Android 线性布局（LinearLayout）相关官方文档 - 参考部分
Android 线性布局（LinearLayout）相关官方文档 - 参考部分
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Android 官方文档线性布局相关资源链接汇总如下：
android-sdk-macosx-4.4.2/docs/guide/topics/ui/layout/linear.html
android-sdk-macosx-4.4.2/docs/reference/android/widget/LinearLayout.html
android-sdk-macosx-4.4.2/docs/reference/android/widget/LinearLayout.LayoutParams.html
由于在线文档访问困难，这里给出的是本地文档的相对路径。
重点摘要：
译文来源：reference/android/widget/LinearLayout.html
Nested Classes
Inherited XML Attrs
Constants
3.1、继承的常量
Inherited Constants
3.1.1、From class android.view.ViewGroup
3.1.2、From class android.view.View
Inherited Fields
Ctors
Methods
线性布局 LinearLayout
extends ViewGroup| java.lang.Object | |||
| ↳ | android.view.View | ||
| ↳ | android.view.ViewGroup | ||
| ↳ | android.widget.LinearLayout | ||
 Known Direct Subclasses
NumberPicker, RadioGroup, SearchView, TabWidget, TableLayout, TableRow, ZoomControls
|
类概述
Class Overview
一个在单行或单行排列其子视图的布局。行的方向可以通过调用 setOrientation() 来设置。也可以指定重力（gravity），它会通过调用 setOrientation() 来指定所有子元素的对齐方式；或通过设置 LinearLayout.LayoutParams 的权重（weight）成员变量来指定特定的子视图扩展以填充布局中的余下空间。默认方向是水平方向（horizontal）。
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.
查看 线性布局指南。
See the Linear Layout guide.
也可以查看 android.widget.LinearLayout.LayoutParams 获得布局属性。
Also see android.widget.LinearLayout.LayoutParams for layout attributes。
XML 属性
XML Attributes
android:baselineAligned（基线对齐）
当设置为 false，避勉布局对齐其子视图的基线。该特性在子视图使用不同重力（gravity）值时特别有用。默认值是 true。
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.
必须为布尔值，或是 "true" 或是 "false"。
Must be a boolean value, either "true" or "false".
也可以是包含这一类型值的资源的引用（格式如："@[package:]type:name"）或主题属性（格式如："?[package:][type:]name"）
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.
其相当于全局属性资源标志 baselineAligned。
This corresponds to the global attribute resource symbol baselineAligned.
相关方法
Related Methods
- setBaselineAligned(boolean)
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 (that is, 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.
Related Methods
- setBaselineAlignedChildIndex(int)
android:divider
Drawable to use as a vertical divider between buttons.
May be a reference to another resource, in the form "@[+][package:]type:name" or to a theme attribute in the form "?[package:][type:]name".
May be a color value, in the form of "#rgb", "#argb", "#rrggbb", or "#aarrggbb".
This corresponds to the global attribute resource symbol divider.
Related Methods
- setDividerDrawable(Drawable)
android:gravity
Specifies how an object should position its content, on both the X and Y axes, within its own bounds.
Must be one or more (separated by '|') of the following constant values.
| Constant | Value | Description |
|---|---|---|
top |
0x30 | Push object to the top of its container, not changing its size. |
bottom |
0x50 | Push object to the bottom of its container, not changing its size. |
left |
0x03 | Push object to the left of its container, not changing its size. |
right |
0x05 | Push object to the right of its container, not changing its size. |
center_vertical |
0x10 | Place object in the vertical center of its container, not changing its size. |
fill_vertical |
0x70 | Grow the vertical size of the object if needed so it completely fills its container. |
center_horizontal |
0x01 | Place object in the horizontal center of its container, not changing its size. |
fill_horizontal |
0x07 | Grow the horizontal size of the object if needed so it completely fills its container. |
center |
0x11 | Place the object in the center of its container in both the vertical and horizontal axis, not changing its size. |
fill |
0x77 | Grow the horizontal and vertical size of the object if needed so it completely fills its container. |
clip_vertical |
0x80 | 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_horizontal |
0x08 | 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. |
start |
0x00800003 | Push object to the beginning of its container, not changing its size. |
end |
0x00800005 | Push object to the end of its container, not changing its size. |
This corresponds to the global attribute resource symbol gravity.
Related Methods
- setGravity(int)
android:measureWithLargestChild
When set to true, all children with a weight will be considered having the minimum size of the largest child. If false, all children are measured normally.
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 measureWithLargestChild.
Related Methods
- setMeasureWithLargestChildEnabled(boolean)
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.
| Constant | Value | Description |
|---|---|---|
horizontal |
0 | Defines an horizontal widget. |
vertical |
1 | Defines a vertical widget. |
This corresponds to the global attribute resource symbol orientation.
Related Methods
- setOrientation(int)
android:weightSum
Defines the maximum weight sum. If unspecified, the sum is computed by adding the layout_weight of all of the children. 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.
Must be a floating point value, such as "1.2".
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 weightSum.
