我是 android 编程的新手,我的主要目标是使用 FT200XD USB 转 I2C 桥接器通过 USB 与 MCU 通信。
首先,我尝试通过 UsbManager 检测连接的 USB 设备。据我了解,在创建弹出窗口时应该请求用户的连接许可,但没有请求许可。在调试时很明显控件不会进入广播接收器部分。
我引用了几个示例代码 fragment 并编写了下面的代码。我不知道我做错了什么。
我下载了一个名为“USB 主机 Controller ”的应用程序,它可以检测到 FT200XD。这意味着我的平板电脑具有 USB 主机功能。如果您能为我指出正确的方向或可以共享整个工作代码,那就太好了。
我的代码如下:
Java 文件:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fullscreen);
mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
mPermissionIntent= PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
filter.addAction(UsbManager.EXTRA_PERMISSION_GRANTED);
filter.addAction(ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filter);
}
// Broadcast receiver
public class mUsbReceiver extends BroadcastReceiver {
public void onReceive(Context context, Intent intent) {
Toast.makeText(getApplicationContext(),
"Inside USB Broadcast", Toast.LENGTH_SHORT).show();
}
}
list 文件部分:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.usb"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="12"
android:targetSdkVersion="19" />
<uses-feature android:name="android.hardware.usb.host" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<receiver android:name="mUsbReceiver">
<intent-filter>
<action android:name="android.hardware.usb.action.ACTION_USB_PERMISSION"/>
</intent-filter>
</receiver>
<activity
android:name="com.example.usb.FullscreenActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:label="@string/app_name"
android:theme="@style/FullscreenTheme" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.hardware.usb.action.USB_DEVICE_DETACHED" />
<action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
</intent-filter>
<meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
android:resource="@xml/device_filter" />
</activity>
</application>
</manifest>
Device_filter.xml 文件:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<!-- 0x0403 / 0x6001: FTDI FT232R UART -->
<usb-device vendor-id="1027" product-id="24577" />
<!-- 0x2341 / Arduino -->
<usb-device vendor-id="9025" />
<!-- 0x16C0 / 0x0483: Teensyduino -->
<usb-device vendor-id="5824" product-id="1155" />
<!-- 0x617 / 0x000b: EFPL CC2531 -->
<usb-device vendor-id="1559" product-id="11" />
<!-- vendor-id="0x0403" product-id="0x6015" // converted to Int vendor ID and product ID of my FT200XD-->
<usb-device vendor-id="1027" product-id="24597" />
</resources>
最佳答案
您可能想查看 registerReceiver 的返回代码 - 根据您在代码中发布的内容,我认为它会失败,因为您实际上并未实例化您的 mUsbReceiver。看看这段代码,它是从我编写的一个有效的应用程序中提取的,请注意我设置 BroadcastReceiver 的方式的不同,这也显示了如果您的设备已插入,如何请求权限:
PendingIntent mPermissionIntent = null;
UsbManager mUsbManager = null;
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
UsbDevice usbDevice = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (ACTION_USB_PERMISSION.equals(action)) {
// Permission requested
synchronized (this) {
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
// User has granted permission
// ... Setup your UsbDeviceConnection via mUsbManager.openDevice(usbDevice) ...
} else {
// User has denied permission
}
}
}
if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
// Device removed
synchronized (this) {
// ... Check to see if usbDevice is yours and cleanup ...
}
}
if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
// Device attached
synchronized (this) {
// Qualify the new device to suit your needs and request permission
if ((usbDevice.getVendorId() == MY_VID) && (usbDevice.getProductId() == MY_PID)) {
mUsbManager.requestPermission(usbDevice, mPermissionIntent);
}
}
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
// ... App Specific Setup Here ...
mUsbManager = (UsbManager)getSystemService(Context.USB_SERVICE);
// Register an intent filter so we can get permission to connect
// to the device and get device attached/removed messages
mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
registerReceiver(mUsbReceiver, filter);
// ... More App Specific Setup ...
}
另外 - 对于我的应用程序,我似乎不需要额外的 intent-filter 或元数据 XML 来执行 USB 操作。
关于android - 如何使用 UsbManager 检测连接的 USB 设备?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/25238469/