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在apk中，有时候需要root权限，例如通过apk更新系统库等system的文件等，避免升级固件，或者e68a843231313335323631343130323136353331333337396234在apk中需要直接访问某些设备等。下面是在apk中获取root权限的方法，前提是设备已经root过了。

关键点在于下面这句，通过执行su产生一个具有root权限的进程：

Process p = Runtime.getRuntime().exec("su");

然后，在向这个进程的写入要执行的命令，即可达到以root权限执行命令：

dos = new DataOutputStream(p.getOutputStream());

dos.writeBytes(cmd + "\n");

dos.flush();

或者用下面的方式：

Runtime.getRuntime().exec(new String[]{"/system/bin/su","-c", cmd});

经过测试，以root权限执行命令，只在真机上测试成功，在模拟器上没有成功过。

第一次运行时，会出现请求root权限的界面，选中记住，并允许：

测试程序界面，如果已经root，界面中可以显示出/system分区对应的设备节点：

主要文件：RootCmd.java

[java]

package org.ckl.root;

import java.io.DataInputStream;

import java.io.DataOutputStream;

import java.io.IOException;

import android.util.Log;

public final class RootCmd {

private static final String TAG = "RootCmd";

private static boolean mHaveRoot = false;

// 判断机器Android是否已经root，即是否获取root权限

public static boolean haveRoot() {

if (!mHaveRoot) {

int ret = execRootCmdSilent("echo test"); // 通过执行测试命令来检测

if (ret != -1) {

Log.i(TAG, "have root!");

mHaveRoot = true;

} else {

Log.i(TAG, "not root!");

}

} else {

Log.i(TAG, "mHaveRoot = true, have root!");

}

return mHaveRoot;

}

// 执行命令并且输出结果

public static String execRootCmd(String cmd) {

String result = "";

DataOutputStream dos = null;

DataInputStream dis = null;

try {

Process p = Runtime.getRuntime().exec("su");// 经过Root处理的android系统即有su命令

dos = new DataOutputStream(p.getOutputStream());

dis = new DataInputStream(p.getInputStream());

Log.i(TAG, cmd);

dos.writeBytes(cmd + "\n");

dos.flush();

dos.writeBytes("exit\n");

dos.flush();

String line = null;

while ((line = dis.readLine()) != null) {

Log.d("result", line);

result += line;

}

p.waitFor();

} catch (Exception e) {

e.printStackTrace();

} finally {

if (dos != null) {

try {

dos.close();

} catch (IOException e) {

e.printStackTrace();

}

}

if (dis != null) {

try {

dis.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

return result;

}

// 执行命令但不关注结果输出

public static int execRootCmdSilent(String cmd) {

int result = -1;

DataOutputStream dos = null;

try {

Process p = Runtime.getRuntime().exec("su");

dos = new DataOutputStream(p.getOutputStream());

Log.i(TAG, cmd);

dos.writeBytes(cmd + "\n");

dos.flush();

dos.writeBytes("exit\n");

dos.flush();

p.waitFor();

result = p.exitValue();

} catch (Exception e) {

e.printStackTrace();

} finally {

if (dos != null) {

try {

dos.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

return result;

}

}

相关文件：SystemPartition.java，获取/system分区设备节点，并支持重新mount /system为可读写：

[java]

package org.ckl.root;

import java.io.DataInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import android.util.Log;

public class SystemPartition {

private static final String TAG = "SystemMount";

private static String TMP_PATH = "/sdcard/mount.txt";

private static String mMountPiont = null;

private static boolean mWriteable = false;

private SystemPartition() {

Log.i(TAG, "new SystemMount()");

}

private static class SystemPartitionHolder {

private static SystemPartition instance = new SystemPartition();

}

public SystemPartition getInstance() {

return SystemPartitionHolder.instance;

}

public static String getSystemMountPiont() {

DataInputStream dis = null;

if (mMountPiont == null) {

try {

RootCmd.execRootCmd("mount > " + TMP_PATH);

//              Runtime.getRuntime().exec("mount > " + TMP_PATH);

dis = new DataInputStream(new FileInputStream(TMP_PATH));

String line = null;

int index = -1;

while ( (line = dis.readLine()) != null ) {

index = line.indexOf(" /system ");

if (index > 0) {

mMountPiont = line.substring(0, index);

if (line.indexOf(" rw") > 0) {

mWriteable = true;

Log.i(TAG, "/system is writeable !");

} else {

mWriteable = false;

Log.i(TAG, "/system is readonly !");

}

break;

}

}

} catch (Exception e) {

e.printStackTrace();

} finally {

if (dis != null) {

try {

dis.close();

} catch (IOException e1) {

e1.printStackTrace();

}

dis = null;

}

File f = new File(TMP_PATH);

if (f.exists()) {

f.delete();

}

}

}

if (mMountPiont != null) {

Log.i(TAG, "/system mount piont: " + mMountPiont);

} else {

Log.i(TAG, "get /system mount piont failed !!!");

}

return mMountPiont;

}

public static boolean isWriteable() {

mMountPiont = null;

getSystemMountPiont();

return mWriteable;

}

public static void remountSystem(boolean writeable) {

String cmd = null;

getSystemMountPiont();

if (mMountPiont != null && RootCmd.haveRoot()) {

if (writeable) {

cmd = "mount -o remount,rw " + mMountPiont + " /system";

} else {

cmd = "mount -o remount,ro " + mMountPiont + " /system";

}

RootCmd.execRootCmdSilent(cmd);

isWriteable();

}

}

}