android - 安卓usb枚举

Question

我正在编写一个 android USB 主机应用程序，我正在尝试枚举与平板电脑连接的设备。我遵循开发人员站点中的 android USB 主机文档中的代码。

我的代码如下

AndroidUSBActivity

public class AndroidUSBActivity extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    USBClass usb = new USBClass();
    ArrayList<String> deviceList = usb.GetUSBDevices(getBaseContext());
    final CharSequence[] items = deviceList.toArray(new CharSequence[deviceList.size()]);

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Select a Reader");
    builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int item) {
            String selectedDevice = (String) items[item];
            dialog.dismiss();

            TextView DeivceName = (TextView)findViewById(R.id.textView1);
            DeivceName.setText(selectedDevice);
        }
    });
    AlertDialog alert = builder.create();
    alert.show();
}
}

USB类

public class USBClass {


private static UsbManager mManager = null;
private static HashMap<String, UsbDevice> mdevices;
private static PendingIntent mPermissionIntent;
private static final String ACTION_USB_PERMISSION =
        "com.android.example.USB_PERMISSION";
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {

    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (ACTION_USB_PERMISSION.equals(action)) {
            synchronized (this) {
                UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                    if(device != null){
                        //call method to set up device communication 
                        Log.i("usb", "permission granted for device " + device);
                    }
                } 
                else {
                    Log.i("usb", "permission denied for device " + device);
                }
            }
        }
    }
};   


public ArrayList<String> GetUSBDevices(Context context){
    mManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
    mdevices = new HashMap<String, UsbDevice>();
    ArrayList<String> deviceList = new ArrayList<String>();
    mPermissionIntent = PendingIntent.getBroadcast(context, 0, new Intent("com.android.example.USB_PERMISSION"), 0);
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
    context.registerReceiver(mUsbReceiver, filter);


    // check for existing devices
    for (UsbDevice device :  mManager.getDeviceList().values()) {
        String deviceName = null;
        UsbDeviceConnection connection = null;
        if(device.getVendorId() == 0x0123){
            mManager.requestPermission(device, mPermissionIntent);
            connection = mManager.openDevice(device);
            byte rawBuf[] = new byte[255];
            int len = connection.controlTransfer(0x80, 0x06, 0x0302, 0x0409, rawBuf, 0x00FF, 60);
            rawBuf = Arrays.copyOfRange(rawBuf, 2, len);
            deviceName = new String(rawBuf);
            deviceList.add(deviceName);
            mdevices.put(deviceName, device);
        }

