Question

我可以找到很多关于如何在BaseAdapter类中使用ArrayList来填充GridView的例子，但我遇到了困难传递正确的值。当我只是使用光标位置时，这工作正常，但我需要使用现在是ArrayList。据我所知，解决方案在于正确填充getItem和getItemID。哪里出错 - 有人可以帮忙吗？相关代码如下：

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

allImages = Images.Media.EXTERNAL_CONTENT_URI;
ArrayList<String> imageCollection = new ArrayList<String>();

String[] projection = {
      MediaStore.Images.Media._ID,
      MediaStore.Images.Media.DATA
};
getCursor = getContentResolver().query(
      allImages,
      projection,
      null,
      null,
      null
);
columnIndex = getCursor.getColumnIndexOrThrow(projection[0]);  //-- ID number.
arrayIndex  = getCursor.getColumnIndexOrThrow(projection[1]);  //-- Filepath.
imageCollection.add(String.valueOf(columnIndex));

GridView gridView = (GridView) findViewById(R.id.gridview);
gridView.setAdapter(new ImageAdapter(this, imageCollection));
}  //---End of OnCreate --

public class ImageAdapter extends BaseAdapter {
    private Context context;
    private int colCount;
    private ArrayList<String> tempCollection;

    public ImageAdapter(Context c, ArrayList<String> anyCollection) {
        context = c;
        tempCollection = anyCollection;
        colCount = tempCollection.size();
    }
    //---Returns the number of images---
    public int getCount() {
        return colCount;
    }
    //---Returns the item---
    public Object getItem(int position) {
        return tempCollection.get(position);

    }
    //---Returns the ID of one item. 
    public long getItemId(int position) {
        return position;
    } 

public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView;
    if (convertView == null) {  //---If it's not recycled, initialize some attributes --
        imageView = new ImageView(context);
    } else {
        imageView = (ImageView) convertView;
    }
    String imageID  = String.valueOf(position);  //--- FAILS: always 0, causing FileNotFound Exception below.!!!
    imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
    imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
    imageView.setPadding(5,5,5,5);
    imageView.setCropToPadding(true);
    imageView.setImageURI(                //--- Now create each individual display image --
        Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, imageID)
    );
    return imageView;
} //---End of ImageAdapter class--

Answer 1

在活动中，使用下面的代码将ImageId保存到ArrayList。

if (getCursor != null) {
    while (getCursor.moveToNext()) {
      columnIndex = getCursor.getColumnIndexOrThrow(projection[0]);  
      imageCollection.add(String.valueOf(getCursor.getLong(columnIndex));
    }
 }

在ImageAdapter中，使用getView方法，使用以下代码获取ImageId：

String imageID  = tempCollection.get(position);

从Adapter到GridView提取ArrayList值

1 个答案: