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PercentLayoutHelper

public class PercentLayoutHelper
extends Object

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

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.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Public constructors

PercentLayoutHelper

PercentLayoutHelper (ViewGroup host)

Parameters
`host`	`ViewGroup`

Public methods

adjustChildren

void adjustChildren (int widthMeasureSpec, 
                int heightMeasureSpec)

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

Parameters
`widthMeasureSpec`	`int`: Width MeasureSpec of the parent ViewGroup.
`heightMeasureSpec`	`int`: Height MeasureSpec of the parent ViewGroup.

fetchWidthAndHeight

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.

Parameters
`params`	`ViewGroup.LayoutParams`
`array`	`TypedArray`
`widthAttr`	`int`
`heightAttr`	`int`

getPercentLayoutInfo

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.

Parameters
`context`	`Context`
`attrs`	`AttributeSet`

Returns
`PercentLayoutHelper.PercentLayoutInfo`

handleMeasuredStateTooSmall

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

restoreOriginalParams

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).

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PercentLayoutHelper

Summary

Nested classes

Public constructors

Public methods

Inherited methods

Public constructors

PercentLayoutHelper

Public methods

adjustChildren

fetchWidthAndHeight

getPercentLayoutInfo

handleMeasuredStateTooSmall

restoreOriginalParams