从另一个活动（Android Studio）导入数据

Question

这是我的主班。 我从用户输入中获得双打。

public void onPayClick(View view){
    Intent payIntent = new Intent(this, payActivity.class);

    final EditText amountInput = (EditText) findViewById(R.id.amountInput);
    final EditText yearInput = (EditText) findViewById(R.id.yearInput);
    final EditText interestInput = (EditText) findViewById(R.id.interestInput);

    double amountDouble = Double.parseDouble(amountInput.getText().toString());
    double yearDouble = Double.parseDouble(yearInput.getText().toString());
    double interestDouble = Double.parseDouble(interestInput.getText().toString());

    payIntent.putExtra("amountDouble", amountDouble);
    payIntent.putExtra("yearDouble", yearDouble);
    payIntent.putExtra("interestDouble", interestDouble);

    startActivity(payIntent);
}

这是我的第二项活动，在这里我想计算贷款额，但我只是想打印出一倍的double值，以查看其是否有效，但无效。

TextView printPay = (TextView) findViewById(R.id.printPay);


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

    Bundle payData = getIntent().getExtras();

    if(payData == null){
        printPay.setText("Villa, þú verður að filla upp í alla reiti.");
        return;
    }
    String amountDouble = payData.getString("amountDouble");
    String yearDouble = payData.getString("yearDouble");
    String interestDouble = payData.getString("interestDouble");

    String sum1 = amountDouble;
    printPay.setText(sum1);
}

每次单击payButton时，应用程序崩溃。

Answer 1

在1st Activity您将直接在intent中添加这些值，因此必须从intent而不是从bundle获取这些数据。 除此之外，您还声明了TextView在类的顶部，因此在setContentView(R.layout.activity_pay);之后的onCreate(...)内部定义它为null setContentView(R.layout.activity_pay); 。 在第二个Activity改变

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_pay);
    TextView printPay = (TextView) findViewById(R.id.printPay);

    String amountDouble = String.valueOf(getIntent().getDoubleExtra("amountDouble", 0.0));
    String yearDouble = String.valueOf(getIntent().getDoubleExtra("yearDouble", 0.0);
    String interestDouble = String.valueOf(getIntent().getDoubleExtra("interestDouble", 0.0);

    String sum1 = amountDouble;
    printPay.setText(sum1);
}

getDoubleExtra（java.lang.String，double）的更多信息