Develop Reference

No errror shown in android studio but still setOnClickListener works only on one button while on other button it does not work

My java code:
public class StartActivity extends AppCompatActivity {
private Button mRegBtn;
private Button mLoginBtn;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
mRegBtn = (Button) findViewById(R.id.start_reg_btn);
mLoginBtn = (Button) findViewById(R.id.start_login_btn);
mRegBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent reg_intent = new Intent(StartActivity.this, RegisterActivity.class);
startActivity(reg_intent);
}
});
mLoginBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Intent login_intent = new Intent(StartActivity.this, LoginActivity.class);
startActivity(login_intent);
}
});
}
}
The LogCat shows this:
2020-04-30 12:53:42.391 31407-31407/com.example.chattting E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.chattting, PID: 31407
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.chattting/com.example.chattting.LoginActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2947)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3012)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1716)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:232)
at android.app.ActivityThread.main(ActivityThread.java:6802)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1103)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference
at com.example.chattting.LoginActivity.onCreate(LoginActivity.java:43)
at android.app.Activity.performCreate(Activity.java:6974)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2900)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3012) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1716) 
at android.os.Handler.dispatchMessage(Handler.java:110) 
at android.os.Looper.loop(Looper.java:232) 
at android.app.ActivityThread.main(ActivityThread.java:6802) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1103) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964) 

first answer i give.
Based on your log, the line
"Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.appcompat.app.ActionBar.setTitle(java.lang.CharSequence)' on a null object reference" says, that is having trouble setting an AppBar Title.
My bet is that you have some sort of error, in one of the Activities you are trying to start, from the buttons.
If you want more help, tell what is the button that is failing, and send the Other two activities code.

Android Application crashes when going from an activity to another using intent [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I am trying for hours to do an extremely simple thing, but for some reason it doesn't work...
I'm trying to go from an activity that is used for Log in, to another activity that is used for signing up.
The rest of the code works perfectly, but whenever I press the textview that supposes to bring me to the Registration screen, the app crashes.
I tried everything, even to use a button instead of textview, and many ways of intents I found online, with "finish" and without "finish", but nothing worked, do you guys have any idea what went wrong?
The Activity is added to the manifest.
Thank you!
public class LoginActivityU extends AppCompatActivity implements View.OnClickListener {
String Uname, Pass;
Button loginButton;
EditText userEt;
EditText passwordEt;
HashMap<String, String> hashMap;
ProgressDialog p;
Boolean check = false;
SharedPreferences sp;
SharedPreferences.Editor editor;
TextView tvSignUp;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
sp=this.getSharedPreferences("LocalLogInData", 0);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
Intent intent = getIntent();
setSupportActionBar(toolbar);
loginButton = (Button) findViewById(R.id.btn_login);
userEt = (EditText) findViewById(R.id.input_uname);
passwordEt = (EditText) findViewById(R.id.input_password);
tvSignUp = (TextView) findViewById(R.id.link_signup);
loginButton.setOnClickListener(this);
tvSignUp.setOnClickListener(this);
Uname = sp.getString("Uname", null);
Pass = sp.getString("Pass", null);
Log.d("dds", Uname + Pass);
if (Uname != null && Pass != null)
{
userEt.setText(Uname);
passwordEt.setText(Pass);
hashMap = new HashMap<String, String>();
hashMap.put("username",userEt.getText().toString());
hashMap.put("password",passwordEt.getText().toString());
Login login=new Login();
login.execute("https://example.com");
if(check == false)
{
editor=sp.edit();
editor.remove("Uname");
editor.remove("Pass");
editor.commit();
}
}
}
#Override
public void onClick(View view) {
if (loginButton.isPressed())
{
hashMap = new HashMap<String, String>();
hashMap.put("username",userEt.getText().toString());
hashMap.put("password",passwordEt.getText().toString());
editor=sp.edit();
editor.putString("Uname",userEt.getText().toString());
editor.putString("Pass",passwordEt.getText().toString());
Login login=new Login();
login.execute("https://peulibrary.co.il/api/user/generate_auth_cookie/");
editor.commit();
}
else if (tvSignUp.isPressed())
{
Intent intent = new Intent(this, SignUpActivity.class);
startActivity(intent);
finish();
}
}
Log of crash:
02-03 14:35:51.661 10836-10836/com.example.negev.peulibraryv201 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.negev.peulibraryv201, PID: 10836
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.example.example/com.example.example.example.SignUpActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.FloatingActionButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.FloatingActionButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.negev.peulibraryv201.SignUpActivity.onCreate(SignUpActivity.java:22)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

