Multiline EditText changing into single line

I have a 5-line EditText. I use checkbox to enable or disable the soft keyboard.

checkBoxSystem.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if (checkBoxSystem.isChecked()) {
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.showSoftInput(textArea, InputMethodManager.SHOW_IMPLICIT);
                    textArea.setSelection(textArea.getText().length());
                    textArea.setMinLines(5);
                    textArea.setLines(5);
                    textArea.setInputType(InputType.TYPE_TEXT_FLAG_MULTI_LINE);
                } else {
                    InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                    imm.hideSoftInputFromWindow(textArea.getWindowToken(), 0);
                    textArea.setMinLines(5);
                    textArea.setLines(5);
                    textArea.setInputType(InputType.TYPE_NULL);
                }
            }
        });

However, when I check it, the text turns into single line EditText. Then, when I uncheck it, it returns to his 5-lined position. Then I check the box again, EditText remains 5-lined. The other problem, when I click back, the soft keyboard disappears, but when I touch into EditText, it doesn't appear, so I need to click on the checkbox twice.

How can I prevent the EditText become single lined? And how can I make the keyboard activated, when I just click on the EditText, if the checkbox is checked already?