如何获取 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 非死book 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 非死book 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+。

root@generic_x86_64:/sys/devices/system/cpu # ls cpu0 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。

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    : 0  vendor_id    : GenuineIntel  cpu family    : 6  model        : 70  model name    : Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz  stepping    : 1  cpu MHz        : 0.000  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：

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;    }  }