如何获取 Android 设备的CPU核数、时钟频率以及内存大小

原帖：
http://www.jianshu.com/p/f7add443cd32

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。
下表是 Facebook 公司提供的分级标准，其中 Year 栏表示分级结果。




以下类就是从Facebook 的开源项目Device Year Class中拿出来的

package com.yirui.youbao.util;

import android.annotation.TargetApi;
import android.app.ActivityManager;
import android.content.Context;
import android.os.Build;

import java.io.*;
/**
 * Helper class for accessing hardware specifications, including the number of CPU cores, CPU clock speed
 * and total available RAM.
 */
public class DeviceInfo {

  /**
   * The default return value of any method in this class when an
   * error occurs or when processing fails (Currently set to -1). Use this to check if
   * the information about the device in question was successfully obtained.
   */
  public static final int DEVICEINFO_UNKNOWN = -1;

  /**
   * Reads the number of CPU cores from {@code /sys/devices/system/cpu/}.
   *
   * @return Number of CPU cores in the phone, or DEVICEINFO_UKNOWN = -1 in the event of an error.
   */
  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;
    }
  };

  /**
   * Method for reading the clock speed of a CPU core on the device. Will read from either
   * {@code /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq} or {@code /proc/cpuinfo}.
   *
   * @return Clock speed of a core on the device, or -1 in the event of an error.
   */
  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;
  }

  /**
   * Calculates the total RAM of the device through Android API or /proc/meminfo.
   *
   * @param c - Context object for current running activity.
   * @return Total RAM that the device has, or DEVICEINFO_UNKNOWN = -1 in the event of an error.
   */
  @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;
    }
  }

  /**
   * Helper method for reading values from system files, using a minimised buffer.
   *
   * @param textToMatch - Text in the system files to read for.
   * @param stream      - FileInputStream of the system file being read from.
   * @return A numerical value following textToMatch in specified the system file.
   * -1 in the event of a failure.
   */
  private static int parseFileForValue(String textToMatch, FileInputStream stream) {
    byte[] buffer = new byte[1024];
    try {
      int length = stream.read(buffer);
      for (int i = 0; i < length; i++) {
        if (buffer[i] == '\n' || i == 0) {
          if (buffer[i] == '\n') i++;
          for (int j = i; j < length; j++) {
            int textIndex = j - i;
            //Text doesn't match query at some point.
            if (buffer[j] != textToMatch.charAt(textIndex)) {
              break;
            }
            //Text matches query here.
            if (textIndex == textToMatch.length() - 1) {
              return extractValue(buffer, j);
            }
          }
        }
      }
    } catch (IOException e) {
      //Ignore any exceptions and fall through to return unknown value.
    } catch (NumberFormatException e) {
    }
    return DEVICEINFO_UNKNOWN;
  }

  /**
   * Helper method used by {@link #parseFileForValue(String, FileInputStream) parseFileForValue}. Parses
   * the next available number after the match in the file being read and returns it as an integer.
   * @param index - The index in the buffer array to begin looking.
   * @return The next number on that line in the buffer, returned as an int. Returns
   * DEVICEINFO_UNKNOWN = -1 in the event that no more numbers exist on the same line.
   */
  private static int extractValue(byte[] buffer, int index) {
    while (index < buffer.length && buffer[index] != '\n') {
      if (buffer[index] >= '0' && buffer[index] <= '9') {
        int start = index;
        index++;
        while (index < buffer.length && buffer[index] >= '0' && buffer[index] <= '9') {
          index++;
        }
        String str = new String(buffer, 0, start, index - start);
        return Integer.parseInt(str);
      }
      index++;
    }
    return DEVICEINFO_UNKNOWN;
  }
}

package com.yirui.youbao.util;

import java.util.ArrayList;
import java.util.Collections;

import android.content.Context;

public class YearClass {
  // Year definitions
  public static final int CLASS_UNKNOWN = -1;
  public static final int CLASS_2008 = 2008;
  public static final int CLASS_2009 = 2009;
  public static final int CLASS_2010 = 2010;
  public static final int CLASS_2011 = 2011;
  public static final int CLASS_2012 = 2012;
  public static final int CLASS_2013 = 2013;
  public static final int CLASS_2014 = 2014;

  private static final long MB = 1024 * 1024;
  private static final int MHZ_IN_KHZ = 1000;

  private volatile static Integer mYearCategory;

