Java 使用线程和USB连接后的空白应用程序屏幕
我是Android的初学者。我试图开发一个通过USB连接进行通信的基本应用程序。我必须等待传入的数据,因为我真的不知道它是在什么时候出现的,所以我用而(true)解决了它。对于这个while循环,我尝试使用线程。我没有太多的线程经验 但问题是,现在每当我按下手机上的后退按钮,然后我再次尝试打开我的应用程序时,它只会显示一个空白的应用程序屏幕 你能帮我吗?谢谢 主要活动类别:Java 使用线程和USB连接后的空白应用程序屏幕,java,android,multithreading,usb,Java,Android,Multithreading,Usb,我是Android的初学者。我试图开发一个通过USB连接进行通信的基本应用程序。我必须等待传入的数据,因为我真的不知道它是在什么时候出现的,所以我用而(true)解决了它。对于这个while循环,我尝试使用线程。我没有太多的线程经验 但问题是,现在每当我按下手机上的后退按钮,然后我再次尝试打开我的应用程序时,它只会显示一个空白的应用程序屏幕 你能帮我吗?谢谢 主要活动类别: public class MainActivity extends AppCompatActivity { UsbDev
public class MainActivity extends AppCompatActivity {
UsbDevice device;
Button bShow;
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
UsbManager mUsbManager;
PendingIntent mPermissionIntent;
TextView tvTest, tvAppend;
String sendText = "@V\r\n";
private byte[] bytes;
private static int TIMEOUT = 0;
private boolean forceClaim = true;
int controlTransferResult;
byte[] readBytes = new byte[128];
//byte[] data = new byte[4096];
UsbEndpoint epOut = null, epIn = null;
UsbDeviceConnection connection;
int recvBytes;
String readString = "";
Thread thread;
Runnable r;
UsbInterface intf;
Handler handler= new Handler(){
@Override
public void handleMessage(Message msg) {
tvAppend.append(readString);
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvTest = (TextView) findViewById(R.id.textView);
tvAppend = (TextView) findViewById(R.id.textView2);
bShow= (Button)findViewById(R.id.button);
showData();
}
@Override
public void onPause() {
super.onPause(); // Always call the superclass method first
thread.interrupt();
}
@Override
protected void onStop() {
super.onStop();
thread.interrupt();
}
@Override
protected void onResume() {
super.onResume();
thread = new Thread(r);
thread.start();
}
@Override
protected void onDestroy() {
super.onDestroy();
thread.interrupt();
}
@Override
protected void onRestart() {
super.onRestart();
thread = new Thread(r);
thread.start();
}
public void showData(){
UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
if(deviceList.toString().equals("{}")){
Toast.makeText(MainActivity.this,"No USB device found!", Toast.LENGTH_SHORT).show();
return;
}else{
tvTest.setText(deviceList.toString());
}
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
device = deviceIterator.next();
mUsbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(mUsbReceiver, filter);
mUsbManager.requestPermission(device, mPermissionIntent);
bShow.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
r = new Runnable() {
@Override
public void run() {
synchronized (this) {
while (true) {
Arrays.fill(readBytes, (byte) 0);
recvBytes = connection.bulkTransfer(epIn, readBytes, readBytes.length, 0);
if (recvBytes != 2) {
readString = new String(readBytes);
readString = readString.replace("\u0001`","");
handler.sendEmptyMessage(0);
}
}
}
}
};
thread = new Thread(r);
thread.start();
}
});
}
private final BroadcastReceiver mUsbReceiver = 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
intf = device.getInterface(0);
// look for our bulk endpoints
for (int i = 0; i < intf.getEndpointCount(); i++) {
UsbEndpoint ep = intf.getEndpoint(i);
if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
if (ep.getDirection() == UsbConstants.USB_DIR_OUT) {
epOut = ep;
