PercentLayoutHelper

Artifact: androidx.percentlayout:percentlayout

Added in 1.0.0

Deprecated in 1.0.0

Kotlin |Java

class PercentLayoutHelper

This class is deprecated.

consider using ConstraintLayout and associated layouts instead. The following shows how to replicate the functionality of percentage layouts with a ConstraintLayout. The Guidelines are used to define each percentage break point, and then a Button view is stretched to fill the gap:

<androidx.constraintlayout.widget.ConstraintLayout        xmlns:android="http://schemas.android.com/apk/res/android"        xmlns:app="http://schemas.android.com/apk/res-auto"        android:layout_width="match_parent"        android:layout_height="match_parent">    <androidx.constraintlayout.widget.Guideline        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/left_guideline"        app:layout_constraintGuide_percent=".15"        android:orientation="vertical"/>    <androidx.constraintlayout.widget.Guideline        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/right_guideline"        app:layout_constraintGuide_percent=".85"        android:orientation="vertical"/>    <androidx.constraintlayout.widget.Guideline        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/top_guideline"        app:layout_constraintGuide_percent=".15"        android:orientation="horizontal"/>    <androidx.constraintlayout.widget.Guideline        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/bottom_guideline"        app:layout_constraintGuide_percent=".85"        android:orientation="horizontal"/>    <Button        android:text="Button"        android:layout_width="0dp"        android:layout_height="0dp"        android:id="@+id/button"        app:layout_constraintLeft_toLeftOf="@+id/left_guideline"        app:layout_constraintRight_toRightOf="@+id/right_guideline"        app:layout_constraintTop_toTopOf="@+id/top_guideline"        app:layout_constraintBottom_toBottomOf="@+id/bottom_guideline" /></androidx.constraintlayout.widget.ConstraintLayout>

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. Return this object from public PercentLayoutHelper.PercentLayoutInfo getPercentLayoutInfo() method that you implemented for PercentLayoutHelper.PercentLayoutParams interface.
Override setBaseAttributes with a single line implementation PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
In your ViewGroup override generateLayoutParams to return your LayoutParams.

In your onMeasure 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 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 types
`class PercentLayoutHelper.PercentLayoutInfo` This class is deprecated. use ConstraintLayout and Guidelines for layout support.
`interface PercentLayoutHelper.PercentLayoutParams` This interface is deprecated. this class is deprecated along with its parent class.

Nested types

class PercentLayoutHelper.PercentLayoutInfo

This class is deprecated.

use ConstraintLayout and Guidelines for layout support.

interface PercentLayoutHelper.PercentLayoutParams

This interface is deprecated.

this class is deprecated along with its parent class.

Public constructors
`PercentLayoutHelper(host: ViewGroup)`

Public functions
`Unit`	`adjustChildren(widthMeasureSpec: Int, heightMeasureSpec: Int)` Iterates over children and changes their width and height to one calculated from percentage values.
`java-static Unit`	`fetchWidthAndHeight( params: ViewGroup.LayoutParams!, array: TypedArray!, widthAttr: Int, heightAttr: Int )` Helper method to be called from `setBaseAttributes` override that reads layout_width and layout_height attribute values without throwing an exception if they aren't present.
`java-static PercentLayoutHelper.PercentLayoutInfo!`	`getPercentLayoutInfo(context: Context!, attrs: AttributeSet!)` 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.
`Unit`	`restoreOriginalParams()` Iterates over children and restores their original dimensions that were changed for percentage values.

Public constructors

PercentLayoutHelper

Added in 1.0.0

Deprecated in 1.0.0

PercentLayoutHelper(host: ViewGroup)

Public functions

adjustChildren

Added in 1.0.0

Deprecated in 1.0.0

fun adjustChildren(widthMeasureSpec: Int, heightMeasureSpec: Int): Unit

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

Added in 1.0.0

Deprecated in 1.0.0

java-static fun fetchWidthAndHeight(
    params: ViewGroup.LayoutParams!,
    array: TypedArray!,
    widthAttr: Int,
    heightAttr: Int
): Unit

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

getPercentLayoutInfo

Added in 1.0.0

Deprecated in 1.0.0

java-static fun getPercentLayoutInfo(context: Context!, attrs: AttributeSet!): PercentLayoutHelper.PercentLayoutInfo!

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

handleMeasuredStateTooSmall

Added in 1.0.0

Deprecated in 1.0.0

fun handleMeasuredStateTooSmall(): Boolean

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

Added in 1.0.0

Deprecated in 1.0.0

fun restoreOriginalParams(): Unit

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.