     }
    context.unregisterReceiver(mUsbReceiver);
    return deviceList;
}
}

LOGCAT

06-13 10:13:54.556: D/dalvikvm(2219): Late-enabling CheckJNI
06-13 10:13:54.586: I/System.out(2219): Sending WAIT chunk
06-13 10:13:54.586: W/ActivityThread(2219): Application bri.sample is waiting for the debugger on port 8100...
06-13 10:13:54.596: I/dalvikvm(2219): Debugger is active
06-13 10:13:54.786: I/System.out(2219): Debugger has connected
06-13 10:13:54.786: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:54.986: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:55.186: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:55.406: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:55.596: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:55.796: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:55.996: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:56.206: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:56.406: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:56.645: I/System.out(2219): waiting for debugger to settle...
06-13 10:13:56.846: I/System.out(2219): debugger has settled (1337)
06-13 10:13:57.116: E/UsbManager(2219): exception in UsbManager.openDevice
06-13 10:13:57.116: E/UsbManager(2219): java.lang.SecurityException: User has not given  permission to device   UsbDevice[mName=/dev/bus/usb/001/004,mVendorId=1254,mProductId=20758,mClass=0,mSubclass=0,mProtocol=0,mInterfaces=[Landroid.hardware.usb.UsbInterface;@41679100]
06-13 10:13:57.116: E/UsbManager(2219):     at android.os.Parcel.readException(Parcel.java:1327)
06-13 10:13:57.116: E/UsbManager(2219):     at android.os.Parcel.readException(Parcel.java:1281)
06-13 10:13:57.116: E/UsbManager(2219):     at android.hardware.usb.IUsbManager$Stub$Proxy.openDevice(IUsbManager.java:340)
06-13 10:13:57.116: E/UsbManager(2219):     at android.hardware.usb.UsbManager.openDevice(UsbManager.java:250)
06-13 10:13:57.116: E/UsbManager(2219):     at  bri.sample.USBClass.GetUSBDevices(USBClass.java:66)
06-13 10:13:57.116: E/UsbManager(2219):     at bri.sample.AndroidUSBActivity.onCreate(AndroidUSBActivity.java:19)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.Activity.performCreate(Activity.java:4465)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
06-13 10:13:57.116: E/UsbManager(2219):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-13 10:13:57.116: E/UsbManager(2219):     at android.os.Looper.loop(Looper.java:137)
06-13 10:13:57.116: E/UsbManager(2219):     at android.app.ActivityThread.main(ActivityThread.java:4424)
06-13 10:13:57.116: E/UsbManager(2219):     at java.lang.reflect.Method.invokeNative(Native Method)
06-13 10:13:57.116: E/UsbManager(2219):     at java.lang.reflect.Method.invoke(Method.java:511)
06-13 10:13:57.116: E/UsbManager(2219):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-13 10:13:57.116: E/UsbManager(2219):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-13 10:13:57.116: E/UsbManager(2219):     at dalvik.system.NativeStart.main(Native Method)
06-13 10:13:57.566: D/dalvikvm(2219): threadid=1: still suspended after undo (sc=1 dc=1)
06-13 10:14:04.266: D/AndroidRuntime(2219): Shutting down VM
06-13 10:14:04.266: W/dalvikvm(2219): threadid=1: thread exiting with uncaught exception (group=0x40a531f8)
06-13 10:14:04.296: E/AndroidRuntime(2219): FATAL EXCEPTION: main
06-13 10:14:04.296: E/AndroidRuntime(2219): java.lang.RuntimeException: Unable to start activity ComponentInfo{bri.sample/bri.sample.AndroidUSBActivity}: java.lang.NullPointerException
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.os.Looper.loop(Looper.java:137)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread.main(ActivityThread.java:4424)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at java.lang.reflect.Method.invokeNative(Native Method)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at java.lang.reflect.Method.invoke(Method.java:511)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at dalvik.system.NativeStart.main(Native Method)
06-13 10:14:04.296: E/AndroidRuntime(2219): Caused by: java.lang.NullPointerException
06-13 10:14:04.296: E/AndroidRuntime(2219):     at bri.sample.USBClass.GetUSBDevices(USBClass.java:68)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at bri.sample.AndroidUSBActivity.onCreate(AndroidUSBActivity.java:19)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.Activity.performCreate(Activity.java:4465)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
06-13 10:14:04.296: E/AndroidRuntime(2219):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
06-13 10:14:04.296: E/AndroidRuntime(2219):     ... 11 more

问题

我已插入设备，然后安装应用程序。应用程序第一次启动时，它会崩溃。

score 15 · Accepted Answer

当您尝试使用以下方式访问设备时会发生崩溃

connection = mManager.openDevice(device);

它崩溃是因为它正在抛出 a SecurityException，因为您尚未获得用户使用该设备的许可。看起来您试图在此之前的行中获得用户的许可

mManager.requestPermission(device, mPermissionIntent);

但是您需要了解调用requestPermission()是异步的。它不会在获得许可的情况下立即返回。它的作用是向用户显示一个对话框并询问用户他是否会授予您的应用程序的权限。一旦用户授予或拒绝权限，对话框就会被关闭，并且PendingIntent您传递给requestPermission()的用于广播指示权限已授予（或未授予）的 Intent。您需要在已注册的情况下收听此内容，BroadcastReceiver并且在调用该onReceive()方法时，您可以检查收到的附加内容Intent并决定如何继续。只有当用户授予您权限时，您才能继续调用openDevice()。

这听起来有点复杂，但这就是它的工作方式。

基本上，你需要打电话

mManager.requestPermission(device, mPermissionIntent);

然后等到获得许可后再尝试访问设备。

android - 安卓usb枚举

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