private void setTypefaceFromAttrs(String familyName, int typefaceIndex, int styleIndex) {    Typeface tf = null;    if (familyName != null) {      tf = Typeface.create(familyName, styleIndex);      if (tf != null) {        setTypeface(tf);        return;      }    }    switch (typefaceIndex) {      case SANS:        tf = Typeface.SANS_SERIF;        break;      case SERIF:        tf = Typeface.SERIF;        break;      case MONOSPACE:        tf = Typeface.MONOSPACE;        break;    }    setTypeface(tf, styleIndex);  }

AssetManager mgr = getAssets();Typeface tf = Typeface.createFromAsset(mgr, "fonts/NotoSansCJKsc-Black.otf");tv_1.setTypeface(tf);

public class CustomTextView extends TextView{  public CustomTextView(Context context, AttributeSet attrs)  {    super(context, attrs);  }  //重寫設置字體方法  @Override  public void setTypeface(Typeface tf)  {    tf = Typeface.createFromAsset(getContext().getAssets(), "fonts/NotoSansCJKsc-Light.otf");    super.setTypeface(tf);  }}

  <com.test.fontfamily.CustomTextView    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:padding="6dp"    android:text="自定義字體"    android:textSize="24dp"    />

package com.test.fontfamily;import android.app.Application;import android.content.Context;import android.graphics.Typeface;import android.support.annotation.NonNull;import android.view.View;import android.view.ViewGroup;import android.widget.TextView;import java.lang.ref.SoftReference;import java.lang.reflect.Field;import java.util.HashMap;import java.util.Map;/** * Created by Administrator on 2017/10/24. */public class FontUtils{  private static final String TAG = FontUtils.class.getSimpleName();  private Map<String, SoftReference<Typeface>> mCache = new HashMap<>();  private static FontUtils sSingleton = null;  public static Typeface DEFAULT = Typeface.DEFAULT;  // disable instantiate  private FontUtils()  {  }  public static FontUtils getInstance()  {    // double check    if (sSingleton == null)    {      synchronized (FontUtils.class)      {        if (sSingleton == null)        {          sSingleton = new FontUtils();        }      }    }    return sSingleton;  }  /**   * <p>Replace the font of specified view and it's children</p>   *   * @param root   The root view.   * @param fontPath font file path relative to 'assets' directory.   */  public void replaceFontFromAsset(@NonNull View root, @NonNull String fontPath)  {    replaceFont(root, createTypefaceFromAsset(root.getContext(), fontPath));  }  /**   * <p>Replace the font of specified view and it's children</p>   *   * @param root   The root view.   * @param fontPath font file path relative to 'assets' directory.   * @param style  One of {@link Typeface#NORMAL}, {@link Typeface#BOLD}, {@link Typeface#ITALIC}, {@link Typeface#BOLD_ITALIC}   */  public void replaceFontFromAsset(@NonNull View root, @NonNull String fontPath, int style)  {    replaceFont(root, createTypefaceFromAsset(root.getContext(), fontPath), style);  }  /**   * <p>Replace the font of specified view and it's children</p>   *   * @param root   The root view.   * @param fontPath The full path to the font data.   */  public void replaceFontFromFile(@NonNull View root, @NonNull String fontPath)  {    replaceFont(root, createTypefaceFromFile(fontPath));  }  /**   * <p>Replace the font of specified view and it's children</p>   *   * @param root   The root view.   * @param fontPath The full path to the font data.   * @param style  One of {@link Typeface#NORMAL}, {@link Typeface#BOLD}, {@link Typeface#ITALIC}, {@link Typeface#BOLD_ITALIC}   */  public void replaceFontFromFile(@NonNull View root, @NonNull String fontPath, int style)  {    replaceFont(root, createTypefaceFromFile(fontPath), style);  }  /**   * <p>Replace the font of specified view and it's children with specified typeface</p>   */  private void replaceFont(@NonNull View root, @NonNull Typeface typeface)  {    if (root == null || typeface == null)    {      return;    }    if (root instanceof TextView)    { // If view is TextView or it's subclass, replace it's font      TextView textView = (TextView) root;      // Extract previous style of TextView      int style = Typeface.NORMAL;      if (textView.getTypeface() != null)      {        style = textView.getTypeface().getStyle();      }      textView.setTypeface(typeface, style);    } else if (root instanceof ViewGroup)    { // If view is ViewGroup, apply this method on it's child views      ViewGroup viewGroup = (ViewGroup) root;      for (int i = 0; i < viewGroup.getChildCount(); ++i)      {        