Android 修改字体样式，看这篇就够了

Android 默认字体为「思源黑体」，英文名：Noto Sans

英文字体：Roboto 字体

修改字体步骤：

1.单独设置字体样式

（1）Android系统提供了几种字体样式可供选择

通过设置typeface属性或者fontFamily属性设置
typeface属性：

normal
serif
sans
monospace

fontFamily属性：

casual
cursive
serif
monospace
sans-serif
sans-serif-condensed
serif-monospace
sans-serif-smallcaps

※typeface和fontFamily区别

android:typeface属性是增加API1
android:fontFamily在API16（4.1）中添加了属性

※当同时设置typeface和fontFamily时，只有fontFamily生效

查看一波TextView的源码

    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);}

从方法setTypefaceFromAttrs()看，如果你有set fontFamily属性，那么typefaceattribute将被忽略。

这边会发现这样设置typeface和fontFamily属性对中文不生效，这时候就需要引用外部的字体样式（这里谷歌设计规范推荐使用NOTO字体https://www.google.com/get/noto/）

2）使用字体样式文件设置(otf，ttf文件都可以)

在assets下新建一个fonts文件，把字体样式文件放进去

在代码中设置

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

2.批量设置字体样式

（1）自定义TextView

public class CustomTextView extends TextView
{public CustomTextView(Context context, AttributeSet attrs){super(context, attrs);}//重写设置字体方法@Overridepublic void setTypeface(Typeface tf){tf = Typeface.createFromAsset(getContext().getAssets(), "fonts/NotoSansCJKsc-Light.otf");super.setTypeface(tf);}
}

之后在XML布局文件中使用CustomTextView代替TextView

    <com.test.fontfamily.CustomTextViewandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:padding="6dp"android:text="自定义字体"android:textSize="24dp"/>

（2）更换整个App的字体

思路：遍历找到所有的TextView然后替换字体
百度了一下找到下面工具类

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 instantiateprivate FontUtils(){}public static FontUtils getInstance(){// double checkif (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 fontTextView textView = (TextView) root;// Extract previous style of TextViewint 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 viewsViewGroup 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 fontTextView textView = (TextView) root;textView.setTypeface(typeface, style);} else if (root instanceof ViewGroup){ // If view is ViewGroup, apply this method on it's child viewsViewGroup 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();}}
}

阅读源码发现这里面主要方法有

replaceFont()

替换一个页面中的所有字体
用递归的方式去查找view是否是TextView或者TextView的子类，然后进行替换
不过这种方法效率不高
用法：
在页面中
FontUtils.getInstance().replaceFontFromAsset(View root, String fontPath)

modifyObjectField()

替换App所有字体
利用反射替换系统默认字体
用法：
a.新建一个BaseApplication继承Application在onCreate方法中
FontUtils.getInstance().replaceSystemDefaultFontFromAsset(this,"fonts/NotoSansCJKsc-Thin.otf");
b.在AppTheme中添加
<item name="android:typeface">monospace</item>
c.清单文件中使用BaseApplication