Thomas :
So i am trying to build a story telling app and it seems to keep crashing and I have not found a solution to my problem yet. I believe that it due to my array class called Page or something is wrong when it is trying to call drawables from my resources.
I have tried re writing my entire code, changing values anything that I know of.
This is one of the class where i created an array to hold my vaules i used a constructor to better story things into the array.
public class Story {
private Page[] pages;
public Story(){
pages = new Page[7];
pages[0] = new Page(R.drawable.page0,
R.string.page0,
new Choice(R.string.page0_choice1,1),
new Choice(R.string.page0_choice2,2));
pages[1] = new Page(R.drawable.page1,
R.string.page1,
new Choice(R.string.page1_choice1, 3),
new Choice(R.string.page1_choice2, 4));
pages[2] = new Page(R.drawable.page2,
R.string.page2,
new Choice(R.string.page2_choice1, 4),
new Choice(R.string.page2_choice2, 6));
pages[3] = new Page(R.drawable.page3,
R.string.page3,
new Choice(R.string.page3_choice1, 4),
new Choice(R.string.page3_choice2, 5));
pages[4] = new Page(R.drawable.page4,
R.string.page4,
new Choice(R.string.page4_choice1, 5),
new Choice(R.string.page4_choice2, 6));
pages[5] = new Page(R.drawable.page5, R.string.page5);
pages[6] = new Page(R.drawable.page6, R.string.page6);
}
public Page getPage(int pageNumber) {
if(pageNumber >= pages.length) {
pageNumber = 0;
}
return pages[pageNumber];
This is another class withing my code that seems to be where my error is coming from I have tried messing with this class the most.
public class StoryActivity extends AppCompatActivity {
public static final String TAG = StoryActivity.class.getSimpleName();
private Story story;
public ImageView storyImageView;
private TextView storyTextView;
private Button choice1Button;
private Button choice2Button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
storyImageView = (ImageView)findViewById(R.id.storyImageView);
storyTextView = (TextView)findViewById(R.id.storyTextView);
choice1Button = (Button)findViewById(R.id.choice1Button);
choice2Button = (Button)findViewById(R.id.choice2Button);
// get the intent used to start this activity
Intent intent = getIntent();
String name = intent.getStringExtra(getString(R.string.key_name));
if (name == null || name.isEmpty()) {
name = "Friend";
}
Log.d(TAG, name);
story = new Story();
loadPage(0);
}
private void loadPage(int pageNumber) {
Page page = story.getPage(pageNumber);
Drawable image = ContextCompat.getDrawable(this, page.getImageId());
storyImageView.setImageDrawable(image);
}
}
I expect the app to be able to press the next button without crashing the message i get from the crash log is.
2019-07-25 00:02:39.729 4655-4655/com.thomas.interactivestory E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.thomas.interactivestory, PID: 4655
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.thomas.interactivestory/com.thomas.interactivestory.ui.StoryActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageDrawable(android.graphics.drawable.Drawable)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageDrawable(android.graphics.drawable.Drawable)' on a null object reference
at com.thomas.interactivestory.ui.StoryActivity.loadPage(StoryActivity.java:58)
at com.thomas.interactivestory.ui.StoryActivity.onCreate(StoryActivity.java:49)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Here is my activity_Main.xml file hopefully this help
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:background="@android:color/white"
tools:context="com.thomas.interactivestory.ui.MainActivity">
<ImageView
android:id="@+id/titleImageView"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:contentDescription="@string/signals_from_mars_title_image"
android:cropToPadding="true"
android:scaleType="fitXY"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
android:layout_marginTop="0dp"
app:srcCompat="@drawable/main_title" />
<Button
android:id="@+id/StartButton"
android:layout_width="0dp"
android:layout_marginBottom="0dp"
android:layout_marginLeft="0dp"
android:layout_marginRight="0dp"
android:layout_height="wrap_content"
android:background="@android:color/white"
android:text="@string/start_your_adventure"
android:textColor="#2A8AEC"
android:textSize="16sp"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<EditText
android:id="@+id/NameEditText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginBottom="0dp"
android:layout_marginLeft="0dp"
android:layout_marginRight="0dp"
android:includeFontPadding="true"
android:ems="10"
android:hint="@string/enter_your_name"
android:inputType="textPersonName|textCapWords"
android:maxLength="30"
app:layout_constraintBottom_toTopOf="@+id/StartButton"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
Bartek Lipinski :
Your activity_main.xml is missing storyImageView.