从碎片按钮单击时如何获取下一个活动

Question

Hi i am trying to get my NextActivity when i press on Fab in my View 1

View 1 xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/Fbutton"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="300dp"
        android:layout_marginLeft="180dp"
        android:clickable="true"
        android:paddingRight="16dp"
        android:paddingBottom="16dp"

        />
</RelativeLayout>,

View.java

package com.example.myapplication;

import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import com.google.android.material.floatingactionbutton.FloatingActionButton;

public class View1 extends Fragment {
private FloatingActionButton mFab;
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.view1, container, false);
       mFab.findViewById(R.id.Fbutton);
       mFab.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               Intent intent = new Intent(getActivity(),NextActivity.class);
               startActivity(intent);
           }
       });
        return view;
    }

}

Error

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View com.google.android.material.floatingactionbutton.FloatingActionButton.findViewById(int)' on a null object reference at com.example.myapplication.View1.onCreateView(View1.java:21)

i have tried getContext() View1.this nothing worked

Answer 1

You haven't complete the floating button assigning. Remove mFab.findViewById(R.id.Fbutton); this line. Add

 mFab =  view.findViewById(R.id.Fbutton);

Here view is used to get the ID from the layout.

Answer 2

From the code that you posted most probably the problem is that you are not assigning the return value of findViewById(R.id.Fbutton); to the mFab .

 mFab = findViewById(R.id.Fbutton);