My app cannot launch because of my Homepage

Question

My Homepage has a problem, the app failed to start when i run it. but, when i comment out the code on .Homepage in the AndroidManifest the app can run.

Error at Logcat: 2022-05-31 13:28:30.991 5606-5606/com.example.limbangfoodhuntfortourism E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.limbangfoodhuntfortourism, PID: 5606 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.limbangfoodhuntfortourism/com.example.limbangfoodhuntfortourism.Homepage}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2951) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3016) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1716) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loop(Looper.java:232) at android.app.ActivityThread.main(ActivityThread.java:6806) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1103) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference at com.example.limbangfoodhuntfortourism.Homepage.onCreate(Homepage.java:24) at android.app.Activity.performCreate(Activity.java:6974) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2904) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3016) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1716) at android.os.Handler.dispatchMessage(Handler.java:110) at android.os.Looper.loop(Looper.java:232) at android.app.ActivityThread.main(ActivityThread.java:6806) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1103) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:964)

this is the error: E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.limbangfoodhuntfortourism, PID: 27159 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.limbangfoodhuntfortourism/com.example.limbangfoodhuntfortourism.Homepage}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageResource(int)' on a null object reference

This is my Log in code:

package com.example.limbangfoodhuntfortourism;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.AuthResult;
import com.google.firebase.auth.FirebaseAuth;

public class Login extends AppCompatActivity {
    EditText mEmail, mPassword;
    Button mLoginButton;
    TextView mCreateLinkSignUp, mForgotPassword;
    FirebaseAuth fAuth;
    ProgressBar progressBar;
    ImageView mLogo;

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

        mEmail = findViewById(R.id.email);
        mPassword = findViewById(R.id.password);
        progressBar = findViewById(R.id.progressBarLogin);
        mLoginButton = findViewById(R.id.loginButton);
        mCreateLinkSignUp = findViewById(R.id.signUpNow);
        mForgotPassword = findViewById(R.id.forgotPassword);
        fAuth = FirebaseAuth.getInstance();

        mLoginButton.setOnClickListener((view) ->  {
                String email = mEmail.getText().toString().trim();
                String password = mPassword.getText().toString().trim();

                if(TextUtils.isEmpty(email)) {
                    mEmail.setError("Email is Required.");
                    return;
                }

                if(TextUtils.isEmpty(password)) {
                    mPassword.setError("Password is Required.");
                    return;
                }

                if(password.length() < 6) {
                    mPassword.setError("Password must be >= 6 characters");
                    return;
                }

                progressBar.setVisibility(View.VISIBLE);

                // authenticate the user

                fAuth.signInWithEmailAndPassword(email,password).addOnCompleteListener((task) ->  {
                        if(task.isSuccessful()) {
                            Toast.makeText(Login.this, "Logged in Successfully!", Toast.LENGTH_SHORT).show();
                            startActivity(new Intent(getApplicationContext(),Homepage.class));
                        } else {
                            Toast.makeText(Login.this, "Error!" + task.getException().getMessage(), Toast.LENGTH_SHORT).show();
                            progressBar.setVisibility(View.GONE);
                        }
                });
        });

        mCreateLinkSignUp.setOnClickListener((view) -> {
                startActivity(new Intent(getApplicationContext(), Register.class));
        });

        mLogo = findViewById(R.id.imageView);
        mLogo.setImageResource(R.drawable.main_logo);

        mForgotPassword.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                final EditText resetMail = new EditText(view.getContext());
                final AlertDialog.Builder passwordResetDialog = new AlertDialog.Builder(view.getContext());
                passwordResetDialog.setTitle("Reset Password?");
                passwordResetDialog.setMessage("Enter Your Email To Received Reset Link.");
                passwordResetDialog.setView(resetMail);

                passwordResetDialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        // extract the mail and send reset link

                        String mail = resetMail.getText().toString();
                        fAuth.sendPasswordResetEmail(mail).addOnSuccessListener(new OnSuccessListener<Void>() {
                            @Override
                            public void onSuccess(Void unused) {
                                Toast.makeText(Login.this, "Reset Link Sent To Your Email.", Toast.LENGTH_SHORT).show();
                            }
                        }).addOnFailureListener(new OnFailureListener() {
                            @Override
                            public void onFailure(@NonNull Exception e) {
                                Toast.makeText(Login.this, "Error! Reset Link is Not Sent." + e.getMessage(), Toast.LENGTH_SHORT).show();
                            }
                        });
                    }
                });

                passwordResetDialog.setNegativeButton("No", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        // close the dialog
                    }
                });

                passwordResetDialog.create().show();
            }
        });
    }
}

this is my Homepage:

package com.example.limbangfoodhuntfortourism;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TextView;

import com.google.firebase.auth.FirebaseAuth;

public class Homepage extends AppCompatActivity {
    ImageView mLogo;
    TextView mLogoutLink;
    FirebaseAuth fAuth;

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

        mLogoutLink = findViewById(R.id.Logout);
        mLogo = findViewById(R.id.imageView);
        mLogo.setImageResource(R.drawable.main_logo);

        fAuth = FirebaseAuth.getInstance();
        mLogoutLink.setOnClickListener((view) -> {
            startActivity(new Intent(getApplicationContext(), Logout.class));
        });
    }
}

This is my AndroidManifest code:

<?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.limbangfoodhuntfortourism">

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.LimbangFoodHuntForTourism"
        tools:targetApi="31">
        <activity
            android:name=".Logout"
            android:exported="true" />
        <activity
            android:name=".RestaurantDetails"
            android:exported="true" />
        <activity
            android:name=".Homepage"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Login"
            android:exported="true" />
        <activity
            android:name=".Register"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".MainActivity"
            android:exported="true" />
    </application>

</manifest>

add a logcat error in your question to find what the problem is causing. — M DEV, May 31 '22 at 04:47

score 0 · Answer 1 · answered May 31 '22 at 04:50

0

try this in your login activity

mLogo = findViewById(R.id.imageView);
mLogo.setImageDrawable(ContextCompat.getDrawable(getActivity(), 
R.drawable.main_logo));

lemme know if it works out for you

answered May 31 '22 at 04:50

Yazan

76
10

also see his `.Manifest` file and check what's correct and what's wrong – M DEV May 31 '22 at 05:04
.Manifest looks good to me – Yazan May 31 '22 at 05:18
it give me the error, Cannot resolve method 'getActivity' in 'Login' – Siti Faridah May 31 '22 at 05:36
You can use: 'this' Or `HomePageActivity.this` Instead of: 'getActivity()' – Yazan May 31 '22 at 05:48
already change and no error, but still my homepage cannot launch – Siti Faridah May 31 '22 at 06:12
I think my homepage part have a problem, but i didnt know where to fix – Siti Faridah May 31 '22 at 06:13
share your homepage layout XML file – Yazan May 31 '22 at 06:37
try to run it without this in your HomePageActivity `mLogo.setImageResource(R.drawable.main_logo);` – Yazan May 31 '22 at 06:38

My app cannot launch because of my Homepage

1 Answers1