负数输入（EditText）变得无符号

    android:id="@+id/editText"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:inputType="number" />

EditText editText = findViewById(R.id.editText);
editText.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 (s.length() > 0 && s.charAt(0) == '-') {
            editText.setSelection(1);
        }
    }
});