Android——build.prop 解析
16lz
2021-12-04
一.概念
在Android设备shell终端可以看到/system目录下的build.prop文件,Android的build.prop文件是在Android编译时刻收集的各种property(LCD density/语言/编译时间, etc.),编译完成之后,文件生成在out/target/product/<board>/system/目录下。在Android运行时刻可以通过property_get()[c/c++域] / SystemProperties_get*()[Java域]读取这些属性值,参考Android——SystemProperties的应用
二.生成
build.prop的生成是由make系统解析build/core/Makefile完成:
BUILDINFO_SH := build/tools/buildinfo.sh$(INSTALLED_BUILD_PROP_TARGET): $(BUILDINFO_SH) $(INTERNAL_BUILD_ID_MAKEFILE) $(BUILD_SYSTEM)/version_defaults.mk $(wildcard $(TARGET_DEVICE_DIR)/system.prop)@echo Target buildinfo: $@@mkdir -p $(dir $@)$(hide) TARGET_BUILD_TYPE="$(TARGET_BUILD_VARIANT)" \TARGET_DEVICE="$(TARGET_DEVICE)" \PRODUCT_NAME="$(TARGET_PRODUCT)" \PRODUCT_BRAND="$(PRODUCT_BRAND)" \PRODUCT_DEFAULT_LANGUAGE="$(call default-locale-language,$(PRODUCT_LOCALES))" \PRODUCT_DEFAULT_REGION="$(call default-locale-region,$(PRODUCT_LOCALES))" \PRODUCT_DEFAULT_WIFI_CHANNELS="$(PRODUCT_DEFAULT_WIFI_CHANNELS)" \PRODUCT_MODEL="$(PRODUCT_MODEL)" \PRODUCT_MANUFACTURER="$(PRODUCT_MANUFACTURER)" \PRIVATE_BUILD_DESC="$(PRIVATE_BUILD_DESC)" \BUILD_ID="$(BUILD_ID)" \BUILD_DISPLAY_ID="$(BUILD_DISPLAY_ID)" \BUILD_NUMBER="$(BUILD_NUMBER)" \PLATFORM_VERSION="$(PLATFORM_VERSION)" \PLATFORM_SDK_VERSION="$(PLATFORM_SDK_VERSION)" \PLATFORM_VERSION_CODENAME="$(PLATFORM_VERSION_CODENAME)" \BUILD_VERSION_TAGS="$(BUILD_VERSION_TAGS)" \TARGET_BOOTLOADER_BOARD_NAME="$(TARGET_BOOTLOADER_BOARD_NAME)" \BUILD_FINGERPRINT="$(BUILD_FINGERPRINT)" \TARGET_BOARD_PLATFORM="$(TARGET_BOARD_PLATFORM)" \TARGET_CPU_ABI="$(TARGET_CPU_ABI)" \TARGET_CPU_ABI2="$(TARGET_CPU_ABI2)" \TARGET_AAPT_CHARACTERISTICS="$(TARGET_AAPT_CHARACTERISTICS)" \ bash $(BUILDINFO_SH) > $@$(hide) if [ -f $(TARGET_DEVICE_DIR)/system.prop ]; then \ cat $(TARGET_DEVICE_DIR)/system.prop >> $@; \ fi$(if $(ADDITIONAL_BUILD_PROPERTIES), \$(hide) echo >> $@; \ echo "#" >> $@; \ echo "# ADDITIONAL_BUILD_PROPERTIES" >> $@; \ echo "#" >> $@; )$(hide) $(foreach line,$(ADDITIONAL_BUILD_PROPERTIES), \echo "$(line)" >> $@;)$(hide) build/tools/post_process_props.py $@build_desc :=
1.目标INSTALLED_BUILD_PROP_TARGET就是
INSTALLED_BUILD_PROP_TARGET := $(TARGET_OUT)/build.prop
可以看到定义一些变量的值比如PRODUCT_DEFAULT_LANGUAGE,会在后面脚本中用到。然后调用build/tools/buildinfo.sh这个脚本
bash $(BUILDINFO_SH) > $@将变量输出到build.prop当中:
echo "# begin build properties"echo "# autogenerated by buildinfo.sh"echo "ro.build.id=$BUILD_ID"echo "ro.build.display.id=$BUILD_DISPLAY_ID"echo "ro.build.version.incremental=$BUILD_NUMBER"echo "ro.build.version.sdk=$PLATFORM_SDK_VERSION"echo "ro.build.version.codename=$PLATFORM_VERSION_CODENAME"echo "ro.build.version.release=$PLATFORM_VERSION"echo "ro.build.date=`date`"echo "ro.build.date.utc=`date +%s`"echo "ro.build.type=$TARGET_BUILD_TYPE"echo "ro.build.user=$USER"echo "ro.build.host=`hostname`"echo "ro.build.tags=$BUILD_VERSION_TAGS"echo "ro.product.model=$PRODUCT_MODEL"echo "ro.product.brand=$PRODUCT_BRAND"echo "ro.product.name=$PRODUCT_NAME"echo "ro.product.device=$TARGET_DEVICE"echo "ro.product.board=$TARGET_BOOTLOADER_BOARD_NAME"echo "ro.product.cpu.abi=$TARGET_CPU_ABI"if [ -n "$TARGET_CPU_ABI2" ] ; then echo "ro.product.cpu.abi2=$TARGET_CPU_ABI2"fiecho "ro.product.manufacturer=$PRODUCT_MANUFACTURER"if [ -n "$PRODUCT_DEFAULT_LANGUAGE" ] ; then echo "ro.product.locale.language=$PRODUCT_DEFAULT_LANGUAGE"fiif [ -n "$PRODUCT_DEFAULT_REGION" ] ; then echo "ro.product.locale.region=$PRODUCT_DEFAULT_REGION"fiecho "ro.wifi.channels=$PRODUCT_DEFAULT_WIFI_CHANNELS"echo "ro.board.platform=$TARGET_BOARD_PLATFORM"echo "# ro.build.product is obsolete; use ro.product.device"echo "ro.build.product=$TARGET_DEVICE"echo "# Do not try to parse ro.build.description or .fingerprint"echo "ro.build.description=$PRIVATE_BUILD_DESC"echo "ro.build.fingerprint=$BUILD_FINGERPRINT"echo "ro.build.characteristics=$TARGET_AAPT_CHARACTERISTICS"echo "# end build properties"
buildinfo.sh脚本完了之后,会把$(TARGET_DEVICE_DIR)/system.prop的内容和
# Add the product-defined properties to the build properties.ADDITIONAL_BUILD_PROPERTIES := \ $(ADDITIONAL_BUILD_PROPERTIES) \ $(PRODUCT_PROPERTY_OVERRIDES)
ADDITIONAL_BUILD_PROPERTIES的属性 追加到build.prop。
至此,生成build.prop完毕!
三.属性
ro.sf.lcd_density=240(显示密度)
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