java - 无法启动 Activity : invalid int

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请大家我正在编写这个 Android 应用程序，但我在 logCat 中遇到运行时错误: java.lang.RuntimeException: Unable to start Activity: java.lang.NumberFormatException: Invalid int: ""

public class MainActivity extends Activity{
    EditText et;
    Button guess, randomize;
    TextView tv1, tv2;

    int num1;
    int num2;
    int userAns;
    int answer;
    final Random rand = new Random();

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

        et = (EditText) findViewById(R.id.editText1);
        tv1 = (TextView) findViewById(R.id.textView1);
        tv2 = (TextView) findViewById(R.id.textView2);
        guess = (Button) findViewById(R.id.btnSubmit);
        randomize = (Button) findViewById(R.id.button1);



        randomize(rand);
        tv2.setText(num1 + " + " + num2);
        userAns = Integer.parseInt(et.getText().toString());

        guess.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                answer = num1 + num2;
                if (userAns == answer) {
                    tv1.setText("Correct... The Answer is " +answer);
                } else {
                    tv1.setText("wrong");
                }
            }
        });

        randomize.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                randomize(rand);
            }
        });

    }

    private void randomize(final Random rand) {
        num1 = 1 + rand.nextInt(50);
        num2 = 1 + rand.nextInt(50);
    }

}

Answer 1

numberFormatException 通常是由字符串到 int 转换出错引起的。我怀疑这条线。

userAns = Integer.parseInt(et.getText().toString());

因为它还没有用文本初始化。

将其包装在 try/catch 中

编辑:如何解决

我建议搬家

userAns = Integer.parseInt(et.getText().toString()); 

在guess.setOnClickListener中像这样:

guess.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        answer = num1 + num2;

        try {
            userAns = Integer.parseInt(et.getText().toString());
            if (userAns == answer) {
                tv1.setText("Correct... The Answer is " +answer);
            } else {
                tv1.setText("wrong");
            }
        } catch(Exception e) {
            // output error that 'et' field is emtpy or doesnt contain a number
        }
    }
});