android - 检查 EditText 是否为空

Question

我正在制作一个数学应用程序。我有两个包含两组数字的数组。我让应用程序从每个数组中选择一个随机数。该应用程序在 TextView 中显示这两个数字。它要求用户在 EditText 中输入数字相加的内容。然后当用户按下“提交”时，应用程序会告诉用户他们是对还是错。

该应用程序可以运行，但我有一个主要问题。如果用户未在 EditText 中键入任何内容并按下“提交”，应用将强制关闭。我看过其他问题，询问如何检查 EditText 是否为空。我尝试了不同的方法，但仍然无效。

public class MainActivity extends Activity {
Button submitb, startb, idkb;
EditText et;
TextView tv, rig, wron;

int arrone[] = { 24, 54, 78, 96, 48, 65, 32, 45, 95, 13, 41, 55, 33, 22,
        71, 5, 22, 17, 13, 29, 63, 72, 14, 81, 7 }; // One Set of Numbers//
int arrtwo[] = { 121, 132, 147, 79, 82, 723, 324, 751, 423, 454, 448,
        524, 512, 852, 845, 485, 775, 186, 99 }; // Another set of Numbers//
int random1, random2, add;
int wrong = 0;
int right = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    list();
    startb.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            int num = (int) (Math.random() * 25);
            int mun = (int) (Math.random() * 19);
            random1 = arrone[num];
            random2 = arrtwo[mun];
            String yu = (random1 + " + " + random2 + " =");
            tv.setText(yu);
            et.setHint("");
            idkb.setVisibility(0);
            startb.setText("Next Question");

        }
    });

    startb.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            int bread2 = 0;
            if (bread2 == 0) {
                Toast.makeText(getApplicationContext(),
                        "You didn't answer the question!",
                        Toast.LENGTH_LONG).show();

            }

            int swag = random1 + random2;
            String bread = et.getText().toString();
            bread2 = Integer.parseInt(bread);

            if (bread2 == swag) {
                startb.setText("Next Question");
                tv.setText("Correct");
                et.setText("");
                et.setHint("Click Next Question");
                right++;
                rig.setText("Right:" + right);
                rig.setTextColor(Color.parseColor("#14df11"));
                bread2 = 0;
            }

            else if (bread2 == 0) {
                tv.setText("Wrong, the correct answer is " + swag + ".");

                startb.setText("Next Question");
                et.setText("");
                tv.setHint("Click Next Question");
                wrong++;
                wron.setText("Wrong:" + wrong);
                wron.setTextColor(Color.parseColor("#ff0000"));
                bread2 = 0;
            }

            else {
                tv.setText("Wrong, the correct answer is " + swag + ".");

                startb.setText("Next Question");
                et.setText("");
                et.setHint("Click Next Question");
                wrong++;
                wron.setText("Wrong:" + wrong);
                wron.setTextColor(Color.parseColor("#ff0000"));
                bread2 = 0;

            }

        }

    });

    idkb.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            int swag = random1 + random2;

            tv.setText("The Correct Answer is  " + swag + ".");

            et.setText("");
            tv.setHint("Click Next Question");
            wrong++;
            wron.setText("Wrong:" + wrong);
            wron.setTextColor(Color.parseColor("#ff0000"));

        }
    });

}

private void list() {
    submitb = (Button) findViewById(R.id.b1);
    startb = (Button) findViewById(R.id.b2);
    et = (EditText) findViewById(R.id.et1);
    tv = (TextView) findViewById(R.id.tv1);
    rig = (TextView) findViewById(R.id.rtv);
    wron = (TextView) findViewById(R.id.wtv);
    idkb = (Button) findViewById(R.id.idk);

}

Answer 1

需要考虑的几点:

• 您在 startb 上设置了 OnClickListener 两次，这只是一个拼写错误吗？

• 在第二个 onClick() 中，您有一个条件:

  int bread2 = 0;
  if (bread2 == 0) {
      //rest of code
  }
  

这个条件总是会被满足，这是你想要的吗？

• 您可以使用以下命令检查是否没有输入任何内容:

  String bread = et.getText().toString();
  
  // check if there is any text entered by user
  if (bread.length() > 0) {
      bread2 = Integer.parseInt(bread);
  
      if (bread2 == swag) {
          startb.setText("Next Question");
  
          //the rest of the code
  }