Android Development: How To Replace Part of an EditText with a Spannable

This minimal size example makes the word 'first' large:

public class SpanTest extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        String dispStr = "I'm the first line\nI'm the second line";
        TextView tv = (TextView) findViewById(R.id.textView1);
        int startSpan = dispStr.indexOf("first");
        int endSpan = dispStr.indexOf("line");
        Spannable spanRange = new SpannableString(dispStr);
        TextAppearanceSpan tas = new TextAppearanceSpan(this, android.R.style.TextAppearance_Large);
        spanRange.setSpan(tas, startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        tv.setText(spanRange);
    }
}

You can adapt it to your needs

I answered a smilar question recently: How to use SpannableString with Regex in android?. But I'll add a copy of that answer.

Here's a class that will help you:

public class Replacer {
    private final CharSequence mSource;
    private final CharSequence mReplacement;
    private final Matcher mMatcher;
    private int mAppendPosition;
    private final boolean mIsSpannable;

    public static CharSequence replace(CharSequence source, String regex,
            CharSequence replacement) {

        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(source);
        return new Replacer(source, matcher, replacement).doReplace();
    }

    private Replacer(CharSequence source, Matcher matcher,
            CharSequence replacement) {
        mSource = source;
        mReplacement = replacement;
        mMatcher = matcher;
        mAppendPosition = 0;
        mIsSpannable = replacement instanceof Spannable;
    }

    private CharSequence doReplace() {
        SpannableStringBuilder buffer = new SpannableStringBuilder();
        while (mMatcher.find()) {
            appendReplacement(buffer);
        }
        return appendTail(buffer);
    }

    private void appendReplacement(SpannableStringBuilder buffer) {
        buffer.append(mSource.subSequence(mAppendPosition, mMatcher.start()));
        CharSequence replacement = mIsSpannable
                ? copyCharSequenceWithSpans(mReplacement)
                : mReplacement;
        buffer.append(replacement);

        mAppendPosition = mMatcher.end();
    }

    public SpannableStringBuilder appendTail(SpannableStringBuilder buffer) {
        buffer.append(mSource.subSequence(mAppendPosition, mSource.length()));
        return buffer;
    }

    // This is a weird way of copying spans, but I don't know any better way.
    private CharSequence copyCharSequenceWithSpans(CharSequence string) {
        Parcel parcel = Parcel.obtain();
        try {
            TextUtils.writeToParcel(string, parcel, 0);
            parcel.setDataPosition(0);
            return TextUtils.CHAR_SEQUENCE_CREATOR.createFromParcel(parcel);
        } finally {
            parcel.recycle();
        }
    }
}

And an example of usage:

CharSequence modifiedText = Replacer.replace("ABC aaa AB ABC aa ad ABC", "ABC",
    Html.fromHtml("<font color=\"red\">CBA</font>"));
textView.setText(modifiedText);