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Android: Text View size and different font size

I have read a lot and still have not found the solution. I have an application that displays textviews, what I want to do is when I change the font sizes from the phone settings (large, small, medium) the textview size on the screen remains unchanged.
But after I tried following the sizes hpdi, xhdpi, xxhdpi... and set the textview size to "sp" then with different font sizes the textview size still gets bigger if I choose large font size.
Can anyone help me?

Actually sizes in hpdi, xhdpi, xxhdpi... folders are sizes for different phone screens and put different sizes in them is not related to have fixed font size(even phone size setting set to large).
You have to set size with dp, not sp to phone setting can not effect on text size.

Same text size but it larger on other devices

I have a TextView in which I programmatically setup the text size in 'SP'.
tv.setTextSize(spToPx(5, context));
public static int spToPx(float sp, Context context) {
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp, context.getResources().getDisplayMetrics());
}
First screenshot shows how it should look (and how it looks on my Xiaomi Redmi and Doogee HT7
Second screenshot shows how it looks on other devices with higher or the same dpi.
Normally, if I understand correct, text with the same size in 'dp' or 'sp' should looks the same on other devices (with the same screen size) because it automatically converts 'dp' or 'sp' to the needed amount of pixels depending on dpi.
After reading Android Developer Guideline about devices with different density I was expecting that text would be smaller if I use the same text size on devices with higher dpi. But now I have a situation that I really don't understand.

If you are using values in sp and the user changes the default text size for his device from Settings--->Display---->TextSize, your TextViews will be affected. If on the other hand you use dp values, then no matter what text size the user sets as default, the TextViews in your app will remain the same. This is ofcourse discouraged by Google as bad practice, since the user should be able to change text sizes but it would be what you are looking for.
So, use (TypedValue.COMPLEX_UNIT_DIP,number of your choosing) instead of (TypedValue.COMPLEX_UNIT_SP, sp)

You can add dimens file to your resources . thats how I do it
heres the link where I got the answer

Try this, Add this property in your xml. It will change textsize based on all phone.
style="#android:style/TextAppearance.DeviceDefault.Medium" /*for normal text */
style="#android:style/TextAppearance.DeviceDefault.Small" /*for small text */
style="#android:style/TextAppearance.DeviceDefault.Large" /*for large text */
Hope your problem will solve.

The primary difference between an sp and a dp is that sp’s preserve a
user's font settings. Users who have larger text settings for
accessibility will see font sizes match their text size preferences.
so you could check the settings of two devices and see if there is a difference between them.

I still didn't find right explanation to this issue. The only theory I have is next:
There are density buckets (120 dpi, 160 dpi, 240 dpi, 320 dpi, 480 dpi, 640 dpi). Screen density of your device will be determinated as the closest bucket. For example, if your device has 401 dpi it will be counted as 480 dpi. So, when I create and add view with size of 20 dp it will convert into more pixels than needed. It the hardest for devices that have density right between two buckets. I also checked density of all devices that had wrong image display (like on image 2) and it was almost right between two buckets...
I still don't know why this happens only when I create and add view dynamycally, but the only way to solve this problem was the creating of separate layout with all presetted views instead of adding these views dynamically.

What's the relationship between the font size and the height of TextView in android?

I occured a problem when using RadioButton. The RadioButton's layout_height must be 15dp, and the offical design guide says that 1sp is 1dp, so I set the font size to 1sp, but the TextView's layout_height is a little bigger than 15dp. It seems that when the font size is 15sp, the layout_height of the TextView is 18dp. So what's the relationship between the font size and the layout_height?

First thing I wanted to mention is the font-padding, which is by default included into the TextView size. So to make TextView's size closer to the size of the text itself - specify android:includeFontPadding="false"
Now, if you compare View with layout_height equals to 20 sp and TextView with TextSize 20sp - they are going to be almost equally high.
(There's small difference, as text might contain very high letter like "Å" or the letter like "y" which goes below the baseline)
About sp vs dp.
Scale-independent Pixels - This is like the dp unit, but it is also
scaled by the user's font size preference. It is recommend you use
this unit when specifying font sizes, so they will be adjusted for
both the screen density and the user's preference.
It depends on how big is your font (Settings->Accessibility->Enable/Disable Large Text). You can change it and see the effect.
Hope, it helps.

Best way to set text size?

What is the best way to set the text size so it looks the same on all devices? The biggest problem I am having is setting the text size on the buttons so everything fits or isn't too small. I have tried setting the size in the xml, and I have just tried setting it dynamically by getting the screen size and messing with the screen width and height to set the size. I had tested different things on different devices and thought all was well, until I just tried my app on the Galaxy Nexus and half of my words were getting chopped off inside of the button. I made some adjustments and the font is now way too small on tablets.
Using the xml has worked fine for me before, but most of these new 7" tablets use the large layout, so my images and text are really small if I set the height, width, and text size with the xml. Setting the widths and hights dynamically have helped with the buttons and image sizes, but the font still doesn't look quite right.
Is my best bet just to find a happy medium via xml(large, x-large, etc.) or are there other ways?

Have you seen this article: Supporting Multiple Screens ?
It says:
you should prefer the sp (scale-independent pixel) to define text
sizes. The sp scale factor depends on a user setting and the system
scales the size the same as it does for dp.
The same issue is explained here, Different text size for different hardware

Android - text size on particular resolution - setting programatically

I am programming application, which will be used on various kinds of resolutions, but let's say, we would keep to the density. For medium, high and low I am setting it's own drawables, but it still doesn's solve my problem, so I am wondering, how to set values dependently on actual pixel screen density in Java code?
In this time I have to in XML set smaller letters and smaller textviews to fit it into low resolution screen, on the other hand, high density screen is used from about 60% and text fields are too small. I am wondering if there is some way how to, during the start of the program, in some If loop find out, what the resolution is and then set layout_height and textSize for items I want.
Thanks
edit: Solved myself - http://developer.android.com/reference/android/util/DisplayMetrics.html

well before moving ahead to set the text size programatically, I recommend you to set the Textsize property's value in dip instead of px. it seems that you have marked the textsize value in px.