Check and request to install Facebook App

Last exercise "Start facbook app by startActivity(intent)", without checking if Facebook App installed. To check if a app installed currently, we can call getPackageManager().getApplicationInfo() method; if not installed, NameNotFoundException will be thrown. To open Google Play with with a specified app, startActivity with action of Intent.ACTION_VIEW and url of the target package.

Modify btnStartFacebookOnClickListener from the last exercise:

 OnClickListener btnStartFacebookOnClickListener
 = new OnClickListener(){

  @Override
  public void onClick(View v) {
   
   String facebookPackageName = "com.facebook.katana";
   String facebookClassName = "com.facebook.katana.LoginActivity";
   
   try {
    ApplicationInfo facebookAppInfo = getPackageManager()
      .getApplicationInfo(facebookPackageName, 0);
    Intent intent = new Intent("android.intent.category.LAUNCHER");
    intent.setClassName(facebookPackageName, facebookClassName);
    startActivity(intent);
   } catch (NameNotFoundException e) {
    // Didn't installed
    Toast.makeText(getApplicationContext(), "Facebook not found! INSTALL.", Toast.LENGTH_LONG).show();
    
    //Start Market to downoad and install Facebook App
    Uri uri = Uri.parse("market://details?id=" + facebookPackageName); 
    Intent intent = new Intent(Intent.ACTION_VIEW, uri); 
    startActivity(intent);
   }
   
  }};

Next:
- Launch Facebook app from a specified page, using intent with ACTION_VIEW.