PercentLayoutHelper

extends Object

java.lang.Object
↳	android.support.percent.PercentLayoutHelper

Class Overview

Helper for layouts that want to support percentage based dimensions.

This class collects utility methods that are involved in extracting percentage based dimension attributes and applying them to ViewGroup's children. If you would like to implement a layout that supports percentage based dimensions, you need to take several steps:

You need a ViewGroup.LayoutParams subclass in your ViewGroup that implements PercentLayoutHelper.PercentLayoutParams.
In your LayoutParams(Context c, AttributeSet attrs) constructor create an instance of PercentLayoutHelper.PercentLayoutInfo by calling getPercentLayoutInfo(Context, AttributeSet). Return this object from public PercentLayoutHelper.PercentLayoutInfo getPercentLayoutInfo() method that you implemented for PercentLayoutHelper.PercentLayoutParams interface.
Override setBaseAttributes(TypedArray, int, int) with a single line implementation PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
In your ViewGroup override generateLayoutParams(AttributeSet) to return your LayoutParams.

In your onMeasure(int, int) override, you need to implement following pattern:

 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
     mHelper.adjustChildren(widthMeasureSpec, heightMeasureSpec);
     super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     if (mHelper.handleMeasuredStateTooSmall()) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     }
 }

In your onLayout(boolean, int, int, int, int) override, you need to implement following pattern:

 protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
     super.onLayout(changed, left, top, right, bottom);
     mHelper.restoreOriginalParams();
 }

Summary

Nested Classes
class	PercentLayoutHelper.PercentLayoutInfo	Container for information about percentage dimensions and margins.
interface	PercentLayoutHelper.PercentLayoutParams	If a layout wants to support percentage based dimensions and use this helper class, its `LayoutParams` subclass must implement this interface.

Public Constructors
	PercentLayoutHelper(ViewGroup host)

Public Methods
void	adjustChildren(int widthMeasureSpec, int heightMeasureSpec) Iterates over children and changes their width and height to one calculated from percentage values.
static void	fetchWidthAndHeight(ViewGroup.LayoutParams params, TypedArray array, int widthAttr, int heightAttr) Helper method to be called from `setBaseAttributes(TypedArray, int, int)` override that reads layout_width and layout_height attribute values without throwing an exception if they aren't present.
static PercentLayoutHelper.PercentLayoutInfo	getPercentLayoutInfo(Context context, AttributeSet attrs) Constructs a PercentLayoutInfo from attributes associated with a View.
boolean	handleMeasuredStateTooSmall() Iterates over children and checks if any of them would like to get more space than it received through the percentage dimension.
void	restoreOriginalParams() Iterates over children and restores their original dimensions that were changed for percentage values.

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Inherited Methods

From class java.lang.Object

Object	clone() Creates and returns a copy of this `Object`.
boolean	equals(Object o) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of `Class` that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the `wait()` methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait() Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object.
final void	wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.
final void	wait(long millis) Causes the calling thread to wait until another thread calls the `notify()` or `notifyAll()` method of this object or until the specified timeout expires.

Public Constructors

public PercentLayoutHelper (ViewGroup host)

Public Methods

public void adjustChildren (int widthMeasureSpec, int heightMeasureSpec)

Iterates over children and changes their width and height to one calculated from percentage values.

Parameters

widthMeasureSpec	Width MeasureSpec of the parent ViewGroup.
heightMeasureSpec	Height MeasureSpec of the parent ViewGroup.

public static void fetchWidthAndHeight (ViewGroup.LayoutParams params, TypedArray array, int widthAttr, int heightAttr)

Helper method to be called from setBaseAttributes(TypedArray, int, int) override that reads layout_width and layout_height attribute values without throwing an exception if they aren't present.

public static PercentLayoutHelper.PercentLayoutInfo getPercentLayoutInfo (Context context, AttributeSet attrs)

Constructs a PercentLayoutInfo from attributes associated with a View. Call this method from LayoutParams(Context c, AttributeSet attrs) constructor.

public boolean handleMeasuredStateTooSmall ()

Iterates over children and checks if any of them would like to get more space than it received through the percentage dimension. If you are building a layout that supports percentage dimensions you are encouraged to take advantage of this method. The developer should be able to specify that a child should be remeasured by adding normal dimension attribute with wrap_content value. For example he might specify child's attributes as app:layout_widthPercent="60%p" and android:layout_width="wrap_content". In this case if the child receives too little space, it will be remeasured with width set to WRAP_CONTENT.

Returns

True if the measure phase needs to be rerun because one of the children would like to receive more space.

public void restoreOriginalParams ()

Iterates over children and restores their original dimensions that were changed for percentage values. Calling this method only makes sense if you previously called adjustChildren(int, int).

Results

Interfaces

Classes