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The setOnClickListener(new View.OnClickListener() of my Project is not working

I am developing a small project of test, and I wrote the following code.
I already created in the xml file, a button with id called "registerBtn".
I erased the imports of this source code to shorten space of this source code.
In the java file, I created a variable called mRegisterBtn, in the type of Button.
Inside the method called onCreate(Bundle savedInstanceState) the mRegisterBtn receives the method called findViewById(R.id.registerBtn);
However, in the mRegisterBtn.setOnClickListener, the part of new View.OnClickListener appears in gray color, and it is not working when trying to test this code.
This image shows what I really mean. Please, perceive that the the part of new View.OnClickListener appears in gray color. It means a error. But trying to compile, this code runs, but the button simply does not work.
Can anyone know how to fix this error, please?
public class Register2 extends AppCompatActivity {
Button mRegisterBtn;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register2);
mRegisterBtn = findViewById(R.id.registerBtn);
mRegisterBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Toast.makeText(getApplicationContext(), "Testing", Toast.LENGTH_LONG).show();
}
});
}
}```
<?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"
android:background="#007FFF"
tools:context=".Register">
<Button
android:id="#+id/registerBtn"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:backgroundTint="#color/white"
android:text="Register"
android:textColor="#color/black"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.499" />
</androidx.constraintlayout.widget.ConstraintLayout>

Try using the Activity itself as the Context.
If you want a log, then make one
If you want the gray to go away, use a lambda
Log.d("REGISTER", "Setting listener");
mRegisterBtn.setOnClickListener(view -> {
Log.d("REGISTER", "Clicked!");
Toast.makeText(Register2.this, "Testing", Toast.LENGTH_LONG).show();
});

Android Studio My Button on the second Activity doesn't Work

I think it a very easy Question. I am new to Android Studio and I could not find an answer.
I have an activity that switches per Button to another activity. However, on my second activity, my simple Button just to change the Textview which doesn't work.
Layout
<?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=".StartActivity">
<TextView
android:id="#+id/twText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="127dp"
android:layout_marginLeft="127dp"
android:layout_marginTop="88dp"
android:layout_marginEnd="127dp"
android:layout_marginRight="127dp"
android:layout_marginBottom="624dp"
android:text="Ihr Passwort war Richtig!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/btnChecke"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="134dp"
android:layout_marginLeft="134dp"
android:layout_marginTop="32dp"
android:layout_marginEnd="189dp"
android:layout_marginRight="189dp"
android:layout_marginBottom="371dp"
android:text="Check"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
onCreate method in my second activity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
tw = findViewById(R.id.twText);
btnCheck = findViewById(R.id.btnChecke);
btnCheck.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
tw.setText("work");
}
});
}
And this is how I am starting the second activity (onCreate method from my first activity).
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
tw = findViewById(R.id.twText);
Button btnCheck = findViewById(R.id.btnChecke);
btnCheck.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
setContentView("Work"R.layout.activity_main);
}
});
}
I have checked the variable names in the layout and looks like everything is fine.
Thank you in advance.

This answer is based on the problem which I found before the latest edit from the OP. Here is the version of the edit where I found the problem.
First of all, something is very wrong about the onClickListener of your button. You are setting the content view again, instead of starting your second activity. It looks like, you are just setting the content view of your StartActivity which actually does not launch the MainActivity that you are trying to start.
In order to start a new activity, you need to add the following in your button onClickListener.
btnCheck.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// setContentView(R.layout.activity_main); // This is not the way for starting another activity
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
}
});
Once your MainActivity has started, you should be able to change the text with no problem.

Bundle bundle = getIntent().getExtras()
if(bundle.getString("changeTextView")
TextView .... = (TextView) ....setText();
Hi. If I good understand, you should use Intent with "putExtra()".
Exmple:intent.putExtras("changeTextView");
After that in your onCreate() method you can put:

