native decay animation

Summary: Add support for `useNativeDriver: true` to `Animated.decay`. Add example in Native Animated Example UIExplorer app.

Reviewed By: ritzau

Differential Revision: D3690127

fbshipit-source-id: eaa5e61293ed174191cec72255ea2677dbaa1757

Examples/UIExplorer/js/NativeAnimationsExample.js

@@ -41,12 +41,16 @@ class Tester extends React.Component {
   current = 0;
 
   onPress = () => {
+    const animConfig = (
+      this.current && this.props.reverseConfig ? this.props.reverseConfig : this.props.config
+    );
     this.current = this.current ? 0 : 1;
     const config = {
-      ...this.props.config,
+      ...animConfig,
       toValue: this.current,
     };
 
+    // $FlowIssue #0000000
     Animated[this.props.type](this.state.native, { ...config, useNativeDriver: true }).start();
     Animated[this.props.type](this.state.js, { ...config, useNativeDriver: false }).start();
   };
@@ -344,6 +348,32 @@ exports.examples = [
         </Tester>
       );
     },
+  },{
+    title: 'translateX => Animated.decay',
+    render: function() {
+      return (
+        <Tester
+          type="decay"
+          config={{ velocity: 0.5 }}
+          reverseConfig={{ velocity: -0.5 }}
+        >
+          {anim => (
+            <Animated.View
+              style={[
+                styles.block,
+                {
+                  transform: [
+                    {
+                      translateX: anim
+                    },
+                  ],
+                }
+              ]}
+            />
+          )}
+        </Tester>
+      );
+    },
   },
   {
     title: 'Animated value listener',

Libraries/Animated/src/AnimatedImplementation.js

@@ -351,6 +351,7 @@ class DecayAnimation extends Animation {
   _velocity: number;
   _onUpdate: (value: number) => void;
   _animationFrame: any;
+  _useNativeDriver: bool;
 
   constructor(
     config: DecayAnimationConfigSingle,
@@ -358,13 +359,24 @@ class DecayAnimation extends Animation {
     super();
     this._deceleration = config.deceleration !== undefined ? config.deceleration : 0.998;
     this._velocity = config.velocity;
+    this._useNativeDriver = config.useNativeDriver !== undefined ? config.useNativeDriver : false;
     this.__isInteraction = config.isInteraction !== undefined ? config.isInteraction : true;
   }
 
+  __getNativeAnimationConfig() {
+    return {
+      type: 'decay',
+      deceleration: this._deceleration,
+      velocity: this._velocity,
+    };
+  }
+
   start(
     fromValue: number,
     onUpdate: (value: number) => void,
     onEnd: ?EndCallback,
+    previousAnimation: ?Animation,
+    animatedValue: AnimatedValue,
   ): void {
     this.__active = true;
     this._lastValue = fromValue;
@@ -372,7 +384,11 @@ class DecayAnimation extends Animation {
     this._onUpdate = onUpdate;
     this.__onEnd = onEnd;
     this._startTime = Date.now();
-    this._animationFrame = requestAnimationFrame(this.onUpdate.bind(this));
+    if (this._useNativeDriver) {
+      this.__startNativeAnimation(animatedValue);
+    } else {
+      this._animationFrame = requestAnimationFrame(this.onUpdate.bind(this));
+    }
   }
 
   onUpdate(): void {

ReactAndroid/src/main/java/com/facebook/react/animated/DecayAnimation.java

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.animated;
+
+import com.facebook.react.bridge.ReadableMap;
+
+/**
+ * Implementation of {@link AnimationDriver} providing support for decay animations. The
+ * implementation is copied from the JS version in {@code AnimatedImplementation.js}.
+ */
+public class DecayAnimation extends AnimationDriver {
+
+  private final double mVelocity;
+  private final double mDeceleration;
+
+  private long mStartFrameTimeMillis = -1;
+  private double mFromValue;
+  private double mLastValue;
+
+  public DecayAnimation(ReadableMap config) {
+    mVelocity = config.getDouble("velocity");
+    mDeceleration = config.getDouble("deceleration");
+  }
+
+  @Override
+  public void runAnimationStep(long frameTimeNanos) {
+    long frameTimeMillis = frameTimeNanos / 1000000;
+    if (mStartFrameTimeMillis == -1) {
+      // since this is the first animation step, consider the start to be on the previous frame
+      mStartFrameTimeMillis = frameTimeMillis - 16;
+      mFromValue = mAnimatedValue.mValue;
+      mLastValue = mAnimatedValue.mValue;
+    }
+
+    final double value = mFromValue +
+      (mVelocity / (1 - mDeceleration)) *
+        (1 - Math.exp(-(1 - mDeceleration) * (frameTimeMillis - mStartFrameTimeMillis)));
+
+    if (Math.abs(mLastValue - value) < 0.1) {
+      mHasFinished = true;
+      return;
+    }
+
+    mLastValue = value;
+    mAnimatedValue.mValue = value;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/animated/NativeAnimatedNodesManager.java

