RN 开始学习

1. React Native still has the concept of style inheritance, but limited to text subtrees.
2. All dimensions in React Native are unitless, and represent density-independent pixels.
3. 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.
4. the flex parameter only supporting a single number.
5. For stretch to have an effect, children must not have a fixed dimension along the secondary axis.
6. Pressing the button will call the "onPress" function.
7. The ScrollView works best to present a small amount of things of a limited size. All the elements and views of a ScrollView are rendered, even if they are not currently shown on the screen. If you have a long list of more items than can fit on the screen, you should use a FlatList instead.