Activity Lifecycle if button Home pressed Android example

Problem: erroneous entry of id

<RadioButton android:id="idRadio"
                android:text="My radio button"/>

Solution: @+id/

<RadioButton android:id="@+id/idRadio"
                android:text="My radio button"/>

If you do click on Rebuid project menu item, this operation maybe consume long time on slovly PC.
Some errors dismis when you do rebuild project, or module.
Try this:
Select module where contains red error code and press Debugg or Run button on Android Studio.
If module code contains errors, Android Studio show error report in gradle console.
If not, apk will installed on device.
This is 10 times faster than Clean - Rebuild all project.

Toast in Android application is equivalent of Alert in JavaScript or MessageBox in WinApi.

// Toast android.widget.Toast.makeText(Context context, CharSequence text, int duration)
// public static Toast makeText (Context context, CharSequence text, int duration) 

Toast.makeText(getApplicationContext(), "Hello world!",
                  Toast.LENGTH_SHORT).show();

android:gravity="left|center_vertical" or android:gravity="right|center_vertical"

               
<Button
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="left|center_vertical"
                    android:paddingLeft="20dp"
                    android:text="My Button"
                     />

Errors:
E/Ads(333): The android:configChanges value of the com.google.ads.AdActivity must include screenLayout.
E/Ads(333): The android:configChanges value of the com.google.ads.AdActivity must include uiMode.
E/Ads(333): The android:configChanges value of the com.google.ads.AdActivity must include screenSize.
E/Ads(333): The android:configChanges value of the com.google.ads.AdActivity must include smallestScreenSize.
E/Ads(333): You must have AdActivity declared in AndroidManifest.xml with configChanges.

Solution:
Try to using a lower version of the GoogleAdMobAdsSDK ADS SDK in project:
GoogleAdMobAdsSDK-4.0.4
How add SDK to project

Add activity to AndroidManifest.xml

// .............. blah
    <uses-sdk android:minSdkVersion="4"/>
   <uses-permission android:name="android.permission.INTERNET" />
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application android:icon="@drawable/dicts_ico" android:label="@string/app_name" 
    >
           <meta-data 
        android:value="a12345_your_number" 
        android:name="ADMOB_PUBLISHER_ID" />
        <activity android:name=".MainStartMenu"
                  android:label="@string/app_name"
                  android:configChanges="keyboardHidden|orientation"
                  >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


  <!-- Google ads -->      
<activity android:name="com.google.ads.AdActivity"
              android:configChanges="keyboard|keyboardHidden|orientation"/>

// ......... blah