Android - 通过广播 Intent 传递长数组

Question

我写了一个小的 android 程序，有一个带有广播监听器的主 Activity ，我创建了另一个线程。该线程搜索素数，并将它们加载到一个长数组列表中，每隔 3 秒，将填充的数组通过广播发送到主 Activity 。一切正常，直到我试图从 Intent 中获得额外的长数组。每次都会导致空指针异常。 我尝试使用字符串数组列表，它起作用了，但我很好奇，因为 Intent 有一个“getlongarrayextra”方法。

这是我的代码:

公共(public)类 MainActivity 扩展 Activity {

public static String BROADCAST_THREAD_KEY = "broadcast_key";
public static String EXTRAARRAYID = "primes";
private static long MAXNUM = 2000000;
private PrimeCalculatorThread thread;
TextView textView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textView = (TextView) findViewById(R.id.numberstext);
}

private BroadcastReceiver receiver = new BroadcastReceiver() {
    public void onReceive(android.content.Context context,
            android.content.Intent intent) {
        String origitext = textView.getText().toString();
        long[] primes = intent.getExtras().getLongArray(EXTRAARRAYID);
        Log.d("ASD", "broadcast received" + primes.toString());
        StringBuilder builder = new StringBuilder();
        if (primes != null) {
            for (long prime : primes) {
                builder.append(prime + " - ");
            }
            textView.setText(origitext + "\n" + builder.toString());
        }

    };
};

@Override
protected void onResume() {
    Log.d("ASD", "ONRESUME");
    initReceiverAndStartThread();
    super.onResume();
}

private void initReceiverAndStartThread() {
    IntentFilter filter = new IntentFilter(BROADCAST_THREAD_KEY);
    registerReceiver(receiver, filter);
    thread = new PrimeCalculatorThread(getBaseContext(), MAXNUM);
    thread.start();
    Log.d("ASD", "THREAD STARTED");
}

和第二个线程:

公共(public)类 PrimeCalculatorThread 扩展线程 {

private Context context;
private long maxnum;
List<Long> primes;
boolean isrunning;

public void setIsrunning(boolean isrunning) {
    this.isrunning = isrunning;
}

private long counter = 0;
private long DELAYBETWEENBROADCAST = 3000;

public PrimeCalculatorThread(Context c, long maxnum) {
    this.context = c;
    this.maxnum = maxnum;
    primes = new ArrayList<Long>();
}

@Override
public void run() {
    long startTime = System.currentTimeMillis();
    long estimatedTime;
    isrunning = true;
    for (long i = 0; i < maxnum; i++) {
        Log.d("ASD", Boolean.toString(isrunning));
        if (!isrunning)
            break;
        Log.d("ASD", i + "");
        estimatedTime = System.currentTimeMillis() - startTime;
        if (isPrime(i)) {
            primes.add(i);
            Log.d("ASD", i + "is a prime");
        } else {
            Log.d("ASD", i + "is not a prime");
        }
        if (estimatedTime > counter * DELAYBETWEENBROADCAST
                + DELAYBETWEENBROADCAST) { // elapsed another period
            Log.d("ASD", primes.toString() + " will be sending.");
            sendBroadCast();
            primes.clear();
            counter++;
        }
        try {                       //for debug purposes
            Thread.sleep(250);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

private void sendBroadCast() {
    Intent intent = new Intent(MainActivity.BROADCAST_THREAD_KEY);
    intent.putExtra(MainActivity.EXTRAARRAYID, primes.toArray());
    context.sendBroadcast(intent);
    Log.d("ASD", "BROADCAST SENT" + primes.toString());
}

boolean isPrime(long n) {
    if (n < 2)
        return false;
    if (n == 2 || n == 3)
        return true;
    if (n % 2 == 0 || n % 3 == 0)
        return false;
    long sqrtN = (long) Math.sqrt(n) + 1;
    for (long i = 6L; i <= sqrtN; i += 6) {
        if (n % (i - 1) == 0 || n % (i + 1) == 0)
            return false;
    }
    return true;
}

Answer 1

问题是您正在管理 Long 对象 列表并将其传递到 putExtra 中，这意味着您正在调用 putExtra(String name, Serializable value)。然后您尝试使用 getLongArray() 获取该值，但是您没有放置任何额外的长数组，您看!要解决这个问题，请替换

intent.putExtra(MainActivity.EXTRAARRAYID, primes.toArray());

与

long[] primesArray = new long[primes.size()];
for (int i = 0; i < primes.size(); i++) {
    primesArray[i] = primes.get(i);
}
intent.putExtra(MainActivity.EXTRAARRAYID, primesArray);

这将调用正确的 putExtra(String name, long[] value) 方法。