public class

LinearLayout

extends ViewGroup
java.lang.Object
   ↳ android.view.View
     ↳ android.view.ViewGroup
       ↳ android.widget.LinearLayout
Known Direct Subclasses

Class Overview

A Layout that arranges its children in a single column or a single row. The direction of the row can be set by calling setOrientation(). You can also specify gravity, which specifies the alignment of all the child elements by calling setGravity() or specify that specific children grow to fill up any remaining space in the layout by setting the weight member of LinearLayout.LayoutParams. The default orientation is horizontal.

Also see android.widget.LinearLayout.LayoutParams for layout attributes

Summary

Nested Classes
public class LinearLayout.LayoutParams Per-child layout information associated with ViewLinearLayout. 
XML Attributes
Attribute Name Related Method Description
android:baselineAligned setBaselineAligned(boolean) When set to false, prevents the layout from aligning its children's baselines. 
android:baselineAlignedChildIndex setBaselineAlignedChildIndex(int) When a linear layout is part of another layout that is baseline aligned, it can specify which of its children to baseline align to (i.e which child TextView). 
android:gravity setGravity(int) Specifies how to place an object, both its x and y axis, within a larger containing object. 
android:orientation setOrientation(int) Should the layout be a column or a row? Use "horizontal" for a row, "vertical" for a column. 
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Inherited XML Attributes
From class android.view.ViewGroup
From class android.view.View
Constants
int HORIZONTAL
int VERTICAL
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Inherited Constants
From class android.view.ViewGroup
From class android.view.View
Public Constructors
LinearLayout(Context context)
LinearLayout(Context context, AttributeSet attrs)
Public Methods
LinearLayout.LayoutParams generateLayoutParams(AttributeSet attrs)
Returns a new set of layout parameters based on the supplied attributes set.
int getBaseline()

Return the offset of the widget's text baseline from the widget's top boundary.

int getBaselineAlignedChildIndex()
int getOrientation()
Returns the current orientation.
float getWeightSum()
Returns the desired weights sum.
boolean isBaselineAligned()

Indicates whether widgets contained within this layout are aligned on their baseline or not.

void setBaselineAligned(boolean baselineAligned)

Defines whether widgets contained in this layout are baseline-aligned or not.

void setBaselineAlignedChildIndex(int i)
void setGravity(int gravity)
Describes how the child views are positioned.
void setHorizontalGravity(int horizontalGravity)
void setOrientation(int orientation)
Should the layout be a column or a row.
void setVerticalGravity(int verticalGravity)
void setWeightSum(float weightSum)
Defines the desired weights sum.
Protected Methods
boolean checkLayoutParams(ViewGroup.LayoutParams p)
LinearLayout.LayoutParams generateDefaultLayoutParams()
Returns a set of layout parameters with a width of FILL_PARENT and a height of WRAP_CONTENT when the layout's orientation is VERTICAL.
LinearLayout.LayoutParams generateLayoutParams(ViewGroup.LayoutParams p)
Returns a safe set of layout parameters based on the supplied layout params.
void onLayout(boolean changed, int l, int t, int r, int b)
Called from layout when this view should assign a size and position to each of its children.
void onMeasure(int widthMeasureSpec, int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height.

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Inherited Methods
From class android.view.ViewGroup
From class android.view.View
From class java.lang.Object
From interface android.graphics.drawable.Drawable.Callback
From interface android.view.KeyEvent.Callback
From interface android.view.ViewManager
From interface android.view.ViewParent

XML Attributes

android:baselineAligned

When set to false, prevents the layout from aligning its children's baselines. This attribute is particularly useful when the children use different values for gravity. The default value is true.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol baselineAligned.

Related Methods

android:baselineAlignedChildIndex

When a linear layout is part of another layout that is baseline aligned, it can specify which of its children to baseline align to (i.e which child TextView).

Must be an integer value, such as "100".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol baselineAlignedChildIndex.

android:gravity

Specifies how to place an object, both its x and y axis, within a larger containing object.

Must be one or more (separated by '|') of the following constant values.

ConstantValueDescription
top0x30 Push object to the top of its container, not changing its size.
bottom0x50 Push object to the bottom of its container, not changing its size.
left0x03 Push object to the left of its container, not changing its size.
right0x05 Push object to the right of its container, not changing its size.
center_vertical0x10 Place object in the vertical center of its container, not changing its size.
fill_vertical0x70 Grow the vertical size of the object if needed so it completely fills its container.
center_horizontal0x01 Place object in the horizontal center of its container, not changing its size.
fill_horizontal0x07 Grow the horizontal size of the object if needed so it completely fills its container.
center0x11 Place the object in the center of its container in both the vertical and horizontal axis, not changing its size.
fill0x77 Grow the horizontal and vertical size of the object if needed so it completely fills its container.
clip_vertical0x80 Additional option that can be set to have the top and/or bottom edges of the child clipped to its container's bounds. The clip will be based on the vertical gravity: a top gravity will clip the bottom edge, a bottom gravity will clip the top edge, and neither will clip both edges.
clip_horizontal0x08 Additional option that can be set to have the left and/or right edges of the child clipped to its container's bounds. The clip will be based on the horizontal gravity: a left gravity will clip the right edge, a right gravity will clip the left edge, and neither will clip both edges.

This corresponds to the global attribute resource symbol gravity.

