How does one use Resources.getFraction()?

问题

How do I store a fractional value like 3.1416 in resources? What to write in the XML and how to retrieve it in Java code?

The documentation for getFraction() states:

public float getFraction (int id, int base, int pbase)

Retrieve a fractional unit for a particular resource ID.

Parameters
base The base value of this fraction. In other words, a standard fraction is multiplied by this value.
pbase The parent base value of this fraction. In other words, a parent fraction (nn%p) is multiplied by this value.

Returns
Attribute fractional value multiplied by the appropriate base value

This answer shows a simple example of percentages without going into the details of what the arguments mean.

回答1:

You specify fractions in XML as so:

   <item name="fraction" type="fraction">5%</item>
   <item name="parent_fraction" type="fraction">2%p</item>

Where 5% would be 0.05 when actually used.

Then:

// 0.05f
getResources().getFraction(R.fraction.fraction, 1, 1);
// 0.02f
getResources().getFraction(R.fraction.parent_fraction, 1, 1);
// 0.10f
getResources().getFraction(R.fraction.fraction, 2, 1);
// 0.10f
getResources().getFraction(R.fraction.fraction, 2, 2);
// 0.04f
getResources().getFraction(R.fraction.parent_fraction, 1, 2);
// 0.04f
getResources().getFraction(R.fraction.parent_fraction, 2, 2);

As you can see, depending on the type of fraction, the getFraction method multiples the values accordingly. If you specify a parent fraction (%p), it uses the second argument (pbase), ignoring the first. On the other hand, specifying a normal fraction, only the base argument is used, multiplying the fraction by this.

来源：https://stackoverflow.com/questions/11734470/how-does-one-use-resources-getfraction