How to move from activity 2 to activity 3 in android studio - android-studio

Question

I've created three activities. My first MainActivity has two buttons, one that takes you to Activity2 and one that takes you to Activity3. Both of those buttons work, I've managed to code them correctly.
But then on Activity3 there's a button that's supposed to take you also to Activity2, and it's not working. I've tried several things but I can't seem to figure it out. Is it possible to code several buttons that lead to the same activity? If so please help cause I'm new at coding and stuff. Also here's how I've been coding the buttons :
1-after creating the activity, I go to the Java file and create a new class. In that class I write the following code :
class className : AppCompatActivity(){
override fun onCreate (savedInstance : Bundle?){
super.onCreate(savedInstance)
setContentView(R.layout.activity2)
}
}
Then I add it to the manifest
2-then I go back to the MainActivity and write this :
val anyName = buttonName
anyName.setOnClickListener {
startActivity(Intent(this, class Name :: class.java))
}
Of course android studio takes care of everything and imports everything that's needed but the second I add more than two of those in my MainActivity the whole app crashes.
Please explain this as simply as possible as, again, I'm really new to coding and android studio.
Thank you !

Answer 1

To go back on an activity you can just use finish() on any function, but if you want to take any information with you, you should look for more information about startActivityforResult().
However next time upload the code and not this pseudocode please, it would help a lot!

Answer 2

When you creating a new activity, you need also to add to it the new XML file, which will be display UI in the Activity page.
You can do it in two ways:
1. Custom.
Create a new ClassName.kt (Java.class in Java) and attach inside onCreate() method a XML layout, which will displaying all views in Activity page.
2. With Android Studio.
Just right-click in your package name folder, where appears your, for example, empty activity when you start new an Android Studio Project. Then select new, then in bottom side of drop-downed view select type of new activity what you want. For example, it is Empty Activity. So, lets sum above information: right-click at your package name folder -> new -> type of activity.
For what below info? I see in your example code, which you show as code in Activity number 3, what you have in onCreate() this line of code setContentView(R.layout.activity2). It is line means, what you add XML file into your activity. One XML file for activity can be used only for one activity if you want to show, after click on button another activity. Rather you will see only one screen because two activities use one layout. So, check your activities
need to be something like this:
1.In ActivityOne.
class ActivityOne : Activity() {
override fun onCreate (savedInstance : Bundle?) {
super.onCreate(savedInstance)
setContentView(R.layout.activity1)
}
}
1.In ActivityTwo.
class ActivityOne : Activity() {
override fun onCreate (savedInstance : Bundle?) {
super.onCreate(savedInstance)
setContentView(R.layout.activity2)
}
}
1.In ActivityThree.
class ActivityThree : Activity() {
override fun onCreate (savedInstance : Bundle?) {
super.onCreate(savedInstance)
setContentView(R.layout.activity3)
}
}

Answer 3

Make sure if you want to create a new activity First right click app then goto new -> Activity -> Empty Activity .
finally you can add onClick in your Button tag , then use startActivity method.
public void methodName(View view) {
startActivity(new Intent(this,ActivityName.class));
}
Example Code:
MainActivity.java:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void gotoTwo(View view) {
startActivity(new Intent(this,Activity2.class));
}
public void gotoThree(View view) {
startActivity(new Intent(this,Activity3.class));
}
}
activity_main.xml :
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="200dp"
android:layout_marginRight="240dp"
android:onClick="gotoTwo"
android:text="Activity2" />
Don`t forgot to create a new java you should create a new xml file too