当我在水平或垂直视图中启动我的应用程序时，一旦我旋转屏幕，该应用程序就会运行正常，并崩溃并出现以下错误。从未使用过串行端口或Android服务。
错误：java.lang.RuntimeException：无法停止服务com.xxx.testing.UsbService@1aba8fa1：java.lang.NullPointerException：尝试调用虚拟方法'void com.felhr.usbserial.UsbSerialDevice.close（）'在空对象引用上
在com.xxx.testing.UsbService.onDestroy（UsbService.java:92）
我们将不胜感激。 谢谢
错误
--------- beginning of crash
08-15 17:23:30.475 5966-5966/com.xxx /AndroidRuntime: FATAL EXCEPTION: main
Process: com.xxx t, PID: 5966
java.lang.RuntimeException: Unable to stop service com.xxx.testing.UsbService@1aba8fa1: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.felhr.usbserial.UsbSerialDevice.close()' on a null object reference
at android.app.ActivityThread.handleStopService(ActivityThread.java:2911)
at android.app.ActivityThread.access$2200(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1381)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.felhr.usbserial.UsbSerialDevice.close()' on a null object reference
at com.xxx.testing.UsbService.onDestroy(UsbService.java:92)
at android.app.ActivityThread.handleStopService(ActivityThread.java:2894)
USB服务
@Override
public void onCreate() {
this.context = this;
serialPortConnected = false;
UsbService.SERVICE_CONNECTED = true;
setFilter();
usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
findSerialPortDevice();
}
@Override
public IBinder onBind(Intent intent) {
return binder;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
super.onStartCommand(intent, flags, startId);
return START_NOT_STICKY;
}
@Override
public void onDestroy() {
unregisterReceiver(usbReceiver);
serialPort.close();
UsbService.SERVICE_CONNECTED = false;
super.onDestroy();
}
private class ConnectionThread extends Thread {
@Override
public void run() {
serialPort = UsbSerialDevice.createUsbSerialDevice(device, connection);
if (serialPort != null) {
if (serialPort.open()) {
serialPort.setBaudRate(BAUD_RATE);
serialPort.setDataBits(UsbSerialInterface.DATA_BITS_8);
serialPort.setStopBits(UsbSerialInterface.STOP_BITS_1);
serialPort.setParity(UsbSerialInterface.PARITY_NONE);
serialPort.setFlowControl(UsbSerialInterface.FLOW_CONTROL_OFF);
serialPort.read(mCallback);
isReadyToSend = true;
// Everything went as expected. Send an intent to MainActivity
Intent intent = new Intent(ACTION_USB_READY);
context.sendBroadcast(intent);
} else {
// Serial port could not be opened, maybe an I/O error or if CDC driver was chosen, it does not really fit
// Send an Intent to Main Activity
if (serialPort instanceof CDCSerialDevice) {
Intent intent = new Intent(ACTION_CDC_DRIVER_NOT_WORKING);
context.sendBroadcast(intent);
} else {
Intent intent = new Intent(ACTION_USB_DEVICE_NOT_WORKING);
context.sendBroadcast(intent);
}
}
} else {
// No driver for given device, even generic CDC driver could not be loaded
Intent intent = new Intent(ACTION_USB_NOT_SUPPORTED);
context.sendBroadcast(intent);
}
}
}
public void setHandler(Handler mHandler) {
this.mHandler = mHandler;
}
private void setFilter() {
IntentFilter filter = new IntentFilter();
filter.addAction(ACTION_USB_PERMISSION);
filter.addAction(ACTION_USB_DETACHED);
filter.addAction(ACTION_USB_ATTACHED);
registerReceiver(usbReceiver, filter);
}
private void requestUserPermission() {
PendingIntent mPendingIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
usbManager.requestPermission(device, mPendingIntent);
}
public class UsbBinder extends Binder {
public UsbService getService() {
return UsbService.this;
}
}
private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context arg0, Intent arg1) {
if (arg1.getAction().equals(ACTION_USB_PERMISSION)) {
boolean granted = arg1.getExtras().getBoolean(UsbManager.EXTRA_PERMISSION_GRANTED);
if (granted) // User accepted our USB connection. Try to open the device as a serial port
{
Intent intent = new Intent(ACTION_USB_PERMISSION_GRANTED);
arg0.sendBroadcast(intent);
connection = usbManager.openDevice(device);
serialPortConnected = true;
new ConnectionThread().run();
