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Android

Rubio Salinas
Rubio Salinas
3,051 Points
Posted by Rubio Salinas
Rubio Salinas
3,051 Points

Build a simple android app with java. factTextView issue

So i keep getting an error when I try to run the app. "error. cannot find symbol variable factTextView". Any help would be greatly appreciated 

import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class FunFactsActivity extends AppCompatActivity {
    // Declare our View variables
    private TextView factTextView;
    private Button showFactButton = findViewById(R.id.showFactButton);

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

        // Assign the Views from the layout file to the corresponding variables
        factTextView = findViewById(R.id.factTextView); // <-- HERE IS THE ISSUE
        View.OnClickListener listener = new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // The button was clicked, so update the fact TextView with a new fact
                String fact= "Ostriches can run faster than horses";
                factTextView.setText(fact);
            }
        };
        showFactButton.setOnClickListener(listener);

    }

}

1 Answer

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,253 Points
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

It seems like there's a conflict in your reference to the text view.

First of all, I'll clean up your code a little bit in your OP, so we can read it a little better. You can see the Markdown Cheatsheet so you can see how to add code to posts to the community in the future. :)

Without being able to investigate the actual program in Android Studio, the first thing I'd suggest is your locate the TextView in Design View and see if it has the correct ID. Look at the property inspector.... make sure it has the correct ID factTextView.

Good luck :)

Rubio Salinas
Rubio Salinas
3,051 Points
Rubio Salinas
Rubio Salinas
3,051 Points

I checked it, fixed it and am still having issues with it. I have no more errors, but the app automatically closes on startup. This is what I see in red on logcat 07-18 22:27:22.311 4588-4588/? E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.rubio.funfacts, PID: 4588 java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.rubio.funfacts/com.example.rubio.funfacts.FunFactsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5254) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:117) at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:149) at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:29) at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:54) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:202) at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:183) at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519) at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190) at com.example.rubio.funfacts.FunFactsActivity.<init>(FunFactsActivity.java:12) at java.lang.reflect.Constructor.newInstance(Native Method) at java.lang.Class.newInstance(Class.java:1606) at android.app.Instrumentation.newActivity(Instrumentation.java:1066) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)  at android.app.ActivityThread.access$800(ActivityThread.java:151)  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)  at android.os.Handler.dispatchMessage(Handler.java:102)  at android.os.Looper.loop(Looper.java:135)  at android.app.ActivityThread.main(ActivityThread.java:5254)  at java.lang.reflect.Method.invoke(Native Method)  at java.lang.reflect.Method.invoke(Method.java:372)