Conflicting Android error messages: The specified child already has a parent. You must call removeView() on the child's parent first

Question

Originally I got this error:

The specified child already has a parent. You must call removeView() on the child's parent first

at

customSection.addView(customLayout);

So I added

((LinearLayout)customLayout.getParent()).removeView(customLayout);

and now get

java.lang.NullPointerException

So if the child has a parent, and I must first remove the child from the parent, why does getParent() return null?

I have an abstract fragment that allows derived classes to supply a custom layout for the list adapter. Relevant code:

Binding:

public void bind(DataObject row) {
    View customLayout = getChildItemView(row);
    if (customLayout != null) {
        ((LinearLayout) customLayout.getParent()).removeView(customLayout);
        customSection.removeAllViews();
        customSection.addView(customLayout);
        customSection.setVisibility(View.VISIBLE);
    } else {
        customLayout.setVisibility(View.INVISIBLE);
    }

}

protected View getChildItemView(CommonRow row) {
    if (parentView == null) {
        parentView = (LinearLayout) LayoutInflater.from(getActivity())
                .inflate(R.layout.list_item_custom_section,
                        new LinearLayout(getActivity()), true);
        label = (TextView) parentView.findViewById(R.id.txtData1Label);
        value = (TextView) parentView.findViewById(R.id.txtData1Value);
    }
    label.setText("Minimum");
    value.setText(manager.formatMoney(((SpecificDataRow) row).minimum));
    return parentView;
}

I've also tried inflater.inflate(R.layout.list_item_custom_section, null) ... false, null / false, what gives?

EDIT:

@allprog, I knew some cleanup was needed. I wrote this at the end of the day somewhat in a hurry. I have since cleaned up the code, and separated out the binding and inflating of the view. Cleaned up code:

private class ViewHolder {
....

       public ViewHolder(View v) {
            Butterknife.inject(this, v);
            View custom = createCustomView(customSection);
            if (custom != null) {
                customSection.setVisibility(View.VISIBLE);
                customSection.addView(custom);
            }
        }

        public void bind(CommonRow row) {
            ......

            bindCustomView(row, customSection);
        }

}

Child class:

    @Override
    protected View createCustomView(ViewGroup parent) {
        return LayoutInflater.from(getActivity()).inflate(R.layout.list_item_custom_section, parent, false);
    }


    @Override
    protected void bindCustomView(CommonRow row, ViewGroup section) {
        TextView label = Views.findById(section, R.id.txtData1Label);
        TextView value = Views.findById(section, R.id.txtData1Value);

        label.setText("Minimum");
        value.setText(manager.formatMoney(((SpecificRow) row).minimum));
    }

suitianshi got it first, with my original [unkempt] code that was the solution.

Solution 1

try this:

public void bind(DataObject row) {
    View customLayout = getChildItemView(row);
    if (customLayout != null) {
         if(customLayout.getParent() != null) {
             ((LinearLayout)customLayout.getParent()).removeView(customLayout);
         }

         customSection.removeAllViews();
         customSection.addView(customLayout);
         customSection.setVisibility(View.VISIBLE);
    } else {
         customLayout.setVisibility(View.INVISIBLE);
    }

}

I have read related source code, getParent should return non-null value when view has a parent. You should make sure it actually has a parent before casting and calling removeView

Wish this helps.

source code :

in View :

public final ViewParent getParent() {
        return mParent;
    }

in ViewGroup.addViewInner

if (child.getParent() != null) {
     throw new IllegalStateException("The specified child already has a parent. " +
         "You must call removeView() on the child's parent first.");
}

Solution 2

As I can see your parentView is a field variable, this is the key. So what I suspect is really going on:

First call of bind(): you creating parentView and it is not have a parent yet, customSection.addView(customLayout); works fine, but after you added a check for parent it fails here.

Second call of bind(): parentView is now have a parent and your added check should work now, but you failed at the previous step. Without a check you are failing here with exception in title.

Solution: check for the presence of parent and remove it only if necessery.

Comments

[Jack]

I understand that part, the problem is that customSection.addView(customLayout) fails with the error in OP title. So I can check for null all day but it still does not help me remove the customLayout from its original, [apparantly null] parent. Does not make sense to me.

[suitianshi]

added source code to my answer. You mean you get that exception but getParent reuturns null? that's really strange!

[suitianshi]

and did you try casting ViewParent to ViewGroup instead of LinearLayout ?

[Krylez]

All of the addView methods in ViewGroup eventually go through addViewInner(). This is where the IllegalStateException comes from. If getParent() returns null, this never gets thrown in the first place. Are you absolutely sure you're not accidentally adding the same view to the same parent more than once? android.googlesource.com/platform/frameworks/base/+/refs/hea‌​ds/…