My button for changing activity is not working

Question

So....i am trying to make this button change from main activity to Disciplinas_Activity. But whenever I try to run the app and click the button, the app crashes. Keep in mind i have other 3 button completly identical ,(other then the fact that they direct to different activities), in the same activity and they all work with the same base code.

Here is the .xml code for Main Activity

<TextView
    android:id="@+id/textView_emailnotverified"
    android:layout_width="172dp"
    android:layout_height="34dp"
    android:background="@color/white"
    android:text="Email não Verificado!"
    android:textColor="#E41F1F"
    android:textSize="18dp"
    android:visibility="gone"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.066"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.516" />

<TextView
    android:id="@+id/textView_studentEmail"
    android:layout_width="237dp"
    android:layout_height="40dp"
    android:text="Email do aluno"
    android:textColor="@color/white"
    android:textSize="18dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.856"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.395" />

<ImageView
    android:id="@+id/imageView4"
    android:layout_width="332dp"
    android:layout_height="168dp"
    android:scaleX="2"
    android:scaleY="1.3"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.493"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.028"
    app:srcCompat="@drawable/etpr" />

<TextView
    android:id="@+id/welcommingtextview5"
    android:layout_width="337dp"
    android:layout_height="39dp"
    android:text="ESCOLA TÉCNICA E PROFISSIONAL DO RIBATEJO"
    android:textAlignment="center"
    android:textColor="@color/white"
    android:textSize="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.459"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.15" />

<TextView
    android:id="@+id/ETPRTitle5"
    android:layout_width="258dp"
    android:layout_height="30dp"
    android:text="BEM-VINDO À ETPR"
    android:textAlignment="center"
    android:textColor="@color/white"
    android:textSize="24dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.496"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.105" />

<Button
    android:id="@+id/Button_LOGOUT"
    android:layout_width="114dp"
    android:layout_height="59dp"
    android:text="Logout"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.934" />

<Button
    android:id="@+id/button_Testes"
    android:layout_width="108dp"
    android:layout_height="47dp"
    android:text="Testes"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.867"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.644" />

<Button
    android:id="@+id/button_pdf"
    android:layout_width="121dp"
    android:layout_height="41dp"
    android:text="PDF"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.894"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.753" />

<Button
    android:id="@+id/button_historia"
    android:layout_width="191dp"
    android:layout_height="47dp"
    android:text="Sobre o criador"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.149"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.76" />

<ImageView
    android:id="@+id/imageView_perfil"
    android:layout_width="122dp"
    android:layout_height="118dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.055"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.376"
    app:srcCompat="@mipmap/ic_launcher" />

<TextView
    android:id="@+id/textView_studentname"
    android:layout_width="236dp"
    android:layout_height="33dp"
    android:text="Nome do aluno"
    android:textColor="@color/white"
    android:textSize="18dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.857"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.329" />

<Button
    android:id="@+id/button_emailverification"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Verificar agora"
    android:visibility="gone"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.88"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.527" />

<Button
    android:id="@+id/changeprofileBTN"
    android:layout_width="245dp"
    android:layout_height="41dp"
    android:text="Mude a imagem de perfil"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.897"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.453" />

<Button
    android:id="@+id/button_disciplinas"
    android:layout_width="194dp"
    android:layout_height="55dp"
    android:text="Disciplinas"
    android:clickable="true"
    android:focusable="true"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.106"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.644" />

Here is my .java code for main activity

public class MainActivity extends AppCompatActivity {
TextView fullname, email, verifymessage;
FirebaseAuth fAuth;
FirebaseFirestore fstore;
String userID;
Button resendVerification, LogoutBTN, changeprofileBTN, tests, createrInfo, pdfdatabase, buttonDisciplinas;
ImageView profileImage;
StorageReference storageReference;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    fullname = findViewById(R.id.textView_studentname);
    email    = findViewById(R.id.textView_studentEmail);

