android 获取app使用的CPU

public static int getAppCpuUsedPercent(String packageName)
{ 
String[] cpuInfos = null;
int AppCpuUsedPercent = -1;
try
{
int pid = android.os.Process.myPid();
BufferedReader reader = new BufferedReader(new InputStreamReader(
Runtime.getRuntime().exec("top -n 1").getInputStream()), 500);
String load = reader.readLine();
while(load != null) {
if(load.contains(packageName) && load.contains(String.valueOf(pid))) {
break;
}
load = reader.readLine();
}
reader.close();
cpuInfos = load.split("%");
AppCpuUsedPercent = Integer.parseInt(cpuInfos[0].substring(cpuInfos[0].length() - 3).trim());
}
catch (Exception ex)
{
ex.printStackTrace();
}
return AppCpuUsedPercent;
}