This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
When clicking a Button to switch from the main Activity to my "ColoursGame" Activity the app crashes.
I'm still a beginner so not an expert at debugging.
The main activity code
Button colorsGame = (Button) findViewById(R.id.colours);
colorsGame.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, ColoursGame.class));
}
});
Manifest new activity
<activity android:name=".ColoursGame"
android:label="ColourGame"
android:theme="#style/AppTheme.NoActionBar"></activity>
ColoursGame Activity OnCreate code
public class ColoursGame extends Activity {
int livesCount = 3;
String x;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_colours_game);
Button start = (Button) findViewById(R.id.startColors);
start.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
vSwitch.showNext();
x = String.valueOf(livesCount);
lives.setText(x);
text();
textColor();
backgroundColor();
start();
}
});
}
The Error
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.aynaar.numbersgameforkids, PID: 3278
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.aynaar.numbersgameforkids/com.aynaar.numbersgameforkids.ColoursGame}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2548)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2323)
at com.aynaar.numbersgameforkids.ColoursGame.<init>(ColoursGame.java:42)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1078)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2538)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
at com.aynaar.numbersgameforkids.ColoursGame.<init>(ColoursGame.java:42)
Don't call findViewById outside of onCreate, there's no Window to call findViewById at that point.
If you still get a NullPointer, then you must have #+id/startColors in activity_colours_game.xml
Answer explanation here
Button start = (Button) findViewById(R.id.startColors);
According to the error you are trying to reach a button that doesnt exist in your activity layout file (whatever it is). Check the id of your button and make sure it is placed on the layout page that related with your "ColoursGame" Activity.
Related
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 2 years ago.
When the register button is clicked the app should load another activity however it just crashes. Tried looking here and here for help but I still couldn't fix it. I also tried removing 'implements View.OnClickListner' and using it how its shown in the examples and it didn't work. Also tried changing the xml file to a LinearLayout and that didn't work either. Thanks in advance!
public class LogInActivity extends AppCompatActivity implements View.OnClickListener {
//user input variables
EditText emailAddressInput;
EditText passwordInput;
Button logInButton;
Button registerButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//set the layout to activity_login.xml
setContentView(R.layout.activity_login);
//get user inputs and set to the variables
emailAddressInput = (EditText)findViewById(R.id.emailAddressInput);
passwordInput = (EditText)findViewById(R.id.passwordInput);
logInButton = (Button)findViewById(R.id.logInButton);
registerButton = (Button)findViewById(R.id.registerButton);
logInButton.setOnClickListener(this);
registerButton.setOnClickListener(this);
}
#Override
public void onClick(View view) {
Intent registerIntent = new Intent (LogInActivity.this,RegisterActivity.class);
switch (view.getId())
{
case R.id.logInButton:
break;
case R.id.registerButton:
startActivity(registerIntent);
break;
}
}
}
EDIT:
the logcat:
2020-04-04 16:02:10.759 12718-12718/com.example.blooddonorsystem E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.blooddonorsystem, PID: 12718
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.blooddonorsystem/com.example.blooddonorsystem.RegisterActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter)' on a null object reference
at com.example.blooddonorsystem.RegisterActivity.onCreate(RegisterActivity.java:56)
at android.app.Activity.performCreate(Activity.java:7825)
at android.app.Activity.performCreate(Activity.java:7814)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
In your RegisterActivity, seems like the Spinner you are setting the adapter to is null. Make sure it has correct value, usually its an ArrayAdapter of String.
The error is not in LoginActivity but in RegisterActivity.There is a null pointer exception in RegisterActivity when you are setting adapter to a spinner.
This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
findViewById returns null
(4 answers)
Closed 4 years ago.
I'm trying to set the onClickListener on an ImageButton but I get the following error:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.bordi.hotel, PID: 18420
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bordi.hotel/com.example.bordi.hotel.DetaiImage}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.bordi.hotel.DetaiImage.onCreate(DetaiImage.java:28)
at android.app.Activity.performCreate(Activity.java:7009)
at android.app.Activity.performCreate(Activity.java:7000)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
Below is the code I'm using:
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
close = (ImageButton) findViewById(R.id.closeDetail);
close.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
DetaiImage.super.onBackPressed();
}
});
}
Thanks in advance for your help!
