Android components callbacks' running thread

AndroidManifest.xml

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

    <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=".MainIntentService"
            android:exported="false" />

        <receiver
            android:name=".MainReceiver"
            android:enabled="true"
            android:exported="false">
            <intent-filter>
                <action android:name="com.perqin.myapplication.MAIN" />
            </intent-filter>
        </receiver>

        <provider
            android:name=".MainContentProvider"
            android:authorities="com.perqin.myapplication.provider"
            android:enabled="true"
            android:exported="false"></provider>
    </application>

</manifest>

logcat

09-12 09:29:08.342 30158-30158/com.perqin.myapplication I/MainActivity: onCreate: Thread ID = 1
09-12 09:29:08.354 30158-30176/com.perqin.myapplication I/MainContentProvider: query: Thread ID = 2374
09-12 09:29:08.389 30158-30193/com.perqin.myapplication I/MainIntentService: onHandleIntent: Thread ID = 2378
09-12 09:29:09.632 30158-30158/com.perqin.myapplication I/MainReceiver: onReceive: Thread ID = 1

MainActivity.java

package com.perqin.myapplication;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends Activity {
    private static final String TAG = "MainActivity";

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

        Log.i(TAG, "onCreate: Thread ID = " + Thread.currentThread().getId());
        new Thread(new Runnable() {
            @Override
            public void run() {
                MainIntentService.startAction(MainActivity.this);
                sendBroadcast(new Intent("com.perqin.myapplication.MAIN"));
                getContentResolver().query(
                        Uri.parse("content://com.perqin.myapplication.provider/main"),
                        null, null, null, null
                );
            }
        }).start();
    }
}

MainContentProvider.java

package com.perqin.myapplication;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.util.Log;

public class MainContentProvider extends ContentProvider {
    private static final String TAG = "MainContentProvider";

    public MainContentProvider() {
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        return -1;
    }

    @Override
    public String getType(Uri uri) {
        return "plain/text";
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        return null;
    }

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        Log.i(TAG, "query: Thread ID = " + Thread.currentThread().getId());
        return null;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        return -1;
    }
}

MainIntentService.java

package com.perqin.myapplication;

import android.app.IntentService;
import android.content.Intent;
import android.content.Context;
import android.util.Log;

public class MainIntentService extends IntentService {
    private static final String TAG = "MainIntentService";
    private static final String ACTION_MAIN = "com.perqin.myapplication.action.MAIN";

    public MainIntentService() {
        super("MainIntentService");
    }

    public static void startAction(Context context) {
        Intent intent = new Intent(context, MainIntentService.class);
        intent.setAction(ACTION_MAIN);
        context.startService(intent);
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        Log.i(TAG, "onHandleIntent: Thread ID = " + Thread.currentThread().getId());
    }
}

MainReceiver.java

package com.perqin.myapplication;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

public class MainReceiver extends BroadcastReceiver {
    private static final String TAG = "MainReceiver";

    @Override
    public void onReceive(Context context, Intent intent) {
        Log.i(TAG, "onReceive: Thread ID = " + Thread.currentThread().getId());
    }
}