} else // User not accepted our USB connection. Send an Intent to the Main Activity
{
Intent intent = new Intent(ACTION_USB_PERMISSION_NOT_GRANTED);
arg0.sendBroadcast(intent);
}
} else if (arg1.getAction().equals(ACTION_USB_ATTACHED)) {
if (!serialPortConnected)
findSerialPortDevice(); // A USB device has been attached. Try to open it as a Serial port
} else if (arg1.getAction().equals(ACTION_USB_DETACHED)) {
// Usb device was disconnected. send an intent to the Main Activity
Intent intent = new Intent(ACTION_USB_DISCONNECTED);
arg0.sendBroadcast(intent);
serialPortConnected = false;
serialPort.close();
}
}
};
private void findSerialPortDevice() {
// This snippet will try to open the first encountered usb device connected, excluding usb root hubs
HashMap<String, UsbDevice> usbDevices = usbManager.getDeviceList();
if (!usbDevices.isEmpty()) {
boolean keep = true;
for (Map.Entry<String, UsbDevice> entry : usbDevices.entrySet()) {
device = entry.getValue();
int deviceVID = device.getVendorId();
int devicePID = device.getProductId();
String title = String.format("Vendor %s Product %s", device.getVendorId(), device.getProductId());
Log.d("USB", "Found main Device: " + deviceVID + " " + devicePID);
if (deviceVID != 0x1d6b && (devicePID != 0x0001 || devicePID != 0x0002 || devicePID != 0x0003)) {
// There is a device connected to our Android device. Try to open it as a Serial Port.
requestUserPermission();
keep = false;
} else {
connection = null;
device = null;
}
if (!keep)
break;
}
if (!keep) {
// There is no USB devices connected (but usb host were listed). Send an intent to MainActivity.
Intent intent = new Intent(ACTION_NO_USB);
sendBroadcast(intent);
}
} else {
// There is no USB devices connected. Send an intent to MainActivity
Intent intent = new Intent(ACTION_NO_USB);
sendBroadcast(intent);
}
}
活动
public class splash_screen extends AppCompatActivity {
TextView text100, text200, text300, display;
Layout timer1;
// int time= 3600000*8;
public String data;
private UsbService usbService;
private EditText editText;
private MyHandler mHandler;
public StringBuilder stringBuilder = new StringBuilder();
//long time = 3600000 * 10;
long time = 20000;
private long result;
private long result2;
static final String STATE_USER = "user";
private String mUser;
@Override
protected void onCreate(Bundle savedInstanceState) {
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
super.onCreate(savedInstanceState);
setContentView(R.layout.splash_screen);
FullScreencall();
mHandler = new MyHandler(splash_screen.this);
int mUIFlag = View.SYSTEM_UI_FLAG_LOW_PROFILE
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION;
getWindow().getDecorView().setSystemUiVisibility(mUIFlag);
text100 = (TextView) findViewById(R.id.tv_hour);
text200 = (TextView) findViewById(R.id.tv_minute);
text300 = (TextView) findViewById(R.id.tv_second);
View someView1 = findViewById(R.id.timer1);
View someView2 = findViewById(R.id.timer2);
View someView3 = findViewById(R.id.timer3);
someView1.setBackgroundColor(Color.parseColor("#000000"));
someView2.setBackgroundColor(Color.parseColor("#000000"));
someView3.setBackgroundColor(Color.parseColor("#000000"));
if (savedInstanceState != null) {
// Restore value of members from saved state
mUser = savedInstanceState.getString(STATE_USER);
} else {
// Probably initialize members with default values for a new instance
mUser = "NewUser";
}
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putString(STATE_USER, mUser);
// Always call the superclass so it can save the view hierarchy state
super.onSaveInstanceState(savedInstanceState);
}
public void FullScreencall() {
if(Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) { // lower api
int mUIFlag = View.SYSTEM_UI_FLAG_LOW_PROFILE
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN;
getWindow().getDecorView().setSystemUiVisibility(mUIFlag);
} else if(Build.VERSION.SDK_INT >= 19) {
//for new api versions.
