最近有需求仿微信控制字型大小，想了半天查了很多資料，想先把功能實現了再說

public class MyApplication extends MultiDexApplication implements Application.ActivityLifecycleCallbacks{//實現該介面

    private static MyApplication application;
    private List<Activity> activityList;
    private float fontScale;

    @Override
    public void onCreate() {
        super.onCreate();
        application = this;
        fontScale = getFontScale();
        //註冊
        registerActivityLifecycleCallbacks(this);
    }


    public static Context getContext() {
        return application.getApplicationContext();
    }

    //獲取設定字型大小值
    public static float getFontScale() {
        float fontScale = 1.0f;
        if (application != null) {
            fontScale = (float) SharedPreferencesUtils.get(getContext(),"fontScale", 1.0f);
        }
        return fontScale;
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle bundle) {
        if(activityList == null){
            activityList = new ArrayList<>();
        }
        // 禁止字型大小隨系統設定變化
        Resources resources = activity.getResources();
        if (resources != null && resources.getConfiguration().fontScale != fontScale) {
            android.content.res.Configuration configuration = resources.getConfiguration();
            configuration.fontScale = fontScale;
            //設定大小
            resources.updateConfiguration(configuration, resources.getDisplayMetrics());
        }
        activityList.add(activity);
    }

    @Override
    public void onActivityStarted(Activity activity) {

    }

    @Override
    public void onActivityResumed(Activity activity) {

    }

    @Override
    public void onActivityPaused(Activity activity) {

    }

    @Override
    public void onActivityStopped(Activity activity) {

    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {

    }

    @Override
    public void onActivityDestroyed(Activity activity) {
        if(activityList != null){
            activityList.remove(activity);
        }
    }
    
    //呼叫該方法即可
    public static void setAppFontSize(float fontScale,Activity context) {
        if (application != null) {
            List<Activity> activityList = application.activityList;
            if (activityList != null) {
                for (Activity activity : activityList) {
                    //當前頁面設定重啟會閃黑屏
                    if (activity instanceof SetActivity) {
                        continue;
                    }
                    Resources resources = activity.getResources();
                    if (resources != null) {
                        android.content.res.Configuration configuration = resources.getConfiguration();
                        configuration.fontScale = fontScale;
                        resources.updateConfiguration(configuration, resources.getDisplayMetrics());
                        activity.recreate();
                        if (fontScale != application.fontScale) {
                            application.fontScale = fontScale;
                               //儲存設定後的字型大小
                            SharedPreferencesUtils.put(getContext(),"fontScale", fontScale);
                        }
                    }
                }
            }
        }
    }
}
 

以上是application中的用法，先implements Application.ActivityLifecycleCallbacks，註冊後獲取儲存的字型大小，然後進行設定即可

調整字型大小的控制元件：點選下載