Device Year Class 的主要功能是根據 CPU核數、時鐘頻率 以及 內存大小 對設備進行分級。代碼很簡單,只包含兩個類: DeviceInfo-> 獲取設備參數, YearClass-> 根據參數進行分級。 下表是 Facebook 公司提供的分級標準,其中Year欄表示分級結果。 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 關於輸出年份的計算方法可以參考源碼,本文只把壹些比較常用的功能抽取出來做壹個簡要介紹。 獲取 CPU 核數 我們都知道,Linux 中的設備都是以文件的形式存在,CPU 也不例外,因此 CPU 的文件個數就等價與核數。 Android 的 CPU 設備文件位於/sys/devices/system/cpu/目錄,文件名的的格式為cpu\d+。 ? 1 2 3 4 5 6 7 8 9 10 root@generic_x86_64:/sys/devices/system/cpu # ls <b>cpu0</b> cpufreq cpuidle kernel_max modalias offline online possible power present uevent 統計壹下文件個數便可以獲得 CPU 核數。 ? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 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; } }; 回到頂部 獲取時鐘頻率 獲取時鐘頻率需要讀取系統文件 -/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq或者/proc/cpuinfo。 我的 Android 模擬器中並沒有cpuinfo_max_freq文件,因此只能讀取/proc/cpuinfo。 /proc/cpuinfo包含了很多 cpu 數據。 ? 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 代碼如下: 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; } 回到頂部 獲取內存大小 如果 SDK 版本大於等於JELLY_BEAN,可以通過ActivityManager來獲取內從大小。 ? ActivityManager.MemoryInfo memInfo = new ActivityManager.MemoryInfo(); ActivityManager am = (ActivityManager) c.getSystemService(Context.ACTIVITY_SERVICE); am.getMemoryInfo(memInfo); 如果版本低於JELLY_BEAN,則只能讀取系統文件了。 ? FileInputStream stream = new FileInputStream("/proc/meminfo"); totalMem = parseFileForValue("MemTotal", stream); 完整代碼如下: @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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