Question

我想对一个可以通过蓝牙控制Arduino的应用进行编程，但是每次我按一个按钮时，该应用就会崩溃。我在下面找到了代码和错误代码，希望有人可以帮助我。我对这个android应用程序编程完全陌生。

主要活动

package com.example.arduinofernsteuerung;

import android.annotation.SuppressLint;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;


public class MainActivity extends AppCompatActivity {
    private final String DEVICE_ADDRESS = "98:d3:31:f5:a9:e5";
    private final UUID PORT_UUID = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb");

    private BluetoothDevice device;
    private BluetoothSocket socket;
    private OutputStream outputStream;

    Button Vorwaerts, Links, Rechts, Rueckwaerts;

    String command;

    @SuppressLint("ClickableViewAccessibility")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Vorwaerts = (Button) findViewById(R.id.Vorwaerts);
        Links = (Button) findViewById(R.id.Links);
        Rechts = (Button) findViewById(R.id.Rechts);
        Rueckwaerts = (Button) findViewById(R.id.Rueckwaerts);


        Vorwaerts.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {

                if (event.getAction() == MotionEvent.ACTION_DOWN)
                {
                    command = "1";

                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }
                else if(event.getAction() == MotionEvent.ACTION_UP)
                {
                    command = "10";
                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch(IOException e)
                    {
                        e.printStackTrace();
                    }

                }

                return false;
            }

        });


        Rueckwaerts.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event)
            {
                if(event.getAction() == MotionEvent.ACTION_DOWN)
                {
                    command = "2";

                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }
                else if(event.getAction() == MotionEvent.ACTION_UP)
                {
                    command = "10";
                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch(IOException e)
                    {

                    }

                }
                return false;
            }
        });


        Links.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event)
            {
                if(event.getAction() == MotionEvent.ACTION_DOWN)
                {
                    command = "3";

                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }
                else if(event.getAction() == MotionEvent.ACTION_UP)
                {
                    command = "10";
                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch(IOException e)
                    {

                    }

                }
                return false;
            }
        });


        Rechts.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event)
            {
                if(event.getAction() == MotionEvent.ACTION_DOWN)
                {
                    command = "4";

                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch (IOException e)
                    {
                        e.printStackTrace();
                    }
                }
                else if(event.getAction() == MotionEvent.ACTION_UP)
                {
                    command = "10";
                    try
                    {
                        outputStream.write(command.getBytes());
                    }
                    catch(IOException e)
                    {
                        e.printStackTrace();
                    }

                }
                return false;
            }
        });
    }


    public boolean BTinit()
    {
        boolean found = false;

        BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

        if(bluetoothAdapter == null)
        {
            Toast.makeText(getApplicationContext(), "Device doesn't support bluetooth", Toast.LENGTH_SHORT).show();
        }

        if(!bluetoothAdapter.isEnabled())
        {
            Intent enableAdapter = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableAdapter,0);

            try
            {
                Thread.sleep(1000);
            }
            catch(InterruptedException e)
            {
                e.printStackTrace();
            }
        }

        Set<BluetoothDevice> bondedDevices = bluetoothAdapter.getBondedDevices();

        if(bondedDevices.isEmpty())
        {
            Toast.makeText(getApplicationContext(), "Please pair the device first", Toast.LENGTH_SHORT).show();
        }
        else
        {
            for(BluetoothDevice iterator : bondedDevices)
            {
                if(iterator.getAddress().equals(DEVICE_ADDRESS))
                {
                    device = iterator;
                    found = true;
                    break;
                }
            }
        }

        return found;
    }

    public boolean BTconnect()
    {
        boolean connected = true;

        try
        {
            socket = device.createRfcommSocketToServiceRecord(PORT_UUID);
            socket.connect();

            Toast.makeText(getApplicationContext(),
                    "Connection to bluetooth device successful", Toast.LENGTH_LONG).show();
        }
        catch(IOException e)
        {
            e.printStackTrace();
            connected = false;
        }

        if(connected)
        {
            try
            {
                outputStream = socket.getOutputStream();
            }
            catch(IOException e)
            {
                e.printStackTrace();
            }
        }

        return connected;
    }

    @Override
    protected void onStart()
    {
        super.onStart();
    }
}

Android清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.arduinofernsteuerung">

