The only difference is that they take a percentage rather than a dip value. Percentages can also be used for margins and the layout parameters for these are entirely analogous to the standard margin attributes.
LISTVIEW ANDROID STUDIO PERCENTAGE CODE
However, Android Studio (V1.4 preview 3 at the time of writing) does not know this so gives you a warning – the code compiles and runs despite the warning. It is worth noting that layout_ are not required here as they will automatically be added during the layout pass. Being an extension of RelativeLayout it’s entirely possible to overlap items, and there is no reason why you need be concerned about the overall maxWeight as you are with weighted LinearLayouts. Proportional sizing is done using the heightPercent and widthPercent attributes each of which take a percentage value which corresponds to a percentage of the size of the PercentRelativeLayout. The first thing to note is that, because this is a support library, the layout parameters specific to PercentRelativeLayout exist within the app namespace and not the android one.
LISTVIEW ANDROID STUDIO PERCENTAGE HOW TO
So, let’s take a look at how to implement PercentRelativeLayout (I have elected to focus solely on PercentRelativeLayout as it’s a little more flexible and allows us to better explore things, but the principles apply equally well to PercentFrameLayout).įirst we need to include the percent support library: So while it would probably still be good practice to avoid nesting Percent layouts (keeping your layout hierarchy as flat as possible is good practise anyway) the overhead should not be as high. So this addresses the first of the weighted LinearLayout issues as proportional positioning is extended to RelativeLayout and FrameLayout by this library.įrom looking at the Percent classes using the decompiler built in to Android Studio (the source has not been pushed to AOSP at the time of writing) it appears that it may still require a second measurement in certain circumstances, but it appears a little more selective than LinearLayout. The fundamental behaviours of these are identical to RelativeLayout and FrameLayout respectively, but add some additional LayoutParams for proportional width and margin calculation. The Percent library addresses the first of these issues by providing two new layout types: PercentRelativeLayout and PercentFrameLayout. Nesting LinearLayouts which are weighted along the same axis will increase these measurement passes exponentially for each level of nesting. Any View within a LinearLayout which has a weight will need to be measured twice – first to determine it’s intrinsic width so that the LinearLayout can calculate how much space it has to divide up once the intrinsic sizes have been accounted for and then again once the LinearLayout has allocated it additional space based upon the weight. Secondly there is the issue of nested weights. Having too deep a layout hierarchy is bad for performance so it always feels a little inefficient having to use two layouts in this case.
In such cases the only real way of achieving what we need is to include a LinearLayout within a parent RelativeLayout. For example, some of the components of the layout need to be positioned relative to other components, but others need to be positioned proportionally. Before we dive in it’s probably worth considering why the Percent library is actually needed because LinearLayout weights will already do what we need, won’t they? As powerful and useful as LinearLayout weights are, there are actually a couple of issues with them.įirstly there are times where a particular layout requires us to divide space between components proportionally, but the parent layout is not a LinearLayout.
0 kommentar(er)
