Arduino安卓应用程序在启动时崩溃

Question

我有一个用eclipse开发的Android应用程序来打开或关闭LED，但应用程序在启动时崩溃。

以下是我的活动：

ArduinoBlinkLedActivity.java（默认活动）：

package com.example.arduinoblickled;

import java.io.IOException;

import com.example.arduinoblinkled.R;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ToggleButton;



public class ArduinoBlinkLEDActivity extends Activity {


    private ToggleButton buttonLED;
    ArduinoBlinkLED a;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_arduino_blink_led);
        buttonLED = (ToggleButton) findViewById(R.id.toggleButtonLED);
        setContentView(R.layout.activity_arduino_blink_led);



    }

    public void blinkLED(View v){

        byte[] buffer = new byte[1];
        if(buttonLED.isChecked())
            buffer[0]=(byte)0; // button says on, light is off
        else
            buffer[0]=(byte)1; // button says off, light is on
        if (a.mOutputStream != null) {
            try {
                a.mOutputStream.write(buffer);
            } catch (IOException e) {

            }
        }
    }



}

ArduinoBlinkLed.java -

package com.example.arduinoblickled;

import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;





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.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.util.Log;
import android.view.View;
import android.widget.ToggleButton;




import com.android.future.usb.UsbAccessory;
import com.android.future.usb.UsbManager;
import com.example.arduinoblinkled.R;


public class ArduinoBlinkLED extends Activity {

    // TAG is used to debug in Android logcat console
    private static final String TAG = "ArduinoAccessory";

    private static final String ACTION_USB_PERMISSION = "com.google.android.DemoKit.action.USB_PERMISSION";

    public UsbManager mUsbManager;
    public PendingIntent mPermissionIntent;
    public boolean mPermissionRequestPending;
    public ToggleButton buttonLED;

    public UsbAccessory mAccessory;
    public ParcelFileDescriptor mFileDescriptor;
    public FileInputStream mInputStream;
    public FileOutputStream mOutputStream;

    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 = UsbManager.getAccessory(intent);
                    if (intent.getBooleanExtra(
                            UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        openAccessory(accessory);
                    } else {
                        Log.d(TAG, "permission denied for accessory "
                                + accessory);
                    }
                    mPermissionRequestPending = false;
                }
            } else if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action)) {
                UsbAccessory accessory = UsbManager.getAccessory(intent);
                if (accessory != null && accessory.equals(mAccessory)) {
                    closeAccessory();
                }
            }
        }
    };


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mUsbManager = UsbManager.getInstance(this);
        mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);
        registerReceiver(mUsbReceiver, filter);

        if (getLastNonConfigurationInstance() != null) {
            mAccessory = (UsbAccessory) getLastNonConfigurationInstance();
            openAccessory(mAccessory);
        }

        setContentView(R.layout.activity_arduino_blink_led);
        buttonLED = (ToggleButton) findViewById(R.id.toggleButtonLED);

    }

    @Override
    public Object onRetainNonConfigurationInstance() {
        if (mAccessory != null) {
            return mAccessory;
        } else {
            return super.onRetainNonConfigurationInstance();
        }
    }

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

        if (mInputStream != null && mOutputStream != null) {
            return;
        }

        UsbAccessory[] accessories = mUsbManager.getAccessoryList();
        UsbAccessory accessory = (accessories == null ? null : accessories[0]);
        if (accessory != null) {
            if (mUsbManager.hasPermission(accessory)) {
                openAccessory(accessory);
            } else {
                synchronized (mUsbReceiver) {
                    if (!mPermissionRequestPending) {
                        mUsbManager.requestPermission(accessory,mPermissionIntent);
                        mPermissionRequestPending = true;
                    }
                }
            }
        } else {
            Log.d(TAG, "mAccessory is null");
        }
    }

    @Override
    public void onPause() {
        super.onPause();
        closeAccessory();
    }

    @Override
    public void onDestroy() {
        unregisterReceiver(mUsbReceiver);
        super.onDestroy();
    }

    private void openAccessory(UsbAccessory accessory) {
        mFileDescriptor = mUsbManager.openAccessory(accessory);
        if (mFileDescriptor != null) {
            mAccessory = accessory;
            FileDescriptor fd = mFileDescriptor.getFileDescriptor();
            mInputStream = new FileInputStream(fd);
            mOutputStream = new FileOutputStream(fd);
            Log.d(TAG, "accessory opened");
        } else {
            Log.d(TAG, "accessory open fail");
        }
    }


    private void closeAccessory() {
        try {
            if (mFileDescriptor != null) {
                mFileDescriptor.close();
            }
        } catch (IOException e) {
        } finally {
            mFileDescriptor = null;
            mAccessory = null;
        }
    }

    public void blinkLED(View v){

        byte[] buffer = new byte[1];

        if(buttonLED.isChecked())
            buffer[0]=(byte)0; // button says on, light is off
        else
            buffer[0]=(byte)1; // button says off, light is on

        if (mOutputStream != null) {
            try {
                mOutputStream.write(buffer);
            } catch (IOException e) {
                Log.e(TAG, "write failed", e);
            }
        }
    }

}

这是我的LogCat过滤到只显示项目包含“ard”（在新标签页中打开）：