Line-breaking widget layout for Android

I made my own layout that does what I want, but it is quite limited at the moment. Comments and improvement suggestions are of course welcome.

The activity:

package se.fnord.xmms2.predicate;

import se.fnord.android.layout.PredicateLayout;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.widget.TextView;

public class Predicate extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        PredicateLayout l = new PredicateLayout(this);
        for (int i = 0; i < 10; i++) {
            TextView t = new TextView(this);
            t.setText("Hello");
            t.setBackgroundColor(Color.RED);
            t.setSingleLine(true);
            l.addView(t, new PredicateLayout.LayoutParams(2, 0));
        }

        setContentView(l);
    }
}

Or in an XML layout:

<se.fnord.android.layout.PredicateLayout
    android:id="@+id/predicate_layout"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
/>

And the Layout:

package se.fnord.android.layout;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

/**
 * ViewGroup that arranges child views in a similar way to text, with them laid
 * out one line at a time and "wrapping" to the next line as needed.
 * 
 * Code licensed under CC-by-SA
 *  
 * @author Henrik Gustafsson
 * @see http://stackoverflow.com/questions/549451/line-breaking-widget-layout-for-android
 * @license http://creativecommons.org/licenses/by-sa/2.5/
 *
 */
public class PredicateLayout extends ViewGroup {

    private int line_height;

    public PredicateLayout(Context context) {
        super(context);
    }
    
    public PredicateLayout(Context context, AttributeSet attrs){
        super(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        assert(MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.UNSPECIFIED);

        final int width = MeasureSpec.getSize(widthMeasureSpec);

        // The next line is WRONG!!! Doesn't take into account requested MeasureSpec mode!
        int height = MeasureSpec.getSize(heightMeasureSpec) - getPaddingTop() - getPaddingBottom();
        final int count = getChildCount();
        int line_height = 0;
        
        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();
        
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();
                child.measure(
                        MeasureSpec.makeMeasureSpec(width, MeasureSpec.AT_MOST),
                        MeasureSpec.makeMeasureSpec(height, MeasureSpec.UNSPECIFIED));
                
                final int childw = child.getMeasuredWidth();
                line_height = Math.max(line_height, child.getMeasuredHeight() + lp.height);
                
                if (xpos + childw > width) {
                    xpos = getPaddingLeft();
                    ypos += line_height;
                }
                
                xpos += childw + lp.width;
            }
        }
        this.line_height = line_height;
        
        if (MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.UNSPECIFIED){
            height = ypos + line_height;

        } else if (MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.AT_MOST){
            if (ypos + line_height < height){
                height = ypos + line_height;
            }
        }
        setMeasuredDimension(width, height);
    }

    @Override
    protected LayoutParams generateDefaultLayoutParams() {
        return new LayoutParams(1, 1); // default of 1px spacing
    }

    @Override
    protected boolean checkLayoutParams(LayoutParams p) {
        return (p instanceof LayoutParams);
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        final int count = getChildCount();
        final int width = r - l;
        int xpos = getPaddingLeft();
        int ypos = getPaddingTop();

        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != GONE) {
                final int childw = child.getMeasuredWidth();
                final int childh = child.getMeasuredHeight();
                final LayoutParams lp = (LayoutParams) child.getLayoutParams();
                if (xpos + childw > width) {
                    xpos = getPaddingLeft();
                    ypos += line_height;
                }
                child.layout(xpos, ypos, xpos + childw, ypos + childh);
                xpos += childw + lp.width;
            }
        }
    }
}

With the result:

Since May 2016 there is new layout called FlexboxLayout from Google, which is highly configurable for purpose you want.

FlexboxLayout is in Google GitHub repository at https://github.com/google/flexbox-layout at this moment.

You can use it in your project by adding dependency to your build.gradle file:

dependencies {
    implementation 'com.google.android.flexbox:flexbox:3.0.0'
}

More about FlexboxLayout usage and all the attributes you can find in repository readme or in Mark Allison articles here:

https://blog.stylingandroid.com/flexboxlayout-part-1/

https://blog.stylingandroid.com/flexboxlayout-part2/

https://blog.stylingandroid.com/flexboxlayout-part-3/

I implemented something very similar to this, but using what I think is a little more standard way to handle spacing and padding. Please let me know what you guys think, and feel free to reuse without attribution:

package com.asolutions.widget;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

import com.asolutions.widget.R;

public class RowLayout extends ViewGroup {
    public static final int DEFAULT_HORIZONTAL_SPACING = 5;
    public static final int DEFAULT_VERTICAL_SPACING = 5;
    private final int horizontalSpacing;
    private final int verticalSpacing;
    private List<RowMeasurement> currentRows = Collections.emptyList();

    public RowLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        TypedArray styledAttributes = context.obtainStyledAttributes(attrs, R.styleable.RowLayout);
        horizontalSpacing = styledAttributes.getDimensionPixelSize(R.styleable.RowLayout_android_horizontalSpacing,
                DEFAULT_HORIZONTAL_SPACING);
        verticalSpacing = styledAttributes.getDimensionPixelSize(R.styleable.RowLayout_android_verticalSpacing,
                DEFAULT_VERTICAL_SPACING);
        styledAttributes.recycle();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        final int maxInternalWidth = MeasureSpec.getSize(widthMeasureSpec) - getHorizontalPadding();
        final int maxInternalHeight = MeasureSpec.getSize(heightMeasureSpec) - getVerticalPadding();
        List<RowMeasurement> rows = new ArrayList<RowMeasurement>();
        RowMeasurement currentRow = new RowMeasurement(maxInternalWidth, widthMode);
        rows.add(currentRow);
        for (View child : getLayoutChildren()) {
            LayoutParams childLayoutParams = child.getLayoutParams();
            int childWidthSpec = createChildMeasureSpec(childLayoutParams.width, maxInternalWidth, widthMode);
            int childHeightSpec = createChildMeasureSpec(childLayoutParams.height, maxInternalHeight, heightMode);
            child.measure(childWidthSpec, childHeightSpec);
            int childWidth = child.getMeasuredWidth();
            int childHeight = child.getMeasuredHeight();
            if (currentRow.wouldExceedMax(childWidth)) {
                currentRow = new RowMeasurement(maxInternalWidth, widthMode);
                rows.add(currentRow);
            }
            currentRow.addChildDimensions(childWidth, childHeight);
        }

