当我有 2 个 setOnclickListener 时，为什么我的应用程序不断崩溃？

Question

My app keeps crashing when I set 2 setOnclickListener . The interesting thing is, when I only have 1 button intent, it doesn't crash. When I have 2 buttons, the new button does not bring me to new screen, and the old one just crashes the whole app.

Here's my code for the "old" button:

SignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intSignUp=new Intent(LoginActivity.this,MainActivity.class);
                startActivity(intSignUp);
            }
        });

If that's the only thing, then everything works. But when I add following, the new one doesn't work and old one crashes:

Support.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent support=new Intent(LoginActivity.this,Support.class);
                startActivity(support);
            }
        });

Here's the Logcat:

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.hoversfw.notes.LoginActivity.onCreate(LoginActivity.java:96)

And LoginActivity.java Line 96 is the beginning of Support.setOnclickListener. Also, I have everything declared like:

Support=findViewById(R.id.Support);
SignUp=findViewById(R.id.textView);

Here's my XML file code:

<TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="12dp"
        android:text="Already have an account? Sign in!"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.505"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button" />

    <Button
        android:id="@+id/Support"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="25dp"
        android:layout_marginEnd="29dp"
        android:text="Support"
        app:layout_constraintEnd_toStartOf="@+id/about"
        app:layout_constraintHorizontal_chainStyle="packed"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

I also have all ID matched, Android Studio detects no error. I wonder what's causing the problem.

UPDATE
I have everything matched, like java file and xml, no ID is same, everything declared. And I don't think there is any problem with XML.

SignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intSignUp=new Intent(LoginActivity.this,MainActivity.class);
                startActivity(intSignUp);
            }
        });
        /*Support.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent support=new Intent(LoginActivity.this,Support.class);
                startActivity(support);
            }
        });*/

If it's like above, then SignUp it works. If it's like

SignUp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intSignUp=new Intent(LoginActivity.this,MainActivity.class);
                startActivity(intSignUp);
            }
        });
        Support.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent support=new Intent(LoginActivity.this,Support.class);
                startActivity(support);
            }
        });

Both of them doesn't work. (The difference is last one I commented Support.setOnClickListener..... but this one I made it as code.)

Answer 1

I can't confirm directly your error because you don't show your xml, but maybe you can do it.

1. you need check id view in xml same with you call in activiy with findViewById()
2. findViewById must above in your listener

Answer 2

If you are using 2 buttons, then you need to link them as button for both of them.

UPDATED

Since, you are using button and textview. I updated the answer.

This code at xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".Main2Activity">
    <TextView
        android:id="@+id/txtViewSupport"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Support" />

    <Button
       android:id="@+id/btnSignUp"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:text="SignUp" />

</LinearLayout>

This code at Java

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    Button buttonSignUp = findViewById(R.id.btnSignUp);
    TextView textViewSupport = findViewById(R.id.txtViewSupport);
    buttonSignUp.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

        }
    });
    textViewSupport.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

        }
    });
}