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Android Internet Connectivity Listener Problem

I would like to put a Network Detector in an Android application, to inform a Screen immediately the Network state even if that state is changing. I have study similar questions in:
Android: Internet connectivity change listener
So my Java code in Main Activity is:
package com.example.netdetector;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.NetworkInfo;
import android.net.NetworkRequest;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.*;
public class MainActivity extends AppCompatActivity {
private TextView Screen;
#RequiresApi(api = Build.VERSION_CODES.M)
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Screen = (TextView) findViewById(R.id.Screen);
Screen.setText("Start!");
ConnectivityManager.NetworkCallback networkCallback = new ConnectivityManager.NetworkCallback() {
#Override
public void onAvailable(Network network) {
// network available
Screen.setText("Net On!");
}
#Override
public void onLost(Network network) {
// network unavailable
Screen.setText("Net Off!");
}
};
ConnectivityManager connectivityManager =
(ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
connectivityManager.registerDefaultNetworkCallback(networkCallback);
} else {
NetworkRequest request = new NetworkRequest.Builder()
.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET).build();
connectivityManager.registerNetworkCallback(request, networkCallback);
}
}
}
The AndroidManifest.xml is:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.netdetector">
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<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.NetDetector">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
The Layout activity_main.xml is:
<?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">
<TextView
android:id="#+id/Screen"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Hello World!"
android:textSize="25sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.222" />
</androidx.constraintlayout.widget.ConstraintLayout>
There are some issues:
Starting the App with the Network Off, the Screen displays "Start!" instead of "Net Off!"
Starting the App with the Network On, the Screen displays "Net On" that is fine
On changing Internet state while the app is running the Screen displays the right text for a few moments and the app closes immediately.
How can I fix 1 and 3? What went wrong?
Thanks
Nickolas

Splash screen alpha animation not working

So I have an app that currently has two Activities. A SplashScreenActivity and a MainActivity. The transition between the two activities works just fine but the problem lies in the SplashScreenActivity itself. In it, there is a single ImageView that is supposed to be initially invisible and then fade in. But instead the image remains invisible the entire time. Please help. Here's the code:
The SplashScreenActivity:
package com.degioncloud;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ImageView;
public class SplashScreenActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splashscreen);
ImageView logo = (ImageView) findViewById(R.id.iv_logo);
logo.setImageAlpha(0);
logo.animate().alpha(1f).setDuration(1200).withEndAction(new Runnable() {
#Override
public void run() {
Intent i = new Intent(SplashScreenActivity.this, MainActivity.class);
startActivity(i);
overridePendingTransition(android.R.anim.fade_in,android.R.anim.fade_out);
finish();
}
});
}
}
The XML of the SplashScreenActivity:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".SplashScreenActivity">
<ImageView
android:id="#+id/iv_logo"
android:layout_width="200dp"
android:layout_height="200dp"
android:src="#mipmap/ic_launcher"
android:layout_centerInParent="true" />
</RelativeLayout>
My Manifest file:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.degioncloud">
<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.DegionCloud">
<activity android:name=".MainActivity" />
<activity android:name=".SplashScreenActivity"
android:theme="#style/SplashScreenTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
The MainActivty is empty so I don't see a need to share that but if you need any other file then let me know and I will send a copy.

You need to call start() for the animation to begin:
logo.animate().alpha(1f).setDuration(1200).withEndAction(new Runnable() {
#Override
public void run() {
Intent i = new Intent(SplashScreenActivity.this, MainActivity.class);
startActivity(i);
overridePendingTransition(android.R.anim.fade_in,android.R.anim.fade_out);
finish();
}
}).start();

