包含checkedtextview的自定义Listview

Question

I implement custom listview containing a checked textview. My wish is to change the state of the checkbox on click, but it seems not to be simple, as I thought it would be. Additionally I would like to check the checkboxes of items, that are stored in database, how could it be done? At the moment I have an activity which shows the elements, handles the click on the checkbox (not the list item!), but can´t change the checkbox status by items stored in database.

This is my custom list item:

<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="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="5dp">

    <CheckedTextView
            android:id="@+id/name"
            android:layout_width="409dp"
            android:layout_height="30dp"
            android:checkMark="?android:attr/listChoiceIndicatorMultiple"
            android:paddingStart="5dp"
            android:textSize="20sp"
            android:textStyle="bold"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    <TextView
            android:id="@+id/type"
            android:layout_width="409dp"
            android:layout_height="34dp"
            android:paddingStart="5dp"
            android:textSize="18sp"
            android:textStyle="italic"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/name" />

</androidx.constraintlayout.widget.ConstraintLayout>

This is my adapter:

public class CustomAdapter extends BaseAdapter
{
    private List<CustomElement> elems;
    private LayoutInflater inflater;

    public HueBulbAdapter(Context ctx, List<CustomElement> elems)
    {
        this.elems = elems;
        inflater = LayoutInflater.from(ctx);
    }

    @Override
    public int getCount()
    {
        return elems.size();
    }

    @Override
    public Object getItem(int position)
    {
        return null;
    }

    @Override
    public long getItemId(int position)
    {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        ConstraintLayout result = (ConstraintLayout) inflater.inflate(R.layout.custom_elems, parent, false);
        CheckedTextView name = result.findViewById(R.id.name);
        TextView type = result.findViewById(R.id.type);
        CustomElement elem = elems.get(position);
        name.setText(elem.getName());
        type.setText(elem.getType());
        result.setTag(position);
        toggle(name);
        return result;
    }

    private void toggle(CheckedTextView ctv) {
        ctv.setOnClickListener(v -> {
            ctv.setChecked(!ctv.isChecked());
        });
    }
}

And this is my activity:

[...]
elemsView.setOnItemClickListener((parent, view, position, id) ->
        {
            if (!selected.containsKey(elemList.get(position).getName()))
            {
                selected.put(elemList.get(position).getName(), elemList.get(position));
            } else
            {
                selected.remove(elemList.get(position).getName());
            }
        });
[...]

Maybe I am using wrong components to reach my target? Any Ideas how to do it this way or in a better way?

Thanks for your help!

Answer 1

Few suggestions:

1. Add a boolean variable to the CustomElement model to track if item is checked or not checked. Add private boolean isChecked; and generate getter and setter for it.

2. In adapter class, use public Object getItem(int position) to return item in list, and not null . Change to return elems.get(position);

3. In adapter class, replace toggle(name) with:

    name.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { elem.setChecked(!elem.isChecked()); // toggle name.setChecked(elem.isChecked()); } });

4. In your activity class, to access the updated list, use this:

    for (int i = 0; i < mAdapter.getCount(); i++) { CustomElement element = (CustomElement) mAdapter.getItem(i); if (element.isChecked()) {...} else {...} }

5. Optional. Search and implement ViewHolder Pattern in adapter class to improve the loading speed of ListView items.