How to detect bluetooth state with BroadcastReceiver

Question

I got a problem. I have read this topic: How to detect Bluetooth state change using a broadcast receiver? and I wrote my app in the same way but when I run it and turn the bluetooth off the app is going to crash. System version: 4.0.3. Here is the code:

MainActivity:

package com.example.lokalizing;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class MainActivity extends Activity {

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
            final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                                                 BluetoothAdapter.ERROR);
            switch (state) {
            case BluetoothAdapter.STATE_OFF:
                Toast.makeText(context, "Bluetooth off", Toast.LENGTH_LONG);
                break;
            case BluetoothAdapter.STATE_TURNING_OFF:
                Toast.makeText(context, "Turning Bluetooth off", Toast.LENGTH_LONG);
                break;
            case BluetoothAdapter.STATE_ON:
                Toast.makeText(context, "Bluetooth on", Toast.LENGTH_LONG);
                break;
            case BluetoothAdapter.STATE_TURNING_ON:
                Toast.makeText(context, "Turning Bluetooth on", Toast.LENGTH_LONG);
                break;
            }
        }
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toast.makeText(getApplicationContext(), "Włączono program", Toast.LENGTH_LONG).show();
    IntentFilter filter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
    registerReceiver(mReceiver, filter);
}

@Override
public void onDestroy() {
    super.onDestroy();

    /* ... */

    // Unregister broadcast listeners
    unregisterReceiver(mReceiver);
}

public void showToast(String msg) {
    Toast.makeText(getApplicationContext(),msg, Toast.LENGTH_SHORT).show();
}
}

AndroidManifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.lokalizing"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="15"
    android:targetSdkVersion="15" />

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

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >

    <receiver
        android:name="com.example.lokalizing.MainActivity"
        android:enabled="true">
        <intent-filter>
            <action android:name="android.bluetooth.adapter.action.STATE_CHANGED"/>
        </intent-filter>
    </receiver>

    <activity
        android:name=".MainActivity"
        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>

</manifest>

score 3 · Answer 1 · answered Jul 12 '15 at 05:03

3

In the Toast implementation you missed to call the method show();

answered Jul 12 '15 at 05:03

Rajiv Manivannan

504
7
15

score 2 · Answer 2 · answered Feb 08 '15 at 15:48

Remove the <receiver> declaration from your manifest.

You've declared MainActivity as both an <activity> and as a <receiver>. That is a definite no-no.

As you are creating the BroadcastReceiver dynamically in code and registering it in onCreate(). you don't need to have anything in the manifest for that.

How to detect bluetooth state with BroadcastReceiver

2 Answers2