Most efficient way to convert a single char to a CharSequence

Looking at the implementation of the Character.toString(char c) method reveals that they use almost the same code you use:

  public String toString() {
       char buf[] = {value};
       return String.valueOf(buf);
  }

For readability, you should just use Character.toString( c ).

Another efficient way would probably be

new StringBuilder(1).append(c);

It's definitely more efficient that using the + operator because, according to the javadoc:

The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method

textView.setText(String.valueOf(c))

Shorthand, as in fewest typed characters possible:

c+""; // where c is a char

In full:

textView.setText(c+"");

The most compact CharSequence you can get when you have a handful of chars is the CharBuffer. To initialize this with your char value:

CharBuffer.wrap(new char[]{c});

That being said, using Strings is a fair bit more readable and easy to work with.