EditText在设备旋转后自动保存该值

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putString("editTextValue", editText.getText().toString());
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    String editTextValue = savedInstanceState.getString("editTextValue");
    editText.setText(editTextValue);
}

implementation 'androidx.lifecycle:lifecycle-viewmodel:2.3.1'

public class MyViewModel extends ViewModel {
    private MutableLiveData<String> editTextValue = new MutableLiveData<>();

    public void setEditTextValue(String value) {
        editTextValue.setValue(value);
    }

    public LiveData<String> getEditTextValue() {
        return editTextValue;
    }
}

private MyViewModel viewModel;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    viewModel = new ViewModelProvider(this).get(MyViewModel.class);

    final EditText editText = findViewById(R.id.editText);

    viewModel.getEditTextValue().observe(this, new Observer<String>() {
        @Override
        public void onChanged(String value) {
            editText.setText(value);
        }
    });

    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) {
            viewModel.setEditTextValue(s.toString());
        }

        @Override
        public void afterTextChanged(Editable s) {
        }
    });
}