  /**
   * Entry Point of YearClass. Extracts YearClass variable with memoizing.
   * Example usage:
   * <p>
   * <pre>
   *   int yearClass = YearClass.get(context);
   * </pre>
   */
  public static int get(Context c) {
    if (mYearCategory == null) {
      synchronized(YearClass.class) {
        if (mYearCategory == null) {
          mYearCategory = categorizeByYear(c);
        }
      }
    }
    return mYearCategory;
  }

  private static void conditionallyAdd(ArrayList<Integer> list, int value) {
    if (value != CLASS_UNKNOWN) {
      list.add(value);
    }
  }

  /**
   * Calculates the "best-in-class year" of the device. This represents the top-end or flagship
   * devices of that year, not the actual release year of the phone. For example, the Galaxy Duos
   * S was released in 2012, but its specs are very similar to the Galaxy S that was released in
   * 2010 as a then top-of-the-line phone, so it is a 2010 device.
   *
   * @return The year when this device would have been considered top-of-the-line.
   */
  private static int categorizeByYear(Context c) {
    ArrayList<Integer> componentYears = new ArrayList<Integer>();
    conditionallyAdd(componentYears, getNumCoresYear());
    conditionallyAdd(componentYears, getClockSpeedYear());
    conditionallyAdd(componentYears, getRamYear(c));
    if (componentYears.isEmpty())
      return CLASS_UNKNOWN;
    Collections.sort(componentYears);
    if ((componentYears.size() & 0x01) == 1) {  // Odd number; pluck the median.
      return componentYears.get(componentYears.size() / 2);
    } else { // Even number. Average the two "center" values.
      int baseIndex = componentYears.size() / 2 - 1;
      // There's an implicit rounding down in here; 2011.5 becomes 2011.
      return componentYears.get(baseIndex) +
          (componentYears.get(baseIndex + 1) - componentYears.get(baseIndex)) / 2;
    }
  }

  /**
   * Calculates the year class by the number of processor cores the phone has.
   * Evaluations are based off the table below:
   * <table border="1">
   * <thead>
   * <tr><th width="50%">Amount</th><th>Year</th></tr>
   * <thead>
   * <tbody>
   * <tr><td>>4 or More</td><td>2012</td></tr>
   * <tr><td>2 or 3</td><td>2011</td></tr>
   * <tr><td>1</td><td>2008</td></tr>
   * </tbody>
   * </table>
   *
   * @return the year in which top-of-the-line phones had the same number of processors as this phone.
   */
  private static int getNumCoresYear() {
    int cores = DeviceInfo.getNumberOfCPUCores();
    if (cores < 1) return CLASS_UNKNOWN;
    if (cores == 1) return CLASS_2008;
    if (cores <= 3) return CLASS_2011;
    return CLASS_2012;
  }