replaceFont(viewGroup.getChildAt(i), typeface);      }    } // else return  }  /**   * <p>Replace the font of specified view and it's children with specified typeface and text style</p>   *   * @param style One of {@link Typeface#NORMAL}, {@link Typeface#BOLD}, {@link Typeface#ITALIC}, {@link Typeface#BOLD_ITALIC}   */  private void replaceFont(@NonNull View root, @NonNull Typeface typeface, int style)  {    if (root == null || typeface == null)    {      return;    }    if (style < 0 || style > 3)    {      style = Typeface.NORMAL;    }    if (root instanceof TextView)    { // If view is TextView or it's subclass, replace it's font      TextView textView = (TextView) root;      textView.setTypeface(typeface, style);    } else if (root instanceof ViewGroup)    { // If view is ViewGroup, apply this method on it's child views      ViewGroup viewGroup = (ViewGroup) root;      for (int i = 0; i < viewGroup.getChildCount(); ++i)      {        replaceFont(viewGroup.getChildAt(i), typeface, style);      }    } // else return  }  /**   * <p>Create a Typeface instance with specified font file</p>   *   * @param fontPath font file path relative to 'assets' directory.   * @return Return created typeface instance.   */  private Typeface createTypefaceFromAsset(Context context, String fontPath)  {    SoftReference<Typeface> typefaceRef = mCache.get(fontPath);    Typeface typeface = null;    if (typefaceRef == null || (typeface = typefaceRef.get()) == null)    {      typeface = Typeface.createFromAsset(context.getAssets(), fontPath);      typefaceRef = new SoftReference<>(typeface);      mCache.put(fontPath, typefaceRef);    }    return typeface;  }  private Typeface createTypefaceFromFile(String fontPath)  {    SoftReference<Typeface> typefaceRef = mCache.get(fontPath);    Typeface typeface = null;    if (typefaceRef == null || (typeface = typefaceRef.get()) == null)    {      typeface = Typeface.createFromFile(fontPath);      typefaceRef = new SoftReference<>(typeface);      mCache.put(fontPath, typefaceRef);    }    return typeface;  }  /**   * <p>Replace system default font. <b>Note:</b>you should also add code below to your app theme in styles.xml. </p>   * {@code <item name="android:typeface">monospace</item>}   * <p>The best place to call this method is {@link Application#onCreate()}, it will affect   * whole app font.If you call this method after view is visible, you need to invalid the view to make it effective.</p>   *   * @param context {@link Context Context}   * @param fontPath font file path relative to 'assets' directory.   */  public void replaceSystemDefaultFontFromAsset(@NonNull Context context, @NonNull String fontPath)  {    replaceSystemDefaultFont(createTypefaceFromAsset(context, fontPath));  }  /**   * <p>Replace system default font. <b>Note:</b>you should also add code below to your app theme in styles.xml. </p>   * {@code <item name="android:typeface">monospace</item>}   * <p>The best place to call this method is {@link Application#onCreate()}, it will affect   * whole app font.If you call this method after view is visible, you need to invalid the view to make it effective.</p>   *   * @param context {@link Context Context}   * @param fontPath The full path to the font data.   */  public void replaceSystemDefaultFontFromFile(@NonNull Context context, @NonNull String fontPath)  {    replaceSystemDefaultFont(createTypefaceFromFile(fontPath));  }  /**   * <p>Replace system default font. <b>Note:</b>you should also add code below to your app theme in styles.xml. </p>   * {@code <item name="android:typeface">monospace</item>}   * <p>The best place to call this method is {@link Application#onCreate()}, it will affect   * whole app font.If you call this method after view is visible, you need to invalid the view to make it effective.</p>   */  private void replaceSystemDefaultFont(@NonNull Typeface typeface)  {    modifyObjectField(null, "MONOSPACE", typeface);  }  private void modifyObjectField(Object obj, String fieldName, Object value)  {    try    {      Field defaultField = Typeface.class.getDeclaredField(fieldName);      defaultField.setAccessible(true);      defaultField.set(obj, value);    } catch (NoSuchFieldException e)    {      e.printStackTrace();    } catch (IllegalAccessException e)    {      e.printStackTrace();    }  }}

FontUtils.getInstance().replaceFontFromAsset(View root, String fontPath)

FontUtils.getInstance().replaceSystemDefaultFontFromAsset(this,"fonts/NotoSansCJKsc-Thin.otf");

<item name="android:typeface">monospace</item>