getView（）从未在自定义适配器上调用

Question

I am aware that other people have asked this question, but I have looked at other solutions and still can't get it to work.

Adapter code:

private class CustomTextAndImageAdapter extends ArrayAdapter<String> {
    private Context context;
    private Activity activity;
    private ArrayList<String> timeArrayList;
    private ArrayList<Bitmap> weatherIconArrayList;
    private ArrayList<String> descriptionArrayList;
    private ArrayList<String> tempArrayList;
    private ArrayList<String> popArrayList;
    private ArrayList<String> windSpeedArrayList;

    public final void setTimeArrayList(ArrayList<String> timeArrayList)
    {
        this.timeArrayList = timeArrayList;
    }

    public final void setDescriptionArrayList(ArrayList<String> descriptionArrayList)
    {
        this.descriptionArrayList = descriptionArrayList;
    }

    public final void setTempArrayList(ArrayList<String> tempArrayList)
    {
        this.tempArrayList = tempArrayList;
    }

    public final void setPopArrayList(ArrayList<String> popArrayList)
    {
        this.popArrayList = popArrayList;
    }

    public final void setWindSpeedArrayList(ArrayList<String> windSpeedArrayList)
    {
        this.windSpeedArrayList = windSpeedArrayList;
    }

    public final void setWeatherIconArrayList(ArrayList<Bitmap> weatherIconArrayList)
    {
        this.weatherIconArrayList = weatherIconArrayList;
    }

    public CustomTextAndImageAdapter(Context context, Activity activity, int resource)
    {
        super(context, resource);
        this.context = context;
        this.activity = activity;
    }

    @Override
    public View getView(int position, View view, ViewGroup parent)
    {
        Log.d(Constants.LOG_TAG, "getView() method called");
        LayoutInflater inflater = activity.getLayoutInflater();
        View rowView= inflater.inflate(R.layout.itemlistrow, null, false);

        TextView timeTextView = (TextView)rowView.findViewById(R.id.time);
        timeTextView.setText(timeArrayList.get(position));
        Log.d(Constants.LOG_TAG, "Time text view text = " + timeArrayList.get(position));

        ImageView iconImageView = (ImageView) rowView.findViewById(R.id.weatherIcon);
        iconImageView.setImageBitmap(weatherIconArrayList.get(position));

        TextView descriptionTextView = (TextView)rowView.findViewById(R.id.description);
        descriptionTextView.setText(descriptionArrayList.get(position));

        TextView tempTextView = (TextView)rowView.findViewById(R.id.temp);
        tempTextView.setText(tempArrayList.get(position));

        TextView popTextView = (TextView)rowView.findViewById(R.id.pop);
        popTextView.setText(popArrayList.get(position));

        TextView windSpeedTextView = (TextView)rowView.findViewById(R.id.windSpeed);
        windSpeedTextView.setText(windSpeedArrayList.get(position));

        return rowView;
    }
}

List item layout (itemlistrow.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:weightSum="1">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/time" />

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1">
            <ImageView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id="@+id/weatherIcon"
                />
        </LinearLayout>
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1">
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="Sunny"
                android:id="@+id/description"
                />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="11 C"
                android:id="@+id/temp"
                />
        </LinearLayout>
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1">
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text = "Rain:"
                />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text = "Wind:"
                />
        </LinearLayout>
        <LinearLayout
            android:orientation="vertical"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1">
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:id = "@+id/pop"
                />
            <TextView
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text = "@+id/windSpeed"
                />
        </LinearLayout>
    </LinearLayout>
</LinearLayout>

In some of the other solutions, it mentions overriding getCount(). Is this what I am doing wrong? If so, how would I know what to put in for getCount(), as there are multiple different ArrayLists used. Is it a case of picking one of them, as they are all the same length, eg timeArrayList.size()?

Answer 1

Using multiple ArrayList objects like that kind of defeats the purpose of using an ArrayAdapter , whose idea is to have a single source of items. Not to mention that the code right now doesn't look nice at all.

I'd suggest to first create a Weather object that will hold your data:

public class Weather {
    private String time;
    private Bitmap weatherIcon;
    private String description;
    private String temp;
    private String pop;
    private String windSpeed;

    // build object here, provide getters, etc....
    .....
}

Than your adapter can be transformed to something simpler like this:

private class CustomTextAndImageAdapter extends ArrayAdapter<Weather>
{
    private LayoutInflater inflater;

    public CustomTextAndImageAdapter(Context context, Activity activity, int resource, List<Weather> items)
    {
        super(context, resource, items);
        this.inflater = LayoutInflater.from(context);
    }

    @Override
    public View getView(int position, View view, ViewGroup parent)
    {
        View rowView= inflater.inflate(R.layout.itemlistrow, null, false);

        TextView timeTextView = (TextView)rowView.findViewById(R.id.time);
        timeTextView.setText(getItem(position).getTime());

        ImageView iconImageView = (ImageView) rowView.findViewById(R.id.weatherIcon);
        iconImageView.setImageBitmap(getItem(position).getWeatherIcon());

        ........

        return rowView;
    }
}

Main difference is that it's now an ArrayAdapter<Weather> and that you're passing the arguments directly in the constructor of the adapter. Users of the adapter now have to call just 1 constructor, instead of all the final methods that had to be called before.

The other major difference is that you're passing the items list to the super class. Now your adapter knows it's size (internally getCount() will be == items.size() ) so getView() will be called appropriately.

As a final thought - the adapter is still not using the ViewHolder pattern, which you should totally implement! There's been numerous posts for it, so just search a bit and you'll find it.

Answer 2

This is not a good way to populate a ListView using an adapter which populates the data from multiple ArrayList . Generally we use a single source of dataset to be passed to an adapter in case of showing a list in Android.

So in your case, when you'll call the notifyDatasetChanged it shouldn't take effect in the list properly as far as I can guess.

notifyDatasetChanged basically calls the getCount function of the adapter and checks if the size of the ArrayList associated with the adapter is changed or not. If the size of the ArrayList is changed, it refreshes the ListView and the getView function gets called.

In your case, I don't see any getCount function though. getCount usually returns the size of the ArrayList associated with the adapter.

So I would suggest, using a single ArrayList to be passed to the adapter. You can merge multiple ArrayList and can use one joined HashMap in your case too. Its your decision, exactly how you can pass a single list of your dataset to the adapter to populate them into a ListView .