Android Spannable TextView

A spannable TextView can be used in Android to highlight a particular portion of text with a different color, style,
size, and/or click event in a single TextView widget.

Consider that you have defined a TextView as follows:

TextView textview=findViewById(R.id.textview);

Then you can apply different highlighting to it as shown below:

Spannable color: In order to set a different color to some portion of text, a ForegroundColorSpan can be
used, as shown in the following example:

Spannable spannable = new SpannableString(firstWord + lastWord);
spannable.setSpan(new ForegroundColorSpan(firstWordColor), 0, firstWord.length(),
    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spannable.setSpan(new ForegroundColorSpan(lastWordColor), firstWord.length(),
    firstWord.length() + lastWord.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
textview.setText(spannable);

Output created by the code above:

Spannable font: In order to set a different font size to some portion of text, a RelativeSizeSpan can be
used, as shown in the following example:

Spannable spannable = new SpannableString(firstWord + lastWord);
spannable.setSpan(new RelativeSizeSpan(1.1 f), 0, firstWord.length(),
    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); // set size
spannable.setSpan(new RelativeSizeSpan(0.8 f), firstWord.length(), firstWord.length() +
    lastWord.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE); // set size
textview.setText(spannable);

Output created by the code above:

Spannable typeface: In order to set a different font typeface to some portion of text, a custom
TypefaceSpan can be used, as shown in the following example:

Spannable spannable = new SpannableString(firstWord + lastWord);
spannable.setSpan(new CustomTypefaceSpan("SFUIText-Bold.otf", fontBold), 0,
    firstWord.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spannable.setSpan(new CustomTypefaceSpan("SFUIText-Regular.otf", fontRegular),
    firstWord.length(), firstWord.length() + lastWord.length(),
    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
text.setText(spannable);

However, in order to make the above code working, the class CustomTypefaceSpan has to be derived from
the class TypefaceSpan. This can be done as follows:

public class CustomTypefaceSpan extends TypefaceSpan {
    private final Typeface newType;
    public CustomTypefaceSpan(String family, Typeface type) {
        super(family);
        newType = type;
    }
    @Override
    public void updateDrawState(TextPaint ds) {
        applyCustomTypeFace(ds, newType);
    }
    @Override
    public void updateMeasureState(TextPaint paint) {
        applyCustomTypeFace(paint, newType);
    }
    private static void applyCustomTypeFace(Paint paint, Typeface tf) {
        int oldStyle;
        Typeface old = paint.getTypeface();
        if (old == null) {
            oldStyle = 0;
        } else {
            oldStyle = old.getStyle();
        }
        int fake = oldStyle & ~tf.getStyle();
        if ((fake & Typeface.BOLD) != 0) {
            paint.setFakeBoldText(true);
        }
        if ((fake & Typeface.ITALIC) != 0) {
            paint.setTextSkewX(-0.25 f);
        }
        paint.setTypeface(tf);
    }
}

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