Android 10 修改系统默认的字体大小

代码路径：
frameworks/base/core/java/android/content/res/Configuration.java
frameworks/base/ packages/SettingsProvider/res/values/defaults.xml
frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
方法一：在Configuration.java文件中修改字体大小
在Configuration.java文件中setToDefaults() 这个方法中将fontScale修改为1.5

    public void setToDefaults() {
        fontScale = 1;
        mcc = mnc = 0;
        mLocaleList = LocaleList.getEmptyLocaleList();
        locale = null;
        userSetLocale = false;
        touchscreen = TOUCHSCREEN_UNDEFINED;
        keyboard = KEYBOARD_UNDEFINED;
        keyboardHidden = KEYBOARDHIDDEN_UNDEFINED;
        hardKeyboardHidden = HARDKEYBOARDHIDDEN_UNDEFINED;
        navigation = NAVIGATION_UNDEFINED;
        navigationHidden = NAVIGATIONHIDDEN_UNDEFINED;
        orientation = ORIENTATION_UNDEFINED;
        screenLayout = SCREENLAYOUT_UNDEFINED;
        colorMode = COLOR_MODE_UNDEFINED;
        uiMode = UI_MODE_TYPE_UNDEFINED;
        screenWidthDp = compatScreenWidthDp = SCREEN_WIDTH_DP_UNDEFINED;
        screenHeightDp = compatScreenHeightDp = SCREEN_HEIGHT_DP_UNDEFINED;
        smallestScreenWidthDp = compatSmallestScreenWidthDp = SMALLEST_SCREEN_WIDTH_DP_UNDEFINED;
        densityDpi = DENSITY_DPI_UNDEFINED;
        assetsSeq = ASSETS_SEQ_UNDEFINED;
        seq = 0;
        windowConfiguration.setToDefaults();
    }

Settings中系统的字体大小，在/packages/apps/Settings/res/values/arrays.xml文件中的，”entryvalues_font_size”这个tag中分别有定义对应的数值

        0.85
        1.0
        1.15
        1.30
    

方法二：在SettingsProvider应用中修改字体大小
1、在defaults.xml文件中定义一个字体大小

 120%

2、在DatabaseHelper.java文件中loadSystemSettings()方法中设置默认字体大小

private void loadSystemSettings(SQLiteDatabase db) {
        SQLiteStatement stmt = null;
        try {
            stmt = db.compileStatement("INSERT OR IGNORE INTO system(name,value)"
                    + " VALUES(?,?);");

            loadBooleanSetting(stmt, Settings.System.DIM_SCREEN,
                    R.bool.def_dim_screen);
            loadIntegerSetting(stmt, Settings.System.SCREEN_OFF_TIMEOUT,
                    R.integer.def_screen_off_timeout);

            // Set default cdma DTMF type
            loadSetting(stmt, Settings.System.DTMF_TONE_TYPE_WHEN_DIALING, 0);

            // Set default hearing aid
            loadSetting(stmt, Settings.System.HEARING_AID, 0);
            // Set default tty mode
            loadSetting(stmt, Settings.System.TTY_MODE, 0);

            loadIntegerSetting(stmt, Settings.System.SCREEN_BRIGHTNESS,
                    R.integer.def_screen_brightness);

            loadIntegerSetting(stmt, Settings.System.SCREEN_BRIGHTNESS_FOR_VR,
                    com.android.internal.R.integer.config_screenBrightnessForVrSettingDefault);

            loadBooleanSetting(stmt, Settings.System.SCREEN_BRIGHTNESS_MODE,
                    R.bool.def_screen_brightness_automatic_mode);

            loadBooleanSetting(stmt, Settings.System.ACCELEROMETER_ROTATION,
                    R.bool.def_accelerometer_rotation);

            loadDefaultHapticSettings(stmt);

            loadBooleanSetting(stmt, Settings.System.NOTIFICATION_LIGHT_PULSE,
                    R.bool.def_notification_pulse);

            loadUISoundEffectsSettings(stmt);

            loadIntegerSetting(stmt, Settings.System.POINTER_SPEED,
                    R.integer.def_pointer_speed);

            // UNISOC:Bug 1001981  add navigation bar feature support for multil users @{
            // set default navigation bar values.
            loadIntegerSetting(stmt, Settings.System.NAVIGATION_BAR_CONFIG,
                    R.integer.def_navigation_bar_config);
            loadIntegerSetting(stmt, Settings.System.NAVIGATION_BAR_SHOW,
                    R.integer.def_navigation_bar_show);
			loadFractionSetting(stmt, Settings.System.FONT_SCALE, R.fraction.def_font_scale, 1);		
            
            
        } finally {
            if (stmt != null) stmt.close();
        }
    }

用命令控制字体大小

Settings.System.FONT_SCALE
adb shell settings put system font_scale 1.2