Splash screen activity not working

Hi have created splash screen as a separate project by using this link : http://www.androidhive.info/2013/07/how-to-implement-android-splash-screen-2/ . And it did worked on my emulator . However, when I implemented this in my app. It did not worked . I don' know whats wrong with my code. My main.java, splash screen.java and splash.xml are the following. Please note that I did define my activity in manifest file. Any help will be greatly appreciated...
MainActivity.Java
import android.app.Activity;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
public class MainActivity extends Activity implements OnClickListener {
private MediaPlayer mp;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setVolumeControlStream(AudioManager.STREAM_MUSIC);
findViewById(R.id.button_1).setOnClickListener(this);
findViewById(R.id.button_2).setOnClickListener(this);
findViewById(R.id.button_3).setOnClickListener(this);
}
public void onClick(View v) {
int resId=1;
// Release any resources from previous MediaPlayer
if (mp != null) {
mp.release();
}
switch (v.getId()) {
case R.id.button_1: resId = R.raw.button_1; break;
case R.id.button_2: resId = R.raw.button_2; break;
case R.id.button_3:
startActivity(new Intent(MainActivity.this,SecondActivity.class));
return;
}
// Create a new MediaPlayer to play this sound
mp = MediaPlayer.create(this, resId);
mp.start();
}
}
SplashScreen.java
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
public class SplashScreen extends Activity {
// Splash screen timer
private static int SPLASH_TIME_OUT = 3000;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
new Handler().postDelayed(new Runnable() {
/*
* Showing splash screen with a timer. This will be useful when you
* want to show case your app logo / company
*/
#Override
public void run() {
// This method will be executed once the timer is over
// Start your app main activity
Intent i = new Intent(SplashScreen.this, MainActivity.class);
startActivity(i);
// close this activity
finish();
}
}, SPLASH_TIME_OUT);
}
}
activity_splash.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/gradient_background" >
<ImageView
android:id="#+id/imgLogo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:adjustViewBounds="true"
android:scaleType="fitXY"
android:src="#drawable/images235" />
</RelativeLayout>
Android Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.Smit.yourbollywoodyourplaylist"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="11" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="info.androidhive.androidsplashscreentimer.SplashScreen"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:theme="#android:style/Theme.Black.NoTitleBar" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".MainActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".SecondActivity"
android:label="#string/app_name"/>
</application>
</manifest>

It's not clear which package your SplashScreen.java lives in, but
android:name="info.androidhive.androidsplashscreentimer.SplashScreen"
might need to be changed to
android:name=".SplashScreen"
You may have just pasted in the manifest definition from the sample project without adjusting the activity name to match your own project.

NullPointerException while creating activity

this is my codes LoginActivity.java file
package com.example.crims;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.TextView;
public class LoginActivity extends Activity {
TextView screen;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
screen = (TextView) findViewById(R.id.link_to_register);
// Listening to register new account link
screen.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Switching to Register screen
Intent i = new Intent(getApplicationContext(), RegisterActivity.class);
startActivity(i);
}
});
}
}
this is my code for 'activity_login.xml' file
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".LoginActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/hello_world" />
</RelativeLayout>`
And Finally this is my menifest file
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.crims"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<activity
android:name="com.example.crims.LoginActivity"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".RegisterActivity"
android:label="Register New Account">
</activity>
</application>
</manifest>
All of these files are here and i want to find my error as I m new to android app development...

You have NullPointerException(NPE) here:
10-01 21:02:07.580: E/AndroidRuntime(1299):
at com.example.crims.LoginActivity.onCreate(LoginActivity.java:17)
So, check line 17 of LoginActivity.java (you can just double click on this message in the logcat view and you will be navigated to this line).
It seems, line 17 is this:
registerScreen.setOnClickListener(new View.OnClickListener() {
As this is NPE, registerScreen is null. So, you should inspect why it is null. This is because Activity can't find it in line above and it returns null instead:
TextView registerScreen = (TextView) findViewById(R.id.link_to_register);
This can be one of two possibilities: either you do not have widget with id 'link_to_register' in activity_login.xml, or something other is wrong :)
Check this please and show your activity_login.xml file, please.

Listen brother take this code. Change it according to you.
public class MainActivity extends Activity {
TextView screen;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
screen = (TextView) findViewById(R.id.screen);
// Listening to register new account link
screen.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Switching to Register screen
Intent i = new Intent(getApplicationContext(), Register.class);
startActivity(i);
}
});
}
}
You need to register your activity in manifest.xml file too in case if you don't know about it.

How do I display a Simple Google Map in my emulator in android?

I tried to write a simple google map application to display simple map but doesn't give me any output.
I pasted my code below:
AnroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="org.HelloGoogleMaps"
android:versionCode="1"
android:versionName="1.0">
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<application android:icon="#drawable/icon" android:label="#string/app_name">
<uses-library android:name="com.google.android.maps" />
<activity android:name=".HelloGoogleMaps"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
My layout file is:
map.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<com.google.android.maps.MapView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/mapview"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:clickable="true"
android:apiKey="0Z1oyeAgSpj4FSEtenPqiL7RsCXA_pVPQhvtpdA"
/>
</LinearLayout>
And my java class file is:
HelloGoogleMaps.java
package org.HelloGoogleMaps;
import com.google.android.maps.MapView;
import android.app.Activity;
import android.os.Bundle;
public class HelloGoogleMaps extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.map);
MapView mapView = (MapView) findViewById(R.id.mapview);
mapView.setBuiltInZoomControls(true);
}
protected boolean isRouteDisplayed() {
return false;
}
}

I can't see your layout file, but have you set a proper API key?
http://code.google.com/android/maps-api-signup.html

Your HelloGoogleMaps should inherit the MapsActivity
Just change your code to
public class HelloGoogleMaps extends MapActivity {
#Override
protected boolean isRouteDisplayed() {
// TODO Auto-generated method stub
return false;
}
}