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USB 通信错误 - Android 开发

[英]Error in USB Communication - Android Development

 原文  2020-09-07 13:57:05  0   1    java

问题描述

我正在通过 USB 学习 android 通信，我正在开发一个非常简单的应用程序，让我了解 USB 通信的基本概念。 应用程序的功能和文本显示 通过单击按钮（检查 USB 设备）查看连接到平板电脑 USB 的设备的信息，但按下按钮后应用程序会单独关闭。 我需要关于我的应用程序中发生的错误的帮助和指导，如果有人可以帮助我定位和检测错误，这将对我有很大帮助，并且对我的学习非常重要。 从今以后我感谢你

如果有人能根据我在这里的帖子跟上我的发展，lament 会很酷。

下载应用程序进行测试 - Google Drive

在这里下载应用程序

屏幕设计

屏幕设计 - 点击这里

空指针异常

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.android.usb, PID: 7074
    java.lang.NullPointerException
        at com.android.usb.MainActivity.checkInfo(MainActivity.java:80)
        at com.android.usb.MainActivity.access$000(MainActivity.java:25)
        at com.android.usb.MainActivity$1.onClick(MainActivity.java:44)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)

逻辑猫

09-07 10:49:10.170 6370-6370/com.android.usb D/AndroidRuntime: Shutting down VM
09-07 10:49:10.170 6370-6370/com.android.usb W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x415d3ba8)
09-07 10:49:10.170 6370-6370/com.android.usb E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.android.usb, PID: 6370
    java.lang.NullPointerException
        at com.android.usb.MainActivity.checkInfo(MainActivity.java:81)
        at com.android.usb.MainActivity.access$000(MainActivity.java:25)
        at com.android.usb.MainActivity$1.onClick(MainActivity.java:44)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)

acticity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <Button
            android:id="@+id/check"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Check USB Device" />

        <TextView
            android:id="@+id/info"
            android:layout_width="match_parent"
            android:layout_height="677dp" />
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml

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

    <uses-feature android:name="android.hardware.usb.host" />

    <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>

主活动文件

package com.android.usb;

import androidx.appcompat.app.AppCompatActivity;

import java.util.HashMap;
import java.util.Iterator;
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.hardware.usb.UsbDevice;
import android.hardware.usb.UsbManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import java.util.HashMap;
import java.util.Iterator;

public class MainActivity extends AppCompatActivity {

    private static final String ACTION_USB_PERMISSION = "com.android.usb.USB_PERMISSION";
    Button btnCheck;
    TextView textInfo;
    UsbManager usbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btnCheck = (Button) findViewById(R.id.check);
        final TextView textInfo = (TextView) findViewById(R.id.info);
        btnCheck.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View arg0)
            {
                textInfo.setText("");
                checkInfo();
            }
        });

    }

    private void checkInfo()
    {
        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        
        /*------------------------------------------------------------------------------------------------------------*/

        PendingIntent permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(usbReceiver, filter);
        
        /*------------------------------------------------------------------------------------------------------------*/

        HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        String i = "";
        while(deviceIterator.hasNext())
        {
            UsbDevice device = deviceIterator.next();

            /*------------------------------------------------------------------------------------------------------------*/

            usbManager.requestPermission(device, permissionIntent);
            i += "\n" + "DeviceID: " + device.getDeviceId() + "\n"
                    + "DeviceName: " + device.getDeviceName() + "\n"
                    + "DeviceClass: " + device.getDeviceClass() + " - "
                    + "DeviceSubClass: " + device.getDeviceSubclass() + "\n"
                    + "VendorID: " + device.getVendorId() + "\n"
                    + "ProductID: " + device.getProductId() + "\n";
        }

        textInfo.setText(i);

    }

    /*------------------------------------------------------*/

    private final BroadcastReceiver usbReceiver = new BroadcastReceiver()
    {

        public void onReceive(Context context, Intent intent)
        {
            String action = intent.getAction();
            if (ACTION_USB_PERMISSION.equals(action))
            {
                synchronized (this)
                {
                    UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);

                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))
                    {
                        if(device != null)
                        {
                            //call method to set up device communication
                        }
                    }
                    else
                    {
                        Log.d("ERROR", "permission denied for device " + device);
                    }
                }
            }
        }
    };
    
    /*------------------------------------------------------*/
    
}

谢谢你

1 个解决方案

解决方案1
 0  

我解决了应用程序关闭的问题，问题出在 onCreate() 之前的 TextView 语句中。 现在我遇到了一个新问题，我在平板电脑上运行该应用程序并将某些东西插入串行端口，但没有任何反应，它应该显示设备信息，但它没有发生并且平板电脑不显示请求授权的对话框用于连接； 我的代码一定有什么问题？

MainAcivity.java - （应用程序关闭固定）

package com.android.usb;

import androidx.appcompat.app.AppCompatActivity;

import java.util.HashMap;
import java.util.Iterator;
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.hardware.usb.UsbDevice;
import android.hardware.usb.UsbManager;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

import java.util.HashMap;
import java.util.Iterator;

public class MainActivity extends AppCompatActivity {

    private static final String ACTION_USB_PERMISSION = "com.android.usb.USB_PERMISSION";
    Button btnCheck;
    TextView textInfo;
    UsbManager usbManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnCheck = (Button) findViewById(R.id.check);
        textInfo = (TextView) findViewById(R.id.info);
        btnCheck.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View arg0)
            {
                textInfo.setText("");
                checkInfo();
            }
        });

    }

    private void checkInfo()
    {
        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);

        PendingIntent permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(usbReceiver, filter);

        HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        String i = "";
        while(deviceIterator.hasNext())
        {
            UsbDevice device = deviceIterator.next();

            usbManager.requestPermission(device, permissionIntent);
            i += "\n" + "DeviceID: " + device.getDeviceId() + "\n"
                    + "DeviceName: " + device.getDeviceName() + "\n"
                    + "DeviceClass: " + device.getDeviceClass() + " - "
                    + "DeviceSubClass: " + device.getDeviceSubclass() + "\n"
                    + "VendorID: " + device.getVendorId() + "\n"
                    + "ProductID: " + device.getProductId() + "\n";
        }

        textInfo.setText(i);
    }

    /*---------------------------------------------------------------------------------------------------*/

    private final BroadcastReceiver usbReceiver = new BroadcastReceiver()
    {

        public void onReceive(Context context, Intent intent)
        {
            String action = intent.getAction();
            if (ACTION_USB_PERMISSION.equals(action))
            {
                synchronized (this)
                {
                    UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                    /*-----------------------------------------------------------------------------------*/

                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))
                    {
                        if(device != null)
                        {
                            //call method to set up device communication
                        }
                    }
                    else
                    {
                        Log.d("ERROR", "permission denied for device " + device);
                    }
                }
            }
        }
    };
    /*------------------------------------------------------*/
}

再次感谢你

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