Related Methods
Constants
public static final int HORIZONTAL
public static final int SHOW_DIVIDER_BEGINNING
Show a divider at the beginning of the group.
public static final int SHOW_DIVIDER_END
Show a divider at the end of the group.
public static final int SHOW_DIVIDER_MIDDLE
Show dividers between each item in the group.
public static final int SHOW_DIVIDER_NONE
Don't show any dividers.
public static final int VERTICAL
Public Constructors
public LinearLayout (Context context)
public LinearLayout (Context context, AttributeSet attrs)
public LinearLayout (Context context, AttributeSet attrs, int defStyle)
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
- an instance of
ViewGroup.LayoutParamsor one of its descendants
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 Drawable getDividerDrawable ()
Related XML Attributes
- android:divider
Returns
- the divider Drawable that will divide each item.
See Also
setDividerDrawable(Drawable)
public int getDividerPadding ()
Get the padding size used to inset dividers in pixels
See Also
setShowDividers(int)setDividerDrawable(Drawable)setDividerPadding(int)
public int getOrientation ()
Returns the current orientation.
Returns
- either
HORIZONTALorVERTICAL
public int getShowDividers ()
Returns
- A flag set indicating how dividers should be shown around items.
See Also
setShowDividers(int)
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 boolean isMeasureWithLargestChildEnabled ()
When true, all children with a weight will be considered having the minimum size of the largest child. If false, all children are measured normally.
Related XML Attributes
- android:measureWithLargestChild
Returns
- True to measure children with a weight using the minimum size of the largest child, false otherwise.
public void onInitializeAccessibilityEvent (AccessibilityEvent event)
Initializes an AccessibilityEvent with information about this View which is the event source. In other words, the source of an accessibility event is the view whose state change triggered firing the event.
Example: Setting the password property of an event in addition to properties set by the super implementation:
public void onInitializeAccessibilityEvent(AccessibilityEvent event) { super.onInitializeAccessibilityEvent(event); event.setPassword(true); }
If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its onInitializeAccessibilityEvent(View, AccessibilityEvent) is responsible for handling this call.
Note: Always call the super implementation before adding information to the event, in case the default implementation has basic information to add.
Parameters
| event | The event to initialize. |
|---|
public void onInitializeAccessibilityNodeInfo (AccessibilityNodeInfo info)
Initializes an AccessibilityNodeInfo with information about this view. The base implementation sets:
-
setParent(View), -
setBoundsInParent(Rect), -
setBoundsInScreen(Rect), -
setPackageName(CharSequence), -
setClassName(CharSequence), -
setContentDescription(CharSequence), -
setEnabled(boolean), -
setClickable(boolean), -
setFocusable(boolean), -
setFocused(boolean), -
setLongClickable(boolean), -
setSelected(boolean),
Subclasses should override this method, call the super implementation, and set additional attributes.
If an View.AccessibilityDelegate has been specified via calling setAccessibilityDelegate(AccessibilityDelegate) its onInitializeAccessibilityNodeInfo(View, AccessibilityNodeInfo) is responsible for handling this call.
Parameters
| info | The instance to initialize. |
|---|
public void setBaselineAligned (boolean baselineAligned)
Defines whether widgets contained in this layout are baseline-aligned or not.
Related XML Attributes
- android:baselineAligned
Parameters
| baselineAligned | true to align widgets on their baseline, false otherwise |
|---|
public void setBaselineAlignedChildIndex (int i)
Related XML Attributes
- android:baselineAlignedChildIndex
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 setDividerDrawable (Drawable divider)
Set a drawable to be used as a divider between items.
Related XML Attributes
- android:divider
Parameters
| divider | Drawable that will divide each item. |
|---|
See Also
setShowDividers(int)
public void setDividerPadding (int padding)
Set padding displayed on both ends of dividers.
Parameters
| padding | Padding value in pixels that will be applied to each end |
|---|
See Also
setShowDividers(int)setDividerDrawable(Drawable)getDividerPadding()
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
- android:gravity
Parameters
| gravity | See Gravity |
|---|
public void setHorizontalGravity (int horizontalGravity)
public void setMeasureWithLargestChildEnabled (boolean enabled)
When set to true, all children with a weight will be considered having the minimum size of the largest child. If false, all children are measured normally. Disabled by default.
Related XML Attributes
- android:measureWithLargestChild
Parameters
| enabled | True to measure children with a weight using the minimum size of the largest child, false otherwise. |
|---|
public void setOrientation (int orientation)
Should the layout be a column or a row.
Related XML Attributes
- android:orientation
Parameters
| orientation | Pass HORIZONTAL or VERTICAL. Default value is HORIZONTAL. |
|---|
public void setShowDividers (int showDividers)
Set how dividers should be shown between items in this layout
Parameters
| showDividers | One or more of SHOW_DIVIDER_BEGINNING, SHOW_DIVIDER_MIDDLE, or SHOW_DIVIDER_END, or SHOW_DIVIDER_NONE to show no dividers. |
|---|
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 |
|---|
public boolean shouldDelayChildPressedState ()
Return true if the pressed state should be delayed for children or descendants of this ViewGroup. Generally, this should be done for containers that can scroll, such as a List. This prevents the pressed state from appearing when the user is actually trying to scroll the content. The default implementation returns true for compatibility reasons. Subclasses that do not scroll should generally override this method and return false.
Protected Methods
protected boolean checkLayoutParams (ViewGroup.LayoutParams p)
protected LinearLayout.LayoutParams generateDefaultLayoutParams ()
Returns a set of layout parameters with a width of MATCH_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
- an instance of
ViewGroup.LayoutParamsor one of its descendants
protected void onDraw (Canvas canvas)
Implement this to do your drawing.
Parameters
| canvas | the canvas on which the background will be drawn |
|---|
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 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. |
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