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GridLayout

public class GridLayout
extends ViewGroup

java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ androidx.gridlayout.widget.GridLayout


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 accommodates the principle of weight. In the event that no weights are specified, columns and rows are taken as flexible if their views specify some form of alignment within their groups.

The flexibility of a view is therefore influenced by its alignment which is, in turn, typically defined by setting the gravity property of the child's layout parameters. If either a weight or alignment were defined along a given axis then the component is taken as flexible in that direction. If no weight or 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 weight or a gravity. To prevent a column from stretching, ensure that one of the components in the column does not define a weight or 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. To be more precise, GridLayout treats each of its layout parameters as a constraint in the a set of variables that define the grid-lines along a given axis. During layout, GridLayout solves the constraints so as to return the unique solution to those constraints for which all variables are less-than-or-equal-to the corresponding value in any other valid solution.

Interpretation of GONE

For layout purposes, GridLayout treats views whose visibility status is GONE, as having zero width and height. This is subtly different from the policy of ignoring views that are marked as GONE outright. If, for example, a gone-marked view was alone in a column, that column would itself collapse to zero width if and only if no gravity was defined on the view. If gravity was defined, then the gone-marked view has no effect on the layout and the container should be laid out as if the view had never been added to it. GONE views are taken to have zero weight during excess space distribution.

These statements apply equally to rows as well as columns, and to groups of rows or columns.

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

Summary

Nested classes

class GridLayout.Alignment

Alignments specify where a view should be placed within a cell group and what size it should be. 

class GridLayout.LayoutParams

Layout information associated with each of the children of a GridLayout. 

class GridLayout.Spec

A Spec defines the horizontal or vertical characteristics of a group of cells. 

Constants

int ALIGN_BOUNDS

This constant is an alignmentMode.

int ALIGN_MARGINS

This constant is an alignmentMode.

int HORIZONTAL

The horizontal orientation.

int UNDEFINED

The constant used to indicate that a value is undefined.

int VERTICAL

The vertical orientation.

Inherited constants

Fields

public static final GridLayout.Alignment BASELINE

Indicates that a view should be aligned with the baselines of the other views in its cell group.

public static final GridLayout.Alignment BOTTOM

Indicates that a view should be aligned with the bottom edges of the other views in its cell group.

public static final GridLayout.Alignment CENTER

Indicates that a view should be centered with the other views in its cell group.

public static final GridLayout.Alignment END

Indicates that a view should be aligned with the end edges of the other views in its cell group.

public static final GridLayout.Alignment FILL

Indicates that a view should expanded to fit the boundaries of its cell group.

public static final GridLayout.Alignment LEFT

Indicates that a view should be aligned with the left edges of the other views in its cell group.

public static final GridLayout.Alignment RIGHT

Indicates that a view should be aligned with the right edges of the other views in its cell group.

public static final GridLayout.Alignment START

Indicates that a view should be aligned with the start edges of the other views in its cell group.

public static final GridLayout.Alignment TOP

Indicates that a view should be aligned with the top edges of the other views in its cell group.

Inherited fields

Public constructors

GridLayout(Context context, AttributeSet attrs, int defStyle)

GridLayout(Context context, AttributeSet attrs)

GridLayout(Context context)

Public methods

GridLayout.LayoutParams generateLayoutParams(AttributeSet attrs)
int getAlignmentMode()

Returns the alignment mode.

int getColumnCount()

Returns the current number of columns.

int getOrientation()

Returns the current orientation.

Printer getPrinter()

Return the printer that will log diagnostics from this layout.

int getRowCount()

Returns the current number of rows.

boolean getUseDefaultMargins()

Returns whether or not this GridLayout will allocate default margins when no corresponding layout parameters are defined.

boolean isColumnOrderPreserved()

Returns whether or not column boundaries are ordered by their grid indices.

boolean isRowOrderPreserved()

Returns whether or not row boundaries are ordered by their grid indices.

void requestLayout()
void setAlignmentMode(int alignmentMode)

Sets the alignment mode to be used for all of the alignments between the children of this container.

void setColumnCount(int columnCount)

ColumnCount is used only to generate default column/column indices when they are not specified by a component's layout parameters.

void setColumnOrderPreserved(boolean columnOrderPreserved)

When this property is true, GridLayout is forced to place the column boundaries so that their associated grid indices are in ascending order in the view.

void setOrientation(int orientation)

GridLayout uses the orientation property for two purposes:

  • To control the 'direction' in which default row/column indices are generated when they are not specified in a component's layout parameters.

void setPrinter(Printer printer)

Set the printer that will log diagnostics from this layout.

void setRowCount(int rowCount)

RowCount is used only to generate default row/column indices when they are not specified by a component's layout parameters.

void setRowOrderPreserved(boolean rowOrderPreserved)

When this property is true, GridLayout is forced to place the row boundaries so that their associated grid indices are in ascending order in the view.

void setUseDefaultMargins(boolean useDefaultMargins)

When true, GridLayout allocates default margins around children based on the child's visual characteristics.

static GridLayout.Spec spec(int start, float weight)

Equivalent to: spec(start, 1, weight).

static GridLayout.Spec spec(int start)

Return a Spec, spec, where:

  • spec.span = [start, start + 1]

To leave the start index undefined, use the value UNDEFINED.

static GridLayout.Spec spec(int start, GridLayout.Alignment alignment)

Return a Spec, spec, where:

  • spec.span = [start, start + 1]
  • spec.alignment = alignment

To leave the start index undefined, use the value UNDEFINED.

static GridLayout.Spec spec(int start, GridLayout.Alignment alignment, float weight)

Equivalent to: spec(start, 1, alignment, weight).

static GridLayout.Spec spec(int start, int size, GridLayout.Alignment alignment)

Equivalent to: spec(start, size, alignment, 0f).

static GridLayout.Spec spec(int start, int size, GridLayout.Alignment alignment, float weight)

Return a Spec, spec, where:

  • spec.span = [start, start + size]
  • spec.alignment = alignment
  • spec.weight = weight

To leave the start index undefined, use the value UNDEFINED.

static GridLayout.Spec spec(int start, int size, float weight)

Equivalent to: spec(start, 1, default_alignment, weight) - where default_alignment is specified in GridLayout.LayoutParams.

static GridLayout.Spec spec(int start, int size)

Return a Spec, spec, where:

  • spec.span = [start, start + size]

To leave the start index undefined, use the value UNDEFINED.

Protected methods

boolean checkLayoutParams(ViewGroup.LayoutParams p)
GridLayout.LayoutParams generateDefaultLayoutParams()
GridLayout.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp)
void onLayout(boolean changed, int left, int top, int right, int bottom)

void onMeasure(int widthSpec, int heightSpec)

Inherited methods