Java语言
java语言里, 子线程中抛出的RuntimeException, 只会使得子线程结束运行, 不会影响主线程的执行, 进程不会因此crash. 主线程无法catch子线程抛出的exception.
如何处理子线程中抛出的RuntimeException, 有3种方式:
- 使用interface Thread.UncaughtExceptionHandler, 在调用Thread.start()方法之前, 调用Thread实例的setUncaughtExceptionHandler()方法, 实现interface Thread.UncaughtExceptionHandler. 示例代码如下:
Thread thread = new Thread(mThrowExceptionThreadGroup, new Runnable() {
…...
});
thread.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
@Override
public void uncaughtException(Thread thread, Throwable throwable) {
}
});
thread.start();
- 使用ThreadGroup.uncaughtException(), 创建ThreadGroup实例时, 覆写(override)uncaughtException()方法; 创建Thread实例时, 调用构造方法
Thread(ThreadGroup , Runnable ), 传入刚创建的ThreadGroup实例. 示例代码如下:
private final ThreadGroup mThrowExceptionThreadGroup = new ThreadGroup("ThrowException") {
@Override
public void uncaughtException(Thread thread, Throwable e) {
}
};
Thread thread = new Thread(mThrowExceptionThreadGroup, new Runnable() {
});
thread.start()
注意: 上面2种处理方法, 处理子线程抛出的Exception的代码还是运行在子线程里, 如果在uncaughtException()中throw Exception, 进程还是不会crash.
- 如果使用ExecutorService, Future运行子线程, Future.get()方法会抛出ExecutionException(Checked exception), 子线程里产生的RuntimeException会被包含在ExecutionException实例里抛出给调用者. 示例代码如下:
ExecutorService executorService = Executors.newFixedThreadPool(8);
Future future = executorService.submit(new Runnable() {
@Override
public void run() {
int a = 5 / 0;
}
});
try {
future.get();
} catch (InterruptedException | ExecutionException e) {
System.out.println(String.format("handle exception in child thread: %s", e.getCause()));
} finally {
executorService.shutdown();
}
Android环境下
在Android环境下, 情况有所不同. 当子线程抛出RuntimeException时, 进程会crash.
Android framework的处理如下:
在RuntimeInit.commonInit()方法内, 调用Thread.setDefaultUncaughtExceptionHandler(new UncaughtHandler()); 设置Thread.UncaughtExceptionHandler. 在UncaughtHandler内会执行如下语句来显示进程crash dialog:
// Bring up crash dialog, wait for it to be dismissed
ActivityManagerNative.getDefault().handleApplicationCrash( mApplicationObject, new ApplicationErrorReport.CrashInfo(e));
上面的语句会调用到ActivityManagerService.handleApplicationCrash()方法.
