怎么获取 Android 设备的CPU核数、时钟频率以及内存大小

因项目需要，分析了一下 Facebook 的开源项目 - Device Year Class。

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。

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+。

[email protected]_x86_64:/sys/devices/system/cpu # lscpu0cpufreqcpuidlekernel_maxmodaliasofflineonlinepossiblepowerpresentuevent

统计一下文件个数便可以获得 CPU 核数。

public static int getNumberOfCPUCores() {  if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.GINGERBREAD_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 = pathname.getName();    //regex is slow, so checking char by char.    if (path.startsWith("cpu")) {      for (int i = 3; i < path.length(); i++) {        if (path.charAt(i) < '0' || path.charAt(i) > '9') {          return false;        }      }      return true;    }    return false;  }};

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。

processor   : 0vendor_id   : GenuineIntelcpu family  : 6model       : 70model name  : Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHzstepping    : 1cpu MHz     : 0.000cache size  : 1024 KBfdiv_bug    : nohlt_bug     : nof00f_bug    : nocoma_bug    : nofpu     : yesfpu_exception   : yescpuid level : 4wp      : yes

代码如下：

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 (cpuInfoMaxFreqFile.exists()) {        byte[] buffer = new byte[128];        FileInputStream stream = new FileInputStream(cpuInfoMaxFreqFile);        try {          stream.read(buffer);          int endIndex = 0;          //Trim the first number out of the byte buffer.          while (buffer[endIndex] >= '0' && buffer[endIndex] <= '9'              && endIndex < buffer.length) endIndex++;          String str = new String(buffer, 0, endIndex);          Integer freqBound = Integer.parseInt(str);          if (freqBound > maxFreq) maxFreq = freqBound;        } catch (NumberFormatException e) {          //Fall through and use /proc/cpuinfo.        } finally {          stream.close();        }      }    }    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 {        stream.close();      }    }  } catch (IOException e) {    maxFreq = DEVICEINFO_UNKNOWN; //Fall through and return unknown.  }  return maxFreq;}

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。

ActivityManager.MemoryInfo memInfo = new ActivityManager.MemoryInfo();ActivityManager am = (ActivityManager) c.getSystemService(Context.ACTIVITY_SERVICE);am.getMemoryInfo(memInfo);

如果版本低于 JELLY_BEAN ，则只能读取系统文件了。

FileInputStream stream = new FileInputStream("/proc/meminfo");totalMem = parseFileForValue("MemTotal", stream);

完整代码如下：

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)public static long getTotalMemory(Context c) {  // memInfo.totalMem not supported in pre-Jelly Bean APIs.  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {    ActivityManager.MemoryInfo memInfo = new ActivityManager.MemoryInfo();    ActivityManager am = (ActivityManager) c.getSystemService(Context.ACTIVITY_SERVICE);    am.getMemoryInfo(memInfo);    if (memInfo != null) {      return memInfo.totalMem;    } else {      return DEVICEINFO_UNKNOWN;    }  } else {    long totalMem = DEVICEINFO_UNKNOWN;    try {      FileInputStream stream = new FileInputStream("/proc/meminfo");      try {        totalMem = parseFileForValue("MemTotal", stream);        totalMem *= 1024;      } finally {        stream.close();      }    } catch (IOException e) {    }    return totalMem;  }}

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