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 Facebo ...
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 | 1.0GHz | 512MB |
2011 | 2 | 1.2GHz | 1GB |
2012 | 4 | 1.5GHz | 1.5GB |
2013 | n/a | 2.0GHz | 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+
。
root@generic_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; }};
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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。
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;}
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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。
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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原标题:如何获取 Android 设备的CPU核数、时钟频率以及内存大小
关键词:Android
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