如何获取 Android 设备的CPU核数，时钟频率以及内存大小

Device Year Class 的主要功能是根据 CPU核数、时钟频率 以及 内存大小 对设备进行分级。代码很简单，只包含两个类:

DeviceInfo-> 获取设备参数，

YearClass-> 根据参数进行分级。

下表是 Facebook 公司提供的分级标准，其中Year栏表示分级结果。

Year Cores Clock RAM

2008 1 528MHz 192MB

2009 n/a 600MHz 290MB

2010 n/a 10GHz 512MB

2011 2 12GHz 1GB

2012 4 15GHz 15GB

2013 n/a 20GHz 2GB

2014 n/a >2GHz >2GB

关于输出年份的计算方法可以参考源码，本文只把一些比较常用的功能抽取出来做一个简要介绍。

获取 CPU 核数

我们都知道，Linux 中的设备都是以文件的形式存在，CPU 也不例外，因此 CPU 的文件个数就等价与核数。

Android 的 CPU 设备文件位于/sys/devices/system/cpu/目录，文件名的的格式为cpu\d+。

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root@generic_x86_64:/sys/devices/system/cpu # ls <b>cpu0</b> cpufreq

cpuidle

kernel_max

modalias

offline

online

possible

power

present

uevent

统计一下文件个数便可以获得 CPU 核数。

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public static int getNumberOfCPUCores() {

if (BuildVERSIONSDK_INT <= BuildVERSION_CODESGINGERBREAD_MR1) {

// Gingerbread doesn't support giving a single application access to both cores, but a

// handful of devices (Atrix 4G and Droid X2 for example) were released with a dual-core

// chipset and Gingerbread; that can let an app in the background run without impacting

// the foreground application But for our purposes, it makes them single core

return 1;

}

int cores;

try {

cores = new File("/sys/devices/system/cpu/")listFiles(CPU_FILTER)length;

} catch (SecurityException e) {

cores = DEVICEINFO_UNKNOWN;

} catch (NullPointerException e) {

cores = DEVICEINFO_UNKNOWN;

}

return cores;

}

private static final FileFilter CPU_FILTER = new FileFilter() {

@Override

public boolean accept(File pathname) {

String path = pathnamegetName();

//regex is slow, so checking char by char

if (pathstartsWith("cpu")) {

for (int i = 3; i < pathlength(); i++) {

if (pathcharAt(i) < '0' || pathcharAt(i) > '9') {

return false;

}

}

return true;

}

return false;

}

};

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获取时钟频率

获取时钟频率需要读取系统文件 -/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq或者/proc/cpuinfo。

我的 Android 模拟器中并没有cpuinfo_max_freq文件，因此只能读取/proc/cpuinfo。

/proc/cpuinfo包含了很多 cpu 数据。

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processor : 0

vendor_id : GenuineIntel

cpu family : 6

model : 70

model name : Intel(R) Core(TM) i7-4770HQ CPU @ 220GHz

stepping : 1

cpu MHz : 0000

cache size : 1024 KB

fdiv_bug : no

hlt_bug : no

f00f_bug : no

coma_bug : no

fpu : yes

fpu_exception : yes

cpuid level : 4

wp : yes

代码如下：

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public static int getCPUMaxFreqKHz() {

int maxFreq = DEVICEINFO_UNKNOWN;

try {

for (int i = 0; i < getNumberOfCPUCores(); i++) {

String filename =

"/sys/devices/system/cpu/cpu" + i + "/cpufreq/cpuinfo_max_freq";

File cpuInfoMaxFreqFile = new File(filename);

if (cpuInfoMaxFreqFileexists()) {

byte[] buffer = new byte[128];

FileInputStream stream = new FileInputStream(cpuInfoMaxFreqFile);

try {

streamread(buffer);

int endIndex = 0;

//Trim the first number out of the byte buffer

while (buffer[endIndex] >= '0' && buffer[endIndex] <= '9'

&& endIndex < bufferlength) endIndex++;

String str = new String(buffer, 0, endIndex);

Integer freqBound = IntegerparseInt(str);

if (freqBound > maxFreq) maxFreq = freqBound;

} catch (NumberFormatException e) {

//Fall through and use /proc/cpuinfo

} finally {

streamclose();

}

}

}

if (maxFreq == DEVICEINFO_UNKNOWN) {

FileInputStream stream = new FileInputStream("/proc/cpuinfo");

try {

int freqBound = parseFileForValue("cpu MHz", stream);

freqBound = 1000; //MHz -> kHz

if (freqBound > maxFreq) maxFreq = freqBound;

} finally {

streamclose();

}

}

} catch (IOException e) {

maxFreq = DEVICEINFO_UNKNOWN; //Fall through and return unknown

}

return maxFreq;

}

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获取内存大小

如果 SDK 版本大于等于JELLY_BEAN，可以通过ActivityManager来获取内从大小。

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ActivityManagerMemoryInfo memInfo = new ActivityManagerMemoryInfo();

ActivityManager am = (ActivityManager) cgetSystemService(ContextACTIVITY_SERVICE);

amgetMemoryInfo(memInfo);

如果版本低于JELLY_BEAN，则只能读取系统文件了。

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FileInputStream stream = new FileInputStream("/proc/meminfo");

totalMem = parseFileForValue("MemTotal", stream);

完整代码如下：

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@TargetApi(BuildVERSION_CODESJELLY_BEAN)

public static long getTotalMemory(Context c) {

// memInfototalMem not supported in pre-Jelly Bean APIs

if (BuildVERSIONSDK_INT >= BuildVERSION_CODESJELLY_BEAN) {

ActivityManagerMemoryInfo memInfo = new ActivityManagerMemoryInfo();

ActivityManager am = (ActivityManager) cgetSystemService(ContextACTIVITY_SERVICE);

amgetMemoryInfo(memInfo);

if (memInfo != null) {

return memInfototalMem;

} else {

return DEVICEINFO_UNKNOWN;

}

} else {

long totalMem = DEVICEINFO_UNKNOWN;

try {

FileInputStream stream = new FileInputStream("/proc/meminfo");

try {

totalMem = parseFileForValue("MemTotal", stream);

totalMem = 1024;

} finally {

streamclose();

}

} catch (IOException e) {

}

return totalMem;

}

}

getTotalPrivateDirty()就是获得自己进程所独占的内存

getTotalPss()意思就是假如有A,B,C,D,E 5个进程共享一片10kb的内存，A,B,F 3个进程又另外共享了30kb的内存，那么进程A调用这个函数返回就是10/5+30/3=12

所以理论上只要监视getTotalPrivateDirty()就能监视自己进程的内存变化

最后附上代码

public void getThisProcessMemeryInfo() {

int pid = AndroidosProcessmyPid();

androidosDebugMemoryInfo[] memoryInfoArray = activityManagergetProcessMemoryInfo(new int[] {pid});

Logd(TAG, "本应用当前使用了" + (float)memoryInfoArray[0]getTotalPrivateDirty() / 1024 + "mb的内存");

}

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