我目前正在编写一个在 Android 上与 Arduino Board 交互的应用程序。我可以很好地将串行数据发送到我的 Arduino，但是当我开始尝试接收数据时，我的应用程序在启动时崩溃了。
我目前已将其设置为文本字段从用户那里获取数据，然后发送到 Arduino，Arduino 执行一项功能。
对于我的接收，我在启动时创建了一个新线程，以不断监听来自 Arduino 的数据。每当执行此线程中的代码时，它就会崩溃。
我使用这个库作为我的基础：https ://github.com/mik3y/usb-serial-for-android
以下是此应用程序提供的其他功能的所有相关代码，省略的代码是未实现的：
import java.io.IOException;
import java.io.InputStream;
import java.text.DecimalFormat;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.hoho.android.usbserial.driver.UsbSerialDriver;
import android.hardware.usb.UsbManager;
import android.content.Intent;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.content.Context;
import android.util.Log;
import com.hoho.android.usbserial.driver.UsbSerialProber;
public class MainActivity extends Activity implements SensorEventListener, LocationListener{
private EditText sendTextField;
TextView uartRX;
public Handler Handler;
UsbManager manager;
/** Called to create application activity*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
uartRX = (TextView)findViewById(R.id.rxUART);
sendTextField = (EditText) findViewById(R.id.sendTextField);
Handler = new Handler() {
@Override public void handleMessage(Message msg) {
String text = (String)msg.obj;
uartRX.append(text);
}
};
Thread t = new Thread(new Runnable() {
public void run()
{
Message msg = new Message();
msg.obj = "Start Serial Listen\n";
Handler.sendMessage(msg);
rxUART();
}
public void rxUART()
{
manager = (UsbManager) getSystemService(Context.USB_SERVICE);
UsbSerialDriver rxDriver = UsbSerialProber.acquire(manager);
if (rxDriver != null) {
try {
rxDriver.open();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
int byteSize = 0;
String data = "";
while(true)
{
byte[] arr = null;
try {
rxDriver.setBaudRate(115200);
rxDriver.read(arr, byteSize);
data = new String(arr);
Message msg = new Message();
msg.obj = data;
Handler.sendMessage(msg);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
t.start();
}
public void sendUART(String data)
{
manager = (UsbManager) getSystemService(Context.USB_SERVICE);
// Find the first available driver.
UsbSerialDriver driver = UsbSerialProber.acquire(manager);
if (driver != null) {
try {
driver.open();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
driver.setBaudRate(115200);
byte buffer[] = new byte[16];
int numBytesRead = driver.read(buffer, 1000);
Log.d(TAG, "Read " + numBytesRead + " bytes.");
byte temp[] = data.getBytes();
driver.write(temp, 16);
} catch (IOException e) {
// Deal with error.
} finally {
try {
driver.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
public void onClickSendBtn(View v)
{
String data = "";
data = sendTextField.getText().toString();
sendUART(data);
sendTextField.setText(" ");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
谁能帮我弄清楚为什么应用程序在线程中创建的代码上崩溃？
注意：代码不在线程中时也会崩溃。代码最初是由 sendUART() 调用以检查响应的函数。也没有 while(true)。
日志猫：
11-02 09:49:22.988: E/AndroidRuntime(22652): FATAL EXCEPTION: Thread-964
11-02 09:49:22.988: E/AndroidRuntime(22652): java.lang.NullPointerException
11-02 09:49:22.988: E/AndroidRuntime(22652): at com.example.sensortest.MainActivity$2.rxUART(MainActivity.java:143)
11-02 09:49:22.988: E/AndroidRuntime(22652): at com.example.sensortest.MainActivity$2.run(MainActivity.java:119)
11-02 09:49:22.988: E/AndroidRuntime(22652): at java.lang.Thread.run(Thread.java:856)
引用的行号是：
Thread t = new Thread(new Runnable() {
public void run()
{
Message msg = new Message();
msg.obj = "Start Serial Listen\n";
Handler.sendMessage(msg);
rxUART();
}
public void rxUART()
{
manager = (UsbManager) getSystemService(Context.USB_SERVICE);
UsbSerialDriver rxDriver = UsbSerialProber.acquire(manager);
if (rxDriver != null) {
try {
rxDriver.open();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
int byteSize = 0;
String data = "";
while(true)
{
byte[] arr = null;
try {
rxDriver.setBaudRate(115200);
rxDriver.read(arr, byteSize);
data = new String(arr);
Message msg = new Message();
msg.obj = data;
Handler.sendMessage(msg);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
t.start();