如何删除TextView的最后一行？

Question

I am trying to remove\\replace last line of a TextView , but I want a way to do this faster . For example I found this:

String temp = TextView.getText().toString();
temp.substring(0,temp.lastIndexOf("\n"));

But I want to do it faster without copy data from Textview to a string value and dont using Sting.lastIndexOf (because its search in a string).

Can some one help me?

My Question isn't a dupplicate question becuase I want a way without using a string type!!!

Answer 1

I suggest overwriting the TextView class with your own implementation:

public class CustomTextView extends TextView{
  // Overwrite any mandatory constructors and methods and just call super

  public void removeLastLine(){
    if(getText() == null) return;
    String currentValue = getText().toString();
    String newValue = currentValue.substring(0, currentValue.lastIndexOf("\n"));
    setText(newValue);
  }
}

Now you could use something along the lines of:

CustomTextView textView = ...

textView.removeLastLine();

---

Alternatively, since you seem to be looking for a one-liner without creating a String temp for some reason, you could do this:

textView.setText(textView.getText().toString().replaceFirst("(.*)\n[^\n]+$", "$1"));

Regex explanation:

(.*)            # One or more character (as capture group 1)
    \n          # a new-line
      [^\n]     # followed by one or more non new-lines
           $    # at the end of the String

$1              # Replace it with the capture group 1 substring
                # (so the last new-line, and everything after it are removed)

Try it online.

Answer 2

Use the System.getProperty("line.seperator") instead of "\\n"

public void removeLastLine(TextView textView) {
    String temp = textView.getText().toString();
    textView.setText(
        temp.substring(0, temp.lastIndexOf(System.getProperty("line.seperator") )));
}

Answer 3

Try this:

public String removeLastParagraph(String s) {
    int index = s.lastIndexOf("\n");
    if (index < 0) {
        return s;
    }
    else {
        return s.substring(0, index);
    }
}

and use it like:

tv.setText(removeLastParagraph(tv.getText().toString().trim());