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I have written the following code with permissions included in the manifest file.

package com.cognism.device; import java.io.IOException; import android.app.Activity; import android.bluetooth.BluetoothAdapter; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; public class Trial extends Activity { // Declare our Views, so we can access them later private Button activate_buletooth; static final int REQUEST_ENABLE_BT = 0; Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // Set Activity Layout setContentView(R.layout.main); activate_buletooth = (Button)findViewById(R.id.activate_buletooth); // Set Click Listener activate_buletooth.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { if (mBluetoothAdapter == null) { // Device does not support Bluetooth Context context = getApplicationContext(); CharSequence text = "BT not suported"; int duration = Toast.LENGTH_SHORT; Toast toast = Toast.makeText(context, text, duration); toast.show(); } if (!mBluetoothAdapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); } // startActivityForResult(discoverableIntent, REQUEST_ENABLE_BT); } }); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if(requestCode == REQUEST_ENABLE_BT) { if(resultCode == RESULT_CANCELED) { Context context = getApplicationContext(); CharSequence text = "bt not available"; int duration = Toast.LENGTH_SHORT; Toast toast = Toast.makeText(context, text, duration); toast.show(); } else { } } } }

And I have been getting exception and the DDMs shows these errors:

04-18 11:48:03.587: ERROR/AndroidRuntime(616): FATAL EXCEPTION: main 04-18 11:48:03.587: ERROR/AndroidRuntime(616): java.lang.NullPointerException 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at com.cognism.device.Trial$1.onClick(Trial.java:47) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.view.View.performClick(View.java:2485) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.view.View$PerformClick.run(View.java:9080) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.os.Handler.handleCallback(Handler.java:587) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.os.Handler.dispatchMessage(Handler.java:92) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.os.Looper.loop(Looper.java:123) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at android.app.ActivityThread.main(ActivityThread.java:3647) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at java.lang.reflect.Method.invokeNative(Native Method) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at java.lang.reflect.Method.invoke(Method.java:507) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 04-18 11:48:03.587: ERROR/AndroidRuntime(616): at dalvik.system.NativeStart.main(Native Method) 04-18 11:48:03.608: WARN/ActivityManager(61): Force finishing activity com.cognism.device/.Trial 04-18 11:48:04.127: WARN/ActivityManager(61): Activity pause timeout for HistoryRecord{40683988 com.cognism.device/.Trial} 04-18 11:48:06.248: INFO/Process(616): Sending signal. PID: 616 SIG: 9 04-18 11:48:06.267: INFO/ActivityManager(61): Process com.cognism.device (pid 616) has died. 04-18 11:48:06.278: INFO/WindowManager(61): WIN DEATH: Window{4074aa58 com.cognism.device/com.cognism.device.Trial paused=false} 04-18 11:48:10.397: DEBUG/dalvikvm(429): GC_EXPLICIT freed 7K, 55% free 2519K/5511K, external 716K/1038K, paused 59ms 04-18 11:48:15.290: WARN/ActivityManager(61): Activity destroy timeout for HistoryRecord{40683988 com.cognism.device/.Trial} 04-18 11:48:15.457: DEBUG/dalvikvm(446): GC_EXPLICIT freed 20K, 55% free 2577K/5703K, external 716K/1038K, paused 98ms 04-18 11:48:20.458: DEBUG/dalvikvm(536): GC_EXPLICIT freed 55K, 49% free 3054K/5959K, external 716K/1038K, paused 57ms 04-18 11:48:25.508: DEBUG/dalvikvm(488): GC_EXPLICIT freed 6K, 55% free 2527K/5511K, external 716K/1038K, paused 82ms 04-18 11:51:59.923: DEBUG/SntpClient(61): request time failed: java.net.SocketException: Address family not supported by protocol 04-18 11:55:00.207: DEBUG/dalvikvm(61): GC_CONCURRENT freed 834K, 46% free 4391K/8007K, external 2050K/2558K, paused 7ms+8ms 04-18 11:56:59.967: DEBUG/SntpClient(61): request time failed: java.net.SocketException: Address family not supported by protocol
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4 Answers 4

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2

Hi please follows following code for blue-tooth activation:-

public class BluetoothDemo extends Activity { TextView out; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); out = (TextView) findViewById(R.id.out); // Getting the Bluetooth adapter BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); out.append("\nAdapter: " + adapter); // Check for Bluetooth support in the first place // Emulator doesn't support Bluetooth and will return null if(adapter==null) { out.append("\nBluetooth NOT supported. Aborting."); return; } // Starting the device discovery out.append("\nStarting discovery..."); adapter.startDiscovery(); out.append("\nDone with discovery..."); // Listing paired devices out.append("\nDevices Pared:"); Set<BluetoothDevice> devices = adapter.getBondedDevices(); for (BluetoothDevice device : devices) { out.append("\nFound device: " + device); } } }

and don't forget to give this in manifest file...

<uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
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3 Comments

Yeah it says Blueetooth not supporting :(
You Check it on mobile or emulator???? Please Check this code on Device....Okkk
ok i will try it on device .. was doing on emulator first ..!!
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if (mBluetoothAdapter == null) { .... // code does not use "return" } if (!mBluetoothAdapter.isEnabled()) // crash here if mBluetoothAdapter == null {

It's your onclick code that's not right. If the adapter is null, the second if will crash.

Try:

if (mBluetoothAdapter == null) { .... } else if (!mBluetoothAdapter.isEnabled()) {

Also, judging be a quick google on this, mBluetoothAdapter should be initialized inside onCreate rather than at class scope.

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Hi Mat, i changed the code and i came to know that the BluetoothAdapter has null in it .. so that means my emulatore doesnot supposrt bluetooth rite ? and what can be doen to correct it ?
maybe, maybe not. The way you initialize mBluetoothAdapter doesn't match what you can find on google (edited my post), and there are requirements for the manifest that I have no way of knowing if you followed.
sorry couldn't reply , the problem wasn't solved witht his , turns out the emulator had some issues , got that fixed , works fine now.
1

I've had the exact same problem. It turned out you need both bluetooth and bluetooth-admin permissions. Admin alone, is not enough.

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I had exactly the same issue. Every use of my "bluetoothAdapter" resulted in an application crash, until I added the "<uses-permission …>" tag in the manifest file, like that :

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="charles.software" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".VitaleReader" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-permission android:name="android.permission.BLUETOOTH" /> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /> </manifest>

Note the two lines added at the end of the file, just before the "</manifest>" tag.

Now it works.

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