react-native/Libraries/Components/View/View.js

/**
 * 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.
 *
 * @providesModule View
 * @flow
 */
'use strict';

const NativeMethodsMixin = require('NativeMethodsMixin');
const Platform = require('Platform');
const PropTypes = require('prop-types');
const React = require('React');
const ReactNativeStyleAttributes = require('ReactNativeStyleAttributes');
const ReactNativeViewAttributes = require('ReactNativeViewAttributes');
const ViewPropTypes = require('ViewPropTypes');

const createReactClass = require('create-react-class');
const invariant = require('fbjs/lib/invariant');
const requireNativeComponent = require('requireNativeComponent');

import type {ViewProps} from 'ViewPropTypes';

export type Props = ViewProps;

/**
 * The most fundamental component for building a UI, `View` is a container that supports layout with
 * [flexbox](docs/flexbox.html), [style](docs/style.html),
 * [some touch handling](docs/handling-touches.html), and
 * [accessibility](docs/accessibility.html) controls. `View` maps directly to the
 * native view equivalent on whatever platform React Native is running on, whether that is a
 * `UIView`, `<div>`, `android.view`, etc.
 *
 * `View` is designed to be nested inside other views and can have 0 to many children of any type.
 *
 * This example creates a `View` that wraps two colored boxes and a text component in a row with
 * padding.
 *
 * ```javascript
 * class ViewColoredBoxesWithText extends Component {
 *   render() {
 *     return (
 *       <View style={{flexDirection: 'row', height: 100, padding: 20}}>
 *         <View style={{backgroundColor: 'blue', flex: 0.3}} />
 *         <View style={{backgroundColor: 'red', flex: 0.5}} />
 *         <Text>Hello World!</Text>
 *       </View>
 *     );
 *   }
 * }
 * ```
 *
 * > `View`s are designed to be used with [`StyleSheet`](docs/style.html) for clarity
 * > and performance, although inline styles are also supported.
 *
 * ### Synthetic Touch Events
 *
 * For `View` responder props (e.g., `onResponderMove`), the synthetic touch event passed to them
 * are of the following form:
 *
 * - `nativeEvent`
 *   - `changedTouches` - Array of all touch events that have changed since the last event.
 *   - `identifier` - The ID of the touch.
 *   - `locationX` - The X position of the touch, relative to the element.
 *   - `locationY` - The Y position of the touch, relative to the element.
 *   - `pageX` - The X position of the touch, relative to the root element.
 *   - `pageY` - The Y position of the touch, relative to the root element.
 *   - `target` - The node id of the element receiving the touch event.
 *   - `timestamp` - A time identifier for the touch, useful for velocity calculation.
 *   - `touches` - Array of all current touches on the screen.
 */
// $FlowFixMe(>=0.41.0)
const View = createReactClass({
  displayName: 'View',
  // TODO: We should probably expose the mixins, viewConfig, and statics publicly. For example,
  // one of the props is of type AccessibilityComponentType. That is defined as a const[] above,
  // but it is not rendered by the docs, since `statics` below is not rendered. So its Possible
  // values had to be hardcoded.
  mixins: [NativeMethodsMixin],

  // `propTypes` should not be accessed directly on View since this wrapper only
  // exists for DEV mode. However it's important for them to be declared.
  // If the object passed to `createClass` specifies `propTypes`, Flow will
  // create a static type from it.
  propTypes: ViewPropTypes,

  /**
   * `NativeMethodsMixin` will look for this when invoking `setNativeProps`. We
   * make `this` look like an actual native component class.
   */
  viewConfig: {
    uiViewClassName: 'RCTView',
    validAttributes: ReactNativeViewAttributes.RCTView
  },

  contextTypes: {
    isInAParentText: PropTypes.bool,
  },

  render: function() {
    invariant(
      !(this.context.isInAParentText && Platform.OS === 'android'),
      'Nesting of <View> within <Text> is not supported on Android.');

    // WARNING: This method will not be used in production mode as in that mode we
    // replace wrapper component View with generated native wrapper RCTView. Avoid
    // adding functionality this component that you'd want to be available in both
    // dev and prod modes.
    return <RCTView {...this.props} />;
  },
});

const RCTView = requireNativeComponent('RCTView', View, {
  nativeOnly: {
    nativeBackgroundAndroid: true,
    nativeForegroundAndroid: true,
  }
});

if (__DEV__) {
  const UIManager = require('UIManager');
  const viewConfig = UIManager.viewConfigs && UIManager.viewConfigs.RCTView || {};
  for (const prop in viewConfig.nativeProps) {
    const viewAny: any = View; // Appease flow
    if (!viewAny.propTypes[prop] && !ReactNativeStyleAttributes[prop]) {
      throw new Error(
        'View is missing propType for native prop `' + prop + '`'
      );
    }
  }
}

let ViewToExport = RCTView;
if (__DEV__) {
  ViewToExport = View;
}

// No one should depend on the DEV-mode createClass View wrapper.
module.exports = ((ViewToExport : any) : typeof RCTView);