CODEWITHSUNDEEP
javaandroidipcaidl
Einar Sundgren
Einar Sundgren

Reputation: 4433

IPC call to service causes NullPointerException when called from main thread but not on button event

I'm trying to create a service with an IPC connection defined in an .aidl file.

The service starts and the service connection can bind to it, but when the IPC API is called from the same thread it causes a NullPointerException. When the call to the IPC API is put in an event on a button press it works.

How can this be fixed so that the call can be done without having a button event to start it.

My MainActivicty

       public class MainActivity extends AppCompatActivity {

        public final String TAG = "Main Activity";
        IMyAidlInterface iMyAidlInterface;
        private ServiceConnection mConnection = new ServiceConnection() {
            public void onServiceConnected(ComponentName className, IBinder service) {
                iMyAidlInterface = IMyAidlInterface.Stub.asInterface(service);
            }

            public void onServiceDisconnected(ComponentName className) {
                iMyAidlInterface = null;
            }
        };


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            Intent interFaceServiceIntent = new Intent(this, IMyAidlService.class);
            bindService(interFaceServiceIntent, mConnection, Context.BIND_AUTO_CREATE);

            Intent sigGenIntent = new Intent(this, signalGenerator.class);
            startService(sigGenIntent);

            Button b = findViewById(R.id.button);

/*
* The following block is what I want to be able to execute. Currently it causes * a NullPointerException 
* Caused by: java.lang.NullPointerException: Attempt to invoke interface method * 'int com.aidltest.IMyAidlInterface.getPid()' on a null object reference
*/
            try {
                iMyAidlInterface.getPid();
            } catch (RemoteException e) {
                e.printStackTrace();
            }
/*
*  The block below using the same interface from within a button event works
*   without problem.
*/

            b.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    try {
                        iMyAidlInterface.getPid();
                    } catch (RemoteException e) {
                        e.printStackTrace();
                    }
                }
            });
        }
    }

For reference my Aidl:

package com.aidltest;
interface IMyAidlInterface {
    int getPid();
    void basicTypes(int anInt, long aLong, boolean aBoolean, float aFloat,
            double aDouble, String aString);
}

And my Manifest:

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service
            android:name=".IMyAidlService"
            android:enabled="true"
            android:exported="true">
        </service>
    </application>

</manifest>

Upvotes: 0

Views: 333

Answers (1)

Larry Schiefer
Larry Schiefer

Reputation: 15775

This is happening because iMyAidlInterface is null in your onCreate call. It is not set until your connection listener calls you back via onServiceConnected. Binding is an async operation.

Upvotes: 1

Related Questions