/*
* 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 android.transition;
import android.graphics.Rect;
import android.view.View;
import android.view.ViewGroup;
/**
* A propagation that varies with the distance to the epicenter of the Transition
* or center of the scene if no epicenter exists. When a View is visible in the
* start of the transition, Views farther from the epicenter will transition
* sooner than Views closer to the epicenter. When a View is not in the start
* of the transition or is not visible at the start of the transition, it will
* transition sooner when closer to the epicenter and later when farther from
* the epicenter. This is the default TransitionPropagation used with
* {@link android.transition.Explode}.
*/
public class CircularPropagation extends VisibilityPropagation {
private static final String TAG = "CircularPropagation";
private float mPropagationSpeed = 3.0f;
/**
* Sets the speed at which transition propagation happens, relative to the duration of the
* Transition. A <code>propagationSpeed</code> of 1 means that a View centered farthest from
* the epicenter and View centered at the epicenter will have a difference
* in start delay of approximately the duration of the Transition. A speed of 2 means the
* start delay difference will be approximately half of the duration of the transition. A
* value of 0 is illegal, but negative values will invert the propagation.
*
* @param propagationSpeed The speed at which propagation occurs, relative to the duration
* of the transition. A speed of 4 means it works 4 times as fast
* as the duration of the transition. May not be 0.
*/
public void setPropagationSpeed(float propagationSpeed) {
if (propagationSpeed == 0) {
throw new IllegalArgumentException("propagationSpeed may not be 0");
}
mPropagationSpeed = propagationSpeed;
}
@Override
public long getStartDelay(ViewGroup sceneRoot, Transition transition,
TransitionValues startValues, TransitionValues endValues) {
if (startValues == null && endValues == null) {
return 0;
}
int directionMultiplier = 1;
TransitionValues positionValues;
if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
positionValues = startValues;
directionMultiplier = -1;
} else {
positionValues = endValues;
}
int viewCenterX = getViewX(positionValues);
int viewCenterY = getViewY(positionValues);
Rect epicenter = transition.getEpicenter();
int epicenterX;
int epicenterY;
if (epicenter != null) {
epicenterX = epicenter.centerX();
epicenterY = epicenter.centerY();
} else {
int[] loc = new int[2];
sceneRoot.getLocationOnScreen(loc);
epicenterX = Math.round(loc[0] + (sceneRoot.getWidth() / 2)
+ sceneRoot.getTranslationX());
epicenterY = Math.round(loc[1] + (sceneRoot.getHeight() / 2)
+ sceneRoot.getTranslationY());
}
double distance = distance(viewCenterX, viewCenterY, epicenterX, epicenterY);
double maxDistance = distance(0, 0, sceneRoot.getWidth(), sceneRoot.getHeight());
double distanceFraction = distance/maxDistance;
long duration = transition.getDuration();
if (duration < 0) {
duration = 300;
}
return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
}
private static double distance(float x1, float y1, float x2, float y2) {
double x = x2 - x1;
double y = y2 - y1;
return Math.hypot(x, y);
}
}