View decorView = getWindow().getDecorView();
// Hide both the navigation bar and the status bar.
// SYSTEM_UI_FLAG_FULLSCREEN is only available on Android 4.1 and higher, but as
// a general rule, you should design your app to hide the status bar whenever you
// hide the navigation bar.
int uiOptions = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
decorView.setSystemUiVisibility(uiOptions);
}
}
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
switch (intent.getAction()) {
case UsbService.ACTION_USB_PERMISSION_GRANTED: // USB PERMISSION GRANTED
//Toast.makeText(context, "USB Ready", Toast.LENGTH_SHORT).show();
break;
case UsbService.ACTION_USB_PERMISSION_NOT_GRANTED: // USB PERMISSION NOT GRANTED
Toast.makeText(context, "USB Permission not granted", Toast.LENGTH_SHORT).show();
break;
case UsbService.ACTION_NO_USB: // NO USB CONNECTED
// Toast.makeText(context, "No USB connected", Toast.LENGTH_SHORT).show();
break;
case UsbService.ACTION_USB_DISCONNECTED: // USB DISCONNECTED
Toast.makeText(context, "USB disconnected", Toast.LENGTH_SHORT).show();
break;
case UsbService.ACTION_USB_NOT_SUPPORTED: // USB NOT SUPPORTED
Toast.makeText(context, "USB device not supported", Toast.LENGTH_SHORT).show();
break;
}
}
};
private void startService(Class<?> service, ServiceConnection serviceConnection, Bundle extras) {
Intent serviceIntent = new Intent(this, UsbService.class);
this.startService(serviceIntent);
startService(serviceIntent);
if (!UsbService.SERVICE_CONNECTED) {
Intent startService = new Intent(this, UsbService.class);
if (extras != null && !extras.isEmpty()) {
Set<String> keys = extras.keySet();
for (String key : keys) {
String extra = extras.getString(key);
startService.putExtra(key, extra);
}
}
startService(startService);
}
Intent bindingIntent = new Intent(this, service);
bindService(bindingIntent, serviceConnection, Context.BIND_AUTO_CREATE);
}
private final ServiceConnection usbConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName arg0, IBinder arg1) {
usbService = ((UsbService.UsbBinder) arg1).getService();
usbService.setHandler(mHandler);
usbService.sendATGetACC();
}
@Override
public void onServiceDisconnected(ComponentName arg0) {
usbService = null;
}
};
@Override
public void onResume() {
super.onResume();
setFilters(); // Start listening notifications from UsbService
startService(UsbService.class, usbConnection, null); // Start UsbService(if it was not started before) and Bind it
}
@Override
public void onPause() {
try {
unregisterReceiver(mUsbReceiver);
unbindService(usbConnection);
} catch (IllegalArgumentException ex) {
}
super.onPause();
}
@Override
public void onDestroy() {
try {
if (mUsbReceiver != null)
unregisterReceiver(mUsbReceiver);
} catch (Exception e) {
}
stopService(new Intent(splash_screen.this, UsbService.class));
super.onDestroy();
}
private void setFilters() {
IntentFilter filter = new IntentFilter();
filter.addAction(UsbService.ACTION_USB_PERMISSION_GRANTED);
filter.addAction(UsbService.ACTION_NO_USB);
filter.addAction(UsbService.ACTION_USB_DISCONNECTED);
filter.addAction(UsbService.ACTION_USB_NOT_SUPPORTED);
filter.addAction(UsbService.ACTION_USB_PERMISSION_NOT_GRANTED);
registerReceiver(mUsbReceiver, filter);
}
public class MyHandler extends Handler {
private final WeakReference<splash_screen> mActivity;
public MyHandler(splash_screen activity) {
mActivity = new WeakReference<>(activity);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case UsbService.MESSAGE_FROM_SERIAL_PORT:
String data = (String) msg.obj;
if (data != null && !data.isEmpty()) {
Log.d("REPLY", "data value" + data);
mActivity.get().time(data);
break;
} else {
Log.d("REPLY", "novalue");
}
}
}
}
public void time(String data) {
long sec = Integer.parseInt(data);
Log.d("REPLY", "Recieved data" + sec);
result = TimeUnit.SECONDS.toMillis(sec);
Log.d("REPLY", "Result value" + result);
result2 = time - result;
Log.d("REPLY", "Result2 value" + result2);
Log.d("REPLY", "Time value" + time);
if (result >= time) {
//usbService.sendATGetSTOP();
Intent mainIntent = new Intent(splash_screen.this,
MainActivity.class);
mainIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
splash_screen.this.startActivity(mainIntent);
splash_screen.this.finish();
} else {
if (result >= time) {
// usbService.sendATGetSTOP();
Intent mainIntent = new Intent(splash_screen.this,
MainActivity.class);
mainIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
splash_screen.this.startActivity(mainIntent);
splash_screen.this.finish();
} else {
// Log.d("REPLY", "result2 value " + result2);
splashScreenUseAsyncTask();
}
}
}
private void splashScreenUseAsyncTask() {
// Create a AsyncTask object.