The activities in android studio don't switch after pressing the button

I've already tried searching the Google on how to switch activities in android studio, even in the official documentation with tutorial. I did it exactly like it was said but I am still unable to get redirected to another activity after clicking a button.
I've entered an onClick name of the method to the button
it looks like this: https://i.imgur.com/pmsztaL.png (can't post images yet)
and this is my MainActivity.class file with said method
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void handleButtonAddNew(View view) {
MainActivity.this.startActivity(new Intent(MainActivity.this, AddItemActivity.class));
}
}
After pressing the button in a phone, the button does nothing.
This is my AddItemActivity.class
public class AddItemActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_item);
}
public void handleButtonRemember(View view) {
finish();
}
}
How come the button doesn't work, what did I do wrong?
EDITS
EDIT: Successfully ran emulator and the buttons did in fact work, the problem lies within my phone, the buttons there don't want to work. Where could be the issue now?
EDIT: XML Layout of MainActivity.class
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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/buttonAddNew"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="188dp"
android:layout_marginRight="188dp"
android:layout_marginBottom="264dp"
android:text="#string/buttonAdd"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
<ScrollView
android:id="#+id/scrollView2"
android:layout_width="395dp"
android:layout_height="715dp"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" />
</ScrollView>
</android.support.constraint.ConstraintLayout>
EDIT: The problem was with scroll view blocking the clickable button so on my phone the button didn't register any clicks, after removing the scrollview the button works normally.

I'm afraid that this button doesn't get any listeners attached.
The programatic approach
From the Official Android Documentation
I'd suggest you use this in your onCreate callback:
Button button = (Button) findViewById(R.id.your_btn_id);
button.setOnClickListener((view) -> { theMethodYouWantToCallHere(view); });
XML approach
Please double check the following using this approach
Your activity is registered in the AndroidManifest.xml
You're including the android namespace to the XML file in the parent container of the layout file. IE: xmlns:android="http://schemas.android.com/apk/res/android"
Make sure you're setting the content view for the activity with setContentView(R.layout.your_layout_file);
Once 2 is satisfied make sure you're using the android namespace. IE: android:onClick="yourMethod"
As you're currently doing: Make sure the onClick callbacked method has the View view parameter; no more, no less
Make sure the onClick function is public in the activity.
And that no other clickable views are covering the view you're registering the onClick listener for :)
Including the namespace: xmlns:android="http://schemas.android.com/apk/res/android"
XML file
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:fitsSystemWindows="true"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button android:text="Click me!" android:onClick="clicked" android:layout_height="wrap_content" android:layout_width="wrap_content"/>
</FrameLayout>
The activity
public class MainActivity extends AppCompatActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void clicked(View view){
Toast.makeText(this, "Hey! Im clicked!",Toast.LENGTH_SHORT).show();
}
}

How to Implement a method inside Activity class

I'm just starting to learn Android programming with Android Studio and unfortunately, but I have a big problem with probably a very simple thing, namely in the layout file of the main activity, I assigned the startActivity() method to the android:onClick property of the both buttons (android:onClick="startActivity()").
And now I should in the MainActivity class, implement startActivity() method but.... I do not know how to do it.
I saw that I should have in MainActivity: public void startActivity(View v). I tried and I was looking for solutions for a few hours and I already lost hope.
Especially that I can implement e.g. View.OnClickListener but methods, startActivity() can not do anymore. How could I implement this method?
I assigned the startActivity() method to the android:onClick property of the both buttons in activity_main.xml:
<Button
android:id="#+id/button"
android:onClick="startActivity()"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginTop="24dp"
android:text="#string/button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:ignore="OnClick" />
<Button
android:id="#+id/button2"
android:onClick="startActivity()"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="32dp"
android:layout_marginTop="16dp"
android:text="#string/button2"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/button"
tools:ignore="OnClick" />
Next i should in the MainActivity class, implement startActivity() method but.... I do not know how to do it :
public class MainActivity extends AppCompatActivity implements startActivity() {
Button b1, b2;
EditText et1, et2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = findViewById(R.id.button);
b2 = findViewById(R.id.button2);
et1 = findViewById(R.id.editText);
et2 = findViewById(R.id.editText2);
public void startActivity(View v) {
if (v.getId() == R.id.button) {
String name = et1.getText().toString();
int age = Integer.parseInt(et2.getText().toString());
Intent i = new Intent(this, ResultActivity.class);
i.putExtra("name", name);
i.putExtra("age", age);
startActivity(i);
} else {
Intent i = new Intent(Intent.ACTION_VIEW,
Uri.parse("http://www.google.pl/"));
startActivity(i); }
}
}

