Android框架层为IMountService增加新接口
在为Android 增加多分区的支持时,可能会需要获得当前 USB 连接的挂载口,可能标准的Android 框架并未提供这样的接口给开发者,这时就需要我们自己为它提供接口了。先来看一下上层(应用)如何得到一个IMountService 的。
private synchronized IMountService getMountService() {
if (mMountService == null) {
IBinder service = ServiceManager.getService("mount");
if (service != null) {
mMountService = IMountService.Stub.asInte易做图ce(service);
} else {
Log.e(TAG, "Can't get mount service");
}
}
return mMountService;
}
关于Binder 可以参考下这篇文章:Android深入浅出之Binder机制http://www.zzzyk.com/kf/201204/128312.html。
Android 2.2新增接口
Android 2.2为IMountService 新增接口非常容易,在frameworks/base/core/java/android/os/storage 有一个IMountService.aidl 文件,可以直接在这个文件里面新增一个接口提供给上层,如:
/*add by terry*/
String getUsbMountPointPath();
该文件负责生成IMountService.java文件,接着进入frameworks/base/services/java/com/android/server ,打开MountService.java 该文件继承于IMountService.aidl生成的类
class MountService extends IMountService.Stub
在这个类里面实现我们为IMountService.aidl 新增的接口
public String getUsbMountPointPath(){
return usbMountPointPath;
}
OK。通过上面的操作, StorageManage 就可以很方便的得到这个为其新增的接口,上层便可以访问了。
编译步骤:
1):编译framework/base (生成IMountService.java)
2):编译framework/base/service (编译MountService)
3):编译framework/base (编译StorageManage以提供给上层调用)
Android 4.0 以上新增接口
相比于Android 2.2,在Android 4.0框架层 为IMountService 新增一个接口就显得比较复杂了。
按照Android 2.2 新增接口的方法,我们会先进入frameworks/base/core/java/android/os/storage 查找IMountService.aidl文件,进入目录,ls 一下,会发现并没有该文件,取而代之的是IMountService.java。这是怎么回事?打开该文件:映入眼帘首先会看到该警告:
/**
* WARNING! Update IMountService.h and IMountService.cpp if you change this
* file. In particular, the ordering of the methods below must match the
* _TRANSACTION enum in IMountService.cpp
*
* @hide - Applications should use android.os.storage.StorageManager to access
* storage functions.
*/
该警告提示我们,如果要修改这个文件,必须先修改IMountService.h 头文件和 IMountService.cpp 文件 ,并且还需要注意枚举里面的顺序。按照警告可以一步步修改了。
进入frameworks/base/include/storage 打开IMountService.h ,新增这个方法:
virtual int32_t getUsbMountPointPath() = 0 ;
完成后进入frameworks/base/libs/storage 打开IMountService.cpp ,在枚举里面新增方法枚举:
enum {
TRANSACTION_registerListener = IBinder::FIRST_CALL_TRANSACTION,
TRANSACTION_unregisterListener,
TRANSACTION_isUsbMassStorageConnected,
TRANSACTION_setUsbMassStorageEnabled,
TRANSACTION_isUsbMassStorageEnabled,
TRANSACTION_mountVolume,
TRANSACTION_unmountVolume,
TRANSACTION_formatVolume,
TRANSACTION_getStorageUsers,
TRANSACTION_getVolumeState,
TRANSACTION_createSecureContainer,
TRANSACTION_finalizeSecureContainer,
TRANSACTION_destroySecureContainer,
TRANSACTION_mountSecureContainer,
TRANSACTION_unmountSecureContainer,
TRANSACTION_isSecureContainerMounted,
TRANSACTION_renameSecureContainer,
TRANSACTION_getSecureContainerPath,
TRANSACTION_getSecureContainerList,
TRANSACTION_shutdown,
TRANSACTION_finishMediaUpdate,
TRANSACTION_mountObb,
TRANSACTION_unmountObb,
TRANSACTION_isObbMounted,
TRANSACTION_getMountedObbPath,
TRANSACTION_isExternalStorageEmulated,
TRANSACTION_decryptStorage,
TRANSACTION_encryptStorage,
TRANSACTION_getUsbMountPointPath,
};
接着新增要实现的方法
int32_t getUsbMountPointPath()
{
Parcel data, reply;
data.writeInte易做图ceToken(IMountService::getInte易做图ceDescriptor());
if (remote()->transact(TRANSACTION_getUsbMountPointPath, data, &reply) != NO_ERROR) {
LOGD("getVolumeState could not contact remote\n");
return -1;
}
int32_t err = reply.readExceptionCode();
if (err < 0) {
LOGD("getVolumeState caught exception %d\n", err);
return err;
}
return reply.readInt32();
}
OK,这个方法到了这里,CPP部分就算完成了。接下来可以为IMountService.java加接口了。
再次进入frameworks/base/core/java/android/os/storage ,打开IMountService.java 文件。
实现该接口,增加以下方法:
public String getUsbMountPointPath() throws RemoteException {
Parcel _data = Parcel.obtain();
Parcel _reply = Parcel.obtain();
String _result;
try {
_data.writeInte易做图ceToken(DESCRIPTOR);
mRemote.transact(Stub.TRANSACTION_getUsbMountPointPath, _data, _reply, 0);
_reply.readException();
_result = _reply.readString();
&
补充:移动开发 , Android ,