    LogoutBTN      = (Button) findViewById(R.id.Button_LOGOUT);
    tests          =(Button) findViewById(R.id.button_Testes);
    createrInfo    =(Button) findViewById(R.id.button_historia);
    pdfdatabase    =(Button) findViewById(R.id.button_pdf);
    buttonDisciplinas = findViewById(R.id.button_disciplinas);

    buttonDisciplinas.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this, Disciplinas_Activity.class));
        }
    });


    tests.setOnClickListener(new View.OnClickListener() {// menu dos testes
        @Override
        public void onClick(View v) {
            startActivity(new Intent(getApplicationContext(),Testes_Activity.class));
        }
    });

    createrInfo.setOnClickListener(new View.OnClickListener() {//página sobre a história da app
        @Override
        public void onClick(View v) {
            startActivity(new Intent(getApplicationContext(),AboutMe_Activity.class));
        }
    });

    pdfdatabase.setOnClickListener(new View.OnClickListener() {//pdf database
        @Override
        public void onClick(View v) {
            startActivity(new Intent(getApplicationContext(),PDF_Activity.class));
        }
    });

    LogoutBTN.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            FirebaseAuth.getInstance().signOut();
            startActivity(new Intent(getApplicationContext(),LoginScreen.class));
            finish();
        }
    });

    profileImage = findViewById(R.id.imageView_perfil);
    changeprofileBTN = findViewById(R.id.changeprofileBTN);

    fAuth    = FirebaseAuth.getInstance();
    fstore   = FirebaseFirestore.getInstance();
    storageReference = FirebaseStorage.getInstance().getReference();

    StorageReference profileRef = storageReference.child("utilizadores/"+fAuth.getCurrentUser().getUid()+"/perfil.jpg");
    profileRef.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
        @Override
        public void onSuccess(Uri uri) {
            Picasso.get().load(uri).into(profileImage);
        }
    });

    resendVerification = findViewById(R.id.button_emailverification);
    verifymessage      = findViewById(R.id.textView_emailnotverified);


    userID = fAuth.getCurrentUser().getUid();

    DocumentReference documentReference = fstore.collection("utilizadores").document(userID);
    documentReference.addSnapshotListener(this, new EventListener<DocumentSnapshot>() {
        @Override
        public void onEvent(@Nullable DocumentSnapshot documentSnapshot, @Nullable FirebaseFirestoreException error) {
            fullname.setText(documentSnapshot.getString("NomeCompleto"));
            email.setText(documentSnapshot.getString("Email"));
        }
    });


    FirebaseUser user = fAuth.getCurrentUser();

    if (!user.isEmailVerified()){
        verifymessage.setVisibility(View.VISIBLE);
        resendVerification.setVisibility(View.VISIBLE);

        resendVerification.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                user.sendEmailVerification().addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        Toast.makeText(v.getContext(),"Email de verificação enviado.", Toast.LENGTH_SHORT).show();
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.d("tag","Erro: Email de verificação não enviado " + e.getMessage());

                    }
                });
            }
        });
    }

    changeprofileBTN.setOnClickListener(new View.OnClickListener() { //mudar imagem de perfil
        @Override
        public void onClick(View v) {
            Intent openGalleryIntent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
            startActivityForResult(openGalleryIntent,1000);
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == 1000 ){
        if (resultCode == Activity.RESULT_OK){//se o resultado for igual então abre  galeria
            Uri imageUri = data.getData();
            //profileImage.setImageURI(imageUri); //insere imagem escolhida na galeria

            uploadImageToFirebase(imageUri);
            
            
        }
    }
}

private void uploadImageToFirebase(Uri imageUri) { //upload da imagem para base de dados
    StorageReference fileReference = storageReference.child("utilizadores/"+fAuth.getCurrentUser().getUid()+"/perfil.jpg");
    fileReference.putFile(imageUri).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {
            fileReference.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
                @Override
                public void onSuccess(Uri uri) {
                    Picasso.get().load(uri).into(profileImage);
                }
            });

        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Toast.makeText(MainActivity.this,"Erro", Toast.LENGTH_SHORT).show();
        }
    });
}

}

Here is .xml code for DisciplinasActivity

 <LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:id="@+id/Relative_Layout_Title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginTop="32dp"
        android:layout_marginRight="20dp">

