Android: Layout_weight correct understanding,

Android: Layout_weight correct understanding,
Preface

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Today, when I was reading a book, I accidentally found that "android: Layout_weight is the control that occupies the screen importance, and the smaller the value, the higher the importance". At that time, I suddenly felt that something was wrong. android: layout_weight should be the screen weight of the control. The larger the value, the larger the proportion. After reading the information, I wrote a blog to record the summary and sharing.

Incorrect understanding

• Android: the greater the value of Layout_weight, the greater the weight, the larger the proportion
• Android: the smaller the value of Layout_weight, the larger the weight, the larger the proportion
• Android: Layout_weight
  
  • The larger the general value, the larger the weight, the larger the proportion
  • When width or height is fill_parent or match_parent, the smaller the value, the larger the weight.

These are all incorrect understandings. For example, the first misunderstanding is that when writing android: Layout_weight, the width or height is set to 0dip, the second is to set the width or height to fill_parent or match_parent, and the third is not to come to any conclusion.

Correct understanding

The correct understanding is:

Android: Layout_weight is the weight of the control to occupy the screen. You can use the formula to calculate the correct proportion to occupy the screen.

The following formula uses width as an example:

Actual width = control width + remaining width * (control weight/total weight)

• Scenario 1(When width is 0dp ):
  Assume that there are two controls. The first weight is 1 and the second weight is 2. The total weight is 3,
  The first actual width = 0 + screen width * (1/3) = 1/3 screen width
  The second actual width = 0 + screen width * (2/3) = 2/3 screen width

• Case 2(When width is fill_parent or match_parent ):
  Assume that there are two controls. The first weight is 1 and the second weight is 2. The total weight is 3,
  The first actual width = screen width + (-1 * screen width) * (1/3) = 2/3 screen width
  The second actual width = screen width + (-1 * screen width) * (2/3) = 1/3 screen width

Note: remaining width = screen width-width of the first control-width of the second control = (-1 * screen width)

In this case, the larger the weight, the smaller the proportion occupied.

• Case 3(When width is wrap_content or custom value ):
  It can be entered according to the formula.

Summary

In fact, when Google defines android: Layout_weight, we hope we can quickly divide the layout by proportion. Therefore, we recommend that you use android: when Layout_weight is used, the width and height are set to 0dp (when 0dp is used, the larger the weight ratio is), facilitating calculation.

References

Http://mobile.51cto.com/abased-375428.htm