How to use getApplicationContext in BroadcastRecei

问题:

I am using the broadcaster class to listen to sms messages using this code

package com.escortme.basic;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.SmsMessage;
import android.widget.Toast;

public class SMSReceiverActivity extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Parse the SMS.
        Bundle bundle = intent.getExtras();
        SmsMessage[] msgs = null;
        String str = "";
        if (bundle != null)
        {
            // Retrieve the SMS.
            Object[] pdus = (Object[]) bundle.get("pdus");
            msgs = new SmsMessage[pdus.length];
            for (int i=0; i<msgs.length; i++)
            {
                msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]);
                // In case of a particular App / Service.
                //if(msgs[i].getOriginatingAddress().equals("+91XXX"))
                //{
                str += "SMS from " + msgs[i].getOriginatingAddress();
                str += " :";
                str += msgs[i].getMessageBody().toString();
                str += "\n";
                //}
            }
            // Display the SMS as Toast.
            Toast.makeText(context, str, Toast.LENGTH_SHORT).show();


            Pol_ViewActivity appState = ((Pol_ViewActivity)getApplicationContext()); // ERROR
            appState.move_map_to("33.786047","-59.187287");
        }
    }
}

and it's defined in manifest like so

    <receiver 
      android:name="com.escortme.basic.SMSReceiverActivity"
      android:enabled="true">
      <intent-filter>
        <action android:name="android.provider.Telephony.SMS_RECEIVED" />
      </intent-filter>
    </receiver>

But the problem is it says "The method getApplicationContext() is undefined for the type SMSReceiverActivity".

Does anyone know why this is happening and how to fix it? Thanks

回答1:

Look at the method signature for onReceive()

public void onReceive(Context context, Intent intent) {

You are being passed a context as a parameter. You should be using that context when you need one.

Pol_ViewActivity appState = ((Pol_ViewActivity)context); 

EDIT: also I don't know exactly what it is you are trying to do. But you probably shouldn't be trying to obtain an Activity object and call a method on it like you seem to be doing.

回答2:

I hope this may help you my frnd.

Try importing this package (import android.telephony.gsm.SmsManager;)

//---sends a SMS message to another device--- private void sendSMS(String phoneNumber, String message) {
String SENT = "SMS_SENT"; String DELIVERED = "SMS_DELIVERED";

    PendingIntent sentPI = PendingIntent.getBroadcast(this, 0,
        new Intent(SENT), 0);

    PendingIntent deliveredPI = PendingIntent.getBroadcast(this, 0,
        new Intent(DELIVERED), 0);

    //---when the SMS has been sent---
    registerReceiver(new BroadcastReceiver(){
        @Override
        public void onReceive(Context arg0, Intent arg1) {
            switch (getResultCode())
            {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "SMS sent", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_GENERIC_FAILURE:
                    Toast.makeText(getBaseContext(), "Generic failure", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NO_SERVICE:
                    Toast.makeText(getBaseContext(), "No service", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_NULL_PDU:
                    Toast.makeText(getBaseContext(), "Null PDU", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case SmsManager.RESULT_ERROR_RADIO_OFF:
                    Toast.makeText(getBaseContext(), "Radio off", 
                            Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }, new IntentFilter(SENT));

    //---when the SMS has been delivered---
    registerReceiver(new BroadcastReceiver(){
        @Override
        public void onReceive(Context arg0, Intent arg1) {
            switch (getResultCode())
            {
                case Activity.RESULT_OK:
                    Toast.makeText(getBaseContext(), "SMS delivered", 
                            Toast.LENGTH_SHORT).show();
                    break;
                case Activity.RESULT_CANCELED:
                    Toast.makeText(getBaseContext(), "SMS not delivered", 
                            Toast.LENGTH_SHORT).show();
                    break;                      
            }
        }
    }, new IntentFilter(DELIVERED));        

    SmsManager sms = SmsManager.getDefault();
    sms.sendTextMessage(phoneNumber, null, message, sentPI, deliveredPI);               
}    

回答3:

One reason for getting the application context would be to get the the WIFI_SERVICE as it must be looked up on the Application context or memory will leak on devices < Android N.

As Someone Somewhere once said, within onReceive(), just use context.getApplicationContext().