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POBluetooth in Android
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copied!<p>I'm currently developing a Sofware using bluetooth to communicate.</p> <p>Here is my bluetooth class:</p> <pre><code>public class btClass extends Activity implements View.OnClickListener { private BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); private static final int REQUEST_ENABLE_BT = 10; private Context context; private btReceiver mReceiver = new btReceiver(); private String[] result = new String[]{""}; private Activity hangar; public btClass() { if (!this.adapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent,REQUEST_ENABLE_BT); int result = 0; onActivityResult(REQUEST_ENABLE_BT, result, enableBtIntent); if(result != RESULT_OK) { String exception = "Bluetooth failure!\r\nEnabling bluetooth adapter failed!"; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this.context); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } } } @Override protected void onCreate(Bundle intent) { super.onCreate(intent); this.hangar = this.getParent(); this.context = this.getApplicationContext(); } public void onClick(View v) { doDiscovery(); } private void doDiscovery() { if(this.adapter.isDiscovering()) this.adapter.cancelDiscovery(); if(!this.adapter.startDiscovery()) { String exception = "Bluetooth failure!\r\nDiscovering bluetooth devices failed!"; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this.context); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } // Register the BroadcastReceiver IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); try { this.registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestr } catch(Exception e) { String exception = "'registerReceiver' threw Exception of type '" + e.getMessage(); StackTraceElement[] trace = e.getStackTrace(); for(int i = 0; i < trace.length; i++) exception = exception + "\r\n" + trace[i]; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } while(this.adapter.isDiscovering()) ; unregisterReceiver(this.mReceiver); result = new String[]{""}; if(this.mReceiver != null) result = this.mReceiver.foundDevicesNames(); } public String[] getBluetoothDevices() { return result; } } </code></pre> <p>Now the problem is that I'm catching a "nullPointerException" when I call startActivityForResult in line 16.</p> <p>Where is my fault?</p> <p>Greets Henrik</p> <p>EDIT: the new code:</p> <pre><code>package de.schweigstill.hangar; import android.bluetooth.*; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.LinearLayout; import android.app.Activity; import android.app.AlertDialog; public class btClass extends Activity implements View.OnClickListener { private BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); private static final int REQUEST_ENABLE_BT = 10; private Context context; private btReceiver mReceiver = new btReceiver(); private String[] result = new String[]{""}; private HangarActivity hangar; public btClass(Context context) { super(); } @Override public void onCreate(Bundle intent) { super.onCreate(intent); this.hangar = (HangarActivity)this.getParent(); this.context = this.getApplicationContext(); } public void onClick(View v) { if (!this.adapter.isEnabled()) { Intent enableBtIntent = new intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent,REQUEST_ENABLE_BT); int result = 0; onActivityResult(REQUEST_ENABLE_BT, result, enableBtIntent); if(result != RESULT_OK) { String exception = "Bluetooth failure!\r\nEnabling bluetooth adapter failed!"; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this.context); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } } doDiscovery(); } private void doDiscovery() { try { if(this.adapter.isDiscovering()) this.adapter.cancelDiscovery(); if(!this.adapter.startDiscovery()) { String exception = "Bluetooth failure!\r\nDiscovering bluetooth devices failed!"; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this.context); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } // Register the BroadcastReceiver IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); this.registerReceiver(mReceiver, filter); // Don't forget to unregister during onDestr while(this.adapter.isDiscovering()) ; unregisterReceiver(this.mReceiver); result = new String[]{""}; if(this.mReceiver != null) { result = this.mReceiver.foundDevicesNames(); for(int i = 0; i < result.length; i++) this.hangar.aAd.add(result[i]); } } catch(Exception e) { String exception = "In 'doDiscovery()' has an Exception of type '" + e.toString() + "' been thrown \r\n Trace:";//.getMessage(); StackTraceElement[] trace = e.getStackTrace(); for(int i = 0; i < trace.length; i++) exception = exception + "\r\n" + trace[i]; AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this); dlgAlert.setMessage(exception); dlgAlert.setTitle("Hangar error"); dlgAlert.setPositiveButton("OK", null); dlgAlert.setCancelable(true); dlgAlert.create().show(); } } public String[] getBluetoothDevices() { return result; } } </code></pre>

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