我写了一个小的安卓程序，其中包含一个主活动和一个广播监听器，并创建了另一个线程。该线程搜索素数，并将其加载到长整型数组列表中，每隔3秒钟通过广播将填充好的数组发送到主活动。一切都很好，直到我尝试从意图中获取长整型数组额外信息，这导致每次空指针异常。
我尝试使用字符串数组列表，它可以工作，但我很好奇为什么意图有一个“getlongarrayextra”方法。
这是我的代码： public class MainActivity extends Activity {
这是我的代码： public class MainActivity extends 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");
}
第二个线程：
public class PrimeCalculatorThread extends Thread {
这是一个计算质数的线程类。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;
}
}