So I\'d like to change the android:fontFamily in Android but I don\'t see any pre-defined fonts in Android. How do I select one of the pre-defined ones? I don\'         
        
If you want it programatically, you could use
label.setTypeface(Typeface.SANS_SERIF, Typeface.ITALIC);
Where SANS_SERIF you can use:
DEFAULTDEFAULT_BOLDMONOSPACESANS_SERIFSERIFAnd where ITALIC you can use:
BOLDBOLD_ITALICITALICNORMALAll is stated on Android Developers
For android-studio 3 and above you can use this style and then all textView font change in app.
create this style in your style.xml :
<!--OverRide all textView font-->
<style name="defaultTextViewStyle" parent="android:Widget.TextView">
        <item name="android:fontFamily">@font/your_custom_font</item>
</style>
Then use it in your theme :
<!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="android:textViewStyle">@style/defaultTextViewStyle</item>
    </style>
I am using excellent library Calligraphy by Chris Jenx designed to allow you to use custom fonts in your android application. Give it a try!
I had to parse /system/etc/fonts.xml in a recent project. Here are the current font families as of Lollipop:
╔════╦════════════════════════════╦═════════════════════════════╗
║    ║ FONT FAMILY                ║ TTF FILE                    ║
╠════╬════════════════════════════╬═════════════════════════════╣
║  1 ║ casual                     ║ ComingSoon.ttf              ║
║  2 ║ cursive                    ║ DancingScript-Regular.ttf   ║
║  3 ║ monospace                  ║ DroidSansMono.ttf           ║
║  4 ║ sans-serif                 ║ Roboto-Regular.ttf          ║
║  5 ║ sans-serif-black           ║ Roboto-Black.ttf            ║
║  6 ║ sans-serif-condensed       ║ RobotoCondensed-Regular.ttf ║
║  7 ║ sans-serif-condensed-light ║ RobotoCondensed-Light.ttf   ║
║  8 ║ sans-serif-light           ║ Roboto-Light.ttf            ║
║  9 ║ sans-serif-medium          ║ Roboto-Medium.ttf           ║
║ 10 ║ sans-serif-smallcaps       ║ CarroisGothicSC-Regular.ttf ║
║ 11 ║ sans-serif-thin            ║ Roboto-Thin.ttf             ║
║ 12 ║ serif                      ║ NotoSerif-Regular.ttf       ║
║ 13 ║ serif-monospace            ║ CutiveMono.ttf              ║
╚════╩════════════════════════════╩═════════════════════════════╝
Here is the parser (based off FontListParser):
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import android.util.Xml;
/**
 * Helper class to get the current font families on an Android device.</p>
 * 
 * Usage:</p> {@code List<SystemFont> fonts = FontListParser.safelyGetSystemFonts();}</p>
 */
public final class FontListParser {
    private static final File FONTS_XML = new File("/system/etc/fonts.xml");
    private static final File SYSTEM_FONTS_XML = new File("/system/etc/system_fonts.xml");
    public static List<SystemFont> getSystemFonts() throws Exception {
        String fontsXml;
        if (FONTS_XML.exists()) {
            fontsXml = FONTS_XML.getAbsolutePath();
        } else if (SYSTEM_FONTS_XML.exists()) {
            fontsXml = SYSTEM_FONTS_XML.getAbsolutePath();
        } else {
            throw new RuntimeException("fonts.xml does not exist on this system");
        }
        Config parser = parse(new FileInputStream(fontsXml));
        List<SystemFont> fonts = new ArrayList<>();
        for (Family family : parser.families) {
            if (family.name != null) {
                Font font = null;
                for (Font f : family.fonts) {
                    font = f;
                    if (f.weight == 400) {
                        break;
                    }
                }
                SystemFont systemFont = new SystemFont(family.name, font.fontName);
                if (fonts.contains(systemFont)) {
                    continue;
                }
                fonts.add(new SystemFont(family.name, font.fontName));
            }
        }
        for (Alias alias : parser.aliases) {
            if (alias.name == null || alias.toName == null || alias.weight == 0) {
                continue;
            }
            for (Family family : parser.families) {
                if (family.name == null || !family.name.equals(alias.toName)) {
                    continue;
                }
                for (Font font : family.fonts) {
                    if (font.weight == alias.weight) {
                        fonts.add(new SystemFont(alias.name, font.fontName));
                        break;
                    }
                }
            }
        }
        if (fonts.isEmpty()) {
            throw new Exception("No system fonts found.");
        }
        Collections.sort(fonts, new Comparator<SystemFont>() {
            @Override
            public int compare(SystemFont font1, SystemFont font2) {
                return font1.name.compareToIgnoreCase(font2.name);
            }
        });
        return fonts;
    }
    public static List<SystemFont> safelyGetSystemFonts() {
        try {
            return getSystemFonts();
        } catch (Exception e) {
            String[][] defaultSystemFonts = {
                    {
                            "cursive", "DancingScript-Regular.ttf"
                    }, {
                            "monospace", "DroidSansMono.ttf"
                    }, {
                            "sans-serif", "Roboto-Regular.ttf"
                    }, {
                            "sans-serif-light", "Roboto-Light.ttf"
                    }, {
                            "sans-serif-medium", "Roboto-Medium.ttf"
                    }, {
                            "sans-serif-black", "Roboto-Black.ttf"
                    }, {
                            "sans-serif-condensed", "RobotoCondensed-Regular.ttf"
                    }, {
                            "sans-serif-thin", "Roboto-Thin.ttf"
                    }, {
                            "serif", "NotoSerif-Regular.ttf"
                    }
            };
            List<SystemFont> fonts = new ArrayList<>();
            for (String[] names : defaultSystemFonts) {
                File file = new File("/system/fonts", names[1]);
                if (file.exists()) {
                    fonts.add(new SystemFont(names[0], file.getAbsolutePath()));
                }
            }
            return fonts;
        }
    }
    /* Parse fallback list (no names) */
