Exception when trying to send a message to firebase server

Question

Can you please find out what is wrong with this code?

public class NewMessageActivity extends AppCompatActivity {

private DatabaseReference mDatabaseReference;
String mDisplayName = "John";
EditText mNewMessageField;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    final EditText mNewMessageField = (EditText) findViewById(R.id.newMessageText);
    setContentView(R.layout.activity_new_message);
    ImageButton mSendButton = (ImageButton) findViewById(R.id.sendButton);
    mSendButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            sendMessage();
            finish();
        }
    });
}

private void sendMessage(){
    mDatabaseReference= FirebaseDatabase.getInstance().getReference();
    String input = mNewMessageField.getText().toString();
    SingleMessage singleMessage = new SingleMessage(input, mDisplayName);
    mDatabaseReference.child("messages").push().setValue(singleMessage);
}

}

Immediately after I press the send button, the app stops working and I get this error message:

FATAL EXCEPTION: main java.lang.NullPointerException at com. .NewMessageActivity.sendMessage(NewMessageActivity.java:42) at com. .NewMessageActivity.access$000(NewMessageActivity.java:14) at com.***.NewMessageActivity$1.onClick(NewMessageActivity.java:33) at android.view.View.performClick(View.java:4209) at android.view.View$PerformClick.run(View.java:17457) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:153) at android.app.ActivityThread.main(ActivityThread.java:5341) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:929) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696) at dalvik.system.NativeStart.main(Native Method) 11-28 20:05:51.566 508-527/? E/AppErrorDialog: Failed to get ILowStorageHandle instance

Answer 1

You need to call setContentView( ) before you search for the EditText widget. You also must use the instance of mNewMessageField declared at package level. Don't declare a new instance in onCreate() .

setContentView(R.layout.activity_new_message);
mNewMessageField = (EditText) findViewById(R.id.newMessageText);  // <= CHANGED
if (mNewMessageField == null) {
    System.out.println("mNewMessageField is NULL");
}

To get more clues, add this debug output:

private void sendMessage(){
    mDatabaseReference= FirebaseDatabase.getInstance().getReference();
    if (mNewMessageField == null) {
        System.out.println("mNewMessageField is NULL");
    }
    Editable ed = mNewMessageField.getText();

    if (ed == null) {
        System.out.println("Editable is NULL");
    }
    String input = mNewMessageField.getText().toString();
    System.out.println("input=" + input);

    SingleMessage singleMessage = new SingleMessage(input, mDisplayName);
    mDatabaseReference.child("messages").push().setValue(singleMessage);
}