当从另一个 class 使用 synchronized() 调用 notify() 方法时，它没有被调用形式

Question

I'm trying to fire a notification when the battery level is less the %10.

here is my notification class located at MainActivity.java

    public void notify(View view) {
        String title = "Warning! low battery";
        String text = "Please plug your mobile device to a charger";

        Intent intent = new Intent(this, MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent,0);

        Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_qs_battery_saver)
                .setContentTitle(title)
                .setContentText(text)
                .setContentIntent(pendingIntent)
                .build();

        notificationManager.notify(notificationID++, notification);
    }

I'm trying to fire it from the BatteryReceiver class:

package com.michal.ex2;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;
import android.util.Log;
import android.view.View;

public class BatteryReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        String action = intent.getAction();
        if(intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)) {

            IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
            Intent batteryStatus = context.registerReceiver(null, ifilter);
            int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
            int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, 100);
            int percent = (level * 100) / scale;

            int plugged = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
            boolean isPlugged;
            isPlugged = plugged == BatteryManager.BATTERY_PLUGGED_AC || plugged == BatteryManager.BATTERY_PLUGGED_USB;

            if ((percent == 10) && !isPlugged) {
                Log.d("mylog", "low battery");
                //notify();
                synchronized(mActivity){
                    mActivity.notify();
            }

        }

    }
}

First i tried calling calling notify from MainActivity, but the app crash with the error: java.lang.IllegalMonitorStateException: object not locked by thread before notify()

I've searched for a solution and found that I need to lock the notify, so I tried calling it with synchronized():

synchronized(mActivity){
          mActivity.notify();

but nothing happened. The battery receiver works alright(I'm getting the right log message) but notify() is not been called.

Answer 1

Maybe the function you'are calling is not the MainActivity.notify(View view) but the Object.notify() . Therefore nothing happens. Give an appropriate function argument.

mActivity.notify(null);