ArrayList的Android Class Cast异常

Question

我创建了一个 extends ArrayList<OtherClass> 的类。然后我将该类的一个实例作为 Intent 的额外实例，例如 intent.putExtra("questionlist", questionsList);In other Activity 我得到了额外的像 questionsList = (QuestionList) getIntent().getSerializableExtra("questionlist"); 并按照代码所示进行投射，但它会弹出 ClassCastException. What is problem here. Thanks.

public void startTest(){
    Intent intent = new Intent("com.example.testznanja.TESTACTIVITY");
    intent.putExtra("player", player);
    intent.putExtra("numberofquestions", numberOfQuestions);
    intent.putExtra("numberofmistakes", numberOfMistakes);
    intent.putExtra("questionlist", questionsList);
    startActivity(intent);
}



private void initialize() {
    playerList = new PlayerList(this.getCacheDir());
    questionText = (TextView) findViewById(R.id.questionText);
    questionText.setGravity(Gravity.CENTER_HORIZONTAL);
    correctAnswers = (TextView) findViewById(R.id.questionsAnswers);
    b1 = (Button) findViewById(R.id.beginTest);
    b2 = (Button) findViewById(R.id.button2);
    b3 = (Button) findViewById(R.id.button3);
    b4 = (Button) findViewById(R.id.button4);
    timer = (TextView) findViewById(R.id.timer);
    testPlayer = (Player) getIntent().getSerializableExtra("key");
    numberOfQuestions = getIntent().getIntExtra("numberofquestions", 0);
    numberOfMistakes = getIntent().getIntExtra("numberofanswers", 0);
    questionsList =  (QuestionList) getIntent().getSerializableExtra("questionlist");
    questionsList.shrinkToRandomQuestions(numberOfQuestions);
}




public class QuestionList extends ArrayList<Question>{

private Context context;
private ArrayList<String> answersList = new ArrayList<String>();

public QuestionList(Context c) {
    context = c;
}

}

Answer 1

OtherClass 必须是 Serializable 才能将其作为 Serializable 额外传递给 Intent。 ArrayList<?> 是 Serializable 是不够的。