java - 如何用后退按钮终止 Activity ？

Question

这是我无意中发现的。我有一个问答游戏，有一个弹出窗口显示正确答案，有一个弹出窗口显示错误答案，游戏结束后我有一个弹出窗口显示结果。但是，今天我在游戏中间按后退按钮返回到我的主屏幕(不是游戏主屏幕，而是我的操作系统主屏幕)，游戏仍然在后台，就像所有其他 Android 应用程序一样。几秒钟后，我的错误答案出现了。 :) 时间到了，答案自然是错误的。之后我的最终结果弹出窗口继续出现。那么，当我按下后退按钮时如何终止该 Activity 呢？我不知道你们是否需要我的代码，但以防万一，这是我的游戏 Activity :

public class NeogranicenoPetGresaka extends Activity implements OnClickListener{

    MyCount brojacVremena = new MyCount(6000, 1000);

LinkedList<Long> mAnsweredQuestions = new LinkedList<Long>();

    private String generateWhereClause(){
        StringBuilder result = new StringBuilder();
        for (Long l : mAnsweredQuestions){
            result.append(" AND _ID <> " + l);
        }
        return result.toString();
    }

    Button bIzlazIzKviza, bOdgovor1, bOdgovor2, bOdgovor3, bOdgovor4;
    TextView question, netacniOdg, score, countdown;
    int brojacPogresnihOdgovora = 0;
    int brojacTacnihOdgovora = 0;
    public static String tacanOdg;

    Runnable mLaunchTask = new Runnable() {
        public void run() {
            nextQuestion();
            brojacVremena.start();
        }
     };
    Runnable mLaunchTaskFinish = new Runnable() {
         public void run() {
            brojacVremena.cancel();
            finish();
         }
      };


    private class Answer {
        public Answer(String opt, boolean correct) {
            option = opt;
            isCorrect = correct;
        }

        String option;
        boolean isCorrect;
    }
    Handler mHandler = new Handler();

    final OnClickListener clickListener = new OnClickListener() {
        public void onClick(View v) {

            Answer ans = (Answer) v.getTag();
            if (ans.isCorrect) {
                brojacVremena.cancel();
                brojacTacnihOdgovora = brojacTacnihOdgovora + 5;
                Intent i = new Intent("rs.androidaplikacijekvizopstekulture.TACANODGOVOR");
                startActivity(i);
                mHandler.postDelayed(mLaunchTask,1200);
            }
        /*else{
            brojacVremena.cancel();
            brojacPogresnihOdgovora++;
            Intent i = new Intent(getApplicationContext(), PogresanOdgovor.class);
            i.putExtra("tacanOdgovor", tacanOdg);
            startActivity(i);
            mHandler.postDelayed(mLaunchTask,2200);
            }*/
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

        setContentView(R.layout.neograniceno);

        Typeface dugmad = Typeface.createFromAsset(getAssets(), "Bebas.ttf");
        Typeface pitanje = Typeface.createFromAsset(getAssets(), "myriad.ttf");
        bIzlazIzKviza = (Button) findViewById(R.id.bIzlazIzKvizaN);
        netacniOdg = (TextView) findViewById(R.id.tvBrojPitanjaN);
        question = (TextView) findViewById(R.id.tvPitanjeN);
        bOdgovor1 = (Button) findViewById(R.id.bOdgovorN1);
        bOdgovor2 = (Button) findViewById(R.id.bOdgovorN2);
        bOdgovor3 = (Button) findViewById(R.id.bOdgovorN3);
        bOdgovor4 = (Button) findViewById(R.id.bOdgovorN4);
        score = (TextView) findViewById(R.id.tvSkor2N);
        countdown = (TextView) findViewById(R.id.tvCountdownN);
        bOdgovor1.setTypeface(dugmad);
        bOdgovor2.setTypeface(dugmad);
        bOdgovor3.setTypeface(dugmad);
        bOdgovor4.setTypeface(dugmad);
        bIzlazIzKviza.setTypeface(dugmad);
        netacniOdg.setTypeface(dugmad);
        question.setTypeface(pitanje);
        score.setTypeface(dugmad);
        countdown.setTypeface(dugmad);

        nextQuestion(); //startuje prvo pitanje!
        brojacVremena.start();  //startuje brojac vremena
    }


    public class MyCount extends CountDownTimer {

        public MyCount(long millisInFuture, long countDownInterval) {
            super(millisInFuture, countDownInterval);
        }