Looking at the crash log, it seems that you are attaching a click listener to your FloatingActionButton before instantiating it. Please make sure that you call findViewById and instantiate the view first, and only call setOnClickListener after. The problem is in SignUpActivity.

seeing the logs it is clear that the Problem should be in your signup activity.
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.support.design.widget.FloatingActionButton.setOnClickListener(android.view.View$OnClickListener)'
indicates that there is a widget you are referring is not initialized or null

Arithmetic Android app crashes, no errors in the code [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 5 years ago.
I'm making an Android app, it should ask for arithmetic equations and check the answer. There should be different difficulty levels as well. My app crashes when choosing the difficulty level from AlertDialog. I have no errors in Android Studio.
Here is the code for choosing level:
public void onClick(View view) {
if(view.getId()==R.id.play_btn){
//play button
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Choose a level")
.setSingleChoiceItems(levelNames, 0, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
//start gameplay
startPlay(which);
}
});
AlertDialog ad = builder.create();
ad.show();
}
private void startPlay(int chosenLevel){
//start gameplay
Intent playIntent = new Intent(this, PlayGame.class);
playIntent.putExtra("level", chosenLevel);
this.startActivity(playIntent);
}
Can someone help me understand why my app crashes?
Here is the log:
9758-9758/org.example.braintraining E/AndroidRuntime: FATAL EXCEPTION: main
Process: org.example.braintraining, PID: 9758
java.lang.RuntimeException: Unable to start activity ComponentInfo{org.example.braintraining/org.example.braintraining.PlayGame}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
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:1388)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference
at org.example.braintraining.PlayGame.onCreate(PlayGame.java:104)
at android.app.Activity.performCreate(Activity.java:6289)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758) 
at android.app.ActivityThread.access$900(ActivityThread.java:177) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:145) 
at android.app.ActivityThread.main(ActivityThread.java:5942) 
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:1388) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1183) 
Here is the code for onCreate method of PlayGame class:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_playgame);
gamePrefs = getSharedPreferences(GAME_PREFS, 0);
//text and image views
question = (TextView)findViewById(R.id.question);
answerTxt = (TextView)findViewById(R.id.answer);
response = (ImageView)findViewById(R.id.response);
scoreTxt = (TextView)findViewById(R.id.score);
//hide tick cross initially
response.setVisibility(View.INVISIBLE);
//number, enter and clear buttons
btn1 = (Button)findViewById(R.id.btn1);
btn2 = (Button)findViewById(R.id.btn2);
btn3 = (Button)findViewById(R.id.btn3);
btn4 = (Button)findViewById(R.id.btn4);
btn5 = (Button)findViewById(R.id.btn5);
btn6 = (Button)findViewById(R.id.btn6);
btn7 = (Button)findViewById(R.id.btn7);
btn8 = (Button)findViewById(R.id.btn8);
btn9 = (Button)findViewById(R.id.btn9);
btn0 = (Button)findViewById(R.id.btn0);
enterBtn = (Button)findViewById(R.id.enter);
clearBtn = (Button)findViewById(R.id.clear);
//listen for clicks
btn1.setOnClickListener(this);
btn2.setOnClickListener(this);
btn3.setOnClickListener(this);
btn4.setOnClickListener(this);
btn5.setOnClickListener(this);
btn6.setOnClickListener(this);
btn7.setOnClickListener(this);
btn8.setOnClickListener(this);
btn9.setOnClickListener(this);
btn0.setOnClickListener(this);
enterBtn.setOnClickListener(this);
clearBtn.setOnClickListener(this);
//get passed level number
if(savedInstanceState!=null){
//restore state
}
else{
Bundle extras = getIntent().getExtras();
if(extras !=null)
{
int passedLevel = extras.getInt("level", -1);
if(passedLevel>=0) level = passedLevel;
level=savedInstanceState.getInt("level");
int exScore = savedInstanceState.getInt("score");
scoreTxt.setText("Score: "+exScore);
}
}
//initialize random
random = new Random();
//play
chooseQuestion();
}

