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Problem when I try to open another window from a button the app closes completely "Android Studio"

i'm a student and i'm working on a mobile app.
The probleme is that my app was working, but now when i click on the button to open another window it closes.
Here is my code:
`
public class MainActivity extends AppCompatActivity {
Button b_inscrire_etudiant;
Button b_inscrire_enseignant;
Button b_inscrire_admin;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b_inscrire_etudiant = findViewById(R.id.b_inscrire_etudiant);
b_inscrire_enseignant = findViewById(R.id.b_inscrire_enseignat);
b_inscrire_admin = findViewById(R.id.b_inscrire_admin);
b_inscrire_etudiant.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(MainActivity.this , InscriptionEtudiant.class);
startActivity(i);
}
});
b_inscrire_enseignant.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(MainActivity.this , InscriptionEnseignant.class);
startActivity(i);
}
});
b_inscrire_admin.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(MainActivity.this , InscriptionAdmin.class);
startActivity(i);
}
});
}
}
`
I worked as usual "using Intent" besides it worked well until now.
Here is my Manifest file:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.example.myusto">
<application
android:allowBackup="true"
android:dataExtractionRules="#xml/data_extraction_rules"
android:fullBackupContent="#xml/backup_rules"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="#style/Theme.MyUsto"
tools:targetApi="31">
<activity
android:name=".InscriptionEnseignant"
android:exported="false">
<meta-data
android:name="android.app.lib_name"
android:value="" />
</activity>
<activity
android:name=".InscriptionEtudiant"
android:exported="false">
<meta-data
android:name="android.app.lib_name"
android:value="" />
</activity>
<activity
android:name=".InscriptionAdmin"
android:exported="false">
<meta-data
android:name="android.app.lib_name"
android:value="" />
</activity>
<activity
android:name=".Connexion"
android:exported="false">
<meta-data
android:name="android.app.lib_name"
android:value="" />
</activity>
<activity
android:name=".MainActivity"
android:exported="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
</application>
</manifest>
ps: I solved the problem, by the way two were missing

Thank you for the answers.
It's true, it was missing a part of the code which was not written in the manifest file

Open android service or activity on boot api 29

this is my manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.openboot">
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<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/AppTheme">
<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=".StartAppOnBoot" >
<intent-filter>
<action android:name="android.intent.action.BOOT_COMPLETED" />
<action android:name="android.intent.action.QUICKBOOT_POWERON" />
</intent-filter>
</receiver>
</application>
</manifest>
My BroadcastReceiver that "receives" the boot completed intent:
public class StartAppOnBoot extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (Intent.ACTION_BOOT_COMPLETED.equals(intent.getAction())) {
Intent i = new Intent(context, MainActivity.class);
i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(i);
}
}
My MainActivity that I need to open:
public class MainActivity extends AppCompatActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
I need MainActivity to open when the phone turns on, but I don't see the way to do it.

public class MainActivity extends AppCompatActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Intent intent = new
Intent(getApplicationContext,StartAppOnBoot.class);
sendBroadcast(intent);
}
reference
https://developer.android.com/guide/components/broadcasts#java

How to change or set new activity launcher app? (in Java)

I have a payment activity and splash activity that it shows app of contents after user will buy it. payment activity is default Launcher in Manifest.xml that I want to set launcher Activity to splash activity and payment activity disabled after payment.
Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.exa.iu2">
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<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/AppTheme">
<activity android:name=".PaymentActivity" android:theme="#style/SplashTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<action android:name="android.intent.action.VIEW"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW"/>
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.BROWSABLE"/>
<data android:scheme="return" android:host=“zrp”/>
</intent-filter>
</activity>
<activity-alias
android:name=".PaymentActivity"
android:icon="#mipmap/ic_launcher"
android:label="#string/app_name"
android:roundIcon="#mipmap/ic_launcher_round"
android:enabled="false" android:targetActivity=".SplashActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<action android:name="android.intent.action.VIEW"/>
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity-alias>
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:screenOrientation="portrait"
android:theme="#style/AppTheme.NoActionBar"/>
</application>
</manifest>
in Payment Activity and "If payment is success"
public void onCallbackResultVerificationPayment(boolean isPaymentSuccess, String refID, PaymentRequest paymentRequest) {
if(isPaymentSuccess){
Toast.makeText(PaymentActivity.this, “Payment Success” + refID, Toast.LENGTH_SHORT).show();
ComponentName cm = new ComponentName("com.exa.iu2", "com.exa.iu2"+".SplashActivity");
ComponentName cm2 = new ComponentName("com.exa.iu2", "com.exa.iu2"+".PaymentActivity");
PackageManager pm = getApplication().getPackageManager();
pm.setComponentEnabledSetting(cm, PackageManager.COMPONENT_ENABLED_STATE_ENABLED,PackageManager.DONT_KILL_APP);
pm.setComponentEnabledSetting(cm2, PackageManager.COMPONENT_ENABLED_STATE_DISABLED,0);
}else {
Toast.makeText(PaymentActivity.this, “Don’t success”, Toast.LENGTH_SHORT).show();
}
}
});
Thx

I suggest you create a Hub or Startup activity in which decide what to display. The new activity has to be set as Main -> Launcher activity, obviously.

