android developer android developer - 4 months ago 73
Android Question

Auto-fit TextView for Android

Background



Many times we need to auto-fit the font of the TextView to the boundaries given to it.

The problem



Sadly, even though there are many threads and posts (and suggested solutions) talking about this problem (example here , here and here), none of them actually work well.

That's why, I've decided to test each of them till I find the real deal.

I think that the requirements from such a textView should be:


  1. Should allow using any font,typeface,style and set of characters .

  2. Should handle both width and height

  3. No truncation unless text cannot fit because of the limitation, we've
    given to it (example: too long text, too small available size). However, we could request for horizontal/vertical scrollbar if we wish, just for those cases.

  4. Should allow multi-line or single-line. In case of multi-line, allow max&min lines.

  5. Should not be slow in computation. Using a loop for finding the best size? At least optimize it and don't increment your sampling by 1 each time.

  6. In case of multi-line, should allow to prefer resizing or using more lines , and/or allow to choose the lines ourselves by using the "\n" character .



What I've tried



I've tried so many samples (including those of the links, I've written about), and I've also tried to modify them to handle the cases, I've talked about, but none really work.

I've made a sample project that allows me to visually see if the TextView auto-fits correctly.

Currently, my sample project only randomize the text (the English alphabet plus digits) and the size of the textView, and let it stay with single line, but even this doesn't work well on any of the samples I've tried.

Here's the code (also available here) :

res/layout/activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" tools:context=".MainActivity">
<Button android:id="@+id/button1" android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" android:text="Button" />
<FrameLayout android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_above="@+id/button1"
android:layout_alignParentLeft="true" android:background="#ffff0000"
android:layout_alignParentRight="true" android:id="@+id/container"
android:layout_alignParentTop="true" />

</RelativeLayout>


src/.../MainActivity.java

public class MainActivity extends Activity
{
private final Random _random =new Random();
private static final String ALLOWED_CHARACTERS ="qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890";

@Override
protected void onCreate(final Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ViewGroup container=(ViewGroup)findViewById(R.id.container);
findViewById(R.id.button1).setOnClickListener(new OnClickListener()
{
@Override
public void onClick(final View v)
{
container.removeAllViews();
final int maxWidth=container.getWidth();
final int maxHeight=container.getHeight();
final FontFitTextView fontFitTextView=new FontFitTextView(MainActivity.this);
final int width=_random.nextInt(maxWidth)+1;
final int height=_random.nextInt(maxHeight)+1;
fontFitTextView.setLayoutParams(new LayoutParams(width,height));
fontFitTextView.setSingleLine();
fontFitTextView.setBackgroundColor(0xff00ff00);
final String text=getRandomText();
fontFitTextView.setText(text);
container.addView(fontFitTextView);
Log.d("DEBUG","width:"+width+" height:"+height+" text:"+text);
}
});
}

private String getRandomText()
{
final int textLength=_random.nextInt(20)+1;
final StringBuilder builder=new StringBuilder();
for(int i=0;i<textLength;++i)
builder.append(ALLOWED_CHARACTERS.charAt(_random.nextInt(ALLOWED_CHARACTERS.length())));
return builder.toString();
}
}


The question



Does anybody know of a solution for this common problem that actually work?

Even a solution that has much less features that what I've written about, for example one that has just a constant number of lines of text, and adjusts its font according to its size , yet never have weird glitches and having the text get too large/small compared to its available space.




Github project



EDIT: since this is such an important TextView, I've decided to publish a library, so that everyone could easily use it, and contribute to it, here.

Answer

UPDATE: Thanks to MartinH's simple fix here, this code also takes care of android:drawableLeft, android:drawableRight, android:drawableTop and android:drawableBottom tags.


My answer here should make you happy Auto Scale TextView Text to Fit within Bounds

I have modified your test case:

@Override
protected void onCreate(final Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final ViewGroup container = (ViewGroup) findViewById(R.id.container);
    findViewById(R.id.button1).setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(final View v) {
            container.removeAllViews();
            final int maxWidth = container.getWidth();
            final int maxHeight = container.getHeight();
            final AutoResizeTextView fontFitTextView = new AutoResizeTextView(MainActivity.this);
            final int width = _random.nextInt(maxWidth) + 1;
            final int height = _random.nextInt(maxHeight) + 1;
            fontFitTextView.setLayoutParams(new FrameLayout.LayoutParams(
                    width, height));
            int maxLines = _random.nextInt(4) + 1;
            fontFitTextView.setMaxLines(maxLines);
            fontFitTextView.setTextSize(500);// max size
            fontFitTextView.enableSizeCache(false);
            fontFitTextView.setBackgroundColor(0xff00ff00);
            final String text = getRandomText();
            fontFitTextView.setText(text);
            container.addView(fontFitTextView);
            Log.d("DEBUG", "width:" + width + " height:" + height
                    + " text:" + text + " maxLines:" + maxLines);
        }
    });
}

