当我使用这段代码时：

process = Runtime.getRuntime().exec("su");

os = new DataOutputStream(process.getOutputStream());

总有一个错误,任何想法？在Android虚拟设备上运行

W/System.err(3211): java.io.IOException: Error running exec(). Command: [su] Working Directory: null Environment: null

W/System.err(3211): at java.lang.ProcessManager.exec(ProcessManager.java:211)

W/System.err(3211): at java.lang.Runtime.exec(Runtime.java:174)

W/System.err(3211): at java.lang.Runtime.exec(Runtime.java:247)

W/System.err(3211): at java.lang.Runtime.exec(Runtime.java:190)

W/System.err(3211): at com.example.executeandroidtest.ShellUtils.execCommand(MainActivity.java:661)

W/System.err(3211): at com.example.executeandroidtest.MainActivity$3.run(MainActivity.java:410)

W/System.err(3211): at java.lang.Thread.run(Thread.java:818)

W/System.err(3211): Caused by: java.io.IOException: Permission denied

W/System.err(3211): at java.lang.ProcessManager.exec(Native Method)

W/System.err(3211): at java.lang.ProcessManager.exec(ProcessManager.java:209)

W/System.err(3211): ... 6 more