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Add docs pages for basics: Dimensions and Layout #8364

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2 changes: 1 addition & 1 deletion docs/Basics-Component-ListView.md
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ title: ListView
layout: docs
category: The Basics
permalink: docs/basics-component-listview.html
next: basics-network
next: basics-dimensions
---

On mobile devices, lists are a core element in many applications. The [`ListView`](/react-native/docs/listview.html#content) component is a special type of [`View`](/react-native/docs/basics-component-view.html) that displays a *vertically* scrolling list of changing, but similarly structured, data.
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63 changes: 63 additions & 0 deletions docs/Basics-Dimensions.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,63 @@
---
id: basics-dimensions
title: Dimensions
layout: docs
category: The Basics
permalink: docs/basics-dimensions.html
next: basics-layout
---

A component's dimensions determine its size on the screen.

#### Fixed Dimensions

The simplest way to set the dimensions of a component is by adding a fixed `width` and `height` to style. All dimensions in React Native are unitless, and represent density-independent pixels.

```ReactNativeWebPlayer
import React from 'react';
import { AppRegistry, View } from 'react-native';

class AwesomeProject {
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@artyomtrityak artyomtrityak Jun 23, 2016

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should this and same next in this review be extended from Component?

class AwesomeProject extends React.Component or

import React, { Component } from 'react';
class AwesomeProject extends Component

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I was thinking the same thing too. Since this has been accepted and started to ship, I will create a PR to make the extends on these. No need to block this now, imho.

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Does this work without Component? It works in the React Native Web Player but dunno about in RN itself.

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Let me try running locally on the simulator....

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Yeah, seems to run without Component. Seems weird. Since we are calling registerComponent on something that isn't technically a Component. Is there some sort of implied extension when we omit it or something?

render() {
return (
<View>
<View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} />
<View style={{width: 100, height: 100, backgroundColor: 'skyblue'}} />
<View style={{width: 150, height: 150, backgroundColor: 'steelblue'}} />
</View>
);
}
};

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);
```

Setting dimensions this way is common for components that should always render at exactly the same size, regardless of screen dimensions.

#### Flex Dimensions

Use `flex` in a component's style to have the component expand and shrink dynamically based on available space. Normally you will use `flex: 1`, which tells a component to fill all available space, shared evenly amongst each other component with the same parent. The larger the `flex` given, the higher the ratio of space a component will take compared to its siblings.

> A component can only expand to fill available space if its parent has dimensions greater than 0. If a parent does not have either a fixed `width` and `height` or `flex`, the parent will have dimensions of 0 and the `flex` children will not be visible.

```ReactNativeWebPlayer
import React from 'react';
import { AppRegistry, View } from 'react-native';

class AwesomeProject {
render() {
return (
// Try removing the `flex: 1` on the parent View.
// The parent will not have dimensions, so the children can't expand.
// What if you add `height: 300` instead of `flex: 1`?
<View style={{flex: 1}}>
<View style={{flex: 1, backgroundColor: 'powderblue'}} />
<View style={{flex: 2, backgroundColor: 'skyblue'}} />
<View style={{flex: 3, backgroundColor: 'steelblue'}} />
</View>
);
}
};

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);
```
104 changes: 104 additions & 0 deletions docs/Basics-Layout.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,104 @@
---
id: basics-layout
title: Layout
layout: docs
category: The Basics
permalink: docs/basics-layout.html
next: basics-network
---

A component can specify the layout of its children using the flexbox algorithm. Flexbox is designed to provide a consistent layout on different screen sizes.

You will normally use a combination of `flexDirection`, `alignItems`, and `justifyContent` to achieve the right layout.

> Flexbox works the same way in React Native as it does in CSS on the web, with a few exceptions. The most notable one: the defaults are different, with `flexDirection` defaulting to `column` instead of `row`, and `alignItems` defaulting to `stretch` instead of `flex-start`.

#### Flex Direction

Adding `flexDirection` to a component's `style` determines the **primary axis** of its layout. Should the children be organized horizontally (`row`) or vertically (`column`)? The default is `column`.

```ReactNativeWebPlayer
import React from 'react';
import { AppRegistry, View } from 'react-native';

class AwesomeProject {
render() {
return (
// Try setting `flexDirection` to `column`.
<View style={{flex: 1, flexDirection: 'row'}}>
<View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} />
</View>
);
}
};

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);
```

#### Justify Content

Adding `justifyContent` to a component's style determines the **distribution** of children along the **primary axis**. Should children be distributed at the start, the center, the end, or spaced evenly? Available options are `flex-start`, `center`, `flex-end`, `space-around`, and `space-between`.

```ReactNativeWebPlayer
import React from 'react';
import { AppRegistry, View } from 'react-native';

class AwesomeProject {
render() {
return (
// Try setting `justifyContent` to `center`.
// Try setting `flexDirection` to `row`.
<View style={{
flex: 1,
flexDirection: 'column',
justifyContent: 'space-between',
}}>
<View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} />
</View>
);
}
};

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);
```

#### Align Items

Adding `alignItems` to a component's style determines the **alignment** of children along the **secondary axis** (if the primary axis is `row`, then the secondary is `column`, and vice versa). Should children be aligned at the start, the center, the end, or stretched to fill? Available options are `flex-start`, `center`, `flex-end`, and `stretch`.

> For `stretch` to have an effect, children must not have a fixed dimension along the secondary axis. In the following example, setting `alignItems: stretch` does nothing until the `width: 50` is removed from the children.

```ReactNativeWebPlayer
import React from 'react';
import { AppRegistry, View } from 'react-native';

class AwesomeProject {
render() {
return (
// Try setting `alignItems` to 'flex-start'
// Try setting `justifyContent` to `flex-end`.
// Try setting `flexDirection` to `row`.
<View style={{
flex: 1,
flexDirection: 'column',
justifyContent: 'center',
alignItems: 'center',
}}>
<View style={{width: 50, height: 50, backgroundColor: 'powderblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'skyblue'}} />
<View style={{width: 50, height: 50, backgroundColor: 'steelblue'}} />
</View>
);
}
};

AppRegistry.registerComponent('AwesomeProject', () => AwesomeProject);
```

#### API Reference

We've covered the basics, but there are many other styles you may need for layouts. The full list is available [here](./docs/flexbox.html).