Using android:layout_weight in Layout Tricks

I have referred to this site for Layout Tricks.

Over there one attribute is declared as android:layout_weight="1".

So my confusion is regarding android:layout_weight:

1. where is the exact use of android:layout_weight ?
2. Where开发者_如何学运维 should we use android:layout_weight ?

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From what I understand of layout_weight, the closest comparison I could find is when you pass some % in HTML for the width or height of your div. In our context, the weigth seems to refer to the % of width or heigth your widget should get for itself compared to its neighbours in a given ViewGroup. You can find another exemple with more explanation here.
If you look the way they use it, it sticks exactly to the definition. They give a height of 0dip to keep the whole space free, and then uses equal weigths for the 2 widgets to make same th same height.

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layout_weight is quite simply a priority to apply to a view class, the higher, the larger the control or group will be in proportion to it's mates inside that group. The default is 0, so a weight of 1 makes it twice as large as other default controls. No mystery.