android - 通过 USB 从 Android 应用程序发送和接收数据

Question

我正在尝试通过 USB 将 PIC 微处理器连接到平板电脑应用程序。发送按钮应触发由 "$$$" 组成的字符串的发送。到 PIC。通过消除过程，它似乎一直到底部的“requestWait”行。该按钮保持突出显示，应用程序似乎挂起。我怀疑 requestWait 没有答案，所以它无限期地等待。我会很感激一些帮助。我已经查看了 AdbTest 和 Missile Launcher 应用程序，但对于我的 Android 专业知识水平来说，它们的内容太多了。

后来补充:

查看 UsbRequest queue(..) 的代码, result = native_queue_direct(...) .

我认为这是 native 代码。请问我在哪里可以找到？

import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Iterator;

import android.content.Context;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbInterface;
import android.hardware.usb.UsbManager;
import android.hardware.usb.UsbRequest;
import android.view.View;
import android.widget.Toast;

    @Override
    protected void onResume() {
        super.onResume();

        mManager = (UsbManager) getSystemService(Context.USB_SERVICE);

        // check for existing devices
        UsbDevice device;

        HashMap<String, UsbDevice> deviceList = mManager.getDeviceList();
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        while (deviceIterator.hasNext()) {
            device = deviceIterator.next();
            if (device.getVendorId() == 1027) {
                UsbInterface intf = device.getInterface(0);
                if (setUsbInterface(device, intf)) {
                    break;
                }
            }
        }

        private UsbManager          mManager;
        private UsbDevice           mDevice;
        private UsbDeviceConnection mDeviceConnection;
        private UsbInterface        mInterface;

        private ScorerDevice        mScorerDevice ;

        // ***********************************

        // Sets the current USB device and interface
        private boolean setUsbInterface(UsbDevice device, UsbInterface intf) {
            if (mDeviceConnection != null) {
                if (mInterface != null) {
                    mDeviceConnection.releaseInterface(mInterface);
                    mInterface = null;
                }
                mDeviceConnection.close();
                mDevice = null;
                mDeviceConnection = null;
            }

            if (device != null && intf != null) {
                UsbDeviceConnection connection = mManager.openDevice(device);
                if (connection != null) {
                    if (connection.claimInterface(intf, true)) {

                        toast = Toast.makeText(getApplicationContext(), "claim interface succeeded", Toast.LENGTH_SHORT);
                        toast.show();

                        mDevice = device;
                        mDeviceConnection = connection;
                        mInterface = intf;
                        mScorerDevice = new ScorerDevice(this, mDeviceConnection, intf);

                        toast = Toast.makeText(getApplicationContext(), "USB started", Toast.LENGTH_SHORT);
                        toast.show();

                        mScorerDevice.start();
                        return true;
                    } else {

                        toast = Toast.makeText(getApplicationContext(), "claim interface failed", Toast.LENGTH_SHORT);
                        toast.show();

                        connection.close();
                    }
                } else {

                    toast = Toast.makeText(getApplicationContext(), "USB failed", Toast.LENGTH_SHORT);
                    toast.show();
                }
            }

            if (mDeviceConnection == null && mScorerDevice != null) {
                mScorerDevice.stop();
                mScorerDevice = null;
            }
            return false;
        }

        // ***********************************

        public int onClick_Send(View view) {

            String dollars = "$$$";
            byte[] bytes = dollars.getBytes();

            int len = bytes.length;
            int offset = 0;

            int PacketSize = mScorerDevice.mEndpointOut.getMaxPacketSize();

            if ((len > PacketSize) || (offset < 0) || (len < 0) || ((offset + len) > bytes.length))
                throw new IndexOutOfBoundsException();

            ByteBuffer sendBuffer = ByteBuffer.allocate(PacketSize);

            UsbRequest request = new UsbRequest();
            Boolean ret = request.initialize(mDeviceConnection, mScorerDevice.mEndpointOut);
            if (!ret ) {
                return -1;
            }

            ret = request.queue(sendBuffer, len);
            if (!ret ) {
                return -1;
            }

            request = mDeviceConnection.requestWait();
            if (request == null) {
                return -1;
            }

        }        

Answer 1

这在大多数设备上是不可能的，因为它们不支持 USB 主机模式。有些设备有 USB OTG 支持或 USB 主机端口 ，但到目前为止，这些都是比较少见的设备。

理论上，您可以在 Win/Linux 上编写应用程序以通过 USB 访问手机，但反之则不行。

但是你可以Read This并尝试。

对于与设备通信，请参阅 - How to establish communication between android device and usb.

愿它有帮助...