I aim to use two different modes for tabs. The modes are SOFT_INPUT_ADJUST_RESIZE and SOFT_INPUT_ADJUST_NOTHING.
getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE);
The code line above simply doesn't work by itself. App always behaves in a state ADJUST_NOTHING. However, if windowSoftInputMode="adjustResize" is inserted into <activity> tag in AndroidManifest.xml file, app window is resized as default. Additionally, when you call following line
getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_NOTHING);
it will behave as expected and nothing is resized.
P.S. improvement to the answer