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add percentage dimensions section to the Height and Width page #2101

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merged 2 commits into from
Aug 1, 2020
Merged

add percentage dimensions section to the Height and Width page #2101

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1b778e4
add percentage dimensions section to the Height and Width page
Simek Jul 26, 2020
ae48b89
grammar tweaks
rachelnabors Jul 29, 2020
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71 changes: 53 additions & 18 deletions docs/height-and-width.md
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Original file line number Diff line number Diff line change
Expand Up @@ -14,13 +14,19 @@ import React from 'react';
import { View } from 'react-native';

const FixedDimensionsBasics = () => {
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>
);
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>
);
};

export default FixedDimensionsBasics;
Expand All @@ -32,26 +38,55 @@ Setting dimensions this way is common for components that should always render a

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 other components 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.
> 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.

```SnackPlayer name=Flex%20Dimensions
import React from 'react';
import { View } from 'react-native';

const FlexDimensionsBasics = () => {
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>
);
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>
);
};

export default FlexDimensionsBasics;
```

After you can control a component's size, the next step is to [learn how to lay it out on the screen](flexbox.md).

## Percentage Dimensions

If you want to fill a certain portion of the screen, but you _don't_ want to use the `flex` layout, you _can_ use **percentage values** in the component's style. Similar to flex dimensions, percentage dimensions require parent with a defined size.

```SnackPlayer name=Percentage%20Dimensions
import React from 'react';
import { View } from 'react-native';

const PercentageDimensionsBasics = () => {
// Try removing the `height: '100%'` on the parent View.
// The parent will not have dimensions, so the children can't expand.
return (
<View style={{ height: '100%' }}>
<View style={{
height: '15%', backgroundColor: 'powderblue'
}} />
<View style={{
width: '66%', height: '35%', backgroundColor: 'skyblue'
}} />
<View style={{
width: '33%', height: '50%', backgroundColor: 'steelblue'
}} />
</View>
);
};

export default PercentageDimensionsBasics;
```