从SD卡读取网格视图库

Question

I have a grid view that loads all the images from a specific folder into itself. I'm trying to get it so that when a user click an individual image within the grid view it sets an enlarged version of itself within an image view. I think what I need to try and do is when the grid view is created and the images loaded into it, I need to attach an array to both the imageview created holding the image within the gridview and the location of it within the SD card. So when an image is loaded; save location of image and attach it to the imageview within gridview. What I have so far loads the last picture loaded from the SD card into the enlarged image view.

Main.java

public class Main extends Activity{

ImageView photoHolder;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.gallery);


    photoHolder = (ImageView) findViewById(R.id.photoHolderView);
    photoHolder.setVisibility(View.GONE);
    GridView gridView = (GridView) findViewById(R.id.grid_view);
    gridView.setVisibility(View.VISIBLE);
    gridView.setAdapter(new ImageAdapter(this));
    gridView.setOnItemClickListener(new OnItemClickListener() 
    {
        @Override
        public void onItemClick(AdapterView<?> a, View view, int position, long id) {

            photoHolder.setVisibility(View.VISIBLE);
            photoHolder.setImageURI(ImageAdapter.uri);


    }
});
}

}

ImageAdapter.java

public class ImageAdapter extends BaseAdapter {

public static Uri uri;

private Context mContext;
File root = new File(Environment.getExternalStorageDirectory()
        + File.separator + "Custom" + File.separator);
private File[] fileName = root.listFiles();
int count = fileName.length;

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

public int getCount() {
    return fileName.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) {

    uri = Uri.fromFile(fileName[position]);

    ImageView imageView;
    if (convertView == null) { // if it's not recycled, initialize some
                                // attributes
        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.setImageURI(uri);
    return imageView;
}
}

On a side note it crashes quite a lot due to memory leaks, any idea how I would create a "sample/thumbnail" size image whilst loading it from the SD card?

Answer 1

You are right in stating that you need to keep track of the filenane/location for each of the thumbnail. The easiest way would be to amend your getView method and add one line:

imageView.setImageURI(uri);
imageView.setTag(uri);   //new line added
return imageView;

Then, in your onItemClickListener you get the clicked imageview - and get its tag - that will be the filename on the SD card:

public void onItemClick(AdapterView<?> a, View view, int position, long id) {

    photoHolder.setVisibility(View.VISIBLE);
    photoHolder.setImageURI((Uri)view.getTag());
}

As for the memory issue when loading the bitmap, you can use BitmapFactory.Options to indicate the scaling factor - have a look at this page on Android developer website - it contains the sample code you need.