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https://github.com/zhigang1992/react-native.git
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8a7eb170dd
Summary: * Any animation can be looped on the javascript thread * Only basic animations supported natively at this stage, loops run using the native driver cannot contain animations of type sequence, parallel, stagger, or loop Motivation: We need a spinner in our app that is displayed and animated while the javascript thread is tied up with other tasks. This means it needs to be offloaded from the javascript thread, so that it will continue to run while those tasks are churning away. I originally submitted PR #9513, which has served our needs, but brentvatne pointed out a better way to do it. Had hoped his suggestion would be implemented by janicduplessis or another fb employee, but after 5 months I thought I'd give it another push. I've put together an implementation that basically matches the suggested API. Let me know what you think, and whether others can pick it up from here and get it in to core. Personal Motivation: I am leaving my current organisation on Feb 10th, so am trying to clean thing Closes https://github.com/facebook/react-native/pull/11973 Differential Revision: D4704381 fbshipit-source-id: 42a2cdf5d53a7c0d08f86a58485f7f38739e6cd9
71 lines
2.4 KiB
Java
71 lines
2.4 KiB
Java
/**
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* Copyright (c) 2015-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD-style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*/
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package com.facebook.react.animated;
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import com.facebook.react.bridge.ReadableMap;
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/**
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* Implementation of {@link AnimationDriver} providing support for decay animations. The
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* implementation is copied from the JS version in {@code AnimatedImplementation.js}.
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*/
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public class DecayAnimation extends AnimationDriver {
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private final double mVelocity;
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private final double mDeceleration;
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private long mStartFrameTimeMillis = -1;
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private double mFromValue = 0d;
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private double mLastValue = 0d;
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private int mIterations;
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private int mCurrentLoop;
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public DecayAnimation(ReadableMap config) {
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mVelocity = config.getDouble("velocity");
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mDeceleration = config.getDouble("deceleration");
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mIterations = config.hasKey("iterations") ? config.getInt("iterations") : 1;
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mCurrentLoop = 1;
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mHasFinished = mIterations == 0;
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}
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@Override
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public void runAnimationStep(long frameTimeNanos) {
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long frameTimeMillis = frameTimeNanos / 1000000;
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if (mStartFrameTimeMillis == -1) {
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// since this is the first animation step, consider the start to be on the previous frame
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mStartFrameTimeMillis = frameTimeMillis - 16;
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if (mFromValue == mLastValue) { // first iteration, assign mFromValue based on mAnimatedValue
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mFromValue = mAnimatedValue.mValue;
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} else { // not the first iteration, reset mAnimatedValue based on mFromValue
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mAnimatedValue.mValue = mFromValue;
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}
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mLastValue = mAnimatedValue.mValue;
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}
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final double value = mFromValue +
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(mVelocity / (1 - mDeceleration)) *
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(1 - Math.exp(-(1 - mDeceleration) * (frameTimeMillis - mStartFrameTimeMillis)));
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if (Math.abs(mLastValue - value) < 0.1) {
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if (mIterations == -1 || mCurrentLoop < mIterations) { // looping animation, return to start
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// set mStartFrameTimeMillis to -1 to reset instance variables on the next runAnimationStep
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mStartFrameTimeMillis = -1;
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mCurrentLoop++;
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} else { // animation has completed
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mHasFinished = true;
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return;
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}
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}
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mLastValue = value;
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mAnimatedValue.mValue = value;
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}
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}
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