Auto Scale TextView Text to Fit within Bounds

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囚心锁ツ
囚心锁ツ 2020-11-21 05:49

I\'m looking for an optimal way to resize wrapping text in a TextView so that it will fit within its getHeight and getWidth bounds. I\'m not simply looking for

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  •  死守一世寂寞
    2020-11-21 06:05

    My need was to resize text in order to perfectly fit view bounds. Chase's solution only reduces text size, this one enlarges also the text if there is enough space.

    To make all fast & precise i used a bisection method instead of an iterative while, as you can see in resizeText() method. That's why you have also a MAX_TEXT_SIZE option. I also included onoelle's tips.

    Tested on Android 4.4

    /**
     *               DO WHAT YOU WANT TO PUBLIC LICENSE
     *                    Version 2, December 2004
     *
     * Copyright (C) 2004 Sam Hocevar 
     *
     * Everyone is permitted to copy and distribute verbatim or modified
     * copies of this license document, and changing it is allowed as long
     * as the name is changed.
     *
     *            DO WHAT YOU WANT TO PUBLIC LICENSE
     *   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
     *
     *  0. You just DO WHAT YOU WANT TO.
     */
    
    import android.content.Context;
    import android.text.Layout.Alignment;
    import android.text.StaticLayout;
    import android.text.TextPaint;
    import android.util.AttributeSet;
    import android.util.TypedValue;
    import android.widget.TextView;
    
    /**
     * Text view that auto adjusts text size to fit within the view.
     * If the text size equals the minimum text size and still does not
     * fit, append with an ellipsis.
     *
     * @author Chase Colburn
     * @since Apr 4, 2011
     */
    public class AutoResizeTextView extends TextView {
    
        // Minimum text size for this text view
        public static final float MIN_TEXT_SIZE = 26;
    
        // Maximum text size for this text view
        public static final float MAX_TEXT_SIZE = 128;
    
        private static final int BISECTION_LOOP_WATCH_DOG = 30;
    
        // Interface for resize notifications
        public interface OnTextResizeListener {
            public void onTextResize(TextView textView, float oldSize, float newSize);
        }
    
        // Our ellipse string
        private static final String mEllipsis = "...";
    
        // Registered resize listener
        private OnTextResizeListener mTextResizeListener;
    
        // Flag for text and/or size changes to force a resize
        private boolean mNeedsResize = false;
    
        // Text size that is set from code. This acts as a starting point for resizing
        private float mTextSize;
    
        // Temporary upper bounds on the starting text size
        private float mMaxTextSize = MAX_TEXT_SIZE;
    
        // Lower bounds for text size
        private float mMinTextSize = MIN_TEXT_SIZE;
    
        // Text view line spacing multiplier
        private float mSpacingMult = 1.0f;
    
        // Text view additional line spacing
        private float mSpacingAdd = 0.0f;
    
        // Add ellipsis to text that overflows at the smallest text size
        private boolean mAddEllipsis = true;
    
        // Default constructor override
        public AutoResizeTextView(Context context) {
            this(context, null);
        }
    
        // Default constructor when inflating from XML file
        public AutoResizeTextView(Context context, AttributeSet attrs) {
            this(context, attrs, 0);
        }
    
        // Default constructor override
        public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
            mTextSize = getTextSize();
        }
    
        /**
         * When text changes, set the force resize flag to true and reset the text size.
         */
        @Override
        protected void onTextChanged(final CharSequence text, final int start, final int before, final int after) {
            mNeedsResize = true;
            // Since this view may be reused, it is good to reset the text size
            resetTextSize();
        }
    
        /**
         * If the text view size changed, set the force resize flag to true
         */
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            if (w != oldw || h != oldh) {
                mNeedsResize = true;
            }
        }
    
        /**
         * Register listener to receive resize notifications
         * @param listener
         */
        public void setOnResizeListener(OnTextResizeListener listener) {
            mTextResizeListener = listener;
        }
    
        /**
         * Override the set text size to update our internal reference values
         */
        @Override
        public void setTextSize(float size) {
            super.setTextSize(size);
            mTextSize = getTextSize();
        }
    
        /**
         * Override the set text size to update our internal reference values
         */
        @Override
        public void setTextSize(int unit, float size) {
            super.setTextSize(unit, size);
            mTextSize = getTextSize();
        }
    
        /**
         * Override the set line spacing to update our internal reference values
         */
        @Override
        public void setLineSpacing(float add, float mult) {
            super.setLineSpacing(add, mult);
            mSpacingMult = mult;
            mSpacingAdd = add;
        }
    
        /**
         * Set the upper text size limit and invalidate the view
         * @param maxTextSize
         */
        public void setMaxTextSize(float maxTextSize) {
            mMaxTextSize = maxTextSize;
            requestLayout();
            invalidate();
        }
    
        /**
         * Return upper text size limit
         * @return
         */
        public float getMaxTextSize() {
            return mMaxTextSize;
        }
    
        /**
         * Set the lower text size limit and invalidate the view
         * @param minTextSize
         */
        public void setMinTextSize(float minTextSize) {
            mMinTextSize = minTextSize;
            requestLayout();
            invalidate();
        }
    
        /**
         * Return lower text size limit
         * @return
         */
        public float getMinTextSize() {
            return mMinTextSize;
        }
    