} else if (ep.getDirection() == UsbConstants.USB_DIR_IN) {
epIn = ep;
}
}
}
if (epOut == null || epIn == null) {
throw new IllegalArgumentException("Not all endpoints found.");
}
connection = mUsbManager.openDevice(device);
connection.claimInterface(intf, forceClaim);
bytes = sendText.getBytes();
tvAppend.setText("a" + bytes.length);
connection.controlTransfer(0x40, 0, 0, 0, null, 0, 0);// reset
connection.controlTransfer(0x40, 0, 1, 0, null, 0, 0);// clear Rx
connection.controlTransfer(0x40, 0, 2, 0, null, 0, 0);// clear Tx
controlTransferResult = connection.controlTransfer(0x40, 0x03, 0x4138, 0, null, 0, 0);
ByteBuffer buffer = ByteBuffer.allocate(bytes.length+1);
UsbRequest request = new UsbRequest();
buffer.put(bytes);
request.initialize(connection, epOut);
request.queue(buffer, bytes.length);
}
}
else {
Log.d("MyActivity", "permission denied for device " + device);
}
}
}
}
};
}
public类MainActivity扩展了AppCompatActivity{
USB设备;
按钮显示;
私有静态最终字符串操作\u USB\u PERMISSION=“com.android.example.USB\u PERMISSION”;
UsbManager musbanager;
悬而未决的犯罪意图;
文本视图tvTest,tvAppend;
字符串sendText=“@V\r\n”;
专用字节[]字节;
私有静态int超时=0;
私有布尔forceClaim=true;
int控制传递结果;
字节[]读取字节=新字节[128];
//字节[]数据=新字节[4096];
UsbEndpoint epOut=null,epIn=null;
UsbDeviceConnection连接;
int recvBytes;
字符串readString=“”;
螺纹;
可运行r;
UsbInterface intf;
Handler=newhandler(){
@凌驾
公共无效handleMessage(消息消息消息){
append.append(readString);
}
};
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvTest=(TextView)findViewById(R.id.TextView);
tvAppend=(TextView)findViewById(R.id.textView2);
bShow=(按钮)findViewById(R.id.Button);
showData();
}
@凌驾
公共无效暂停(){
super.onPause();//始终首先调用超类方法
thread.interrupt();
}
@凌驾
受保护的void onStop(){
super.onStop();
thread.interrupt();
}
@凌驾
受保护的void onResume(){
super.onResume();
螺纹=新螺纹(r);
thread.start();
}
@凌驾
受保护的空onDestroy(){
super.ondestory();
thread.interrupt();
}
@凌驾
受保护的void onRestart(){
super.onRestart();
螺纹=新螺纹(r);
thread.start();
}
公共void showData(){
UsbManager manager=(UsbManager)getSystemService(Context.USB_服务);
HashMap deviceList=manager.getDeviceList();
if(deviceList.toString().equals(“{}”)){
Toast.makeText(MainActivity.this,“未找到USB设备!”,Toast.LENGTH\u SHORT.show();
返回;
}否则{
tvetest.setText(deviceList.toString());
}
迭代器deviceIterator=deviceList.values().Iterator();
device=deviceIterator.next();
mUsbManager=(UsbManager)getSystemService(Context.USB_服务);
mPermissionIntent=PendingIntent.getBroadcast(this,0,新意图(ACTION\u USB\u权限),0);
IntentFilter筛选器=新建IntentFilter(操作\u USB\u权限);
寄存器接收器(mUsbReceiver,过滤器);
请求权限(设备、mPermissionIntent);
bShow.setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图v){
r=新的可运行(){
@凌驾
公开募捐{
已同步(此){
while(true){
数组.fill(readBytes,(byte)0);
recvBytes=connection.bulkTransfer(epIn,readBytes,readBytes.length,0);
如果(recvBytes!=2){
readString=新字符串(readBytes);
readString=readString.replace(“\u0001`”,”);
handler.sendEmptyMessage(0);
}
}
}
}
};
螺纹=新螺纹(r);
thread.start();
}
});
}
专用最终广播接收器mUsbReceiver=新广播接收器(){
公共void onReceive(上下文、意图){
String action=intent.getAction();
if(动作\u USB\u权限等于(动作)){
已同步(此){
UsbDevice设备=(UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_设备);
if(intent.getBooleanExtra(UsbManager.EXTRA_权限_授予,false)){
如果(设备!=null){
//调用方法来设置设备通信
intf=device.getInterface(0);
//寻找我们的批量端点
对于(int i=0;i