如何逐字在文本下划线？

Question

how can i underline word by word in a sentence in android studio? so my program would be like this if i click a button the underline will start at first and when i click again the button it will move again to the next word.

for Example:

_The_ *** *** ***** **** *** **** ***.

so if i want to click the button the underline will move next to it word or 3 asterisk.

The _***_ *** ***** **** *** **** ***.

and click again to the next asterisk.

this is my code using for this:

public class MainActivity extends AppCompatActivity {

Button btn;
TextView txt;
int counter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btn = findViewById(R.id.button);
    txt = findViewById(R.id.display);

    txt.setText("the red fox jumps over the lazy dog.");
    final String [] compare1 = txt.getText().toString().split("\\s");
    final String arr[] = txt.getText().toString().split(" ",2);
    final String fword = arr[0];
    String rword = arr[1];
    final String reprword = rword.replaceAll("[a-z]", "*");
    txt.setText(fword + " " + reprword);
    final String [] display = txt.getText().toString().split("\\s");
    /*final ArrayList<String> getters = new ArrayList<String>(Arrays.asList(display));*/

    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            if(counter <= display.length) {
                if(compare1[counter].length() == display[counter].length())
                {
                    txt.setText(formatText(fword + " " + reprword,display[counter]));
                }

                counter++;
            }
            else
            {


            }
        }
    });
}
public CharSequence formatText(String base, String highlight) {
    int start = base.indexOf(highlight);
    if (start >= 0) {
        SpannableString span = new SpannableString(base);
        span.setSpan(new UnderlineSpan(), start, start + highlight.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
        return span;
    }
    return base;
}
}

I change the other half the sentence to test it for this.

Answer 1

base.indexOf(highlight) ==> indexOf() returns the first occurrence of highlight in base, thats why the underline span jumps to first "the" instead of the next occurrence. You can use indexOf(String str, int fromIndex) . The following code tracks the "fromIndex" in this variable "nextStartIndex", and also underlining resets to first word after completing the sentence.

public class UnderlineWordsActivity extends AppCompatActivity {

    private Button btn;
    private TextView txt;
    private int counter=0;
    private int nextStartIndex=0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn = findViewById(R.id.button);
        txt = findViewById(R.id.display);
        txt.setText("the red fox jumps over the lazy dog.");

        final String[] arr = txt.getText().toString().split(" ", 2);
        final String firstWord = arr[0];
        String remainingWords = arr[1];
        final String reprword = remainingWords.replaceAll("[a-z]", "*");
        String text = firstWord+" "+reprword;
        txt.setText(text);

        final String[] display = txt.getText().toString().split("\\s");


       btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (counter >= display.length) {
                    counter = 0;
                    nextStartIndex = 0;
                }
                txt.setText(formatText(text, display[counter]));
                counter++;
            }
        });
    }

    public CharSequence formatText(String base, String highlight) {
        int start = base.indexOf(highlight,nextStartIndex);
        nextStartIndex = start+highlight.length();
        if (start >= 0) {
            SpannableString span = new SpannableString(base);
            span.setSpan(new UnderlineSpan(), start, nextStartIndex, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
            return span;
        }
        return base;
    }
}