One app opens another sub-app+ app installation does not appear on the phone desktop

Boss temporarily let me do a demo, to implement an app to open another app

Requirements: Click on the Open button, have installed the words opened, no installation display installation

Sub-program can no longer display icon on mobile phone page

Parent Program Core Code

                       public void OnClick (View arg0) {
				//TODO auto-generated method stub
				Intent Intent = new Intent ();
				COM.EXAMPLE.DEMO2: Child package name               com.example.demo2.MainActivity: subroutine open page
		        componentname cn = New ComponentName (" Com.example.demo2 "," com.example.demo2.MainActivity ");
		        Intent.setcomponent (CN);
		        Intent.setaction ("Android.intent.action.MAIN");
		        try {
		            Startactivityforresult (intent, RESULT_OK);
		        } catch (Exception e) {
		            Toast.maketext ( Mainactivity.this, "No sub-apps, please download Install", Toast.length_short). Show ();
		        }
			}

Subroutines only need to set a line of code under the manifest file

<application
        android:allowbackup= "true"
        android:icon= "@drawable/ic_launcher"
        android:label= "@ String/app_name "
        android:theme=" @style/apptheme ">
        <activity
            android:name=" Com.example.demo2.MainActivity "
            android:label=" @string/app_name ">
            <intent-filter>
                < Action android:name= "Android.intent.action.MAIN"/>
                <!--<category Android:name= " Android.intent.category.LAUNCHER "/>-->//comment out this line
            </intent-filter>
        </activity>
    </application>