UPDATE:

I am posting code here at per android developer's request:

Final effect:

enter image description here

Sample Layout file:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp" >

<com.vj.widgets.AutoResizeTextView
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:ellipsize="none"
    android:maxLines="2"
    android:text="Auto Resized Text, max 2 lines"
    android:textSize="100sp" /> <!-- maximum size -->

<com.vj.widgets.AutoResizeTextView
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:ellipsize="none"
    android:gravity="center"
    android:maxLines="1"
    android:text="Auto Resized Text, max 1 line"
    android:textSize="100sp" /> <!-- maximum size -->

<com.vj.widgets.AutoResizeTextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Auto Resized Text"
    android:textSize="500sp" /> <!-- maximum size -->

</LinearLayout>

And the java code:

import android.annotation.TargetApi;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.RectF;
import android.os.Build;
import android.text.Layout.Alignment;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.util.AttributeSet;
import android.util.SparseIntArray;
import android.util.TypedValue;
import android.widget.TextView;

public class AutoResizeTextView extends TextView {
private interface SizeTester {
    /**
     * 
     * @param suggestedSize
     *            Size of text to be tested
     * @param availableSpace
     *            available space in which text must fit
     * @return an integer < 0 if after applying {@code suggestedSize} to
     *         text, it takes less space than {@code availableSpace}, > 0
     *         otherwise
     */
    public int onTestSize(int suggestedSize, RectF availableSpace);
}

private RectF mTextRect = new RectF();

private RectF mAvailableSpaceRect;

private SparseIntArray mTextCachedSizes;

private TextPaint mPaint;

private float mMaxTextSize;

private float mSpacingMult = 1.0f;

private float mSpacingAdd = 0.0f;

private float mMinTextSize = 20;

private int mWidthLimit;

private static final int NO_LINE_LIMIT = -1;
private int mMaxLines;

private boolean mEnableSizeCache = true;
private boolean mInitializedDimens;

public AutoResizeTextView(Context context) {
    super(context);
    initialize();
}

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

public AutoResizeTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    initialize();
}

private void initialize() {
    mPaint = new TextPaint(getPaint());
    mMaxTextSize = getTextSize();
    mAvailableSpaceRect = new RectF();
    mTextCachedSizes = new SparseIntArray();
    if (mMaxLines == 0) {
        // no value was assigned during construction
        mMaxLines = NO_LINE_LIMIT;
    }
}

@Override
public void setTextSize(float size) {
    mMaxTextSize = size;
    mTextCachedSizes.clear();
    adjustTextSize();
}

@Override
public void setMaxLines(int maxlines) {
    super.setMaxLines(maxlines);
    mMaxLines = maxlines;
    adjustTextSize();
}

public int getMaxLines() {
    return mMaxLines;
}

@Override
public void setSingleLine() {
    super.setSingleLine();
    mMaxLines = 1;
    adjustTextSize();
}

@Override
public void setSingleLine(boolean singleLine) {
    super.setSingleLine(singleLine);
    if (singleLine) {
        mMaxLines = 1;
    } else {
        mMaxLines = NO_LINE_LIMIT;
    }
    adjustTextSize();
}

@Override
public void setLines(int lines) {
    super.setLines(lines);
    mMaxLines = lines;
    adjustTextSize();
}

@Override
public void setTextSize(int unit, float size) {
    Context c = getContext();
    Resources r;

    if (c == null)
        r = Resources.getSystem();
    else
        r = c.getResources();
    mMaxTextSize = TypedValue.applyDimension(unit, size,
            r.getDisplayMetrics());
    mTextCachedSizes.clear();
    adjustTextSize();
}

@Override
public void setLineSpacing(float add, float mult) {
    super.setLineSpacing(add, mult);
    mSpacingMult = mult;
    mSpacingAdd = add;
}