        <TextView
            android:id="@+id/Menu_Title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Disciplinas"
            android:textColor="@color/white"
            android:textSize="22sp">
        </TextView>

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/Menu_Title"
            android:layout_marginTop="6dp"
            android:text="ETPR"
            android:textColor="@color/white"
            android:textSize="14sp">
        </TextView>

        <TextView
            android:id="@+id/Name_Data"
            android:textColor="@color/white"
            android:textSize="16sp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toStartOf="@id/user_icon"
            android:text="Nome">
        </TextView>

        <TextView
            android:id="@+id/Email_Data"
            android:textColor="@color/white"
            android:textSize="16dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/Name_Data"
            android:layout_toStartOf="@id/user_icon"
            android:text="Email">

        </TextView>

        <ImageView
            android:id="@+id/user_icon"
            android:layout_width="62dp"
            android:layout_height="62dp"
            android:layout_alignParentRight="true"
            app:srcCompat="@drawable/cara">
        </ImageView>

    </RelativeLayout>

    <GridLayout
        android:id="@+id/MainGrid"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@+id/Relative_Layout_Title"
        android:alignmentMode="alignMargins"
        android:columnCount="2"
        android:columnOrderPreserved="false"
        android:rowCount="2">

        <androidx.cardview.widget.CardView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:layout_margin="12dp"
            android:layout_marginTop="70dp"
            app:cardCornerRadius="12dp"
            app:cardElevation="6dp">

            <LinearLayout
                android:id="@+id/LinearLayoutSdac"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:orientation="vertical"
                android:padding="16dp">

                <ImageView
                    android:layout_width="80dp"
                    android:layout_height="80dp"
                    android:layout_gravity="center"
                    android:src="@drawable/sdac_icon"/>

                <TextView
                    android:layout_width="56dp"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:layout_marginTop="12dp"
                    android:text="SDAC"
                    android:textColor="@color/black"
                    android:textSize="18sp">
                </TextView>

            </LinearLayout>

        </androidx.cardview.widget.CardView>

        <androidx.cardview.widget.CardView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:layout_margin="12dp"
            android:layout_marginTop="70dp"
            app:cardCornerRadius="12dp"
            app:cardElevation="6dp">

            <LinearLayout
                android:id="@+id/LinearLayoutEletronica"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:orientation="vertical"
                android:padding="16dp">

                <ImageView
                    android:layout_width="80dp"
                    android:layout_height="80dp"
                    android:layout_gravity="center"
                    android:src="@drawable/eletronica_icon"
                    app:srcCompat="@drawable/eletronica_icon" />

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:layout_marginTop="12dp"
                    android:text="Eletrónica"
                    android:textColor="@color/black"
                    android:textSize="18sp"/>

            </LinearLayout>

        </androidx.cardview.widget.CardView>

        <androidx.cardview.widget.CardView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:layout_margin="12dp"
            android:layout_marginTop="70dp"
            app:cardCornerRadius="12dp"
            app:cardElevation="6dp">

            <LinearLayout
                android:id="@+id/LinearLayoutCD"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:orientation="vertical"
                android:padding="16dp">

                <ImageView
                    android:layout_width="80dp"
                    android:layout_height="80dp"
                    android:layout_gravity="center"
                    android:src="@drawable/cd_icon"
                    app:srcCompat="@drawable/cd_icon" />

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:layout_marginTop="12dp"
                    android:text="CD"
                    android:textColor="@color/black"
                    android:textSize="18sp" />

            </LinearLayout>

        </androidx.cardview.widget.CardView>

        <androidx.cardview.widget.CardView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_rowWeight="1"
            android:layout_columnWeight="1"
            android:layout_margin="12dp"
            android:layout_marginTop="70dp"
            app:cardCornerRadius="12dp"
            app:cardElevation="6dp">

            <LinearLayout
                android:id="@+id/LinearLayoutIMEI"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:orientation="vertical"
                android:padding="16dp">

                <ImageView
                    android:layout_width="80dp"
                    android:layout_height="80dp"
                    android:layout_gravity="center"
                    android:src="@drawable/imei_icon"
                    app:srcCompat="@drawable/imei_icon" />