        int longestRowWidth = 0;
        int totalRowHeight = 0;
        for (int index = 0; index < rows.size(); index++) {
            RowMeasurement row = rows.get(index);
            totalRowHeight += row.getHeight();
            if (index < rows.size() - 1) {
                totalRowHeight += verticalSpacing;
            }
            longestRowWidth = Math.max(longestRowWidth, row.getWidth());
        }
        setMeasuredDimension(widthMode == MeasureSpec.EXACTLY ? MeasureSpec.getSize(widthMeasureSpec) : longestRowWidth
                + getHorizontalPadding(), heightMode == MeasureSpec.EXACTLY ? MeasureSpec.getSize(heightMeasureSpec)
                : totalRowHeight + getVerticalPadding());
        currentRows = Collections.unmodifiableList(rows);
    }

    private int createChildMeasureSpec(int childLayoutParam, int max, int parentMode) {
        int spec;
        if (childLayoutParam == LayoutParams.FILL_PARENT) {
            spec = MeasureSpec.makeMeasureSpec(max, MeasureSpec.EXACTLY);
        } else if (childLayoutParam == LayoutParams.WRAP_CONTENT) {
            spec = MeasureSpec.makeMeasureSpec(max, parentMode == MeasureSpec.UNSPECIFIED ? MeasureSpec.UNSPECIFIED
                    : MeasureSpec.AT_MOST);
        } else {
            spec = MeasureSpec.makeMeasureSpec(childLayoutParam, MeasureSpec.EXACTLY);
        }
        return spec;
    }

    @Override
    protected void onLayout(boolean changed, int leftPosition, int topPosition, int rightPosition, int bottomPosition) {
        final int widthOffset = getMeasuredWidth() - getPaddingRight();
        int x = getPaddingLeft();
        int y = getPaddingTop();

        Iterator<RowMeasurement> rowIterator = currentRows.iterator();
        RowMeasurement currentRow = rowIterator.next();
        for (View child : getLayoutChildren()) {
            final int childWidth = child.getMeasuredWidth();
            final int childHeight = child.getMeasuredHeight();
            if (x + childWidth > widthOffset) {
                x = getPaddingLeft();
                y += currentRow.height + verticalSpacing;
                if (rowIterator.hasNext()) {
                    currentRow = rowIterator.next();
                }
            }
            child.layout(x, y, x + childWidth, y + childHeight);
            x += childWidth + horizontalSpacing;
        }
    }

    private List<View> getLayoutChildren() {
        List<View> children = new ArrayList<View>();
        for (int index = 0; index < getChildCount(); index++) {
            View child = getChildAt(index);
            if (child.getVisibility() != View.GONE) {
                children.add(child);
            }
        }
        return children;
    }

    protected int getVerticalPadding() {
        return getPaddingTop() + getPaddingBottom();
    }

    protected int getHorizontalPadding() {
        return getPaddingLeft() + getPaddingRight();
    }

    private final class RowMeasurement {
        private final int maxWidth;
        private final int widthMode;
        private int width;
        private int height;

        public RowMeasurement(int maxWidth, int widthMode) {
            this.maxWidth = maxWidth;
            this.widthMode = widthMode;
        }

        public int getHeight() {
            return height;
        }

        public int getWidth() {
            return width;
        }

        public boolean wouldExceedMax(int childWidth) {
            return widthMode == MeasureSpec.UNSPECIFIED ? false : getNewWidth(childWidth) > maxWidth;
        }

        public void addChildDimensions(int childWidth, int childHeight) {
            width = getNewWidth(childWidth);
            height = Math.max(height, childHeight);
        }

        private int getNewWidth(int childWidth) {
            return width == 0 ? childWidth : width + horizontalSpacing + childWidth;
        }
    }
}

This also requires an entry under /res/values/attrs.xml, which you can create if it's not already there.

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="RowLayout">
        <attr name="android:verticalSpacing" />
        <attr name="android:horizontalSpacing" />
    </declare-styleable>
</resources>

Usage in an xml layout looks like this:

<?xml version="1.0" encoding="utf-8"?>
<com.asolutions.widget.RowLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:padding="10dp"
    android:horizontalSpacing="10dp"
    android:verticalSpacing="20dp">
    <FrameLayout android:layout_width="30px" android:layout_height="40px" android:background="#F00"/>
    <FrameLayout android:layout_width="60px" android:layout_height="40px" android:background="#F00"/>
    <FrameLayout android:layout_width="70px" android:layout_height="20px" android:background="#F00"/>
    <FrameLayout android:layout_width="20px" android:layout_height="60px" android:background="#F00"/>
    <FrameLayout android:layout_width="10px" android:layout_height="40px" android:background="#F00"/>
    <FrameLayout android:layout_width="40px" android:layout_height="40px" android:background="#F00"/>
    <FrameLayout android:layout_width="40px" android:layout_height="40px" android:background="#F00"/>
    <FrameLayout android:layout_width="40px" android:layout_height="40px" android:background="#F00"/>
</com.asolutions.widget.RowLayout>