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

public class MainActivity extends Activity {

private EditText editText;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText = (EditText) findViewById(R.id.editText1);
    editText.setText("+374");
    Selection.setSelection(editText.getText(), editText.getText().length());
    editText.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence s, int start, int before,
                int count) {
            // TODO Auto-generated method stub

        }

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count,
                int after) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable s) {
            if (!s.toString().startsWith("+374")) {
                editText.setText("+374");
                Selection.setSelection(editText.getText(), editText
                        .getText().length());

            }

        }

    });
}

}

you can create class extend AppCompatEditText or EditText.

public class CEditTextMaster extends AppCompatEditText {

        private boolean isNeedNoChangeSomeCharacters;
        private String charactersNoChange;

        public CEditTextMaster(Context context) {
            super(context);
            init(context, null);
        }

        public CEditTextMaster(Context context, AttributeSet attrs) {
            super(context, attrs);
            init(context, attrs);
        }

        public CEditTextMaster(Context context, AttributeSet attrs, int defStyleAttr) {
            super(context, attrs, defStyleAttr);
            init(context, attrs);
        }

        public void init(Context context, @Nullable AttributeSet attrs) {

            if (isInEditMode())
                return;

            addTextChangedListener(new TextWatcher() {
                @Override
                public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                }

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {

                }

                @Override
                public void afterTextChanged(Editable s) {
                    if (isNeedNoChangeSomeCharacters && charactersNoChange != null) {
                        if (!getText().toString().startsWith(charactersNoChange)) {
                            removeTextChangedListener(this);
                            if (charactersNoChange.length() > s.length()) {
                                setText(charactersNoChange);
                            } else {
                                setText(charactersNoChange + getText());
                            }
                            setSelection(getText().toString().length());
                            addTextChangedListener(this);
                        }
                    }
                }
            });

        }

        @Override
        protected void onSelectionChanged(int selStart, int selEnd) {
            if (isNeedNoChangeSomeCharacters && charactersNoChange != null) {
                if (length() > charactersNoChange.length() && selStart < charactersNoChange.length()) {
                    setSelection(charactersNoChange.length(),selEnd);
                }
            }
        }


        @Override
        public void setText(CharSequence text, BufferType type) {
            super.setText(text, type);
            if (isNeedNoChangeSomeCharacters && charactersNoChange != null) {
                if (!getText().toString().trim().startsWith(charactersNoChange)) {
                    setText(charactersNoChange + getText());
                }
            }
        }

        public void setCharactersNoChangeInitial(String charactersNoChange) {
            isNeedNoChangeSomeCharacters = true;
            this.charactersNoChange = charactersNoChange;
            if (!getText().toString().trim().startsWith(charactersNoChange)) {
                setText(getText());
            }
        }

}

for use:

edt.setCharactersNoChangeInitial("+734 ");