Attempt to invoke virtual method '(java.lang.String)' on a null object reference

Question

New to Java and Android Studio here.

Working on this image application, and I am trying to format a query from a search bar that replaces any white space into underscores and returns a string with the formatted string.

Been having a hard time trying to analyze this code, it seems that it's returning a null value.

Error

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.image_chan/com.example.image_chan.Main}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.image_chan.core.SearchFormatter.FormatToTagsStr(java.lang.String)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.example.image_chan.core.SearchFormatter.FormatToTagsStr(java.lang.String)' on a null object reference
        at com.example.image_chan.Main.handleIntent(Main.java:102)
        at com.example.image_chan.Main.onCreate(Main.java:52)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

Code

SearchFormatter.java

Located inside app/core/SearchFormatter.java

This also has another function that instead returns a String array.

package com.example.image_chan.core;

import java.util.ArrayList;

public class SearchFormatter {
    /*...*/
    public String FormatToTagsStr(String unformatted) {
        String lowCase = unformatted.toLowerCase();
        String[] unconvTags = lowCase.split(", ");

        ArrayList<String> converted = new ArrayList<String>();

        for (String tag : unconvTags) {
            String trimmed = tag.trim();

            String formatted = trimmed
                    .replaceAll("\\s+", "_")
                    .replaceAll(",", "");

            converted.add(formatted);
        }

        return converted.toString();
    }
    /*...*/
}

Main.java

Located inside app/Main.java

The main activity file, the error is contained inside handleIntent which handles search queries using a search view.

package com.example.image_chan;
/*...IMPORTS...*/

public class Main extends AppCombatActivity implements GalleryFragment.GalleryListener {
    /*...*/
    private void handleIntent(Intent intent) {
        if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
            String query = intent.getStringExtra(SearchManager.QUERY);
            
            String convTags = formatter.FormatToTagsStr(query);
            System.out.println(convTags); // seems to be printing null
            
            // DefaultImageBoards.SAFEBOORU.search(int limit, String query)
            DefaultImageBoards.SAFEBOORU.search(100, convTags).async((List<SafebooruImage> images) -> {
                /*...*/
            }
        }
    }
    /*...*/
}

I may be wrong here, but it seems it's returning an empty array or is it not initialized, is it true?

Any help would be appreciated, thank you!

You haven't initialized ```formatter``` – private static Dec 05 '20 at 17:17 — private static, Dec 05 '20 at 17:17

score 0 · Accepted Answer · answered Dec 05 '20 at 17:20

0

Looking at this message:

Attempt to invoke virtual method 'java.lang.String com.example.image_chan.core.SearchFormatter.FormatToTagsStr(java.lang.String)' on a null object reference

The 'FormatToTagsStr' is being invoked on a SearchFormatter object. This message is reporting that the SearchFormatter is null.

So I guess you need to look for where 'formatter' is being set.

answered Dec 05 '20 at 17:20

Lee Marshall

302
1
3

Oh, I see! Rookie mistake on my part that I only did `private SearchFormatter formatter;`. Thank you! – CLORO Dec 05 '20 at 17:23

Attempt to invoke virtual method '(java.lang.String)' on a null object reference

1 Answers1