launching Activity only once(First app use) Using Boolean flags

Question

So i got my firstScreen that i want to be shown just on the first app use. and i have my mainActivity which will follow the firstScreen. Im only starting with android and i don't want to use the solutions brought in here: How to launch activity only once when app is opened for first time? AND Can I have an android activity run only on the first time an application is opened? because i dont know SharedPreferrences yet.

So how can i achieve that using Boolean flags?

I have got:boolean firstTimeUse = false; In my firstScreenActivity

And when i start myMainActivity i set the flag to true;

firstTimeUse = true;
Intent intent = new Intent(FirstScreen.this,MainActivity.class);
startActivity(intent);

The problem is the MainActivity doesn't recognize the Boolean variable. Am i doing it wrong? Or i can still make some modifications and do it with flags?

EDIT FirstScreen.java:

package com.example.predesignedmails;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.method.ScrollingMovementMethod;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageButton;
import android.widget.TextView;

public class FirstScreen extends AppCompatActivity
{
    TextView welcomeTextTextView;

    String welcomeText;

    ImageButton goToMainImageButton;

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

        viewsInitialization();

        welcomeText = "Welcome to Pre Designed Mails.\n"
                + "In here you will have a tons of Emails templates for about every purpose you will need.\n"
                + "Just fill the small details and click Send.\n\n"
                + "Send E-mails fast and efficient!";

        welcomeTextTextView.setText(welcomeText);
        welcomeTextTextView.setMovementMethod(new ScrollingMovementMethod());

        goToMainImageButton.setOnClickListener(new View.OnClickListener()
        {   
            @Override
            public void onClick(View v) 
            {
                Intent intent = new Intent(FirstScreen.this,MainActivity.class);
                startActivity(intent);
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) 
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.first_screen, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) 
    { 
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings)
        {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onResume()
    {
         super.onResume();

        if (SettingsManager.getBoolean(this, SettingsManager.FIRST_LAUNCH, true))
        {
            SettingsManager.saveBoolean(this, SettingsManager.FIRST_LAUNCH, false);

            // First launch code
            Log.d("FirstLaunchCheckUp","First Launch");
        }
    }

    private void viewsInitialization()
    {
        welcomeTextTextView = (TextView) findViewById(R.id.welcome_text_text_view_id);
        goToMainImageButton = (ImageButton) findViewById(R.id.go_to_main_button_id);
    }
}

The onResume() method i added manually. It wasn't added automatically when i crated a new activity in Eclipse.

MainActivity.java:

package com.example.predesignedmails;

import android.support.v7.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity 
{
Button hatefullMailButton;
Button loveMailsButton;
Button welcomeScreenButton;

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

    getWindow().getDecorView().setBackgroundColor(getResources().getColor(R.color.main_activity_background_color)); // Setting background color

    viewsInitialization();

    hatefullMailButton.setOnClickListener(new View.OnClickListener()
    {   
        @Override
        public void onClick(View v) 
        {
            Intent intent = new Intent(MainActivity.this,HatefulMailsActivity.class);
            startActivity(intent);
        }
    });
    loveMailsButton.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            Intent intent = new Intent(MainActivity.this,LoveMailsActivity.class);
            startActivity(intent);
        }
    });
    welcomeScreenButton.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v) 
        {
            Intent intent = new Intent(MainActivity.this,FirstScreen.class);
            startActivity(intent);
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) 
{
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) 
{
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) 
    {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

private void viewsInitialization()
{
    hatefullMailButton = (Button) findViewById(R.id.hateful_email_button_id);
    loveMailsButton = (Button) findViewById(R.id.love_email_button_id);
    welcomeScreenButton = (Button) findViewById(R.id.welcome_screen_button_id);
}

}

Answer 1

In your Activity

@Override
protected void onResume() {
    super.onResume();
    if (SettingsManager.getBoolean(this, SettingsManager.FIRST_LAUNCH, true)){
        SettingsManager.saveBoolean(this, SettingsManager.FIRST_LAUNCH, false);
        //your first launch code
    }
}

SharedPreference helper class

public class SettingsManager
{
    public static final String FIRST_LAUNCH= "first_lauch";

    public static String getString(Context context, String key, String defValue) {
        return PreferenceManager.getDefaultSharedPreferences(context).getString(key, defValue);
    }

    public static int getInt(Context context, String key, int defValue) {
        return PreferenceManager.getDefaultSharedPreferences(context).getInt(key, defValue);
    }

    public static boolean getBoolean(Context context, String key, boolean defValue) {
        return PreferenceManager.getDefaultSharedPreferences(context).getBoolean(key, defValue);
    }

    public static void saveString(Context context, String key, String value) {
        PreferenceManager.getDefaultSharedPreferences(context).edit().putString(key, value).commit();
    }

    public static void saveInt(Context context, String key, int value) {
        PreferenceManager.getDefaultSharedPreferences(context).edit().putInt(key, value).commit();
    }

    public static void saveBoolean(Context context, String key, boolean value) {
        PreferenceManager.getDefaultSharedPreferences(context).edit().putBoolean(key, value).commit();
    }
}

For the future you can write more simple methods on this SettingsManager, like

public static int getFirstLaunch(Context context) {
    return getBoolean(context, FIRST_LAUNCH, true);
}

public static int saveFirstLaunch(Context context, boolean value) {
    return saveBoolean(context, FIRST_LAUNCH, value);
}

And use it like

@Override
protected void onResume() {
    super.onResume();
    if (SettingsManager.getFirstLaunch(this)){
        SettingsManager.saveFirstLaunch(this, false);
        //your first launch code
    }
}

Answer 2

The reason why firstScreen does not recognize boolean firstTimeUse in mainActivity is because it does not yet exist. Only after you have executed the line startActivity(intent) will there exist an object of class mainActivity. Basically, you cannot set a boolean on something that does not yet exist.

Instead, what you can do is pass extra information to an activity that is to be started. When the just-started-activity is initializing itself it can read the extra information and act on it.

So build your intent for the activity you want to start and also set extra information in the 'extras':

Intent intent = new Intent(FirstScreen.this,MainActivity.class);
intent.putExtra("firstTimeUse", true);
startActivity(intent);

Now for your MainActivity to know the value of firstTimeUse it must read the extras:

public class MainActivity {

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

        boolean firstTimeUse = getIntent().getBooleanExtra("firstTimeUse", false);
        // do processing dependent on whether it's the first time or not
    }
}

This should solve your problem of "the MainActivity doesn't recognize the Boolean variable".