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference at org.example.braintraining.PlayGame.onCreate(PlayGame.java:10‌​4)
Either the code might be failing in two scenarios:
You are starting new activity by passing the playIntent. Please check the code in PlayGame.java, in onCreate() you should be getting the string value (level) from Intent rather than from Bundle, something like
String chosenLevel;
Intent i = this.getIntent();
if(i != null){
chosenLevel = i.getStringExtra("level");
}
2.if you are rotating the screen, once you are in the play game activity where you are not saving the required value before the activity is destroyed and trying to retrieve it back once the activity is recreated .
Solution would be to use the put methods to store values in onSaveInstanceState():
protected void onSaveInstanceState(Bundle bundle) {
super.onSaveInstanceState(bundle);
bundle.putString("value", chosenLevel);
}
And restore the value from Bundle in onCreate() or you can use onRestoreInstanceState(), which is called after onStart(), whereas onCreate() is called before onStart().:
public void onCreate(Bundle bundle) {
if (bundle!= null){
chosenValue = bundle.getString("value");
}
}

Getting Crash When trying to initiate an Activity

Almost all of the current navigation in the application is working perfectly fine and when doing the same things for other parts i navigate with.
I am getting this error when trying to navigate from one activity to another:
FATAL EXCEPTION: main
Process: com.package, PID: 15338
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.package/ui.activity.AccountActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
at ui.activity.BaseActivity.setInitialFragment(BaseActivity.java:181)
at ui.activity.BaseActivity.setInitialFragment(BaseActivity.java:174)
at ui.activity.BaseActivity.setInitialFragment(BaseActivity.java:160)
at ui.activity.AccountActivity.setInitialFragment(AccountActivity.java:38)
at ui.activity.BaseActivity.onCreate(BaseActivity.java:56)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
I can track where the Null reference is being made and have tried a few things to try and bypass it but they all crash the application.
Here is the block where i initiate the activity:
#Override
public void onMyAccountOptionSelected() {
Intent intent = new Intent(this, AccountActivity.class);
startActivity(intent);
}
Then it gets caught here on view.getId(), this one is in baseActivity:
private void setInitialFragment(View view, Fragment fragment) {
if (this.getCurrentFragment() == null) {
FragmentManager fragmentManager = this.getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(view.getId(), fragment).commit();
}
}
I am initially calling setInitialFragment() in AccountActivity which extends my baseActivity:
#Override
protected void setInitialFragment() {
fragment = (AccountFragment) AccountFragment.newInstance();
setInitialFragment(fragment);
}
As you can see above there is now an AccountFragment, in this class i extend from an abstractFragment and have a method to declare a newInstance:
public static Fragment newInstance() {
AccountFragment fragment = new AccountFragment();
return fragment;
}
I cant find anywhere else where it may be affecting the process used for navigating to this activity. I am hoping to find a method to make a quick fix or to find a more appropriate way to solve this.
Any help is much appreciated!

You didn't provide us with all the information needed to be really helpfull.
i'm imaging that your setInitialFragment in your AccountActivity would be something like this:
public class AccountActivity extends BaseActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.container);
AccountFragment fragment = AccountFragment.getInstance();
setInitialFragment(fragment);
}
}
Based on what you posted, your are calling 2 different methods, this:
setInitialFragment(Fragment fragment);
is not the same as this
setInitialFragment(View view, Fragment fragment)

Why is dialog.show() causing my app to crash?

I've been trying to get a dialog message to work on android and the app always crash when it reaches "dialog.show();"
public class Logic extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(context);
dialogBuilder.setTitle("Alarm");
dialogBuilder.setMessage(messageActivity.getMes());
dialogBuilder.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
AlertDialog dialog = dialogBuilder.create();
dialog.show();
}
}
Here is my logcat:
FATAL EXCEPTION: main
Process: it226.myapplicationit226androidapp, PID: 19598
java.lang.RuntimeException: Unable to start receiver it226.myapplicationit226androidapp.Logic: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2732)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.view.ViewRootImpl.setView(ViewRootImpl.java:571)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:310)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:85)
at android.app.Dialog.show(Dialog.java:319)
at it226.myapplicationit226androidapp.Logic.onReceive(Logic.java:65)
at android.app.ActivityThread.handleReceiver(ActivityThread.java:2725)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)

You can't create dialog from receiver.
Creating dialogs is allowed only from UI components (which have looper).
You could start transparent activity with dialog, which would be the same for user.

You can't create a dialog using the context of a BroadcastReceiver, you has two options to solve this problem:
first one is to create a regular Activity which has only the size of the dialog as a shown part and the full remaining is transparent:
Intent newIntent = new Intent(context, Displayer.class);
newIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(newIntent);
second one is to hold your Activity context and then use it in creating the dialog, but at this method you have to make sure what is the activity that is currently open:
// in your activity onCreate
ctx = YourActivity.this; // let's suppose ctx is static and general var
////////////////////////////////////////////////
// in the BroadcastReceiver
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(YourActivity.ctx);