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Android Reference

GridLayout


android.widget

Class GridLayout

  • All Implemented Interfaces:
    Drawable.Callback, AccessibilityEventSource, KeyEvent.Callback, ViewManager, ViewParent


    public class GridLayout
    extends ViewGroup
    A layout that places its children in a rectangular grid.

    The grid is composed of a set of infinitely thin lines that separate the viewing area into cells. Throughout the API, grid lines are referenced by grid indices. A grid with N columns has N + 1 grid indices that run from 0 through N inclusive. Regardless of how GridLayout is configured, grid index 0 is fixed to the leading edge of the container and grid index N is fixed to its trailing edge (after padding is taken into account).

    Row and Column Specs

    Children occupy one or more contiguous cells, as defined by their rowSpec and columnSpec layout parameters. Each spec defines the set of rows or columns that are to be occupied; and how children should be aligned within the resulting group of cells. Although cells do not normally overlap in a GridLayout, GridLayout does not prevent children being defined to occupy the same cell or group of cells. In this case however, there is no guarantee that children will not themselves overlap after the layout operation completes.

    Default Cell Assignment

    If a child does not specify the row and column indices of the cell it wishes to occupy, GridLayout assigns cell locations automatically using its: orientation, rowCount and columnCount properties.

    Space

    Space between children may be specified either by using instances of the dedicated Space view or by setting the leftMargin, topMargin, rightMargin and bottomMargin layout parameters. When the useDefaultMargins property is set, default margins around children are automatically allocated based on the prevailing UI style guide for the platform. Each of the margins so defined may be independently overridden by an assignment to the appropriate layout parameter. Default values will generally produce a reasonable spacing between components but values may change between different releases of the platform.

    Excess Space Distribution

    GridLayout's distribution of excess space is based on priority rather than weight.

    A child's ability to stretch is inferred from the alignment properties of its row and column groups (which are typically set by setting the gravity property of the child's layout parameters). If alignment was defined along a given axis then the component is taken as flexible in that direction. If no alignment was set, the component is instead assumed to be inflexible.

    Multiple components in the same row or column group are considered to act in parallel. Such a group is flexible only if all of the components within it are flexible. Row and column groups that sit either side of a common boundary are instead considered to act in series. The composite group made of these two elements is flexible if one of its elements is flexible.

    To make a column stretch, make sure all of the components inside it define a gravity. To prevent a column from stretching, ensure that one of the components in the column does not define a gravity.

    When the principle of flexibility does not provide complete disambiguation, GridLayout's algorithms favour rows and columns that are closer to its right and bottom edges.

    Limitations
    GridLayout does not provide support for the principle of weight, as defined in LinearLayout.LayoutParams.weight. In general, it is not therefore possible to configure a GridLayout to distribute excess space between multiple components.

    Some common use-cases may nevertheless be accommodated as follows. To place equal amounts of space around a component in a cell group; use CENTER alignment (or gravity). For complete control over excess space distribution in a row or column; use a LinearLayout subview to hold the components in the associated cell group. When using either of these techniques, bear in mind that cell groups may be defined to overlap.

    See GridLayout.LayoutParams for a full description of the layout parameters used by GridLayout.



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