我试图建立一个可以：
的应用程序在三个文本视图中显示当前加速计读数 通过蓝牙将加速度计读数发送到PC /笔记本电脑/ Mac上的串行终端。
我使用Coolterm作为串行终端模拟器，下面是我的尝试 问题是当我打开它时应用程序正在崩溃，而下面是我抓住的例外
package com.sajad.bluetooth_acc;
import android.app.Activity;
import android.bluetooth.BluetoothDevice;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends Activity implements SensorEventListener {
private SensorManager sensorManager;
TextView xCoor; // declare X axis object
TextView yCoor; // declare Y axis object
TextView zCoor; // declare Z axis object
private Button btsend;
private BluetoothAdapter mBluetoothAdapter ;
private BluetoothSocket btSocket ;
private ConnectedThread mConnectedThread;
// SPP UUID service - this should work for most devices
private static final UUID BTMODULEUUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
// String for MAC address
private static String address;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
xCoor = (TextView) findViewById(R.id.xcoor); // create X axis object
yCoor = (TextView) findViewById(R.id.ycoor); // create Y axis object
zCoor = (TextView) findViewById(R.id.zcoor); // create Z axis object
sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
// add listener. The listener will be (this) class
sensorManager.registerListener(this,
sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_NORMAL);
checkBTState();
btsend = (Button) findViewById(R.id.btsend);
btsend.setOnClickListener(btToggleOnClickListener);
}
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
public void onSensorChanged(SensorEvent event) {
// check sensor type
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
// assign directions
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
xCoor.setText("X: " + x);
yCoor.setText("Y: " + y);
zCoor.setText("Z: " + z);
}
}
// Click event on Button
private OnClickListener btToggleOnClickListener = new OnClickListener() {
@Override
public void onClick(View v) {
TextView edtx = (TextView) findViewById(R.id.xcoor);
TextView edty = (TextView) findViewById(R.id.ycoor);
TextView edtz = (TextView) findViewById(R.id.zcoor);
String x_val = edtx.getText().toString();
String y_val = edty.getText().toString();
String z_val = edtz.getText().toString();
String XYZ =
new StringBuilder()
.append(x_val)
.append(y_val)
.append(z_val)
.toString();
mConnectedThread.write(XYZ); // Send via Bluetooth
Toast.makeText(getBaseContext(), "accelerometer readings sent !", Toast.LENGTH_SHORT).show();
// OutputStream mmOutStream = null;
}
};
private BluetoothSocket createBluetoothSocket(BluetoothDevice device) throws IOException {
return device.createRfcommSocketToServiceRecord(BTMODULEUUID);
//creates secure outgoing connecetion with BT device using UUID
}
@Override
public void onResume() {
super.onResume();
//Get the MAC address from the DeviceListActivty via EXTRA
address = ("74:E5:43:72:0E:27");
//create device and set the MAC address
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
try {
btSocket = createBluetoothSocket(device);
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(getBaseContext(), "Socket creation failed", Toast.LENGTH_LONG).show();
}
// Establish the Bluetooth socket connection.
try
{
btSocket.connect();
} catch (IOException e) {
e.printStackTrace();
try
{
btSocket.close();
} catch (IOException e2)
{
e2.printStackTrace();
}
}
mConnectedThread = new ConnectedThread(btSocket);
mConnectedThread.start();
// send a character when resuming.beginning transmission to check device is connected
//If it is not an exception will be thrown in the write method and finish() will be called
mConnectedThread.write("x");
}
@Override
public void onPause()
{
super.onPause();
try
{
//Don't leave Bluetooth sockets open when leaving activity
btSocket.close();
} catch (IOException e2) {
e2.printStackTrace();
}
}
//Checks that the Android device Bluetooth is available and prompts to be turned on if off
private void checkBTState() {
if(mBluetoothAdapter==null) {
Toast.makeText(getBaseContext(), "Device does not support bluetooth", Toast.LENGTH_LONG).show();
} else {
if (mBluetoothAdapter.isEnabled()) {
} else {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, 1);
}
}
}
//create new class for connect thread
private class ConnectedThread extends Thread {
private final OutputStream mmOutStream;
//creation of the connect thread
public ConnectedThread(BluetoothSocket socket) {
OutputStream tmpOut = null;
try {
//Create I/O streams for connection
tmpOut = socket.getOutputStream();
} catch (IOException e) {
}
mmOutStream = tmpOut;
}
public void run() {
}
//write method
public void write (String input){
byte[] msgBuffer = input.getBytes(); //converts entered String into bytes
try {
mmOutStream.write(msgBuffer); //write bytes over BT connection via outstream
} catch (IOException e) {
//if you cannot write, close the application
Toast.makeText(getBaseContext(), "Connection Failure", Toast.LENGTH_LONG).show();
finish();
}
}
}
}
LOG
01-01 02:14:49.636 30800-30800/com.sajad.bluetooth_acc E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.sajad.bluetooth_acc, PID: 30800
java.lang.RuntimeException: Unable to resume activity {com.sajad.bluetooth_acc/com.sajad.bluetooth_acc.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.BluetoothDevice android.bluetooth.BluetoothAdapter.getRemoteDevice(java.lang.String)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3160)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3191)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2529)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.bluetooth.BluetoothDevice android.bluetooth.BluetoothAdapter.getRemoteDevice(java.lang.String)' on a null object reference
at com.sajad.bluetooth_acc.MainActivity.onResume(MainActivity.java:171)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1259)
at android.app.Activity.performResume(Activity.java:6361)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:3149)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:3191)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2529)
at android.app.ActivityThread.access$900(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1391)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:234)
at android.app.ActivityThread.main(ActivityThread.java:5526)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)