Androidで画像を使わずにオシャレなアイコンを簡単に表示する方法（Font Awesome） ref: http://qiita.com/AbeHaruhiko/items/a7437027231a373acf2a

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CustomFontButton">
        <attr name="customFont" format="string"/>
    </declare-styleable>
</resources>

CachedTypefaces.java

import android.content.Context;
import android.graphics.Typeface;
import android.util.Log;

import java.util.Hashtable;

public class CachedTypefaces {
    private static final String TAG = "CachedTypefaces";

    private static final Hashtable<String, Typeface> cache = new Hashtable<String, Typeface>();

    public static Typeface get(Context context, String assetPath) {
        synchronized (cache) {
            if (!cache.containsKey(assetPath)) {
                try {
                    Typeface t = Typeface.createFromAsset(context.getAssets(), assetPath);
                    cache.put(assetPath, t);
                } catch (Exception e) {
                    Log.e(TAG, "Could not get typeface '" + assetPath + "' because " + e.getMessage());
                    return null;
                }
            }
            return cache.get(assetPath);
        }
    }
}

CustomFontButton.java

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.Button;
import android.widget.TextView;

import jp.caliconography.android.util.CachedTypefaces;

public class CustomFontButton extends Button {
    private static final String TAG = "CustomFontButton";

    public CustomFontButton(Context context) {
        super(context);
    }

    public CustomFontButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        setCustomFont(context, attrs);
    }

    public CustomFontButton(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        setCustomFont(context, attrs);
    }

    private void setCustomFont(Context ctx, AttributeSet attrs) {
        TypedArray a = ctx.obtainStyledAttributes(attrs, R.styleable.CustomFontTextView);
        String customFont = a.getString(R.styleable.CustomFontTextView_customFont);
        setCustomFont(ctx, customFont);
        a.recycle();
    }

    public boolean setCustomFont(Context context, String asset) {
        Typeface tf = null;
        try {
            // ここでフォントファイル読み込み。
            // 読み込み済みならキャッシュから。
            tf = CachedTypefaces.get(context, asset);
        } catch (Exception e) {
            Log.e(TAG, "Could not get typeface: " + e.getMessage());
            return false;
        }

        setTypeface(tf);
        return true;
    }
}

main_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:myapp="http://schemas.android.com/apk/res-auto"
    <!-- ↑xmlnsの追加を忘れずに！ -->

    android:id="@+id/LinearLayout01"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <your.app.package.CustomFontButton
        android:id="@+id/btnSomething"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="&#xf040;"
        android:textSize="30sp"
        android:textColor="#666"
        myapp:customFont="fontawesome-webfont.ttf"
        android:onClick="onClickSomething"/>

</LinearLayout>