简介
我们在React Native中使用flexbox规则来指定某个组件的子元素的布局。Flexbox可以在不同屏幕尺寸上提供一致的布局结构。相对于Native开发的布局更加快捷方便。
Flexbox使用flexDirection、alignItems和 justifyContent三个样式属性就已经能满足大多数布局需求
flexDirection
flexDirection可以决定zu jian组件布局的主轴，子元素会沿着主轴排列，或水平或垂直。
flexDirection的默认值是竖直轴（column）方向
column（默认）
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{flex: 1}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
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column-reverse
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{flex: 1, flexDirection: 'column-reverse'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
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row
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{flex: 1, flexDirection: 'row'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
row-reverse
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{flex: 1, flexDirection: 'row-reverse'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
justifyContent
在组件的style中指定justifyContent可以决定其子元素沿着主轴的排列方式。子元素是应该靠近主轴的起始端还是末尾段分布呢？亦或应该均匀分布？对应的这些可选项有：flex-start、center、flex-end、space-around以及space-between。
flex-start
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column',justifyContent: 'flex-start'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
center
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column',justifyContent: 'center'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
flex-end
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column',justifyContent: 'flex-end'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
space-around
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column',justifyContent: 'space-around'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
space-between
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column',justifyContent: 'space-between'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
alignItems
在组件的style中指定alignItems可以决定其子元素沿着次轴（与主轴垂直的轴，比如若主轴方向为row，则次轴方向为column）的排列方式。子元素是应该靠近次轴的起始端还是末尾段分布呢？亦或应该均匀分布？对应的这些可选项有：flex-start、center、flex-end以及stretch。
flex-start
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column', justifyContent: 'center', alignItems: 'flex-start'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
center
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column', justifyContent: 'center', alignItems: 'center'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
flex-end
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column', justifyContent: 'center', alignItems: 'flex-end'}}>
<View style={{width: 50, height: 50, backgroundColor: 'red'}} />
<View style={{width: 50, height: 50, backgroundColor: 'green'}} />
<View style={{width: 50, height: 50, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
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stretch
注意：
要使stretch选项生效的话，子元素在次轴方向上不能有固定的尺寸。以下面的代码为例：只有将子元素样式中的width: 50去掉之后，alignItems: 'stretch'才能生效。
export default class AsomeProject extends Component {
constructor(props) {
super(props);
}
render() {
return (
<View style={{ flex: 1, flexDirection: 'column', justifyContent: 'center', alignItems: 'stretch'}}>
<View style={{height: 50, backgroundColor: 'red'}} />
<View style={{height: 150, backgroundColor: 'green'}} />
<View style={{height: 100, backgroundColor: 'blue'}} />
</View>
);
}
}
AppRegistry.registerComponent('AsomeProject', () => AsomeProject);
这里写图片描述
