Android Studio Serial Port

Android Studio 版本

Android Studio Arctic Fox | 2020.3.1 Patch 4

建立android_serialport_api & jni

點擊下載android_serialport_api & jni 檔案

建立android_serialport_api

main ->  java 新增Package android_serialport_api

將Download中SerialPort.java放入新增android_serialport_api

建立JNI

File -> New -> Folder -> JNI Folder 

將Download下來的jni 內容五個檔案放入新增的jni

指定Android.mk

android_serialport_api & jni 新增完畢後

build.gradle(app)android {}中加入指定Android.mk

externalNativeBuild {
    ndkBuild {
        path file('src/main/jni/Android.mk')
    }
}

Layout

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/command"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="50dp"
        android:layout_marginRight="15dp"
        android:hint="請輸入指令" />

    <Button
        android:id="@+id/sendmsg_bt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/command"
        android:layout_centerVertical="true"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="10dp"
        android:layout_marginRight="15dp"
        android:text="發送訊息" />

    <TextView
        android:id="@+id/showtext"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/sendmsg_bt"
        android:layout_centerInParent="true"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="30dp"
        android:layout_marginRight="15dp"
        android:layout_marginBottom="30dp"
        android:scrollbars="vertical"/>

</RelativeLayout>

MainActivity

設定SerialPort

mSerialPort = new SerialPort(new File("/dev/tty0"), 9600, 8,1, 'N');

參數

• 串列埠名稱(Serial port)
• 鮑率(Baud Rate)
• 資料位元長度(Data Bits)
• 資料停止位元(Stop Bits)
• 同位元檢查(Parity Bits)

接收Input訊息

private class ReadThread extends Thread {
    @Override
    public void run() {
        super.run();
        Log.e(TAG, "Read thread is open.");
        while (!isInterrupted()) {
            if (mInputStream == null)
                return;
            try {
                byte[] buffer = new byte[64];
                int size = mInputStream.read(buffer);
                if (size > 0) {
                    onDataReceived(buffer, size);
                }
            } catch (IOException e) {
                e.printStackTrace();
                return;
            }
        }
    }
}

建立一個Thread來獲取Input的訊息

宣告byte[]利用mInputStream.read()

將Input的訊息存入byte[]

宣告int 紀錄訊息長度

顯示訊息

protected void onDataReceived(final byte[] buffer, final int size) {
    runOnUiThread(() -> {
        String receivedMessage = new String(buffer, 0, size);
        recvStr = recvStr + receivedMessage + "\n";
        showtext.setText(recvStr);
    });
}

byte[]訊息使用String(byte[] bytes, int offset, int length)做轉換

• byte[] bytes
• 要解碼的訊息,型態為byte
• offset
• 要從哪的byte開始解碼
• length
• 解碼到哪個byte

完整MainActivity

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.method.ScrollingMovementMethod;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android_serialport_api.SerialPort;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "m";
    protected SerialPort mSerialPort;
    protected InputStream mInputStream;
    protected OutputStream mOutputStream;
    private ReadThread mReadThread;

    private EditText command;
    private Button sendmsg_bt;
    private TextView showtext;

    private String recvStr = "";

    private class ReadThread extends Thread {
        @Override
        public void run() {
            super.run();

            Log.e(TAG, "Read thread is open.");
            while (!isInterrupted()) {
                if (mInputStream == null)
                    return;

                try {
                    byte[] buffer = new byte[64];
                    int size = mInputStream.read(buffer);
                    if (size > 0) {
                        onDataReceived(buffer, size);
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                    return;
                }
            }
        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewinit();
        Set_serial();

    }

    @Override
    protected void onDestroy() {
        Log.d(TAG, "in onDestroy()");
        if (mReadThread != null) {
            mReadThread.interrupt();
        }

        if (mSerialPort != null) {
            mSerialPort.close();
            mSerialPort = null;

            try {
                mOutputStream.close();
                mOutputStream = null;
                mInputStream.close();
                mInputStream = null;
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        super.onDestroy();
    }

    private void viewinit() {
        command = (EditText) findViewById(R.id.command);
        sendmsg_bt = (Button) findViewById(R.id.sendmsg_bt);
        showtext = (TextView) findViewById(R.id.showtext);
        sendmsg_bt.setOnClickListener(send);
        showtext.setMovementMethod(ScrollingMovementMethod.getInstance());

    }

    private void Set_serial() {
        try {
            Log.e(TAG, "Try to open serial port");
            mSerialPort = new SerialPort(new File("/dev/tty0"), 9600, 8,1, 'N');
            mInputStream = mSerialPort.getInputStream();
            mOutputStream = mSerialPort.getOutputStream();
            Log.e(TAG, "Serial port opened!");

            mReadThread = new ReadThread();
            mReadThread.start();
        } catch (SecurityException e) {
            Log.e(TAG, "Security Exception");
            e.printStackTrace();
        } catch (IOException e) {
            Log.e(TAG, "Fail to open serial port");
            e.printStackTrace();
        }
    }

    private Button.OnClickListener send = new Button.OnClickListener() {
        @Override
        public void onClick(View v) {
            String CMD = command.getText().toString();
            byte[] bytes = CMD.getBytes();
            try {
                mOutputStream.write(bytes);
            } catch (IOException e) {
                Log.e(TAG, "Fail to send out message");
                e.printStackTrace();
            }
        }
    };

    protected void onDataReceived(final byte[] buffer, final int size) {
        runOnUiThread(() -> {
            String receivedMessage = new String(buffer, 0, size);
            recvStr = recvStr + receivedMessage + "\n";
            showtext.setText(recvStr);
        });
    }
}

若是無法執行或有問題請看這篇Android Studio Serial_Port 無法執行