@@ -139,6 +139,8 @@ import javax.annotation.Nullable;
       animation = new FrameBasedAnimationDriver(animationConfig);
     } else if ("spring".equals(type)) {
       animation = new SpringAnimation(animationConfig);
+    } else if ("decay".equals(type)) {
+      animation = new DecayAnimation(animationConfig);
     } else {
       throw new JSApplicationIllegalArgumentException("Unsupported animation type: " + type);
     }

ReactAndroid/src/test/java/com/facebook/react/animated/NativeAnimatedNodeTraversalTest.java

@@ -17,7 +17,6 @@ import com.facebook.react.bridge.ReadableMap;
 import com.facebook.react.uimanager.ReactStylesDiffMap;
 import com.facebook.react.uimanager.UIImplementation;
 
-import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -259,6 +258,63 @@ public class NativeAnimatedNodeTraversalTest {
     verifyNoMoreInteractions(mUIImplementationMock);
   }
 
+  @Test
+  public void testDecayAnimation() {
+    createSimpleAnimatedViewWithOpacity(1000, 0d);
+
+    Callback animationCallback = mock(Callback.class);
+    mNativeAnimatedNodesManager.startAnimatingNode(
+      1,
+      1,
+      JavaOnlyMap.of(
+        "type",
+        "decay",
+        "velocity",
+        0.5d,
+        "deceleration",
+        0.998d),
+      animationCallback);
+
+    ArgumentCaptor<ReactStylesDiffMap> stylesCaptor =
+      ArgumentCaptor.forClass(ReactStylesDiffMap.class);
+
+    reset(mUIImplementationMock);
+    mNativeAnimatedNodesManager.runUpdates(nextFrameTime());
+    verify(mUIImplementationMock, atMost(1))
+      .synchronouslyUpdateViewOnUIThread(eq(1000), stylesCaptor.capture());
+    double previousValue = stylesCaptor.getValue().getDouble("opacity", Double.NaN);
+    double previousDiff = Double.POSITIVE_INFINITY;
+    /* run 3 secs of animation */
+    for (int i = 0; i < 3 * 60; i++) {
+      reset(mUIImplementationMock);
+      mNativeAnimatedNodesManager.runUpdates(nextFrameTime());
+      verify(mUIImplementationMock, atMost(1))
+        .synchronouslyUpdateViewOnUIThread(eq(1000), stylesCaptor.capture());
+      double currentValue = stylesCaptor.getValue().getDouble("opacity", Double.NaN);
+      double currentDiff = currentValue - previousValue;
+      // verify monotonicity
+      // greater *or equal* because the animation stops during these 3 seconds
+      assertThat(currentValue).as("on frame " + i).isGreaterThanOrEqualTo(previousValue);
+      // verify decay
+      if (i > 3) {
+        // i > 3 because that's how long it takes to settle previousDiff
+        if (i % 3 != 0) {
+          // i % 3 != 0 because every 3 frames we go a tiny
+          // bit faster, because frame length is 16.(6)ms
+          assertThat(currentDiff).as("on frame " + i).isLessThanOrEqualTo(previousDiff);
+        } else {
+          assertThat(currentDiff).as("on frame " + i).isGreaterThanOrEqualTo(previousDiff);
+        }
+      }
+      previousValue = currentValue;
+      previousDiff = currentDiff;
+    }
+    // should be done in 3s
+    reset(mUIImplementationMock);
+    mNativeAnimatedNodesManager.runUpdates(nextFrameTime());
+    verifyNoMoreInteractions(mUIImplementationMock);
+  }
+
   @Test
   public void testAnimationCallbackFinish() {
     createSimpleAnimatedViewWithOpacity(1000, 0d);