Android 字号

TextView 字号设置

TextView

private void setTextSizeInternal(int unit, float size, boolean shouldRequestLayout) {
    mTextSizeUnit = unit;
    setRawTextSize(TypedValue.applyDimension(unit, size, getDisplayMetricsOrSystem()),
            shouldRequestLayout);
}

TypedValue

如果 unit 标志位是 COMPLEX_UNIT_SP，转化成 dp 值，递归调用自身，并把COMPLEX_UNIT_SP标志为改成COMPLEX_UNIT_DIP

public static float applyDimension(@ComplexDimensionUnit int unit, float value,
                                   DisplayMetrics metrics)
{
    switch (unit) {
        case COMPLEX_UNIT_PX:
            return value;
        case COMPLEX_UNIT_DIP:
            return value * metrics.density;
        case COMPLEX_UNIT_SP:
            if (metrics.fontScaleConverter != null) {
                return applyDimension(
                        COMPLEX_UNIT_DIP,
                        metrics.fontScaleConverter.convertSpToDp(value),
                        metrics);
            } else {
                return value * metrics.scaledDensity;
            }
        case COMPLEX_UNIT_PT:
            return value * metrics.xdpi * INCHES_PER_PT;
        case COMPLEX_UNIT_IN:
            return value * metrics.xdpi;
        case COMPLEX_UNIT_MM:
            return value * metrics.xdpi * INCHES_PER_MM;
    }
    return 0;
}

FontScaleConverter 初始化

ResourcesImpl

FontScaleConverterFactory 静态加载不同档位的缩放倍率， 收到 configuration 的时候会根据实际的 fontscale 插值计算一套合适的倍率

public void updateConfiguration(Configuration config, DisplayMetrics metrics,
                                CompatibilityInfo compat) {
    // ......

    if (mConfiguration.densityDpi != Configuration.DENSITY_DPI_UNDEFINED) {
        mMetrics.densityDpi = mConfiguration.densityDpi;
        mMetrics.density =
                mConfiguration.densityDpi * DisplayMetrics.DENSITY_DEFAULT_SCALE;
    }
    mMetrics.scaledDensity = mMetrics.density *
            (mConfiguration.fontScale != 0 ? mConfiguration.fontScale : 1.0f);
    mMetrics.fontScaleConverter =
            FontScaleConverterFactory.forScale(mConfiguration.fontScale);

    // ......
}

原始数据：

计算方法：AOSPA/android_frameworks_base