错误：您是否在 AndroidManifest.xml 中声明了此活动？ 当试图意图上课时

Question

Here's my code for clicking the button from my class showInforActivity :

btnRegister.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent intent = new Intent(showInfoActivity.this, InformationFragment.class);
                    startActivity(intent);
                }
            });

Whenever I click the button I got error Unable to find explicit activity class {com.example.drawerapplication/com.example.drawerapplication.ui.information.InformationFragment}; have you declared this activity in your AndroidManifest.xml? Unable to find explicit activity class {com.example.drawerapplication/com.example.drawerapplication.ui.information.InformationFragment}; have you declared this activity in your AndroidManifest.xml? and it loads the previous class and layout instead of loading this InformationFragment class:

package com.example.drawerapplication.ui.information;

import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import com.example.drawerapplication.databinding.FragmentInformationBinding;

public class InformationFragment extends Fragment {

    private FragmentInformationBinding binding;

    private EditText name, address, age, contact;
    private Button btnAdd, btnViewData;
    DatabaseHelper mDatabaseHelper;

    public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        binding = FragmentInformationBinding.inflate(inflater, container, false);
        View root = binding.getRoot();

        name = binding.name;
        address = binding.address;
        age = binding.age;
        contact = binding.contact;

        btnAdd = binding.add;
        btnViewData = binding.viewdata;

        mDatabaseHelper = new DatabaseHelper(getActivity());

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                if (name.length() != 0 && address.length() != 0
                && age.length() != 0 && contact.length() != 0){

                    mDatabaseHelper.addData(name.getText().toString(), address.getText().toString(),
                            age.getText().toString().trim(), Long.valueOf(contact.getText().toString().trim()));
                    toastMessages("Data Successfully Inserted!");

                }else {
                    toastMessages("Please complete all the requirements needed");
                }

            }
        });

        btnViewData.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getContext(), ListDataActivity.class);
                startActivity(intent);
            }
        });

        return root;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        binding = null;
    }

    private void toastMessages(String message){
        Toast.makeText(getContext(),message,Toast.LENGTH_SHORT).show();
    }

}

The layout of this InformationFragment is fragment_information :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context=".ui.information.InformationFragment"
    android:layout_marginStart="10dp"
    android:layout_marginEnd="10dp">
...

Heres my **AndroidManifest file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.example.drawerapplication">

    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
        tools:ignore="ScopedStorage" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.DrawerApplication">
        <activity android:name=".ui.information.ListDataActivity"/>
        <activity android:name=".ui.information.showInfoActivity"/>
        <activity
            android:name=".MainActivity"
            android:exported="true"
            android:label="@string/app_name"
            android:theme="@style/Theme.DrawerApplication.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity> 
    </application>

</manifest>

I tried adding InformationFragment there however, it says Class referenced in the manifest, com.example.drawerapplication.InformationFragment, was not found in the project or the libraries

Please let me know what I'm missing or if you need more information. Thanks!

Answer 1

You cannot use an Intent to start/create a Fragment much like you would for an Activity . A Fragment actually lives inside an Activity ie its lifecycle is bound to an Activity . To start a Fragment you have to use the FragmentManager that is available with the Activity instance

This error is coming up because Android thinks that your InformationFragment is an Activity rather than a Fragment and hence it is asking you if you have declared it in your AndroidManifest.xml file because as the rule says, you need to have each Activity in your app declared inside the AndroidManifest.xml file

So, now you can use something like this , inside your showInfoActivity . Technically there are many solutions available as to what you could essentially do and that's why I linked you to all possible solutions rather than just writing them here

Answer 2

You can not use Intent for navigate to Fragment from a Activity . For this reason you are getting this error. As, Intent receive 2 parameter Intent(FromActivity, ToActivity.class) . you are using fragment in 2nd parameter. We know that, when we create a activity then it it declared with AndroidManifest.xml file. Here, in your manifest file there are not any activity called InformationFragment .

You can learn Android Navigation Component to easily communicate with Activity and fragments.