Android ขอควาช่วยเหลือ เกี่ยวกับการเขียนแอฟแอนดรอยหน่อยคับ มือใหม่คับ

package com.example.jakkarin.projectao;

import android.support.v7.app.AppCompatActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.ImageButton;

public class PoliceC extends AppCompatActivity {

    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.poli);

        ImageButton polibtnCall = (ImageButton) findViewById(R.id.policallbtn);
        polibtnCall.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {

                Intent newActivity = new Intent(Intent.ACTION_CALL);
                newActivity.setData(Uri.parse("0945490772"));
                startActivity(newActivity);

            }
        });
    }
    public boolean onCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.poli, menu);
        return true;
    }


}

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <uses-permission android:name="android.permission.CALL_PHONE" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".PoliceC"></activity>
        <activity android:name=".hospitalC"></activity>
        <activity android:name=".FireC"></activity>
        <activity android:name=".KupaiC"></activity>

    </application>

</manifest>