• • bounty将在2天后过期**。回答此问题可获得+50的声誉奖励。obeid_s正在寻找来自声誉良好来源的答案。

我想做的是

• 创建一个应用程序的windows连接android手机。
• 发送和接收数据。
• Windows（C#）是主机设备--〉安卓UsbAccessory.

C编号：

现在我可以选择COM5（Android手机）并连接到它，使用以下代码：

serialPort1.PortName = this.devicesList.Text; // COM5
   serialPort1.Open();
   addToList("SerialPort is opened", Color.Green);

Java（安卓手机）：

UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
     UsbAccessory[] accessories = manager.getAccessoryList();

accessories始终为空，我尝试了找到的每一个代码，但我做不到。
我做错了什么
谢谢。
：：：编辑：：：
Android Studio 代码（Java）

package com.example.camerausb;

import android.app.Activity;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.hardware.usb.UsbAccessory;
import android.hardware.usb.UsbManager;
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.widget.Toast;

import androidx.annotation.Nullable;

import java.io.FileInputStream;
import java.io.FileOutputStream;

public class UsbConnector extends Activity {
    private static final String ACTION_USB_PERMISSION = "com.example.camerausb.UsbConnector.USB_PERMISSION";
    public UsbManager usbManager;
    public UsbAccessory usbAccessory;
    public PendingIntent mPermissionIntent;
    public Context global_context;
    private IntentFilter filter;
    
    private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (ACTION_USB_PERMISSION.equals(action)) {
                synchronized (this) {
                    UsbAccessory accessory = (UsbAccessory) intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);
                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        Toast.makeText(global_context, "Allow Usb Permission", Toast.LENGTH_LONG).show();
                        // TODO:: open Accessory method
                    } else {
                        Toast.makeText(global_context, "Deny Usb Permission", Toast.LENGTH_LONG).show();
                    }
                }
            }
            else if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action)) {
                Toast.makeText(global_context, "Usb detached", Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(global_context, "something else", Toast.LENGTH_LONG).show();
            }
        }

    };

    public UsbConnector(Context context) {
        super();
        global_context = context;
        Toast.makeText(global_context, "started", Toast.LENGTH_LONG).show();
        usbManager = (UsbManager) global_context.getSystemService(Context.USB_SERVICE);
        mPermissionIntent = PendingIntent.getBroadcast(global_context, 0, new Intent(ACTION_USB_PERMISSION), 0);
        filter = new IntentFilter(ACTION_USB_PERMISSION);
        filter.addAction(ACTION_USB_PERMISSION);
        
      filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);
      usbManager.requestPermission(usbAccessory, mPermissionIntent);
        global_context.registerReceiver(mUsbReceiver, filter);
    }

    public BroadcastReceiver getReceiver() {
        return this.mUsbReceiver;
    }
    public IntentFilter getFilter() {
        return this.filter;
    }

    public void resumeAccessory(Intent intent) {
//        Intent intent = getIntent();
        String action = intent.getAction();
        Toast.makeText(global_context, "resume: " + action, Toast.LENGTH_LONG).show();
        UsbAccessory[] accessories = usbManager.getAccessoryList();
        if (accessories != null) {
            Toast.makeText(global_context, "Accessory not NULL", Toast.LENGTH_LONG).show();

        } else {
            Toast.makeText(global_context, "Accessory is NULL", Toast.LENGTH_LONG).show();
        }

    }
}

清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.camerausb">
    <uses-sdk android:minSdkVersion="12" />
    <uses-feature android:name="android.hardware.usb.accessory" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.CameraUsb">

        <activity
            android:name=".MainActivity"
            android:exported="true">
            <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_ACCESSORY_ATTACHED" />
            </intent-filter>

            <meta-data
                android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
                android:resource="@xml/accessory_filter" />
        </activity>
    </application>

</manifest>

xml/附件过滤器：

<?xml version="1.0" encoding="utf-8"?>

<resources>
    <usb-accessory model="DemoKit" manufacturer="Google" version="1.0" />
</resources>