单击（按钮）三个按钮后，通过Intent应用将EditText整数传递给TextView时崩溃

Question

I am trying just to pass the int user input to the next class and print it, see that it works before continuing on using it or something else.

Home.java

start and exit button

public class Home extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button one = (Button) findViewById(R.id.b1);
        one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                goToSecondActivity();
            }
        });
        Button two = (Button) findViewById(R.id.b2);
        two.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
    }
    private void goToSecondActivity() {
        Intent i = new Intent(this, SelectNumberOfPlayers.class);
        startActivity(i);
    }
}

SelectNumberOfPlayers.java

Taking only the numbers from the input and passing it to StartGame.class

public class SelectNumberOfPlayers extends AppCompatActivity {

    EditText numberOfPlayers;
    Button three;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.enter_number_of_players);
        three = (Button) findViewById(R.id.button3);
        three.setOnClickListener(new View.OnClickListener(){

            public void onClick(View v){

                String txt = numberOfPlayers.getText().toString();
                Intent i = new Intent(getApplicationContext(), StartGame.class);
                i.putExtra("players", txt);
                startActivity(i);
            }
        });
    }
}

StartGame.java

Receiving Int and printing to TextView

public class StartGame extends AppCompatActivity {

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

        Intent i = getIntent();

        TextView numOfPlayersVal = (TextView) findViewById(R.id.txt2);
        numOfPlayersVal.setText(i.getStringExtra("Player number"));
    }
}

Where is the error happening? I've set the input keyboard to take only numbers

Answer 1

1. you forgot to initialize youe editext first initialize it in your SelectNumberOfPlayers Activity

numberOfPlayers = (EditText) findViewById(R.id.numberOfPlayers);

2. the key must be same to pass and receive data with intent

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

    Intent i = getIntent();

    TextView numOfPlayersVal = (TextView) findViewById(R.id.txt2);
    numOfPlayersVal.setText(i.getStringExtra("players"));
}