        /**
         * Set flag to add ellipsis to text that overflows at the smallest text size
         * @param addEllipsis
         */
        public void setAddEllipsis(boolean addEllipsis) {
            mAddEllipsis = addEllipsis;
        }
    
        /**
         * Return flag to add ellipsis to text that overflows at the smallest text size
         * @return
         */
        public boolean getAddEllipsis() {
            return mAddEllipsis;
        }
    
        /**
         * Reset the text to the original size
         */
        public void resetTextSize() {
            if(mTextSize > 0) {
                super.setTextSize(TypedValue.COMPLEX_UNIT_PX, mTextSize);
                //mMaxTextSize = mTextSize;
            }
        }
    
        /**
         * Resize text after measuring
         */
        @Override
        protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
            if(changed || mNeedsResize) {
                int widthLimit = (right - left) - getCompoundPaddingLeft() - getCompoundPaddingRight();
                int heightLimit = (bottom - top) - getCompoundPaddingBottom() - getCompoundPaddingTop();
                resizeText(widthLimit, heightLimit);
            }
            super.onLayout(changed, left, top, right, bottom);
        }
    
    
        /**
         * Resize the text size with default width and height
         */
        public void resizeText() {
            int heightLimit = getHeight() - getPaddingBottom() - getPaddingTop();
            int widthLimit = getWidth() - getPaddingLeft() - getPaddingRight();
            resizeText(widthLimit, heightLimit);
        }
    
        /**
         * Resize the text size with specified width and height
         * @param width
         * @param height
         */
        public void resizeText(int width, int height) {
            CharSequence text = getText();
            // Do not resize if the view does not have dimensions or there is no text
            if(text == null || text.length() == 0 || height <= 0 || width <= 0 || mTextSize == 0) {
                return;
            }
    
            // Get the text view's paint object
            TextPaint textPaint = getPaint();
    
            // Store the current text size
            float oldTextSize = textPaint.getTextSize();
    
            // Bisection method: fast & precise
            float lower = mMinTextSize;
            float upper = mMaxTextSize;
            int loop_counter=1;
            float targetTextSize = (lower+upper)/2;
            int textHeight = getTextHeight(text, textPaint, width, targetTextSize);
            while(loop_counter < BISECTION_LOOP_WATCH_DOG && upper - lower > 1) {
                targetTextSize = (lower+upper)/2;
                textHeight = getTextHeight(text, textPaint, width, targetTextSize);
                if(textHeight > height)
                    upper = targetTextSize;
                else
                    lower = targetTextSize;
                loop_counter++;
            }
    
            targetTextSize = lower;
            textHeight = getTextHeight(text, textPaint, width, targetTextSize);
    
            // If we had reached our minimum text size and still don't fit, append an ellipsis
            if(mAddEllipsis && targetTextSize == mMinTextSize && textHeight > height) {
                // Draw using a static layout
                // modified: use a copy of TextPaint for measuring
                TextPaint paintCopy = new TextPaint(textPaint);
                paintCopy.setTextSize(targetTextSize);
                StaticLayout layout = new StaticLayout(text, paintCopy, width, Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, false);
                // Check that we have a least one line of rendered text
                if(layout.getLineCount() > 0) {
                    // Since the line at the specific vertical position would be cut off,
                    // we must trim up to the previous line
                    int lastLine = layout.getLineForVertical(height) - 1;
                    // If the text would not even fit on a single line, clear it
                    if(lastLine < 0) {
                        setText("");
                    }
                    // Otherwise, trim to the previous line and add an ellipsis
                    else {
                        int start = layout.getLineStart(lastLine);
                        int end = layout.getLineEnd(lastLine);
                        float lineWidth = layout.getLineWidth(lastLine);
                        float ellipseWidth = paintCopy.measureText(mEllipsis);
    
                        // Trim characters off until we have enough room to draw the ellipsis
                        while(width < lineWidth + ellipseWidth) {
                            lineWidth = paintCopy.measureText(text.subSequence(start, --end + 1).toString());
                        }
                        setText(text.subSequence(0, end) + mEllipsis);
                    }
                }
            }
    
            // Some devices try to auto adjust line spacing, so force default line spacing
            // and invalidate the layout as a side effect
            setTextSize(TypedValue.COMPLEX_UNIT_PX, targetTextSize);
            setLineSpacing(mSpacingAdd, mSpacingMult);
    
            // Notify the listener if registered
            if(mTextResizeListener != null) {
                mTextResizeListener.onTextResize(this, oldTextSize, targetTextSize);
            }
    
            // Reset force resize flag
            mNeedsResize = false;
        }
    
        // Set the text size of the text paint object and use a static layout to render text off screen before measuring
        private int getTextHeight(CharSequence source, TextPaint originalPaint, int width, float textSize) {
            // modified: make a copy of the original TextPaint object for measuring
            // (apparently the object gets modified while measuring, see also the
            // docs for TextView.getPaint() (which states to access it read-only)
            TextPaint paint = new TextPaint(originalPaint);
            // Update the text paint object
            paint.setTextSize(textSize);
            // Measure using a static layout
            StaticLayout layout = new StaticLayout(source, paint, width, Alignment.ALIGN_NORMAL, mSpacingMult, mSpacingAdd, true);
            return layout.getHeight();
        }
    
    }
    

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