PercentLayoutHelper

Added in 1.0.0
Deprecated in 1.0.0

public class 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:

  1. You need a ViewGroup.LayoutParams subclass in your ViewGroup that implements PercentLayoutHelper.PercentLayoutParams.
  2. 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.
  3. Override setBaseAttributes with a single line implementation PercentLayoutHelper.fetchWidthAndHeight(this, a, widthAttr, heightAttr);
  4. In your ViewGroup override generateLayoutParams to return your LayoutParams.
  5. 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);
        }
    }
    
  6. 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

This class is deprecated.

use ConstraintLayout and Guidelines for layout support.

This interface is deprecated.

this class is deprecated along with its parent class.

Public constructors

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 override that reads layout_width and layout_height attribute values without throwing an exception if they aren't present.

static PercentLayoutHelper.PercentLayoutInfo

Constructs a PercentLayoutInfo from attributes associated with a View.

boolean

Iterates over children and checks if any of them would like to get more space than it received through the percentage dimension.

void

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
public PercentLayoutHelper(@NonNull ViewGroup host)

Public methods

adjustChildren

Added in 1.0.0
Deprecated in 1.0.0
public void adjustChildren(int widthMeasureSpec, int heightMeasureSpec)

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

Parameters
int widthMeasureSpec

Width MeasureSpec of the parent ViewGroup.

int heightMeasureSpec

Height MeasureSpec of the parent ViewGroup.

fetchWidthAndHeight

Added in 1.0.0
Deprecated in 1.0.0
public static void fetchWidthAndHeight(
    ViewGroup.LayoutParams params,
    TypedArray array,
    int widthAttr,
    int heightAttr
)

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
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.

handleMeasuredStateTooSmall

Added in 1.0.0
Deprecated in 1.0.0
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
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
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.