我需要对连接到我的Android手机的USB设备执行文件操作。应该通过android java代码授予权限，并且应该使用JNI执行文件操作。目前我无法授予执行文件操作的权限 - 我得到了一个EACCESS：权限被拒绝错误
我在这里附上了我的代码：
public class MainActivity extends AppCompatActivity {
private UsbAccessory accessory;
private String TAG = "TAG";
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
private PendingIntent mPermissionIntent;
private UsbManager manager;
private UsbDeviceConnection connection;
private HashMap<Integer, Integer> connectedDevices;
TextView tv;
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Example of a call to a native method
tv = (TextView) findViewById(R.id.sample_text);
// tv.setText(stringFromJNI());
connectedDevices = new HashMap<Integer, Integer>();
manager = (UsbManager) getSystemService(Context.USB_SERVICE);
registerReceiver(usbManagerBroadcastReceiver, new IntentFilter(UsbManager.ACTION_USB_DEVICE_ATTACHED));
registerReceiver(usbManagerBroadcastReceiver, new IntentFilter(UsbManager.ACTION_USB_DEVICE_DETACHED));
registerReceiver(usbManagerBroadcastReceiver, new IntentFilter(ACTION_USB_PERMISSION));
mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
/*String str = ndkopenfile();
tv.setText(str);*/
final Handler handler = new Handler();
handler.postDelayed(new Runnable()
{
@Override
public void run()
{
checkForDevices();
}
}, 1000);
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
// public native String stringFromJNI（）;
@Override
public void onDestroy()
{
super.onDestroy();
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
}
// private static native void notifyDeviceAttached(int fd);
//private static native void notifyDeviceDetached(int fd);
public native String ndkopenfile();
private final BroadcastReceiver usbManagerBroadcastReceiver = new BroadcastReceiver()
{
public void onReceive(Context context, Intent intent)
{
try
{
String action = intent.getAction();
Log.d(TAG, "INTENT ACTION: " + action);
if (ACTION_USB_PERMISSION.equals(action))
{
Log.d(TAG, "onUsbPermission");
synchronized (this)
{
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))
{
if(device != null)
{
/* int fd = connectToDevice(device);
Log.d(TAG,"device file descriptor: " + fd);
// notifyDeviceAttached(fd);
String str = ndkopenfile();
tv.setText(str);*/
writetofile();
}
}
else
{
Log.d(TAG, "permission denied for device " + device);
}
}
}
if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action))
{
Log.d(TAG, "onDeviceConnected");
synchronized(this)
{
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (device != null)
{
manager.requestPermission(device, mPermissionIntent);
}
}
}
if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action))
{
Log.d(TAG, "onDeviceDisconnected");
synchronized(this)
{
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
int fd = connectedDevices.get(device.getDeviceId());
Log.d(TAG, "device: " + device.getDeviceId() + " disconnected. fd: " + fd);
// notifyDeviceDetached(fd);
connectedDevices.remove(device.getDeviceId());
}
}
}
catch(Exception e)
{
Log.d(TAG, "Exception: " + e);
}
}
};
private void writetofile() {
// File file = new File("/storage/9E6D-8A07/COMMWR");
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("/storage/9E6D-8A07/COMMWR", Context.MODE_PRIVATE));
outputStreamWriter.write("Hello");
outputStreamWriter.close();
}
catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
private int connectToDevice(UsbDevice device)
{
connection = manager.openDevice(device);
// if we make this, kernel driver will be disconnected
connection.claimInterface(device.getInterface(0), true);
Log.d(TAG, "inserting device with id: " + device.getDeviceId() + " and file descriptor: " + connection.getFileDescriptor());
connectedDevices.put(device.getDeviceId(), connection.getFileDescriptor());
return connection.getFileDescriptor();
}
private void checkForDevices()
{
HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
while(deviceIterator.hasNext())
{
UsbDevice device = deviceIterator.next();
/* if (device.getVendorId()==VID && device.getProductId()==PID)
{
Log.d(TAG, "Found a device: " + device);
manager.requestPermission(device, mPermissionIntent);
}*/
Log.d(TAG, "Found a device: " + device);
manager.requestPermission(device, mPermissionIntent);
}
}
}
JNI代码：
#include <jni.h>
#include <string.h>
#include <stdio.h>
extern "C"
JNIEXPORT jstring JNICALL
Java_nrrsmdm_com_myapplication_MainActivity_ndkopenfile
(JNIEnv *env, jobject obj)
{
int errno = 0;
char myStr[20];
FILE* fp = fopen("/storage/9E6D-8A07/COMMWR","w+");
if(fp!=NULL)
{
fputs("HELLO WORLD!\n", fp);
fflush(fp);
fclose(fp);
return env->NewStringUTF(myStr);
}
else
{ sprintf("error","errno = %d",errno);
fclose(fp);
return env->NewStringUTF("Error opening file!");
}
/* std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());*/
}
答案 0 :(得分：0)
尝试向您的清单添加权限：
<manifest>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
...
<application>
...
<activity>
...
</activity>
</application>
</manifest>
要支持marshmallow，请确保您的活动实现OnRequestPermissionResult并添加代码以请求权限（如果尚未授予）（代码来自对此question的回答）：
public boolean isStoragePermissionGranted() {
if (Build.VERSION.SDK_INT >= 23) {
if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
Log.v(TAG,"Permission is granted");
return true;
} else {
Log.v(TAG,"Permission is revoked");
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
return false;
}
}
else { //permission is automatically granted on sdk<23 upon installation
Log.v(TAG,"Permission is granted");
return true;
}
}
权限结果回调：
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if(grantResults[0]== PackageManager.PERMISSION_GRANTED){
Log.v(TAG,"Permission: "+permissions[0]+ "was "+grantResults[0]);
//resume tasks needing this permission
}
}