Android獲取應用cpu使用率

 public static float getProcessCpuRate()
    {
        
        float totalCpuTime1 = getTotalCpuTime();
        float processCpuTime1 = getAppCpuTime();
        try
        {
            Thread.sleep(360);
            
        }
        catch (Exception e)
        {
        }
        
        float totalCpuTime2 = getTotalCpuTime();
        float processCpuTime2 = getAppCpuTime();
        
        float cpuRate = 100 * (processCpuTime2 - processCpuTime1)
                / (totalCpuTime2 - totalCpuTime1);
        
        return cpuRate;
    }
    
    public static long getTotalCpuTime()
    { // 獲取系統總CPU使用時間
        String[] cpuInfos = null;
        try
        {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    new FileInputStream("/proc/stat")), 1000);
            String load = reader.readLine();
            reader.close();
            cpuInfos = load.split(" ");
        }
        catch (IOException ex)
        {
            ex.printStackTrace();
        }
        long totalCpu = Long.parseLong(cpuInfos[2])
                + Long.parseLong(cpuInfos[3]) + Long.parseLong(cpuInfos[4])
                + Long.parseLong(cpuInfos[6]) + Long.parseLong(cpuInfos[5])
                + Long.parseLong(cpuInfos[7]) + Long.parseLong(cpuInfos[8]);
        return totalCpu;
    }
    
    public static long getAppCpuTime()
    { // 獲取應用占用的CPU時間
        String[] cpuInfos = null;
        try
        {
            int pid = android.os.Process.myPid();
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    new FileInputStream("/proc/" + pid + "/stat")), 1000);
            String load = reader.readLine();
            reader.close();
            cpuInfos = load.split(" ");
        }
        catch (IOException ex)
        {
            ex.printStackTrace();
        }
        long appCpuTime = Long.parseLong(cpuInfos[13])
                + Long.parseLong(cpuInfos[14]) + Long.parseLong(cpuInfos[15])
                + Long.parseLong(cpuInfos[16]);
        return appCpuTime;
    }

計算某個時間段內AppCpuTime與TotalCpuTime的變化，然後按照比例換算成該應用的Cpu使用率。

Android系統本省也有一個類是用來顯示Cpu使用率的：

android/system/frameworks/base/packages/SystemUI/src/com/android/systemui/LoadAverageService.java
閱讀源碼發現也是讀取/proc目錄下的文件來計算Cpu使用率

另外一種方式Runtime.getRuntime().exec("top -d 1 -n 1")，但是每次都獲取到的cpu使用率為0，找不到原因

http://www.m2catalyst.com/tutorial-finding-cpu-usage-for-individual-android-apps/