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:layout_marginTop="12dp"
                    android:text="IMEI"
                    android:textColor="@color/black"
                    android:textSize="18sp" />

            </LinearLayout>

        </androidx.cardview.widget.CardView>

    </GridLayout>

    <Button
        android:id="@+id/ExitButton"
        android:layout_marginTop="20dp"
        android:layout_width="121dp"
        android:layout_height="69dp"
        android:layout_gravity="center"
        android:layout_marginBottom="@+id/RelativeLayout"
        android:text="Sair"
        android:textColor="@color/white"
        android:textSize="16dp" />

</LinearLayout>

Here is my .Java code for DisciplinasActivity

public class Disciplinas_Activity extends AppCompatActivity {

GridLayout gridPrincipal;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_disciplinas);

    gridPrincipal = (GridLayout)findViewById(R.id.MainGrid); //identifica qual a grelha


    //ação
    setSingleEvent(gridPrincipal);
}

private void setSingleEvent(GridLayout gridPrincipal) {
    for (int i =0;i<gridPrincipal.getChildCount();i++)
    {
        CardView cardView = (CardView)gridPrincipal.getChildAt(i);
        final int finalI = i;
        cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(getApplicationContext(),TeacherLoginScreen.class));//muda para Disciplina de Sdac
            }
        });
    }
}

}

What am i missing...? if all the other 3 buttons work...why doesnt this one work? (I am a total newbie but i
I really need the help) 

Answer 1

Consider your code

button = (Button)findViewById(R.id.button1);

• You do not need to explicitly cast widgets anymore unless it's a special case like a RadioButton from a resource ID.
• Please check that the button you're clicking is actually the button you set all this up for.
• Add

android:clickable="true";
android:focusable="true";

to your buttons in the XML layout. I'm guessing ConstraintLayout is creating this problem, you shouldn't come across this issue if you use LinearLayout.

Answer 2

In your .xml code for DisciplinasActivity you have some mistakes on the dimensions that you are using:

    <GridLayout
    ...
    android:id="@+id/MainGrid"
    ...
    android:layout_marginBottom="@+id/Relative_Layout_Title" <!-- E.G 20dp -->
    >
    
     <Button
    android:id="@+id/ExitButton"
    ...
    android:layout_marginBottom="@+id/RelativeLayout" <!-- E.G 20dp -->
    ... />

For margins, padding, etc you have to use a dimension, like dp,in,mm,etc not a reference to other view, or you could use dimmens.xml maybe you are confusing android:layout_marginBottom with android:layout_constraintBottom_toBottomOf or another property. Check for this in all the elements in your .xml

This answer is due to this log that you posted:

ComponentInfo{studying.app.tkappv6/studying.app.tkappv6.Disciplinas_Activity}: java.lang.UnsupportedOperationException: Can't convert to dimension: type=0x12

Answer 3

In the MainActivity

Change the to "v.getContext()" istead of "MainActivity.this"

tests.setOnClickListener(new View.OnClickListener() {// menu dos testes
        @Override
        public void onClick(View v) {
            startActivity(new Intent(v.getContext(), Testes_Activity.class));
        }
    });

    createrInfo.setOnClickListener(new View.OnClickListener() {//página sobre a história da app
        @Override
        public void onClick(View v) {
            startActivity(new Intent(v.getContext(), AboutMe_Activity.class));
        }
    });

    pdfdatabase.setOnClickListener(new View.OnClickListener() {//pdf database
        @Override
        public void onClick(View v) {
            startActivity(new Intent(v.getContext(),PDF_Activity.class));
        }
    });

    LogoutBTN.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            FirebaseAuth.getInstance().signOut();
            startActivity(new Intent(v.getContext(),LoginScreen.class));
            finish();
        }
    });

I was Looking into the code and i've never used this method, but it's strange for me so it's good to pay attention, I think is wrong to set a "Void", if the method is not going to receive any value, but since is a @Override method if it was that way from the beginning you don't need to change;

@Override
public void onSuccess(Void aVoid) {
       Toast.makeText(v.getContext(),"Email de verificação enviado.", Toast.LENGTH_SHORT).show();
}

Give a try and let's see if works!