1. 前言

记得刚来公司 4 个多月的时候，公司的一个产品问我：可以获取 Android cpu 的温度吗？我答道：如果别人可以，我们也可以获取到。其实，我那时确实不知道怎么获取，也没具体去看这个问题。等到最近确实需要这个功能时，实在是找了好多资料，才找到了方案。现在想想，那时回答的实在是很轻率啊。

2. 正文

2.1 两种可选方案

查询网上的文章，有两种方案：
1，通过读取温度传感器的值近似作为 cpu 的温度：这个方案在没有温度传感器的手机上行不通；再者，这也是近似的温度，并不是 cpu 真正的温度；
2，通过读取 cpu 内核信息获取温度：这个方法直接也准确，但是到底读取哪些信息呢？资料并不充分。

2.2 采取的方案

本文采取的是第二种方案。
经过查询资料，有更多的备选可以读取。可以查看下面的类：

public class CpuUtils {
    private CpuUtils() {
        //no instance
    }
    private static final List<String> CPU_TEMP_FILE_PATHS = Arrays.asList(
            "/sys/devices/system/cpu/cpu0/cpufreq/cpu_temp",
            "/sys/devices/system/cpu/cpu0/cpufreq/FakeShmoo_cpu_temp",
            "/sys/class/thermal/thermal_zone0/temp",
            "/sys/class/i2c-adapter/i2c-4/4-004c/temperature",
            "/sys/devices/platform/tegra-i2c.3/i2c-4/4-004c/temperature",
            "/sys/devices/platform/omap/omap_temp_sensor.0/temperature",
            "/sys/devices/platform/tegra_tmon/temp1_input",
            "/sys/kernel/debug/tegra_thermal/temp_tj",
            "/sys/devices/platform/s5p-tmu/temperature",
            "/sys/class/thermal/thermal_zone1/temp",
            "/sys/class/hwmon/hwmon0/device/temp1_input",
            "/sys/devices/virtual/thermal/thermal_zone1/temp",
            "/sys/devices/virtual/thermal/thermal_zone0/temp",
            "/sys/class/thermal/thermal_zone3/temp",
            "/sys/class/thermal/thermal_zone4/temp",
            "/sys/class/hwmon/hwmonX/temp1_input",
            "/sys/devices/platform/s5p-tmu/curr_temp");

    public static final Maybe<CpuTemperatureResult> getCpuTemperatureFinder() {
        return Observable
                .fromIterable(CPU_TEMP_FILE_PATHS)
                .map(new Function<String, CpuTemperatureResult>() {
                    @Override
                    public CpuTemperatureResult apply(String path) {
                        Double temp = readOneLine(new File(path));
                        String validPath = "";
                        double currentTemp = 0.0D;
                        if (isTemperatureValid(temp)) {
                            validPath = path;
                            currentTemp = temp;
                        } else if (isTemperatureValid(temp / (double) 1000)) {
                            validPath = path;
                            currentTemp = temp / (double) 1000;
                        }

                        return new CpuTemperatureResult(validPath, (int) currentTemp);
                    }
                }).filter(new Predicate<CpuTemperatureResult>() {
                    @Override
                    public boolean test(CpuTemperatureResult cpuTemperatureResult) throws Exception {
                        return !TextUtils.isEmpty(cpuTemperatureResult.getFilePath())
                                && (cpuTemperatureResult.getTemp() != 0);
                    }
                }).firstElement();
    }

    private static double readOneLine(File file) {
        FileInputStream fileInputStream = null;
        String s = "";
        try {
            fileInputStream = new FileInputStream(file);
            InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
            BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
            s = bufferedReader.readLine();
            fileInputStream.close();
            inputStreamReader.close();
            bufferedReader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        double result = 0;
        try {
            result = Double.parseDouble(s);
        } catch (NumberFormatException ignored) {
        }
        return result;
    }

    private static boolean isTemperatureValid(double temp) {
        return temp >= -30.0D && temp <= 250.0D;
    }


}