我不知道这是怎么回事，但是我的应用程序正在搜索附近的蓝牙设备，但是当我尝试连接到其中一个蓝牙设备时，该应用程序崩溃了。
请看一看
这是我的 SearchBTDevice.java 。这是调用ConnectBTDevice Activity 的 Activity
package vertex2016.mvjce.edu.bluealert;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGattDescriptor;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.bluetooth.BluetoothAdapter;
import android.provider.Settings;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.Set;
public class SearchBTDevice extends AppCompatActivity {
public BluetoothAdapter BlueAdapter = BluetoothAdapter.getDefaultAdapter();
public ArrayAdapter PairedArrayAdapter;
public ArrayAdapter BTArrayAdapter;
BluetoothDevice btd;
public ListView devicesFound;
private final BroadcastReceiver BTReceiver= new BroadcastReceiver(){
public void onReceive(Context context, Intent intent)
{
String action = intent.getAction();
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
btd = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
BTArrayAdapter.add(btd.getName() + "\t" + btd.getAddress() + "\n");
}
}
};
IntentFilter filter1 = new IntentFilter(BluetoothDevice.ACTION_FOUND);
@Override
protected void onResume() {
super.onResume();
this.registerReceiver(BTReceiver,filter1);
}
@Override
protected void onPause() {
super.onPause();
BlueAdapter.cancelDiscovery();
this.unregisterReceiver(BTReceiver);
Toast.makeText(SearchBTDevice.this, "Discovery Stopped!!", Toast.LENGTH_SHORT).show();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search_btdevice);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LOCKED);
searchBTDevices();
}
public void searchBTDevices()
{
if(!BlueAdapter.startDiscovery())
Toast.makeText(SearchBTDevice.this, "Failed to Start Discovery", Toast.LENGTH_SHORT).show();
else
Toast.makeText(SearchBTDevice.this, "Discovery Startred", Toast.LENGTH_SHORT).show();
BTArrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1);
devicesFound = (ListView)findViewById(R.id.searchpagelistView);
devicesFound.setAdapter(BTArrayAdapter);
devicesFound.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent connectedBTintent = new Intent(SearchBTDevice.this, ConnectedBTDevice.class);
connectedBTintent.putExtra("BluetoothDevice", btd);
startActivity(connectedBTintent);
}
});
}
}
这是我的，已更新，，ConnectBTDevice.java ，它试图建立RFCOMM通道。但这是我的应用崩溃的地方。
package vertex2016.mvjce.edu.bluealert;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.io.IOException;
import java.util.UUID;
public class ConnectedBTDevice extends AppCompatActivity {
public BluetoothDevice btd;
public BluetoothSocket btSocket, tempSocket;
private UUID myUUID;
ArrayAdapter arr;
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_connected_btdevice);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LOCKED);
arr = new ArrayAdapter(this, android.R.layout.simple_list_item_2);
btd = getIntent().getParcelableExtra("BluetoothDevice");
connectBT();
displayStuff();
}
public void connectBT() {
Thread myThread = new Thread() {
public void run() {
tempSocket = null;
try {
tempSocket = btd.createRfcommSocketToServiceRecord(myUUID);
} catch (IOException e) {
e.printStackTrace();
}
BluetoothAdapter.getDefaultAdapter().cancelDiscovery();
try {
btSocket.connect();
arr.add("CONNECTED TO-->" + btd.getName());
} catch (IOException e) {
e.printStackTrace();
try {
btSocket.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
};
myThread.start();
}
public void displayStuff()
{
lv = (ListView)findViewById(R.id.connectedBTlistView);
lv.setAdapter(arr);
}
}
这是我的更新的 logcat 显示的内容
03-22 01:40:47.116 28214-11199/vertex2016.mvjce.edu.bluealert E/AndroidRuntime: FATAL EXCEPTION: Thread-11810
Process: vertex2016.mvjce.edu.bluealert, PID: 28214
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.bluetooth.BluetoothSocket.connect()' on a null object reference
at vertex2016.mvjce.edu.bluealert.ConnectedBTDevice$1.run(ConnectedBTDevice.java:61)
最佳答案
logcat中的例外是告诉您问题所在。您正在尝试在空对象引用上调用BluetoothSocket.connect()。
您正在调用btSocket.connect()，但btSocket尚未初始化，因此为null。
在tempSocket.connect()之前，先调用tempSocket或将btSocket分配给connect()。
关于android - 尽管尝试了教程，但蓝牙设备未在Android应用上连接，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/36098231/