphaForOffset(view));
}
}
});
anim.start();
}
private void snapChild(final View view, float velocity) {
final boolean canAnimViewBeDismissed = mCallback.canChildBeDismissed(view);
ValueAnimator anim = createTranslationAnimation(view, 0);
int duration = SNAP_ANIM_LEN;
anim.setDuration(duration);
anim.setInterpolator(RecentsConfiguration.getInstance().linearOutSlowInInterpolator);
anim.addUpdateListener(new AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
view.setAlpha(getAlphaForOffset(view));
}
mCallback.onSwipeChanged(mCurrView, view.getTranslationX());
}
});
anim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
if (FADE_OUT_DURING_SWIPE && canAnimViewBeDismissed) {
view.setAlpha(1.0f);
}
mCallback.onSnapBackCompleted(view);
}
});
anim.start();
}
public boolean onTouchEvent(MotionEvent ev) {
if (!mDragging) {
if (!onInterceptTouchEvent(ev)) {
return mCanCurrViewBeDimissed;
}
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_OUTSIDE:
case MotionEvent.ACTION_MOVE:
if (mCurrView != null) {
float delta = getPos(ev) - mInitialTouchPos;
setSwipeAmount(delta);
mCallback.onSwipeChanged(mCurrView, delta);
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if (mCurrView != null) {
endSwipe(mVelocityTracker);
}
break;
}
return true;
}
private void setSwipeAmount(float amount) {
// don't let items that can't be dismissed be dragged more than
// maxScrollDistance
if (CONSTRAIN_SWIPE
&& (!isValidSwipeDirection(amount) || !mCallback.canChildBeDismissed(mCurrView))) {
float size = getSize(mCurrView);
float maxScrollDistance = 0.15f * size;
if (Math.abs(amount) >= size) {
amount = amount > 0 ? maxScrollDistance : -maxScrollDistance;
} else {
amount = maxScrollDistance * (float) Math.sin((amount/size)*(Math.PI/2));
}
}
setTranslation(mCurrView, amount);
if (FADE_OUT_DURING_SWIPE && mCanCurrViewBeDimissed) {
float alpha = getAlphaForOffset(mCurrView);
mCurrView.setAlpha(alpha);
}
}
private boolean isValidSwipeDirection(float amount) {
if (mSwipeDirection == X) {
if (mRtl) {
return (amount <= 0) ? mAllowSwipeTowardsEnd : mAllowSwipeTowardsStart;
} else {
return (amount <= 0) ? mAllowSwipeTowardsStart : mAllowSwipeTowardsEnd;
}
}
// Vertical swipes are always valid.
return true;
}
private void endSwipe(VelocityTracker velocityTracker) {
velocityTracker.computeCurrentVelocity(1000 /* px/sec */);
float velocity = getVelocity(velocityTracker);
float perpendicularVelocity = getPerpendicularVelocity(velocityTracker);
float escapeVelocity = SWIPE_ESCAPE_VELOCITY * mDensityScale;
float translation = getTranslation(mCurrView);
// Decide whether to dismiss the current view
boolean childSwipedFarEnough = DISMISS_IF_SWIPED_FAR_ENOUGH &&
Math.abs(translation) > 0.6 * getSize(mCurrView);
boolean childSwipedFastEnough = (Math.abs(velocity) > escapeVelocity) &&
(Math.abs(velocity) > Math.abs(perpendicularVelocity)) &&
(velocity > 0) == (translation > 0);
boolean dismissChild = mCallback.canChildBeDismissed(mCurrView)
&& isValidSwipeDirection(translation)
&& (childSwipedFastEnough || childSwipedFarEnough);
if (dismissChild) {
// flingadingy
dismissChild(mCurrView, childSwipedFastEnough ? velocity : 0f);
} else {
// snappity
mCallback.onDragCancelled(mCurrView);
snapChild(mCurrView, velocity);
}
}
public interface Callback {
View getChildAtPosition(MotionEvent ev);
boolean canChildBeDismissed(View v);
void onBeginDrag(View v);
void onSwipeChanged(View v, float delta);
void onChildDismissed(View v);
void onSnapBackCompleted(View v);
void onDragCancelled(View v);
}
}