You forgot setContentView(R.layout.activity_main);
after super.onCreate(savedInstanceState);
and if you have not a prior global declaration in your activity of close, do it like this:
ImageButton close = (ImageButton) findViewById(R.id.closeDetail);
I am fairly new to Android and creating my first app. I am using using following code:
public class MainActivity extends AppCompatActivity {
int netScore = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void addOne(View view) {
netScore = netScore + 1;
displayScore(netScore);
}
private void displayScore(int printScore) {
TextView varScore = (TextView) findViewById(R.id.score);
varScore.setText(printScore);
}
}
When I click the button, it throws this error in debug:
FATAL EXCEPTION: main
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
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$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
Does anybody have an idea about this error?
Did try adding the onClick in the xml-layout like this?
android:onClick="method"
If so, make sure that there are no typos.
In your case it would probably be:
android:onClick="addOne"
You can also listen for the click events programmatically. Check out this.
You can set the TextView in OnCreate method:
TextView varScore = (TextView) findViewById(R.id.score);
after that add the ClickListener to the varScore:
enter code here
varScope.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// do anything whatever you want
}
});
At first, try to initiate the TextView in the onCreate method.
BTW could you please show us your .xml file?
First, I'm new to android SDK but I have a decent amount of experience in java. I'm attempting a tutorial on the SDK to get into it. I completed writing everything required but when I go to run it, the app crashes and I get this fatal error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.Button.setOnClickListener(android.view.View$OnClickListener)'
on a null object reference
Ok, sure. Clearly, there is an issue with View.OnClickListener. Spelling, check. Capitalization, check. Parenthesis, check. Brackets, check. Semicolons, check. Next I checked the documentation for View.OnClickListener. I see its only method is onClick(View v). Ok well everything is fine there. The IDE isn't giving me any other errors. So at this point, I figure I need outside help. For referance, this is the button id:
android:id="#+id/button"
This is MainActivity.java
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.content.Intent;
import android.view.View;
public class MainActivity extends AppCompatActivity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v){
goToSecondActivity();
}
});
}
private void goToSecondActivity() {
Intent intent = new Intent(this, SecondActivity.class);
startActivity(intent);
}
}
And here is the logcat
08-20 16:00:01.171 2565-2565/com.example.joe.helloworld E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.joe.helloworld, PID: 2565
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.joe.helloworld/com.example.joe.helloworld.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.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$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.joe.helloworld.MainActivity.onCreate(MainActivity.java:16)
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)
You've forgotten to call setContentView() with the layout id that contains the Button.
Since there is no content layout, calls to findViewById() return null.
setContentView(R.layout.activity_main);
Right after super.onCreate(...)
You forgot to set the layout for the user to view :
setContentView(R.layout.activity_main);
Also Instead of using :
button.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v){
goToSecondActivity();
}
});
}
Just use this :
button.setOnClickListener(new Button.OnClickListener()
{
#Override
public void onClick(View v){
goToSecondActivity();
}
});
}
That means inside setOnClickListener use new Button.OnClickListener instead of View.OnClickListener
I'm getting this error and I don't know why. This same code was working before; the problem started occuring after an update at some point.
Stack trace:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.domain.appname, PID: 17964
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.domain.appname/com.domain.appname.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.domain.appname.NavigationDrawerFragment.setUp(int, android.support.v4.widget.DrawerLayout)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441)
at android.app.ActivityThread.access$800(ActivityThread.java:162)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1349)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5431)
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:914)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:707)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.domain.appname.NavigationDrawerFragment.setUp(int, android.support.v4.widget.DrawerLayout)' on a null object reference
at com.domain.appname.MainActivity.onCreate(MainActivity.java:40)
at android.app.Activity.performCreate(Activity.java:6056)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2332)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441)
at android.app.ActivityThread.access$800(ActivityThread.java:162)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1349)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5431)
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:914)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:707)
Here's the offending code in MainActivity.java:
...
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (BuildConfig.DEBUG){ Log.d(TAG, "Created in debug mode"); }
NavigationDrawerFragment mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
// Set up the drawer.
Log.d(TAG, "Setting up drawer");
mNavigationDrawerFragment.setUp( // Line 40
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout)
);
...
I've found two questions that seem to have similar problems. (Here's the first and the second) The first doesn't seem relevant, and the second is unanswered.
I'm baffled. drawer_layout and navigation_drawer do not throw "symbol unresolved" errors. Like I said, this all used to work...
You are never calling Activity.setContentView(int). This is how it should be:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_containing_drawer);
// Rest.
}