Related Methods

android:orientation

Should the layout be a column or a row? Use "horizontal" for a row, "vertical" for a column. The default is horizontal.

Must be one of the following constant values.

ConstantValueDescription
horizontal0 Defines an horizontal widget.
vertical1 Defines a vertical widget.

This corresponds to the global attribute resource symbol orientation.

Related Methods

Constants

public static final int HORIZONTAL

Constant Value: 0 (0x00000000)

public static final int VERTICAL

Constant Value: 1 (0x00000001)

Public Constructors

public LinearLayout (Context context)

public LinearLayout (Context context, AttributeSet attrs)

Public Methods

public LinearLayout.LayoutParams generateLayoutParams (AttributeSet attrs)

Returns a new set of layout parameters based on the supplied attributes set.

Parameters
attrs the attributes to build the layout parameters from
Returns

public int getBaseline ()

Return the offset of the widget's text baseline from the widget's top boundary. If this widget does not support baseline alignment, this method returns -1.

Returns
  • the offset of the baseline within the widget's bounds or -1 if baseline alignment is not supported

public int getBaselineAlignedChildIndex ()

Returns
  • The index of the child that will be used if this layout is part of a larger layout that is baseline aligned, or -1 if none has been set.

public int getOrientation ()

Returns the current orientation.

Returns

public float getWeightSum ()

Returns the desired weights sum.

Returns
  • A number greater than 0.0f if the weight sum is defined, or a number lower than or equals to 0.0f if not weight sum is to be used.

public boolean isBaselineAligned ()

Indicates whether widgets contained within this layout are aligned on their baseline or not.

Returns
  • true when widgets are baseline-aligned, false otherwise

public void setBaselineAligned (boolean baselineAligned)

Defines whether widgets contained in this layout are baseline-aligned or not.

Related XML Attributes
Parameters
baselineAligned true to align widgets on their baseline, false otherwise

public void setBaselineAlignedChildIndex (int i)

Related XML Attributes
Parameters
i The index of the child that will be used if this layout is part of a larger layout that is baseline aligned.

public void setGravity (int gravity)

Describes how the child views are positioned. Defaults to GRAVITY_TOP. If this layout has a VERTICAL orientation, this controls where all the child views are placed if there is extra vertical space. If this layout has a HORIZONTAL orientation, this controls the alignment of the children.

Related XML Attributes
Parameters
gravity See Gravity

public void setHorizontalGravity (int horizontalGravity)

public void setOrientation (int orientation)

Should the layout be a column or a row.

Related XML Attributes
Parameters
orientation Pass HORIZONTAL or VERTICAL. Default value is HORIZONTAL.

public void setVerticalGravity (int verticalGravity)

public void setWeightSum (float weightSum)

Defines the desired weights sum. If unspecified the weights sum is computed at layout time by adding the layout_weight of each child. This can be used for instance to give a single child 50% of the total available space by giving it a layout_weight of 0.5 and setting the weightSum to 1.0.

Parameters
weightSum a number greater than 0.0f, or a number lower than or equals to 0.0f if the weight sum should be computed from the children's layout_weight

Protected Methods

protected boolean checkLayoutParams (ViewGroup.LayoutParams p)

protected LinearLayout.LayoutParams generateDefaultLayoutParams ()

Returns a set of layout parameters with a width of FILL_PARENT and a height of WRAP_CONTENT when the layout's orientation is VERTICAL. When the orientation is HORIZONTAL, the width is set to WRAP_CONTENT and the height to WRAP_CONTENT.

Returns
  • a set of default layout parameters or null

protected LinearLayout.LayoutParams generateLayoutParams (ViewGroup.LayoutParams p)

Returns a safe set of layout parameters based on the supplied layout params. When a ViewGroup is passed a View whose layout params do not pass the test of checkLayoutParams(android.view.ViewGroup.LayoutParams), this method is invoked. This method should return a new set of layout params suitable for this ViewGroup, possibly by copying the appropriate attributes from the specified set of layout params.

Parameters
p The layout parameters to convert into a suitable set of layout parameters for this ViewGroup.
Returns

protected void onLayout (boolean changed, int l, int t, int r, int b)

Called from layout when this view should assign a size and position to each of its children. Derived classes with children should override this method and call layout on each of their their children.

Parameters
changed This is a new size or position for this view
l Left position, relative to parent
t Top position, relative to parent
r Right position, relative to parent
b Bottom position, relative to parent

protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec)

Measure the view and its content to determine the measured width and the measured height. This method is invoked by measure(int, int) and should be overriden by subclasses to provide accurate and efficient measurement of their contents.

CONTRACT: When overriding this method, you must call setMeasuredDimension(int, int) to store the measured width and height of this view. Failure to do so will trigger an IllegalStateException, thrown by measure(int, int). Calling the superclass' onMeasure(int, int) is a valid use.

The base class implementation of measure defaults to the background size, unless a larger size is allowed by the MeasureSpec. Subclasses should override onMeasure(int, int) to provide better measurements of their content.

If this method is overridden, it is the subclass's responsibility to make sure the measured height and width are at least the view's minimum height and width (getSuggestedMinimumHeight() and getSuggestedMinimumWidth()).

Parameters
widthMeasureSpec horizontal space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.
heightMeasureSpec vertical space requirements as imposed by the parent. The requirements are encoded with View.MeasureSpec.