Return the name of the package that invoked this activity. This is who the data in setResult() will be sent to. You can use this information to validate that the recipient is allowed to receive the data. Note: if the calling activity is not expecting a result (that is it did not use the startActivityForResult form that includes a request code), then the calling package will be null. Note: prior to Build.VERSION_CODES.JELLY_BEAN_MR2, the result from this method was unstable. If the process hosting the calling package was no longer running, it would return null instead of the proper package name. You can use getCallingActivity() and retrieve the package name from that instead.解释一下

这段英文是Android官方文档中对于getCallingPackage()方法的解释。它的意思是：返回调用此活动的包的名称。这是要将setResult()中的数据发送到的对象。您可以使用此信息来验证接收方是否有权接收数据。注意：如果调用活动不需要结果（即未使用包含请求代码的startActivityForResult形式），则调用包将为null。注意：在Build.VERSION_CODES.JELLY_BEAN_MR2之前，此方法的结果不稳定。如果托管调用包的进程不再运行，则返回null而不是正确的包名称。您可以使用getCallingActivity()并从中检索包名称。

简单来说，这段话告诉我们，getCallingPackage()方法可以返回调用当前Activity的应用程序的包名，我们可以使用它来验证接收方是否有权接收数据。但是在Android 4.3之前，该方法的结果可能不稳定，如果调用方的进程已经停止运行，它可能会返回null，此时我们可以使用getCallingActivity()方法来获取包名。

相关问题

sudo pip install PyQt5 WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip. Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue. To avoid this problem you can invoke Python with '-m pip' instead of running pip directly. No handlers could be found for logger "pip._internal.network.auth" DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality. WARNING: The directory '/home/trunk/.cache/pip' or its parent directory is not owned or is not writable by the current user. The cache has been disabled. Check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag. ERROR: Could not find a version that satisfies the requirement PyQt5 (from versions: none) ERROR: No matching distribution found for PyQt5

这个问题可能是因为你的 Python 版本太旧而导致的。建议你升级到 Python 3.x 版本，并使用类似以下的命令安装 PyQt5：

pip3 install PyQt5

如果你使用的是 Anaconda，可以使用以下命令安装：

conda install pyqt

另外，你也可以在命令行中使用 `-m pip` 来运行 pip，例如：

sudo python -m pip install PyQt5

这样可以避免一些潜在的问题。如果还有其他问题，请让我知道。

public synchronized void start() { /** * This method is not invoked for the main method thread or "system" * group threads created/set up by the VM. Any new functionality added * to this method in the future may have to also be added to the VM. * * A zero status value corresponds to state "NEW". */ if (threadStatus != 0) throw new IllegalThreadStateException(); /* Notify the group that this thread is about to be started * so that it can be added to the group's list of threads * and the group's unstarted count can be decremented. */ group.add(this); boolean started = false; try { start0(); started = true; } finally { try { if (!started) { group.threadStartFailed(this); } } catch (Throwable ignore) { /* do nothing. If start0 threw a Throwable then it will be passed up the call stack */ } } }帮我分析一下

这段代码是Java中的Thread类的start()方法的实现。start()方法用于启动一个线程，并执行线程的run()方法。

首先，代码使用synchronized关键字来确保start()方法的原子性，避免并发问题。

然后，通过判断threadStatus变量的值，如果不为0，则抛出IllegalThreadStateException异常。这是为了防止重复启动一个已经启动过的线程。

接下来，代码调用group.add(this)将当前线程添加到线程组中，以便能够进行线程管理。

然后，代码使用try-catch-finally块来处理线程启动的过程。在try块中，调用start0()方法来实际启动线程，并将started标志设置为true，表示线程成功启动。在finally块中，通过判断started标志，如果为false，则调用group.threadStartFailed(this)来处理线程启动失败的情况。

需要注意的是，如果start0()方法抛出了异常，则这个异常会被传递到调用栈上层处理。

总的来说，这段代码实现了线程的启动过程，并进行了相关的异常处理和线程管理操作。