I'm am fairly new to Android, and I'm trying to develop an app for a small project of mine using an example Bluetooth Chat App and Spotify Media Notifications. I could not provide the links because stack overflow did not let me but they are available online with a quick google search. I was wondering why I was getting this exception and is there any solution to this?
java.lang.NullPointerException
The line numbers correspond to each of the pieces of code below:
Line 269 if (message.length() > 0)
Line 56 public class BluetoothChatFragment extends Fragment
Line 131 sendMessage(artistName);
How my code is set up:
I have a static broadcast receiver set up exactly like the Spotify link below. I grab the song name and artist and package them into strings. Then I have another broadcast receiver in my Bluetooth fragment. I used another one because I did not know how to get the string into the Bluetooth fragment because I needed to call sendMessage() a private method in the fragment class. It seems like the exception is throwing when I call sendMessage(string) in my fragment.
Static Spotify Broadcast Receiver
package com.example.android.bluetoothchat;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import com.example.android.common.logger.Log;
public class MyBroadcastReceiver extends BroadcastReceiver {
static final class BroadcastTypes {
static final String SPOTIFY_PACKAGE = "com.spotify.music";
static final String PLAYBACK_STATE_CHANGED = SPOTIFY_PACKAGE + ".playbackstatechanged";
static final String QUEUE_CHANGED = SPOTIFY_PACKAGE + ".queuechanged";
static final String METADATA_CHANGED = SPOTIFY_PACKAGE + ".metadatachanged";
}
@Override
public void onReceive(Context context, Intent intent) {
// This is sent with all broadcasts, regardless of type. The value is taken from
// System.currentTimeMillis(), which you can compare to in order to determine how
// old the event is.
long timeSentInMs = intent.getLongExtra("timeSent", 0L);
Intent sendBack = new Intent("Received");
String action = intent.getAction();
String artistName;
String trackName;
if (action.equals(BroadcastTypes.METADATA_CHANGED)) {
artistName = intent.getStringExtra("artist");
trackName = intent.getStringExtra("track");
String msg = "S a " + artistName + '\0';
String msg2 = "S n " + trackName + '\0';
Log.d("Song", msg);
Log.d("Artist", msg2);
sendBack.putExtra("Song", msg);
sendBack.putExtra("Artist", msg2);
} else if (action.equals(BroadcastTypes.PLAYBACK_STATE_CHANGED)) {
boolean playing = intent.getBooleanExtra("playing", false);
// Do something with extracted information
if(playing) {
Log.d("Playing", "S p\0");
sendBack.putExtra("Playing", "S p\0");
}
else {
Log.d("Playing", "S s\0");
sendBack.putExtra("Playing", "S s\0");
}
}
context.sendBroadcast(sendBack);
}
}
Broadcast Receiver in Fragment:
BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String artistName = intent.getStringExtra("Song");
String trackName = intent.getStringExtra("Artist");
String playing = intent.getStringExtra("Playing");
Log.d("Please", artistName);
Log.d("Please", trackName);
Log.d("Please", playing);
sendMessage(artistName);
sendMessage(trackName);
sendMessage(playing);
}
};
sendMessage Method():
private void sendMessage(String message) {
// Check that we're actually connected before trying anything
if (mChatService.getState() != BluetoothChatService.STATE_CONNECTED) {
Toast.makeText(getActivity(), R.string.not_connected, Toast.LENGTH_SHORT).show();
return;
}
// Check that there's actually something to send
if (message.length() > 0) {
// Get the message bytes and tell the BluetoothChatService to write
byte[] send = message.getBytes();
mChatService.write(send);
// Reset out string buffer to zero and clear the edit text field
mOutStringBuffer.setLength(0);
mOutEditText.setText(mOutStringBuffer);
}
}
Any help would be much appreciated!
http://developer.android.com/samples/BluetoothChat/index.html
To me it looks like sendMessage gets called with null instead of an actual string. Note that intent.getStringExtra(some_string) can return null, if some_string cannot be found.
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