Android中的SP和DP区别

sp和dp很类似但唯一的区别是，Android系统允许用户自定义文字尺寸大小（小、正常、大、超大等等），当文字尺寸是“正常”时1sp=1dp=0.00625英寸，而当文字尺寸是“大”或“超大”时，1sp>1dp=0.00625英寸。类似我们在windows里调整字体尺寸以后的效果——窗口大小不变，只有文字大小改变。

dp代码（或者dipdevice independent pixels）

// 文件位置：android4.0\frameworks\base\core\java\android\util\DisplayMetrics.java

publicstaticfinalintDENSITY_DEVICE = getDeviceDensity();

publicfloatdensity;

publicvoidsetToDefaults() {

widthPixels =0;

heightPixels =0;

density = DENSITY_DEVICE / (float) DENSITY_DEFAULT;// 这里dp用的比例

densityDpi = DENSITY_DEVICE;

scaledDensity = density;// 这是sp用的比例

xdpi = DENSITY_DEVICE;

ydpi = DENSITY_DEVICE;

noncompatWidthPixels =0;

noncompatHeightPixels =0;

}

privatestaticintgetDeviceDensity() {

// qemu.sf.lcd_density can be used to override ro.sf.lcd_density

// when running in the emulator, allowing for dynamic configurations.

// The reason for this is that ro.sf.lcd_density is write-once and is

// set by the init process when it parses build.prop before anything else.

returnSystemProperties.getInt("qemu.sf.lcd_density",

SystemProperties.getInt("ro.sf.lcd_density", DENSITY_DEFAULT));// 从系统属性ro.sf.lcd_density里获取屏幕密度

// 文件位置：android4.0\packages\inputmethods\latinime\java\src\com\android\inputmethod\latin\Utils.java

publicstaticfloatgetDipScale(Context context) {

finalfloatscale = context.getResources().getDisplayMetrics().density;

returnscale;

}

publicstaticintdipToPixel(floatscale,intdip) {

return(int) (dip * scale +0.5);// dip到px的换算公式

}      

sp（Scaled Pixels）代码

// 文件位置：android4.0\packages\apps\settings\src\com\android\settings\Display.java

privateSpinner.OnItemSelectedListener mFontSizeChanged

=newSpinner.OnItemSelectedListener() {

publicvoidonItemSelected(android.widget.AdapterView av, View v,

intposition,longid) {

if(position ==0) {// 下面是设置字体比例的代码

mCurConfig.fontScale = .75f;

}elseif(position ==2) {

mCurConfig.fontScale =1.25f;

}else{

mCurConfig.fontScale =1.0f;

}

updateFontScale();

}

publicvoidonNothingSelected(android.widget.AdapterView av) {

}

};

privatevoidupdateFontScale() {

mDisplayMetrics.scaledDensity = mDisplayMetrics.density *

mCurConfig.fontScale;// 将设置的字体比例代码合到scaledDensity里去

floatsize = mTextSizeTyped.getDimension(mDisplayMetrics);

mPreview.setTextSize(TypedValue.COMPLEX_UNIT_PX, size);

}