为防止自己的android应用被crack，可以在程序启动时做一些判断：
1.生成apk时，解压出其中的classes.dex，取得其CRC值，并将该值写入xml文件（如android:tag="4212136116"）；
2.在程序启动时取得该CRC值，与手机上安装的apk包中的classes.dex的实际CRC值比较即可。
下面给出了integrity check的示例代码。
当然该方法存在一些问题，hacker可以通过检查参数为(Context, String, String)的函数，如果其中含有
zipEntry的getCrc()函数和killProcess()函数，可以在该函数开始部分直接插入return，就可以绕过检查了。
改进方法参考：
/*
Validates the application integrity against reverse engineering.
If the validation fails the the application is terminated
automatically without warning.
@param context
Application context used for operations
@param applicaionPackageName
Original application package name, you should
hard-codeencrypt this string and then pass it to this
function un-encrypted,
do not use the java api to get this value.
@param applicationCrc
Application CRC value
/
public static void dapplicationIntegrityCheck(final Context context,
final String applicaionPackageName,
final String applicationCrc)
{
// Check that the application package name has not changed
if (applicaionPackageName != context.getPackageName())
{
android.os.Process.killProcess(android.os.Process.myPid());
}
// Check that the debuggable flag is set to False
try
{
if (0 != (context.getPackageManager().getPackageInfo(context.getPackageName(),
PackageManager.GET_SIGNATURES).applicationInfo.flags &=
ApplicationInfo.FLAG_DEBUGGABLE))
{
android.os.Process.killProcess(android.os.Process.myPid());
}
}
catch (Exception ex)
{
Log.e("HelperFunctions", "Error checking debuggable flag.", ex);
}
// Check that the debugger is not connected
if (Debug.isDebuggerConnected())
{
android.os.Process.killProcess(android.os.Process.myPid());
}
// CRC validation
try
{
ZipFile zipFile = new ZipFile(context.getPackageCodePath());
ZipEntry zipEntry = zipFile.getEntry(new String(Common.CLASS_DEX));
if (zipEntry.getCrc() != Long.parseLong(applicationCrc))
{
android.os.Process.killProcess(android.os.Process.myPid());
}
zipEntry = null;
zipFile = null;
}
catch (Exception ex)
{
Log.e("HelperFunctions", "Error checking crc.", ex);
}
// TO-DO:
// Check that the application name has not changed.
// Keep an encrypted string constant of the application
// name and then compare it with the application
// name string using the proper function to retrieve it
}