Set unchangeable some part of editText android

Create a custom drawable class that will help to convert text into drawable.

public class TextDrawable extends Drawable {

  private final String text;
  private final Paint paint;

  public TextDrawable(String text) {
      this.text = text;
      this.paint = new Paint();
      paint.setColor(Color.BLACK);
      paint.setTextSize(16f);
      paint.setAntiAlias(true);
      paint.setTextAlign(Paint.Align.LEFT);
  }

  @Override
  public void draw(Canvas canvas) {
      canvas.drawText(text, 0, 6, paint);
  }

  @Override
  public void setAlpha(int alpha) {
      paint.setAlpha(alpha);
  }

  @Override
  public void setColorFilter(ColorFilter cf) {
      paint.setColorFilter(cf);
  }

  @Override
  public int getOpacity() {
      return PixelFormat.TRANSLUCENT;
  }
}

Then set the drawable to left of the edittext as

EditText et = (EditText)findViewById(R.id.editText1);
String code = "+374";
et.setCompoundDrawablesWithIntrinsicBounds(new TextDrawable(code), null, null, null);
et.setCompoundDrawablePadding(code.length()*10);

Where the edittext is defined in the layout file as

<EditText
android:id="@+id/editText1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="16sp"
android:ems="10" >
  <requestFocus />
</EditText>

Final Output looks like