    <uses-permission android:name="android.permission.BLUETOOTH"/>

    <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/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    android:paddingBottom="20dp"
    android:paddingLeft="20dp"
    android:paddingRight="20dp"
    android:paddingTop="20dp"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/Vorwaerts"
        android:text="Vorwärts"
        android:layout_height="70dp"
        android:layout_width="120dp"
        android:layout_alignParentTop="true"
        android:layout_marginTop="300dp"
        android:layout_toStartOf="@+id/Rechts"
        android:layout_centerHorizontal="true"/>

    <Button
        android:id="@+id/Links"
        android:text="Links"
        android:layout_height="70dp"
        android:layout_width="120dp"
        android:layout_below="@+id/Vorwaerts"
        android:layout_marginTop="2dp"
        android:layout_marginEnd="13dp"
        android:layout_toStartOf="@+id/Vorwaerts" />

    <Button
        android:id="@+id/Rechts"
        android:text="Rechts"
        android:layout_height="70dp"
        android:layout_width="120dp"
        android:layout_above="@+id/Rueckwaerts"
        android:layout_marginStart="13dp"
        android:layout_marginBottom="3dp"
        android:layout_toEndOf="@+id/Rueckwaerts" />

    <Button
        android:id="@+id/Rueckwaerts"
        android:text="Rückwärts"
        android:layout_width="120dp"
        android:layout_height="70dp"
        android:layout_below="@+id/Links"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="-3dp" />


</RelativeLayout>

错误

2020-03-11 15:01:31.432 20330-20330/com.example.arduinofernsteuerung E/InputEventReceiver: Exception dispatching input event.
2020-03-11 15:01:31.432 20330-20330/com.example.arduinofernsteuerung E/MessageQueue-JNI: Exception in MessageQueue callback: handleReceiveCallback
2020-03-11 15:01:31.438 20330-20330/com.example.arduinofernsteuerung E/MessageQueue-JNI: java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.OutputStream.write(byte[])' on a null object reference
        at com.example.arduinofernsteuerung.MainActivity$1.onTouch(MainActivity.java:54)
        at android.view.View.dispatchTouchEvent(View.java:14372)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3863)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:3492)
        at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:729)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1922)
        at android.app.Activity.dispatchTouchEvent(Activity.java:4051)
        at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
        at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:687)
        at android.view.View.dispatchPointerEvent(View.java:14644)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:6456)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:6243)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5681)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5734)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5700)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:5856)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5708)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5913)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5681)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:5734)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:5700)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:5708)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:5681)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:8840)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:8701)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:8654)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:8976)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:194)
        at android.os.MessageQueue.nativePollOnce(Native Method)
        at android.os.MessageQueue.next(MessageQueue.java:336)
        at android.os.Looper.loop(Looper.java:197)
        at android.app.ActivityThread.main(ActivityThread.java:7811)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1076)
2020-03-11 15:01:31.438 20330-20330/com.example.arduinofernsteuerung D/AndroidRuntime: Shutting down VM
2020-03-11 15:01:31.441 20330-20330/com.example.arduinofernsteuerung E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.arduinofernsteuerung, PID: 20330
    java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.OutputStream.write(byte[])' on a null object reference
        at com.example.arduinofernsteuerung.MainActivity$1.onTouch(MainActivity.java:54)
        at android.view.View.dispatchTouchEvent(View.java:14372)

我写道：现在是public boolean write（）而不是：public boolean BTConnect（）我希望这就是您的意思，但我仍然遇到同样的问题，但是感谢您的快速评论

Answer 1

您的代码有些奇怪，您永远不会调用BTConnect（）方法。这就是为什么当您尝试对其调用write（）时outputStream为null的原因。我认为它可能会那样工作，请尝试并保持联系。

按下按钮后应用程序崩溃-蓝牙Arduino

1 个答案: