Java 尝试从非活动类启动服务时出错

我以前有一个前台服务，我从一个活动启动。启动服务的代码包含在上述活动中

现在我想用一个非活动类来启动这个服务，这个类可以从不同的活动中调用。在执行此操作时，我会遇到一个错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.ComponentName android.content.Context.startService(android.content.Intent)' on a null object reference

工作代码块以前包含在单个活动中（我们称之为“ActivityClass”），如下所示：

private void serviceWrapper(String command){
        Intent service = new Intent(ActivityClass.this, Recorder.class);
        switch (command){
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc...
         }
}

public class ServiceWrapper extends AppCompatActivity {
   // variable to hold context passed
   private Context context;
   public ServiceWrapper(Context context){
      this.context=context;
   }
   public void serviceControl(String command){
        Intent service = new Intent(context, Recorder.class);
        switch (command)
        {
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc....
        }

    private void startWrapper() {
        //Instantiate the class
        ServiceWrapper serviceWrapper = new ServiceWrapper(ActivityClass.this);
        //Check for permissions needed
        if (hasPermissionsGranted(Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS)){
            serviceWrapper.serviceControl("start");
        }
        else {
            //kick off async request for permission
            ActivityCompat.requestPermissions(this, Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS, REQUEST_VIDEO_PERMISSIONS);
        }
    }

我尝试将其移动到非活动类，如下所示：

private void serviceWrapper(String command){
        Intent service = new Intent(ActivityClass.this, Recorder.class);
        switch (command){
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc...
         }
}

public class ServiceWrapper extends AppCompatActivity {
   // variable to hold context passed
   private Context context;
   public ServiceWrapper(Context context){
      this.context=context;
   }
   public void serviceControl(String command){
        Intent service = new Intent(context, Recorder.class);
        switch (command)
        {
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc....
        }

    private void startWrapper() {
        //Instantiate the class
        ServiceWrapper serviceWrapper = new ServiceWrapper(ActivityClass.this);
        //Check for permissions needed
        if (hasPermissionsGranted(Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS)){
            serviceWrapper.serviceControl("start");
        }
        else {
            //kick off async request for permission
            ActivityCompat.requestPermissions(this, Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS, REQUEST_VIDEO_PERMISSIONS);
        }
    }

我想从多个活动中称之为：

private void serviceWrapper(String command){
        Intent service = new Intent(ActivityClass.this, Recorder.class);
        switch (command){
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc...
         }
}

public class ServiceWrapper extends AppCompatActivity {
   // variable to hold context passed
   private Context context;
   public ServiceWrapper(Context context){
      this.context=context;
   }
   public void serviceControl(String command){
        Intent service = new Intent(context, Recorder.class);
        switch (command)
        {
            case "start":
                    service.setAction(Constants.ACTION.STARTFOREGROUND_ACTION);
                    service.putExtra("recordAudio", RECORD_AUDIO);
                    startService(service);
                    break;
            etc....
        }

    private void startWrapper() {
        //Instantiate the class
        ServiceWrapper serviceWrapper = new ServiceWrapper(ActivityClass.this);
        //Check for permissions needed
        if (hasPermissionsGranted(Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS)){
            serviceWrapper.serviceControl("start");
        }
        else {
            //kick off async request for permission
            ActivityCompat.requestPermissions(this, Constants.PERMISSION_SETTINGS.VIDEO_PERMISSIONS, REQUEST_VIDEO_PERMISSIONS);
        }
    }

---

但不幸的是我犯了这个错误。我不是一个知识渊博的程序员，所以如果这是显而易见的，请原谅我。

一般来说，这不是在android上启动前台服务的方式

应该是这样的：

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            context.startForegroundService(new Intent(context, HelloService.class));
 } else {
            context.startService(new Intent(context, HelloService.class));
        }

如果您在活动之外，则需要一种检索应用程序上下文的方法。通常，通过构造函数将上下文存储为变量，以便以后使用。例如，创建一个将应用程序上下文存储为变量的新类实例，在应用程序的其他地方使用该上下文启动服务

或者取决于类扩展或实现的内容

getActivity().getApplicationContext();

---

如果您使用的是intent服务，您应该首先启动该服务，使其初始化，然后再传递您的intent。

谢谢。我想因为我的活动扩展了AppCompatActivity，所以我的solo startService命令起作用，将其更新为context.startService在非活动类中起作用。