I am trying to send a nested ArrayList object via Parcelable intent. Name of custom object is 'ExampleItem' which contains nested custom object 'B'. I am sending from MainActivity to Activity2. I get NullPointerException error "Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference". How do i succesfully send via Parcelable?
Main Activity
public class MainActivity extends AppCompatActivity {
private ArrayList<ExampleItem> mExampleList;
private ArrayList<B> mBList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void Press(View view) {
B b = new B("hello");
mBList = new ArrayList<>();
mBList.add(b);
mExampleList = new ArrayList<>();
mExampleList.add(new ExampleItem(R.drawable.ic_launcher_background, "Line 1", "Line 2", mBList));
mExampleList.add(new ExampleItem(R.drawable.ic_launcher_foreground, "Line 3", "Line 4", mBList));
mExampleList.add(new ExampleItem(R.drawable.ic_launcher_foreground, "Line 5", "Line 6", mBList));
Intent intent = new Intent(MainActivity.this, Activity2.class);
intent.putParcelableArrayListExtra("Example Item", mExampleList);
startActivity(intent);
}
}
Activity2
public class Activity2 extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity2);
Intent intent = getIntent();
ArrayList<ExampleItem> exampleItem = intent.getParcelableArrayListExtra("Example Item");
}
}
ExampleItem
public class ExampleItem implements Parcelable {
private int mImageResource;
private String mText1;
private String mText2;
private ArrayList<B> mList;
public ExampleItem(int imageResource, String text1, String text2, ArrayList<B> list) {
mImageResource = imageResource;
mText1 = text1;
mText2 = text2;
mList = list;
}
protected ExampleItem(Parcel in) {
mImageResource = in.readInt();
mText1 = in.readString();
mText2 = in.readString();
in.readList(mList, this.getClass().getClassLoader());
}
public static final Creator<ExampleItem> CREATOR = new Creator<ExampleItem>() {
@Override
public ExampleItem createFromParcel(Parcel in) {
return new ExampleItem(in);
}
@Override
public ExampleItem[] newArray(int size) {
return new ExampleItem[size];
}
};
public int getImageResource() {
return mImageResource;
}
public String getText1() {
return mText1;
}
public String getText2() {
return mText2;
}
public ArrayList<B> getmList() {
return mList;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(mImageResource);
dest.writeString(mText1);
dest.writeString(mText2);
dest.writeList(mList);
}
}
B
public class B implements Parcelable {
public String str;
@Override
public int describeContents() {
// TODO Auto-generated method stub
return 0;
}
public B(String str) {
this.str = str;
}
private B(Parcel in) {
str = in.readString();
}
public static final Parcelable.Creator<B> CREATOR
= new Parcelable.Creator<B>() {
public B createFromParcel(Parcel in) {
return new B(in);
}
public B[] newArray(int size) {
return new B[size];
}
};
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(str);
}
}
Output Log
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.codinginflow.exampleparcelable, PID: 9376
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.codinginflow.exampleparcelable/com.codinginflow.exampleparcelable.Activity2}: java.lang.NullPointerException: Attempt to invoke interface method 'boolean java.util.List.add(java.lang.Object)' 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 interface method 'boolean java.util.List.add(java.lang.Object)' on a null object reference
at android.os.Parcel.readListInternal(Parcel.java:3632)
at android.os.Parcel.readList(Parcel.java:2559)
at com.codinginflow.exampleparcelable.ExampleItem.<init>(ExampleItem.java:26)
at com.codinginflow.exampleparcelable.ExampleItem$1.createFromParcel(ExampleItem.java:32)
at com.codinginflow.exampleparcelable.ExampleItem$1.createFromParcel(ExampleItem.java:29)
at android.os.Parcel.readParcelable(Parcel.java:3281)
at android.os.Parcel.readValue(Parcel.java:3174)
at android.os.Parcel.readListInternal(Parcel.java:3630)
at android.os.Parcel.readArrayList(Parcel.java:2758)
at android.os.Parcel.readValue(Parcel.java:3195)
at android.os.Parcel.readArrayMapInternal(Parcel.java:3567)
at android.os.BaseBundle.initializeFromParcelLocked(BaseBundle.java:292)
at android.os.BaseBundle.unparcel(BaseBundle.java:236)
at android.os.Bundle.getParcelable(Bundle.java:1001)
at android.content.Intent.getParcelableExtra(Intent.java:8276)
at com.codinginflow.exampleparcelable.Activity2.onCreate(Activity2.java:23)
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)