        @Override
        public void onFinish() {

            brojacPogresnihOdgovora++;
            Intent i = new Intent(getApplicationContext(), PogresanOdgovor.class);
            i.putExtra("tacanOdgovor", tacanOdg);
            startActivity(i);
            mHandler.postDelayed(mLaunchTask,2200);
        }

        @Override
        public void onTick(long millisUntilFinished) {
            countdown.setText("" + millisUntilFinished / 1000);
        }
    }

        public void onClick(View v) {
        // TODO Auto-generated method stub


    }
    @Override
        protected void onPause() {
            // TODO Auto-generated method stub
            super.onPause();
        }

    public void nextQuestion() {


        TestAdapter mDbHelper = new TestAdapter(this);
        mDbHelper.createDatabase();

        try{    //Pokusava da otvori db

            mDbHelper.open();  //baza otvorena

            Cursor c = mDbHelper.getTestData(generateWhereClause());
            mAnsweredQuestions.add(c.getLong(0));

            List<Answer> labels = new ArrayList<Answer>();

            labels.add(new Answer(c.getString(2), true));
            labels.add(new Answer(c.getString(3), false));
            labels.add(new Answer(c.getString(4), false));
            labels.add(new Answer(c.getString(5), false));

            Collections.shuffle(labels);

            tacanOdg = c.getString(2);

            if(brojacPogresnihOdgovora < 20){


        question.setText(c.getString(1));

        bOdgovor1.setText(labels.get(0).option);
        bOdgovor1.setTag(labels.get(0));
        bOdgovor1.setOnClickListener(clickListener);

        bOdgovor2.setText(labels.get(1).option);
        bOdgovor2.setTag(labels.get(1));
        bOdgovor2.setOnClickListener(clickListener);

        bOdgovor3.setText(labels.get(2).option);
        bOdgovor3.setTag(labels.get(2));
        bOdgovor3.setOnClickListener(clickListener);

        bOdgovor4.setText(labels.get(3).option);
        bOdgovor4.setTag(labels.get(3));
        bOdgovor4.setOnClickListener(clickListener);

        netacniOdg.setText("" + brojacPogresnihOdgovora);
        score.setText("Score: " + brojacTacnihOdgovora);
            }
            else{
                brojacVremena.cancel();
                Intent i = new Intent(getApplicationContext(), Rezultat.class);
                i.putExtra("noviRezultat", brojacTacnihOdgovora);
                startActivity(i);
                String brojacTacnihOdgovoraString = String.valueOf(brojacTacnihOdgovora);
                mHandler.postDelayed(mLaunchTaskFinish,4000);
                //SwarmLeaderboard.submitScore(6863, brojacTacnihOdgovora);
                HeyzapLib.submitScore(this, brojacTacnihOdgovoraString, "Osvojili ste " + brojacTacnihOdgovoraString + " poena!", "1T3");
            }
        }
        finally{    // kada zavrsi sa koriscenjem baze podataka, zatvara db
            mDbHelper.close();
        }

    bIzlazIzKviza.setOnClickListener(new OnClickListener() {

        public void onClick(View v) {
            finish();   
        }
    });
    }
}

我尝试将其放入我的代码中，但没有成功:

@Override
    public void onBackPressed() {
            super.onBackPressed();
            this.finish();
    }

也尝试过这个，但没有成功:

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
    if ((keyCode == KeyEvent.KEYCODE_BACK))
    {
        finish();
    }
    return super.onKeyDown(keyCode, event);
}

Answer 1

问题是 Activity 已停止，但您创建的后台线程仍在运行。因此，您需要重写 onStop 并取消任何后台线程。

类似于:

@Override public void onStop() {
    super.onStop();
    brojacVremena.cancel();
}