In AndroidManifest do this
<activity android:name=".SplashActivity"
android:theme="#style/SplashTheme">
<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<action android:name="android.intent.action.VIEW"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>
</activity>
Inside SplashActivity
public class SplashActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
// Check condition to open appropriate activity
// like
// if(paymentDone) start some activity
// else start another activity
finish()
}
}

Android application failed to start activity

I want to know why it cannot open up new java class.
When I try to start new activity, it will be crash.
public class MainActivity extends ActionBarActivity {
EditText emailEt;
TextView registerET;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
emailEt = (EditText) findViewById(R.id.email);
registerET = (TextView) findViewById(R.id.register);
registerET.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Log.i("clicks","You Clicked register page");
Intent myIntent = new Intent(MainActivity.this, RegisterActivity.class);
startActivity(myIntent);
MainActivity.this.finish();
}
});
}
public void OnLogin(View view) {
String username = emailEt.getText().toString();
String type = "login";
BackgroundWorker backgroundWorker = new BackgroundWorker(this);
backgroundWorker.execute(type, username);
}
}
It's possible manifests problem? Am I put it wrong position for the activity?
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.a20_1discussboard">
<uses-permission android:name="android.permission.INTERNET"></uses-permission>"
<application
android:allowBackup="true"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<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>
</application>
<activity android:label="#string/app_name" android:name=".RegisterActivity"/>
</manifest>
It look like can be open up new java class, but it still display MainActivity.
Error Log:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.a20_1discussboard, PID: 2194
java.lang.IllegalStateException: Could not find method onClick(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatTextView with id 'register'
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:327)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:284)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Put proper Menifest format:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.a20_1discussboard">
<uses-permission android:name="android.permission.INTERNET"></uses-permission>"
<application
android:allowBackup="true"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<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:label="#string/app_name"
android:name=".RegisterActivity"/> //<---here
</application>
</manifest>
Don't call finish(), this caused your crash:
registerET.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Log.i("clicks","You Clicked register page");
Intent myIntent = new Intent(MainActivity.this, RegisterActivity.class);
startActivity(myIntent);
//remove finish();
}
});

Try declared activity in application in your AndroidManifest.xml like this.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.a20_1discussboard">
<uses-permission android:name="android.permission.INTERNET"></uses-permission>"
<application
android:allowBackup="true"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<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:label="#string/app_name"
android:name=".RegisterActivity"/>
</application>
</manifest>

Be sure that you add RegisterActivity to your AndroidManifest.xml inside <application> tag:
<application ...>
...
<activity
android:label="#string/app_name"
android:name=".RegisterActivity"/>
</application>

Delete this line from onCreate method: MainActivity.this.finish();
If you want to stop or pause MainActivity, use:
#Override
public void onPause() { }
or
#Override
public void onStop() { }
in MainActivity class.

Thanks all.
Add RegisterActivity to AndroidManifest.xml inside <application> tag and remove MainActivity.this.finish()
It is working now.

Android Splash Screen to FragmentActivity

Is it possible to open a FragmentActivity after Splash screen?
I want to open the FragmentActivity / Fragment after the Splash screen but I get following Error:
Unable to find explicit activity class {com.**********.MainActivity};
have you declared this activity in your AndroidManifest.xml?
My splash screen:
public class SplashScreen extends Activity {
private final int SPLASH_DISPLAY_LENGTH = 3000;
#Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.activity_splash);
new Handler().postDelayed(new Runnable(){
#Override
public void run() {
Intent mainIntent = new Intent(SplashScreen.this,Juli.class);
SplashScreen.this.startActivity(mainIntent);
SplashScreen.this.finish();
}
}, SPLASH_DISPLAY_LENGTH);
}
}
Manifest:
<activity
android:name="com.test.tab.SplashScreen"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

In Manifest add:
<application
android:allowBackup="true"
android:icon="#drawable/ic_launcher"
android:label="#string/app_name"
android:theme="#style/AppTheme" >
<!-- Splash screen -->
<activity
android:name="com.test.tab.SplashScreen"
android:label="#string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!-- Main activity -->
<activity
android:name="com.test.tab.Juli"
android:label="#string/app_name" >
</activity>
</application>