Live editing of users input

Question

Is it possible to auto insert characters into an EditText as the user inputs data?

I.e. if the user is entering a long number such as <

Answer 1

to solve this issue, i write a class "AutoAddTextWatcher" :

1. Auto insert text into EditText.
2. insert text into EditText at positions you are setted.
3. delete text in EditText at positions you are setted, when text length bigger than 1.

code snippet :

mEditText_birthday.addTextChangedListener(new AutoAddTextWatcher(mEditText_birthday,
            "/",
            new TextWatcher() {},
            4, 6));

AutoAddTextWatcher class

import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;


/**
 * Created by henry.chuang on 2016/5/12.
 */
public class AutoAddTextWatcher implements TextWatcher {
    private CharSequence mBeforeTextChanged;
    private TextWatcher mTextWatcher;
    private int[] mArray_pos;
    private EditText mEditText;
    private String mAppentText;

    public AutoAddTextWatcher(EditText editText, String appendText, int... position){
        this.mEditText = editText;
        this.mAppentText = appendText;
        this.mArray_pos = position.clone();
    }
    public AutoAddTextWatcher(EditText editText, String appendText, TextWatcher textWatcher, int... position){
        this(editText, appendText, position);
        this.mTextWatcher = textWatcher;
    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        mBeforeTextChanged = s.toString();

        if(mTextWatcher != null)
            mTextWatcher.beforeTextChanged(s, start, count, after);

    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        for (int i = 0; i < mArray_pos.length; i++) {
            if(((mBeforeTextChanged.length() - mAppentText.length() * i) == (mArray_pos[i] - 1) &&
                    (s.length() - mAppentText.length() * i) == mArray_pos[i])){
                mEditText.append(mAppentText);

                break;
            }

            if(((mBeforeTextChanged.length() - mAppentText.length() * i) == mArray_pos[i] &&
                    (s.length() - mAppentText.length() * i) == (mArray_pos[i] + 1))){
                int idx_start = mArray_pos[i] + mAppentText.length() * i;
                int idx_end = Math.min(idx_start + mAppentText.length(), s.length());

                String sub = mEditText.getText().toString().substring(idx_start,  idx_end);

                if(!sub.equals(mAppentText)){
                    mEditText.getText().insert(s.length() - 1, mAppentText);
                }

                break;
            }

            if(mAppentText.length() > 1 &&
                    (mBeforeTextChanged.length() - mAppentText.length() * i) == (mArray_pos[i] + mAppentText.length()) &&
                    (s.length() - mAppentText.length() * i) == (mArray_pos[i] + mAppentText.length() - 1)){
                int idx_start = mArray_pos[i] + mAppentText.length() * i;
                int idx_end = Math.min(idx_start + mAppentText.length(), s.length());

                mEditText.getText().delete(idx_start, idx_end);

                break;
            }

        }

        if(mTextWatcher != null)
            mTextWatcher.onTextChanged(s, start, before, count);

    }

    @Override
    public void afterTextChanged(Editable s) {
        if(mTextWatcher != null)
            mTextWatcher.afterTextChanged(s);

    }

}

complete demo source :
https://github.com/henrychuangtw/AutoInsertEditText