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对于我的应用程序，我需要使android设备充当USB主机。它需要发送和接收来自USB连接设备的数据。我已经通过了USB Host in Android Developers Site，并开发示例代码如下：将USB设备置于USB主机模式？
Main.java
public class UsbDemoProjActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn = (Button)findViewById(R.id.button1);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(), "button click", 30).show();
Intent it = new Intent(UsbDemoProjActivity.this,Second.class);
startActivity(it);
}
});
}
}
Second.java：
public class Second extends Activity{
UsbDevice device;
UsbManager mUsbManager;
PendingIntent mPermissionIntent;
private static String ACTION_USB_PERMISSION ="com.android.example.USB_PERMISSION";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
System.out.println("111111111");
mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
ACTION_USB_PERMISSION ="com.android.example.USB_PERMISSION";
System.out.println("2222222222");
HashMap<String, UsbDevice> deviceList = mUsbManager.getDeviceList();
device = deviceList.get("deviceName");
System.out.println("33333333333");
mPermissionIntent = PendingIntent.getBroadcast(this, 0,
new Intent(ACTION_USB_PERMISSION), 0);
System.out.println("444444444444");
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
System.out.println("555555555555");
registerReceiver(mUsbReceiver, filter);
System.out.println("66666666666");
mUsbManager.requestPermission(device, mPermissionIntent);
}
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
System.out.println("7777777777777");
if (ACTION_USB_PERMISSION.equals(action)) {
synchronized (this) {
System.out.println("88888888888");
UsbDevice device = (UsbDevice)intent.getParcelableExtra(
UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
if(device != null){
System.out.println("99999999999999");
//call method to set up device communication
}
} else {
//Log.d(TAG, "permission denied for device " + device);
System.out.println("permission denied for device" + device);
}
}
}
}
};
}
然而，当我在Main.java点击按钮页面显示错误：
不幸的是USBDemo PROJ已停止
和logcat中显示错误按照下面的图片，但这里的system.output()线显示其在Second.java类中声明。任何人都可以请帮助我什么是我的应用程序中的错误？
此外，我在示例代码中使用正确的方法访问USB主机模式下的设备？任何人都可以给我一个更好的方法吗
