Question

I am working on creating a Broadcast Receiver. I am extremely new to Android development and Java. I added my code at the bottom. Whenever I press the button the app crashes. I'm assuming something is wrong with connecting the broadcastIntent() function. I appreciate any help :)

Here are the directions from my professor:

1. Create an empty project
2. Create a method in MainActivity.java which creates a Broadcast.

public void broadcastIntent(View view){
       Intent intent = new Intent();
       intent.setAction("my.CUSTOM_INTENT"); sendBroadcast(intent);
   }

3. Add a button to activity_main.xml and link it to this method.
4. Is it working? How can you test it? STOP
5. Create a Broadcast Receiver (accept defaults)
6. Add the following code to your receiver in onReceive() : (remember to comment out the auto generated exception!) what’s an exception?

Toast.makeText(context, "Intent Detected.", Toast.LENGTH_LONG).show();

7. Edit your manifest by adding the following as a child node of <receiver>

<intent-filter>
    <action android:name="my.CUSTOM_INTENT"></action>
</intent-filter>

8. RUN it

MY CODE:

<main activity>

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private Button mybutton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button mybutton = (Button) findViewById(R.id.mybutton);
        broadcastIntent( );
    }

    private void broadcastIntent() {
        Intent intent = new Intent();
        intent.setAction("my.CUSTOM_INTENT");
        sendBroadcast(intent);
        }

}

<activity xml>

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/mybutton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="235dp"
        android:layout_marginEnd="146dp"
        android:layout_marginRight="146dp"
        android:onClick="broadcastIntent"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

<manifest>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.ica4_broadcast">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ICA4Broadcast">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver android:name=".MyReceiver" android:exported="true">
            <intent-filter>
                <action android:name="my.CUSTOM_INTENT"/>
            </intent-filter>
        </receiver>

    </application>

</manifest>

<my receiver>

package com.example.ica4_broadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "Intent Detected" + intent.getAction(), Toast.LENGTH_LONG).show();

    }
}

Answer 1

As far as I can see there is no error in Code

What makes the app to crash?? Yes there could be certain mistakes out of which even one could crash ap

Please check the follwing points:

1. If you have not defined my.CUSTOM_INTENT define it as

public static final String CUSTOM_INTENT = "my.custom.intent.action.TEST";

Necessary to have action (It may be TEST,BLOCK etc)

2. If you have already defined make the following changes in manifest.xml flle.

        <receiver android:name=".MyReceiver" android:exported="true">
            <intent-filter>
                <action android:name="my.CUSTOM_INTENT">
                </action>
               <action android:name="android.intent.action.TEST" >          
                </action>
            </intent-filter>
        </receiver>

3. May be error is due to formatting (very very less chance). Please just try once to have onRecieve() like

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
            String text="Intent Detected";
            text+=intent.getAction();
            Toast.makeText(context,text, Toast.LENGTH_LONG).show();

    }
}