You're incorrectly using onClick attribute. This is wrong:
android:onClick="startActivity()"
it should be:
android:onClick="startActivity"
Read more at https://developer.android.com/guide/topics/ui/controls/button#HandlingEvents
Suggestion
You should avoid using android:onClick in your xml. Use the onClickListener instead. It's important to separate your logic and UI layout so you don't need to think too much whenever your xml layout is changed. Use something like this:
Button button = (Button) findViewById(R.id.your_button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Do something here when button is clicked.
}
});

As mentioned by ישו אוהב אותך9A
https://developer.android.com/guide/topics/ui/controls/button#HandlingEvents
Responding to Click Events
<Button xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/button_send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/button_send"
//onClick function/method name don't use round brackets
android:onClick="sendMessage" />
and in your activity
//JAVA
/** Called when the user touches the button */
public void sendMessage(View view) {
// Do something in response to button click
}
//Kotlin
/** Called when the user touches the button */
fun sendMessage(view: View) {
// Do something in response to button click
}
and remove the tools:ignore="OnClick"
i hope it helps

Firstly, change this
android:onClick="startActivity()"
to this:
android:onClick="startActivity"
Then move your startActivity method below OnCreate method. It is currently inside OnCreate

Android start new activity when clicking widget

I am new with coding Java and xml for android applications and I wanted to know how I start/open a new activity when clicking on something. In this case I am using a relative layout to keep a image and text together as one object. What I want to do is when you click on it it will start/open the new activity. How do I do this? Could someone tell me step by step since I am quite new to this.

First of all, if you want your layout to act (RelativeLayout) like a button (do not handle onClick on layout child components) firstly set in your xml layout file RelativeLayout attribute
android:clickable="true"
Or you can do this directly in your code (in onCreate method)
relativeLayout.setClickable(true);
Than you need to set onClickListener for your layout.
You can do this simply by creating anonymous class
relativeLayout.setOnClickListener(new OnClickListener()
{
#Override
public void onClick(View v)
{
Intent startActivityIntent = new Intent(getApplicationContext(),YourDesiredActivity.class);
startActivity(startActivityIntent);
}
}
UPDATE
Layout is defined in xml file, of course in Android you can do this in code ,but it is better to use xml file.
In your IDEA you have folder res->layout here you should place your layout files. For example layout with name `
relative_root_layout.xml
<xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/relative_layout"
android:layout_height="wrap_content" android:layout_width="wrap_content">
<ImageView
android:id="#+id/image_view">
android:layout_width="wrap_content"
android:src="#drawable/icon"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
ImageView>
<TextView
android:id="#+id/text_view"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="20sp"
android:layout_toRightOf="#+id/image_view"
android:text="Relative layout">
TextView>
RelativeLayout>
But in case you have only text and image it is better to use
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="#android:drawable/btn_image"
android:text="Button with Image"
android:gravity="left"
android:drawablePadding="10dp">
Button>
How you can access your widgets ?
This is very basic thing you have to know if you are developing for android, this is essential part. Please read documentation, read books, watch tutorial or whatever.
In short you need to inflate layout in activity onCreate() method
RelativeLayout mRelativeLayout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.relative_root_layout);
mRelativeLayout = (RelativeLayout) findViewById(R.id.relative_layout);
mRelativeLayout.setOnClickListener(.....)
}
But again this very basic things you must know.

You could set onClickListener for any of your views.
ImageView image = (ImageView) findViewById(R.id.image);
image.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(Youractivity.this, Moveactivity.class));
}
});

Starting a new activity is done by creating an Intent and then calling startActivity, e.g.
Intent intent = new Intent(context, AnotherActivity.class);
context.startActivity(intent);
You can wrap this code in an OnClickListener as other answerers already suggested.
A second option is to add an android:onClick attribute to your RelativeLayout
<RelativeLayout ...
android:onClick="clickMe">
<ImageView .../>
<TextView .../>
</RelativeLayout>
and in your activity
public class MyActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void clickMe(View notused) {
Intent intent = new Intent(this, AnotherActivity.class);
this.startActivity(intent);
}
}
See startactivity for a complete example.