Question

Currently I am looking at http://developer.android.com/resources/tutorials/views/hello-gridview.html
I created test project with additional logs in onCreate(), onResume and getView():

HelloGridViewActivity.java

package com.hello.namespace;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.Toast;

public class HelloGridViewActivity extends Activity {
    private static final String TAG = "HelloGridViewActivity";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        GridView gridview = (GridView) findViewById(R.id.gridview);
        gridview.setAdapter(new ImageAdapter(this));

        gridview.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                Toast.makeText(HelloGridViewActivity.this, "" + position, Toast.LENGTH_SHORT).show();
            }
        });

        Log.e(TAG, "onCreate()");
    }

    protected void onResume() {
        super.onResume();

        Log.e(TAG, "onResume()");
    }
}

ImageAdapter.java

package com.hello.namespace;

import android.content.Context;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class ImageAdapter extends BaseAdapter {
    private static final String TAG = "ImageAdapter";
    private Context mContext;

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return mThumbIds.length;
    }

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

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

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {  // if it's not recycled, initialize some attributes
            Log.e(TAG, "position = " + position);
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }

        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }

    // references to our images
    private Integer[] mThumbIds = {
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7
    };

}

The log output:

05-23 08:59:13.541: E/HelloGridViewActivity(733): onCreate()
05-23 08:59:13.551: E/HelloGridViewActivity(733): onResume()
05-23 08:59:13.711: E/ImageAdapter(733): position = 0
05-23 08:59:14.380: E/ImageAdapter(733): position = 1
05-23 08:59:15.190: E/ImageAdapter(733): position = 2
05-23 08:59:15.771: E/ImageAdapter(733): position = 3
05-23 08:59:16.340: E/ImageAdapter(733): position = 4
05-23 08:59:17.141: E/ImageAdapter(733): position = 5
05-23 08:59:17.721: E/ImageAdapter(733): position = 6
05-23 08:59:18.330: E/ImageAdapter(733): position = 7
05-23 08:59:18.611: E/ImageAdapter(733): position = 8
05-23 08:59:18.631: E/ImageAdapter(733): position = 9
05-23 08:59:18.631: E/ImageAdapter(733): position = 10
05-23 08:59:18.651: E/ImageAdapter(733): position = 11
05-23 08:59:18.651: E/ImageAdapter(733): position = 12
05-23 08:59:18.671: E/ImageAdapter(733): position = 13
05-23 08:59:18.681: E/ImageAdapter(733): position = 14
05-23 08:59:18.691: E/ImageAdapter(733): position = 15
05-23 08:59:18.701: E/ImageAdapter(733): position = 16
05-23 08:59:18.721: E/ImageAdapter(733): position = 17
05-23 08:59:18.721: E/ImageAdapter(733): position = 18
05-23 08:59:18.741: E/ImageAdapter(733): position = 19
05-23 08:59:18.741: E/ImageAdapter(733): position = 20
05-23 08:59:18.891: E/ImageAdapter(733): position = 0

And here are two questions:

1. Why ImageView at position 0 was created twice?

2. Let’s say I want to do something with ImageViews. I’d create ImageView array, initialize its elements in getView(), but I would not be able to use it in onCreate() or even in onResume(), because ImageViews don’t exist yet! What should I do?

Sorry for my English.

Answer 1

1: I assume that you scroll around your List to get this Log (because getView is called only if the View is visible), so its likely that you just scrolled up again, and View at pos 0 was scrolled on top out and is coming from top again…

2: Depends on WHY you want to have your Views in onCreate or onResume. If there is no other solution and you MUST have them, you could simply create all Views yourself in onCreate save them inside a List and just return it in getView. I would try to avoid this, because the ListView instatiates Views ONLY if there are Visible and reuses them. You’ll loose this feature in the implementation I described, so please tell us, WHY you wanna have it in before getView