修改android系统默认字体大小

android系统字体大小在“设置” 中“显示”中“字体大小”设置，一共提四种等级设置：小 、普通 、 大、 超大

四种等级选择相应配置代码位置

packages/apps/setttings/res/values/arrays.xml

<string-array name="entries_font_size">
        <item msgid="6490061470416867723">Small</item>
        <item msgid="3579015730662088893">Normal</item>
        <item msgid="1678068858001018666">Large</item>
        <item msgid="490158884605093126">Huge</item>
    </string-array>

    <string-array name="entryvalues_font_size" translatable="false">
        <item>0.85</item>
        <item>1.0</item>
        <item>1.15</item>
        <item>1.30</item>
    </string-array>

以上配置是通过如下代码加载后供给终端用户选择
packages/app/settings/DisplaySettings.java

public void readFontSizePreference(ListPreference pref) {
        try {
            mCurConfig.updateFrom(ActivityManagerNative.getDefault().getConfiguration());
        } catch (RemoteException e) {
            Log.w(TAG, "Unable to retrieve font size");
        }

        // mark the appropriate item in the preferences list
        int index = floatToIndex(mCurConfig.fontScale);
        pref.setValueIndex(index);

        // report the current size in the summary text
        final Resources res = getResources();
        String[] fontSizeNames = res.getStringArray(R.array.entries_font_size);
        pref.setSummary(String.format(res.getString(R.string.summary_font_size),
                fontSizeNames[index]));
    }

在frameworks层会对系统的字体大小设置一个默认值，字体放缩比例为1，也就是对应显示设置中的“普通”字体

frameworks/base/core/java/android/content/res/Configuration.java

/**
     * Set this object to the system defaults.
     */
    public void setToDefaults() {
        fontScale = 1; //此处赋值为默认字体的放缩比例
        mcc = mnc = 0;
        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;
        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;
        seq = 0;
    }