我想从广播接收器中删除windowmanager视图

Question

我是android编程的新手。我的应用程序在WindowManager上得到了NPE，我想删除它。我尝试了mWindowManager.removeView（mFloatingView）;但是它给了我一个空指针异常。请帮助！。对不起，我的英语不好。 这是我的广播接收器代码：

public class PhoneStateReceiver extends BroadcastReceiver {
    private int mId;
    private WindowManager mWindowManager;
    private View mFloatingView;

    @Override
    public void onReceive(final Context context, final Intent intent) {

        try {
            System.out.println("Receiver start");
            String state = intent.getStringExtra(TelephonyManager.EXTRA_STATE);
            final String incomingNumber = intent.getStringExtra(TelephonyManager.EXTRA_INCOMING_NUMBER);
            if (state.equals(TelephonyManager.EXTRA_STATE_RINGING)){
                int LAYOUT_FLAG;
                mFloatingView = LayoutInflater.from(context).inflate(R.layout.notification_layout, null);
                final View collapsedView = mFloatingView.findViewById(R.id.collapse_view);
                final TextView number = mFloatingView.findViewById(R.id.tv_phoneNumber);
                final TextView info = mFloatingView.findViewById(R.id.tv_info);
                final TextView howmany = mFloatingView.findViewById(R.id.tv_howmany);
                final Button closeButtonCollapsed = mFloatingView.findViewById(R.id.close_button);
                number.setText(incomingNumber);
                StringRequest jsonArrayRequest = new StringRequest(Request.Method.POST, Functions.FETCH_DATA_URL, new Response.Listener<String>() {
                    @SuppressWarnings("LogNotTimber")
                    @Override
                    public void onResponse(String response) {
                        Log.d(TAG, "FETCH DATA RESPONSE FROM RECIEVER: " + response);
                        for (int i = 0; i < response.length(); i++) {
                            try {
                                JSONArray jsonObject = new JSONArray(response);

                                info.setText(jsonObject.getJSONObject(0).getString("info1"));
                                String PhoneNumber = jsonObject.getJSONObject(0).getString("phone_number");
                                howmany.setText(jsonObject.getJSONObject(0).getString("times_contacted"));

                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }, new Response.ErrorListener() {
                    @SuppressWarnings("LOGNOTTIMBER")
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.e("Volley", error.toString());
                    }
                }) {
                    @SuppressWarnings("LogNotTimber")
                    @Override
                    protected Map<String, String> getParams() {
                        Map<String, String> params = new HashMap<>();
                        params.put("phone_number", incomingNumber);
                        Log.d(TAG, "SENDING FROM BROADCAST RECEIVER: " + params.toString());
                        return params;
                    }
                };
                RequestQueue requestQueue = Volley.newRequestQueue(context.getApplicationContext());
                requestQueue.add(jsonArrayRequest);
                closeButtonCollapsed.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        mWindowManager.removeView(mFloatingView);
                    }
                });
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
                } else {
                    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_PHONE;
                }
                final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        WindowManager.LayoutParams.WRAP_CONTENT, LAYOUT_FLAG,
                        WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                        PixelFormat.TRANSLUCENT);

                params.gravity = Gravity.CENTER_VERTICAL | Gravity.CENTER;        //Initially view will be added to top-left corner
                params.x = 0;
                params.y = 100;

                //Add the view to the window
                mWindowManager = (WindowManager) context.getSystemService(WINDOW_SERVICE);
                mWindowManager.addView(mFloatingView, params);

                //….
                //….

                mFloatingView.findViewById(R.id.root_container).setOnTouchListener(new View.OnTouchListener() {
                    private int initialX;
                    private int initialY;
                    private float initialTouchX;
                    private float initialTouchY;


                    @Override
                    public boolean onTouch(View v, MotionEvent event) {
                        switch (event.getAction()) {
                            case MotionEvent.ACTION_DOWN:

                                initialX = params.x;
                                initialY = params.y;

                                initialTouchX = event.getRawX();
                                initialTouchY = event.getRawY();
                                return true;
                            case MotionEvent.ACTION_UP:
                                int Xdiff = (int) (event.getRawX() - initialTouchX);
                                int Ydiff = (int) (event.getRawY() - initialTouchY);

                                return true;
                            case MotionEvent.ACTION_MOVE:
                                //Calculate the X and Y coordinates of the view.
                                params.x = initialX + (int) (event.getRawX() - initialTouchX);
                                params.y = initialY + (int) (event.getRawY() - initialTouchY);
                                mWindowManager.updateViewLayout(mFloatingView, params);
                                return true;
                        }
                        return false;
                    }
                });
            }
            if (state.equals(TelephonyManager.EXTRA_STATE_OFFHOOK)){
                Toast.makeText(context,"Call Received State",Toast.LENGTH_LONG).show();
            }
            if (state.equals(TelephonyManager.EXTRA_STATE_IDLE)){
                Toast.makeText(context,"Call idle State",Toast.LENGTH_LONG).show();
                mWindowManager.removeView(mFloatingView);

            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

如果我按下关闭按钮，则什么也没有发生。但是在调试控制台中，其空指针异常。我想在通话状态为空闲时删除该窗口。