/**
 * Set the lower text size limit and invalidate the view
 * 
 * @param minTextSize
 */
public void setMinTextSize(float minTextSize) {
    mMinTextSize = minTextSize;
    adjustTextSize();
}

private void adjustTextSize() {
    if (!mInitializedDimens) {
        return;
    }
    int startSize = (int) mMinTextSize;
    int heightLimit = getMeasuredHeight() - getCompoundPaddingBottom()
            - getCompoundPaddingTop();
    mWidthLimit = getMeasuredWidth() - getCompoundPaddingLeft()
            - getCompoundPaddingRight();
    mAvailableSpaceRect.right = mWidthLimit;
    mAvailableSpaceRect.bottom = heightLimit;
    super.setTextSize(
            TypedValue.COMPLEX_UNIT_PX,
            efficientTextSizeSearch(startSize, (int) mMaxTextSize,
                    mSizeTester, mAvailableSpaceRect));
}

private final SizeTester mSizeTester = new SizeTester() {
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    @Override
    public int onTestSize(int suggestedSize, RectF availableSPace) {
        mPaint.setTextSize(suggestedSize);
        String text = getText().toString();
        boolean singleline = getMaxLines() == 1;
        if (singleline) {
            mTextRect.bottom = mPaint.getFontSpacing();
            mTextRect.right = mPaint.measureText(text);
        } else {
            StaticLayout layout = new StaticLayout(text, mPaint,
                    mWidthLimit, Alignment.ALIGN_NORMAL, mSpacingMult,
                    mSpacingAdd, true);
            // return early if we have more lines
            if (getMaxLines() != NO_LINE_LIMIT
                    && layout.getLineCount() > getMaxLines()) {
                return 1;
            }
            mTextRect.bottom = layout.getHeight();
            int maxWidth = -1;
            for (int i = 0; i < layout.getLineCount(); i++) {
                if (maxWidth < layout.getLineWidth(i)) {
                    maxWidth = (int) layout.getLineWidth(i);
                }
            }
            mTextRect.right = maxWidth;
        }

        mTextRect.offsetTo(0, 0);
        if (availableSPace.contains(mTextRect)) {
            // may be too small, don't worry we will find the best match
            return -1;
        } else {
            // too big
            return 1;
        }
    }
};

/**
 * Enables or disables size caching, enabling it will improve performance
 * where you are animating a value inside TextView. This stores the font
 * size against getText().length() Be careful though while enabling it as 0
 * takes more space than 1 on some fonts and so on.
 * 
 * @param enable
 *            enable font size caching
 */
public void enableSizeCache(boolean enable) {
    mEnableSizeCache = enable;
    mTextCachedSizes.clear();
    adjustTextSize(getText().toString());
}

private int efficientTextSizeSearch(int start, int end,
        SizeTester sizeTester, RectF availableSpace) {
    if (!mEnableSizeCache) {
        return binarySearch(start, end, sizeTester, availableSpace);
    }
    int key = getText().toString().length();
    int size = mTextCachedSizes.get(key);
    if (size != 0) {
        return size;
    }
    size = binarySearch(start, end, sizeTester, availableSpace);
    mTextCachedSizes.put(key, size);
    return size;
}

private static int binarySearch(int start, int end, SizeTester sizeTester,
        RectF availableSpace) {
    int lastBest = start;
    int lo = start;
    int hi = end - 1;
    int mid = 0;
    while (lo <= hi) {
        mid = (lo + hi) >>> 1;
        int midValCmp = sizeTester.onTestSize(mid, availableSpace);
        if (midValCmp < 0) {
            lastBest = lo;
            lo = mid + 1;
        } else if (midValCmp > 0) {
            hi = mid - 1;
            lastBest = hi;
        } else {
            return mid;
        }
    }
    // make sure to return last best
    // this is what should always be returned
    return lastBest;

}

@Override
protected void onTextChanged(final CharSequence text, final int start,
        final int before, final int after) {
    super.onTextChanged(text, start, before, after);
    adjustTextSize();
}

@Override
protected void onSizeChanged(int width, int height, int oldwidth,
        int oldheight) {
    mInitializedDimens = true;
    mTextCachedSizes.clear();
    super.onSizeChanged(width, height, oldwidth, oldheight);
    if (width != oldwidth || height != oldheight) {
        adjustTextSize();
    }
}
}

Warning: Beware of this resolved bug in Android HoneyComb (platform 3.1) though.

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