final RetrieveDateTask retrieveDateTask = new RetrieveDateTask();
retrieveDateTask.execute("", "", "");
// Get splash image view object.
final ImageView splashImageView = (ImageView) findViewById(R.id.logo_id);
//for 5 Hours
CountDownTimer countDownTimer = new CountDownTimer(result2, 1000) {
@SuppressLint("DefaultLocale")
@Override
public void onTick(long l) {
long Hours = l / (60 * 60 * 1000) % 24;
long Minutes = l / (60 * 1000) % 60;
long Seconds = l / 1000 % 60;
// tv_days.setText(String.format("%02d", Days));
text100.setText(String.format("%02d", Hours));
text200.setText(String.format("%02d", Minutes));
text300.setText(String.format("%02d", Seconds));
AlphaAnimation anim = new AlphaAnimation(1.0f, 0.0f);
anim.setDuration(500);
anim.setRepeatCount(anim.INFINITE);
anim.setRepeatMode(Animation.REVERSE);
splashImageView.startAnimation(anim);
}
@Override
public void onFinish() {
if (!retrieveDateTask.isAsyncTaskComplete()) {
this.start();
}
}
};
// Start the count down timer.
countDownTimer.start();
}
// This is the async task class that get data from network.
@SuppressLint("StaticFieldLeak")
private class RetrieveDateTask extends AsyncTask<String, String, String> {
// Indicate whether AsyncTask complete or not.
private boolean asyncTaskComplete = false;
public boolean isAsyncTaskComplete() {
return asyncTaskComplete;
}
public void setAsyncTaskComplete(boolean asyncTaskComplete) {
this.asyncTaskComplete = asyncTaskComplete;
}
// This method will be called before AsyncTask run.
@Override
protected void onPreExecute() {
this.asyncTaskComplete = false;
}
// This method will be called when AsyncTask run.
@Override
protected String doInBackground(String... strings) {
try {
// Simulate a network operation which will last for 10 seconds.
Thread currTread = Thread.currentThread();
currTread.sleep(result2);
} catch (Exception ex) {
ex.printStackTrace();
} finally {
return null;
}
}
// This method will be called after AsyncTask run.
@Override
protected void onPostExecute(String s) {
//usbService.sendATGetSTOP();
this.asyncTaskComplete = true;
//usbService.sendATGetACC();
// Start SplashScreenMainActivity.
Intent mainIntent = new Intent(splash_screen.this,
MainActivity.class);
mainIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
splash_screen.this.startActivity(mainIntent);
splash_screen.this.finish();
}
}
}
答案 0 :(得分：0)
旋转屏幕时，它将重新创建活动。我建议检查onDestroy（）以查看USB是否为空。然后，在create（）中更改方向后进行调试，以查看是否也重新创建了USB。我们可以利用onSaveInstance（）在更改方向之前保存一些数据。
https://developer.android.com/guide/topics/resources/runtime-changes
答案 1 :(得分：0)
在onDestroy（）中使用它：
if (serialPort != null){
serialPort.close();
}
代替：
serialPort.close();