    public static Config parse(InputStream in) throws XmlPullParserException, IOException {
        try {
            XmlPullParser parser = Xml.newPullParser();
            parser.setInput(in, null);
            parser.nextTag();
            return readFamilies(parser);
        } finally {
            in.close();
        }
    }
    private static Alias readAlias(XmlPullParser parser) throws XmlPullParserException, IOException {
        Alias alias = new Alias();
        alias.name = parser.getAttributeValue(null, "name");
        alias.toName = parser.getAttributeValue(null, "to");
        String weightStr = parser.getAttributeValue(null, "weight");
        if (weightStr == null) {
            alias.weight = 0;
        } else {
            alias.weight = Integer.parseInt(weightStr);
        }
        skip(parser); // alias tag is empty, ignore any contents and consume end tag
        return alias;
    }
    private static Config readFamilies(XmlPullParser parser) throws XmlPullParserException,
            IOException {
        Config config = new Config();
        parser.require(XmlPullParser.START_TAG, null, "familyset");
        while (parser.next() != XmlPullParser.END_TAG) {
            if (parser.getEventType() != XmlPullParser.START_TAG) {
                continue;
            }
            if (parser.getName().equals("family")) {
                config.families.add(readFamily(parser));
            } else if (parser.getName().equals("alias")) {
                config.aliases.add(readAlias(parser));
            } else {
                skip(parser);
            }
        }
        return config;
    }
    private static Family readFamily(XmlPullParser parser) throws XmlPullParserException,
            IOException {
        String name = parser.getAttributeValue(null, "name");
        String lang = parser.getAttributeValue(null, "lang");
        String variant = parser.getAttributeValue(null, "variant");
        List<Font> fonts = new ArrayList<Font>();
        while (parser.next() != XmlPullParser.END_TAG) {
            if (parser.getEventType() != XmlPullParser.START_TAG) {
                continue;
            }
            String tag = parser.getName();
            if (tag.equals("font")) {
                String weightStr = parser.getAttributeValue(null, "weight");
                int weight = weightStr == null ? 400 : Integer.parseInt(weightStr);
                boolean isItalic = "italic".equals(parser.getAttributeValue(null, "style"));
                String filename = parser.nextText();
                String fullFilename = "/system/fonts/" + filename;
                fonts.add(new Font(fullFilename, weight, isItalic));
            } else {
                skip(parser);
            }
        }
        return new Family(name, fonts, lang, variant);
    }
    private static void skip(XmlPullParser parser) throws XmlPullParserException, IOException {
        int depth = 1;
        while (depth > 0) {
            switch (parser.next()) {
            case XmlPullParser.START_TAG:
                depth++;
                break;
            case XmlPullParser.END_TAG:
                depth--;
                break;
            }
        }
    }
    private FontListParser() {
    }
    public static class Alias {
        public String name;
        public String toName;
        public int weight;
    }
    public static class Config {
        public List<Alias> aliases;
        public List<Family> families;
        Config() {
            families = new ArrayList<Family>();
            aliases = new ArrayList<Alias>();
        }
    }
    public static class Family {
        public List<Font> fonts;
        public String lang;
        public String name;
        public String variant;
        public Family(String name, List<Font> fonts, String lang, String variant) {
            this.name = name;
            this.fonts = fonts;
            this.lang = lang;
            this.variant = variant;
        }
    }
    public static class Font {
        public String fontName;
        public boolean isItalic;
        public int weight;
        Font(String fontName, int weight, boolean isItalic) {
            this.fontName = fontName;
            this.weight = weight;
            this.isItalic = isItalic;
        }
    }
    public static class SystemFont {
        public String name;
        public String path;
        public SystemFont(String name, String path) {
            this.name = name;
            this.path = path;
        }
    }
}
Feel free to use the above class in your project. For example, you could give your users a selection of font families and set the typeface based on their preference.
A small incomplete example:
final List<FontListParser.SystemFont> fonts = FontListParser.safelyGetSystemFonts();
String[] items = new String[fonts.size()];
for (int i = 0; i < fonts.size(); i++) {
    items[i] = fonts.get(i).name;
}
new AlertDialog.Builder(this).setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        FontListParser.SystemFont selectedFont = fonts.get(which);
        // TODO: do something with the font
        Toast.makeText(getApplicationContext(), selectedFont.path, Toast.LENGTH_LONG).show();
    }
}).show();
What you want is not possible. You must need to set TypeFace in your Code.
In XML what you can do is 
android:typeface="sans" | "serif" | "monospace"
other then this you can not play much with the Fonts in XML. :)
For Arial you need to set type face in your code.
To set the font by program, write...
     TextView tv7 = new TextView(this);
     tv7.setText(" TIME ");    
     tv7.setTypeface(Typeface.create("sans-serif-condensed",Typeface.BOLD));
     tv7.setTextSize(12);
     tbrow.addView(tv7);
The name "sans-serif-condensed" is referenced from fonts.xml file which should be created in app--> res--> values folder and it holds the fonts in it.
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="font_family_light">sans-serif-light</string>
    <string name="font_family_medium">sans-serif-medium</string>
    <string name="font_family_regular">sans-serif</string>
    <string name="font_family_condensed">sans-serif-condensed</string>
    <string name="font_family_black">sans-serif-black</string>
    <string name="font_family_thin">sans-serif-thin</string>
</resources>
Hope this is clear!