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7b62dc22ad
Summary: This pull request adds an example to the Dimensions documentations. Specifically, it gives an example of how to get the height and width from the window. I'm submitting this documentation because discovering this information cost me some time and my hope is to save other folks time by having this info right in the docs generated from the comments in this file. Let me know if you need anything else. Closes https://github.com/facebook/react-native/pull/4211 Reviewed By: svcscm Differential Revision: D2719953 Pulled By: androidtrunkagent fb-gh-sync-id: 86d18e3847066211a013a50ce2f2a3e2032f5052
72 lines
2.3 KiB
JavaScript
72 lines
2.3 KiB
JavaScript
/**
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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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* @providesModule Dimensions
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* @flow
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*/
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'use strict';
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var UIManager = require('UIManager');
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var invariant = require('invariant');
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var dimensions = UIManager.Dimensions;
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// We calculate the window dimensions in JS so that we don't encounter loss of
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// precision in transferring the dimensions (which could be non-integers) over
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// the bridge.
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if (dimensions && dimensions.windowPhysicalPixels) {
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// parse/stringify => Clone hack
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dimensions = JSON.parse(JSON.stringify(dimensions));
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var windowPhysicalPixels = dimensions.windowPhysicalPixels;
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dimensions.window = {
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width: windowPhysicalPixels.width / windowPhysicalPixels.scale,
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height: windowPhysicalPixels.height / windowPhysicalPixels.scale,
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scale: windowPhysicalPixels.scale,
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fontScale: windowPhysicalPixels.fontScale,
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};
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// delete so no callers rely on this existing
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delete dimensions.windowPhysicalPixels;
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}
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class Dimensions {
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/**
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* This should only be called from native code.
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*
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* @param {object} dims Simple string-keyed object of dimensions to set
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*/
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static set(dims: {[key:string]: any}): bool {
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Object.assign(dimensions, dims);
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return true;
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}
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/**
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* Initial dimensions are set before `runApplication` is called so they should
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* be available before any other require's are run, but may be updated later.
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*
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* Note: Although dimensions are available immediately, they may change (e.g
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* due to device rotation) so any rendering logic or styles that depend on
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* these constants should try to call this function on every render, rather
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* than caching the value (for example, using inline styles rather than
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* setting a value in a `StyleSheet`).
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*
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* Example: `var {height, width} = Dimensions.get('window');`
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*
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* @param {string} dim Name of dimension as defined when calling `set`.
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* @returns {Object?} Value for the dimension.
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*/
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static get(dim: string): Object {
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invariant(dimensions[dim], 'No dimension set for key ' + dim);
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return dimensions[dim];
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}
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}
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module.exports = Dimensions;
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