Android问答消息提示

Question

嗨，我正在创建一个测试应用程序。我想在我的提交按钮中添加一个函数，如果用户没有在无线电按钮中选择任何答案，就会有一条消息：“请选择一个答案”，这是代码

  public void onClickNext(View view) {
    String level = getIntent().getExtras().getString("level");
    DbHelper db = new DbHelper(this);
    db.getQuestByLevel(level, qnum);

    RadioGroup grp = (RadioGroup) findViewById(R.id.questionAndAnswers);
    RadioButton answer = (RadioButton) findViewById(grp.getCheckedRadioButtonId());
    if (corAnswer != null && corAnswer.equalsIgnoreCase((String) answer.getText())) {
        score++;
        Log.d("answer", "Your score" + score);
    }
    if (qnum <= 5) {

    }
    else {
        Intent intent = new Intent(QuizActivity.this, ResultActivity.class);
        Bundle b = new Bundle();
        b.putInt("score", score);
        intent.putExtras(b);
        startActivity(intent);
        finish();
    }

    txtQuestion.setText(db.question);
    rda.setText(db.optionA);
    rdb.setText(db.optionB);
    rdc.setText(db.optionC);
    rdd.setText(db.optionD);
    corAnswer = db.answer;
    qnum++;
    rdgrp.clearCheck();
}

}

Answer 1

在下一行

RadioButton answer = (RadioButton) findViewById(grp.getCheckedRadioButtonId());

如果没有选中RadioButton，getCheckedRadioButtonId()将返回"-1“，并且由于没有使用该id的视图，”应答“将是null。

这样您就可以执行以下操作

if (answer == null)
{
    Toast.makeText(MyActivity.this, "select an answer please", Toast.LENGTH_SHORT).show();

    // nothing more to do here so 
    return;
}
if (corAnswer!= null && corAnswer.equalsIgnoreCase((String) answer.getText())
{
    // continue as before
}