嘗試停止服務時出現“空 object 參考”

Question

我想停止服務但收到此錯誤：

嘗試在 null object 參考上調用虛擬方法 'boolean android.content.Context.stopService(android.content.Intent)'

這是我停止服務的方法（在 class public class Dialog extends AppCompatActivity中）：

public void stopService(Context context) {
    Intent serviceIntent = new Intent(context, PicovoiceService.class);
    stopService(serviceIntent);
}

這就是我在另一個 class 中調用該方法的方式：

@SuppressLint("ValidFragment")
public class Popup extends DialogFragment {
    private final int _layout;
    private final Dialog mDialog = new Dialog();
    public boolean dialogIsActive = false;

    @SuppressLint("ValidFragment")
    public Popup(int layout) {
        _layout = layout;
    } 

    @SuppressLint({"ClickableViewAccessibility", "ResourceType"})
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        final View view =  inflater.inflate(_layout, container, false);

        // Display fragment_dialog
        if (_layout == R.layout.fragment_dialog) {

            // Toggle the listener
            view.findViewById(R.id.dialogCta).setOnClickListener(v -> {
                if (!dialogIsActive) {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        if (mDialog.hasRecordPermission(getContext())) {
                            mDialog.startService(getContext());
                            dialogIsActive = true;
                        }
                    }
                }
                else {
                    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                        mDialog.stopService(getContext()); // <-- ERROR
                    }
                    dialogIsActive = false;
                }
            });
        }           
        return view;
    }       
}

mDialog.startService(getContext()); 工作正常，但mDialog.stopService(getContext());有什么問題？ ?

更新

我也嘗試過Intent serviceIntent = new Intent(getBaseContext(), PicovoiceService.class); 和Intent serviceIntent = new Intent(getApplicationContext(), PicovoiceService.class); 但我得到同樣的錯誤。

Answer 1

這就是我可以使它工作的方法：

private Intent mServiceIntent = null;

public void startService(Context context) {
    mServiceIntent = new Intent(context, PicovoiceService.class);
    ContextCompat.startForegroundService(context, mServiceIntent);
}

public void stopTheService(Context context) {
    if (mServiceIntent != null) {
        context.stopService(mServiceIntent);
    }
}

當我在stopService()之前使用context時，錯誤消失了。