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

我试图将int用户输入传递给下一个类并打印它，然后在继续使用它或其他东西之前先查看它是否有效。

家.java

开始和退出按钮

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

仅从输入中获取数字并将其传递给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

接收Int并打印到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"));
    }
}

错误在哪里发生？ 我将输入键盘设置为仅包含数字

Answer 1

1.您忘了初始化自己的editext，然后先在SelectNumberOfPlayers活动中对其进行初始化

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

2.密钥必须相同，才能有意传递和接收数据

 @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"));
}