  /**
   * Calculates the year class by the clock speed of the cores in the phone.
   * Evaluations are based off the table below:
   * <table border="1">
   * <thead>
   * <tr><th width="50%">Amount</th><th>Year</th></tr>
   * <thead>
   * <tbody>
   * <tr><td>>2GHz</td><td>2014</td></tr>
   * <tr><td><=2GHz</td><td>2013</td></tr>
   * <tr><td><=1.5GHz</td><td>2012</td></tr>
   * <tr><td><=1.2GHz</td><td>2011</td></tr>
   * <tr><td><=1GHz</td><td>2010</td></tr>
   * <tr><td><=600MHz</td><td>2009</td></tr>
   * <tr><td><=528MHz</td><td>2008</td></tr>
   * </tbody>
   * </table>
   *
   * @return the year in which top-of-the-line phones had the same clock speed.
   */
  private static int getClockSpeedYear() {
    long clockSpeedKHz = DeviceInfo.getCPUMaxFreqKHz();
    if (clockSpeedKHz == DeviceInfo.DEVICEINFO_UNKNOWN) return CLASS_UNKNOWN;
    // These cut-offs include 20MHz of "slop" because my "1.5GHz" Galaxy S3 reports
    // its clock speed as 1512000. So we add a little slop to keep things nominally correct.
    if (clockSpeedKHz <= 528 * MHZ_IN_KHZ) return CLASS_2008;
    if (clockSpeedKHz <= 620 * MHZ_IN_KHZ) return CLASS_2009;
    if (clockSpeedKHz <= 1020 * MHZ_IN_KHZ) return CLASS_2010;
    if (clockSpeedKHz <= 1220 * MHZ_IN_KHZ) return CLASS_2011;
    if (clockSpeedKHz <= 1520 * MHZ_IN_KHZ) return CLASS_2012;
    if (clockSpeedKHz <= 2020 * MHZ_IN_KHZ) return CLASS_2013;
    return CLASS_2014;
  }

  /**
   * Calculates the year class by the amount of RAM the phone has.
   * Evaluations are based off the table below:
   * <table border="1">
   * <thead>
   * <tr><th width="50%">Amount</th><th>Year</th></tr>
   * <thead>
   * <tbody>
   * <tr><td>>2GB</td><td>2014</td></tr>
   * <tr><td><=2GB</td><td>2013</td></tr>
   * <tr><td><=1.5GB</td><td>2012</td></tr>
   * <tr><td><=1GB</td><td>2011</td></tr>
   * <tr><td><=512MB</td><td>2010</td></tr>
   * <tr><td><=256MB</td><td>2009</td></tr>
   * <tr><td><=128MB</td><td>2008</td></tr>
   * </tbody>
   * </table>
   *
   * @return the year in which top-of-the-line phones had the same amount of RAM as this phone.
   */
  private static int getRamYear(Context c) {
    long totalRam = DeviceInfo.getTotalMemory(c);
    if (totalRam <= 0) return CLASS_UNKNOWN;
    if (totalRam <= 192 * MB) return CLASS_2008;
    if (totalRam <= 290 * MB) return CLASS_2009;
    if (totalRam <= 512 * MB) return CLASS_2010;
    if (totalRam <= 1024 * MB) return CLASS_2011;
    if (totalRam <= 1536 * MB) return CLASS_2012;
    if (totalRam <= 2048 * MB) return CLASS_2013;
    return CLASS_2014;
  }
}

使用方法：

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.TextView;
import com.facebook.device.yearclass.YearClass;

public class MainActivity extends Activity {
  private static final String PREF_FILE = "YearClass";
  private static final String PREF_NAME = "yearclass";
  private TextView mYearClass;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    GetOrComputeYearClass findYearClass = new GetOrComputeYearClass();
    findYearClass.execute();
    mYearClass = (TextView) findViewById(R.id.year_class);
  }

  private class GetOrComputeYearClass extends AsyncTask<Void, Void, Integer> {

    @Override
    protected Integer doInBackground(Void... voids) {
      int yearClass = YearClass.CLASS_UNKNOWN;
      SharedPreferences prefs = getSharedPreferences(PREF_FILE, 0);
      if (prefs.contains(PREF_NAME)) {
        yearClass = prefs.getInt(PREF_NAME, YearClass.CLASS_UNKNOWN);
      }
      //Try again if device was previously unknown.
      if (yearClass == YearClass.CLASS_UNKNOWN) {
        yearClass = YearClass.get(getApplicationContext());
        SharedPreferences.Editor editor = prefs.edit();
        editor.putInt(PREF_NAME, yearClass);
        editor.apply();
      }
      return yearClass;
    }

    @Override
    protected void onPostExecute(Integer yearClass) {
      //update UI
      mYearClass.setText(Integer.toString(yearClass));
    }
  }
}

运行在Android设备上，启动本程序之后，在任何窗口可显示当前CPU工作频率等状态，显示当前电压电流电池容量等信息
https://github.com/will86/android-runninginfo