先看一个例子：
int size = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 3,
context.getResources().getDisplayMetrics());
这行代码是把在当前屏幕分辨率的状态下将dip为3的值转换成单位为px值
下面是API介绍：
public static float applyDimension (int unit, float value, DisplayMetrics metrics)
Since: API Level 1
Converts an unpacked complex data value holding a dimension to its final floating point value. The two parameters unit and value are as in TYPE_DIMENSION.
Parameters
| unit | The unit to convert from. |
|---|---|
| value | The value to apply the unit to. |
| metrics | Current display metrics to use in the conversion -- supplies display density and scaling information. |
Returns
- The complex floating point value multiplied by the appropriate metrics depending on its unit.
查看其在framework中的源码
public static float applyDimension(int unit, float value,
DisplayMetrics metrics)
{
switch (unit) {
case COMPLEX_UNIT_PX:
return value;
case COMPLEX_UNIT_DIP:
return value * metrics.density;
case COMPLEX_UNIT_SP:
return value * metrics.scaledDensity;
case COMPLEX_UNIT_PT:
return value * metrics.xdpi * (1.0f/72);
case COMPLEX_UNIT_IN:
return value * metrics.xdpi;
case COMPLEX_UNIT_MM:
return value * metrics.xdpi * (1.0f/25.4f);
}
return 0;
}
如果传入的unit为COMPLIEX_UNIT_PX，则返回值与传入的value值保持一致；反之会根据一定的计算方式转换成px并返回。