将rand变量从一类传递到具有相同值的另一类

Question

Trying to pass a random generated variable in one class to be used in another to sync up the background of my application and the header in another fragment.

public class LoginMain extends AppCompatActivity {
    RelativeLayout loginMain;
    Random rand = new Random();
    int bgPick = rand.nextInt(5) + 1; //distribute int from 1 to 3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login_main);
        //must be called after the content view is set.
        loginMain = (RelativeLayout) findViewById(R.id.activity_login_main);
        randomBG();//method that determines the background image based on the bgPick value.
    }

    public static int getBgPick(){
        return bgPick;
    }

Main Class:

public class MainActivity extends AppCompatActivity {
    AppBarLayout appBarLayout;
    int bgPick = LoginMain.getBgPick();


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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        appBarLayout = (AppBarLayout) findViewById(R.id.appbar);
        randomHeader();//method to determine header image based on bgPick value determined in the LoginMain class.

This results in two bgPick values being made and used separately in each class.

Answer 1

You should consider using intent For example, if you want to pass items from one class to another.

 Intent intent =new Intent(FirstActivity.this,SecondAcitivity.class);
 intent.putExtra("EXTRA_SESSION_ID", sessionId);
 intent.putExtra("EXTRA_String", "California");
 startActivity(intent);

In the SecondActivity;

String s = getIntent().getStringExtra("EXTRA_SESSION_ID");
String place = getIntent().getStringExtra("EXTRA_String");

Answer 2

Solved by using Static and getBgPick Method.

public class LoginMain extends AppCompatActivity {
    RelativeLayout loginMain;
    Random rand = new Random();
    public static int bgPick;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login_main);
        this.bgPick = rand.nextInt(5) + 1; //distribute int from 1 to 3
        //must be called after the content view is set.
        loginMain = (RelativeLayout) findViewById(R.id.activity_login_main);
        randomBG();
    }

    public static int getBgPick(){
        return bgPick;
    }
}

Main Class:

public class MainActivity extends AppCompatActivity {    
    AppBarLayout appBarLayout;
    int bgPick = LoginMain.getBgPick();


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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        appBarLayout = (AppBarLayout) findViewById(R.id.appbar);
        randomHeader();
    }
}