Java 从SD卡获取图像并在Gridview中显示

我正在尝试从SD卡获取所有图像，并将它们显示在gridview中（包含在片段中）。然而，尽管没有抛出异常，gridview中没有显示任何内容，只是一个普通的黑屏。我不确定问题出在哪里，是视图绑定还是将数据提取到游标中。这是片段的当前代码：

public class PhotoGridFragment extends Fragment implements LoaderManager.LoaderCallbacks<Cursor> {

// member variables for
private static final int PHOTO_LIST_LOADER = 0x01;
private ImageCursorAdapter adapter;
private Cursor c;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getLoaderManager().initLoader(PHOTO_LIST_LOADER, null, this);

    adapter = new ImageCursorAdapter(getActivity().getApplicationContext(), c);
}

/* R.layout.grid_item,
null, new String[] { MediaStore.Images.Thumbnails.DATA }, new int[] {R.id.grid_item},
CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER); */

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.photo_item, container, false);     
}


// Loader manager methods
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    String[] projection = { MediaStore.Images.Thumbnails._ID, MediaStore.Images.Thumbnails.DATA };
    CursorLoader cursorLoader = new CursorLoader(getActivity(),
            MediaStore.Images.Media.EXTERNAL_CONTENT_URI, projection,
            null, null, null);
    return cursorLoader;
}

public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
    adapter.swapCursor(cursor);

}

public void onLoaderReset(Loader<Cursor> cursor) {
    adapter.swapCursor(null);
}

private class ImageCursorAdapter extends CursorAdapter {

    private LayoutInflater mLayoutInflater;
    private Context mContext;

    public ImageCursorAdapter(Context context, Cursor c) {
        super(context, c);
        mContext = context;
        mLayoutInflater = LayoutInflater.from(context);
    }

    @Override
    public void bindView(View view, Context context, Cursor cursor) {
        ImageView newView = (ImageView) view.findViewById(R.layout.grid_item);
        String imagePath = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID));
        if (imagePath != null && imagePath.length() != 0 && newView != null) {
            newView.setVisibility(ImageView.VISIBLE);
        }
    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        View v = mLayoutInflater.inflate(R.layout.grid_item, parent, false);
        return v;
    }


}

公共类PhotoGridFragment扩展片段实现LoaderManager.LoaderCallbacks{
//的成员变量
私有静态最终int照片列表加载程序=0x01；
专用映像游标适配器；
专用游标c；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
getLoaderManager（）.initLoader（照片列表加载器，null，this）；
适配器=新的ImageCursorAdapter（getActivity（）.getApplicationContext（），c）；
}
/*R.layout.grid_项目，
null，新字符串[]{MediaStore.Images.Thumbnails.DATA}，新int[]{R.id.grid_item}，
游标适配器。标志（寄存器、内容、观察者）*/
@凌驾
CreateView上的公共视图（布局、充气机、视图组容器、捆绑包保存状态）{
返回充气机。充气（R.layout.photo_项目，容器，假）；
}
//装载机管理器方法
公共加载器onCreateLoader（int-id，Bundle-args）{
String[]projection={MediaStore.Images.Thumbnails.\u ID，MediaStore.Images.Thumbnails.DATA}；
CursorLoader CursorLoader=新的CursorLoader（getActivity（），
MediaStore.Images.Media.EXTERNAL\u CONTENT\u URI，投影，
空，空，空）；
返回游标装入器；
}
public void onLoadFinished（加载器，光标）{
适配器.swapCursor（游标）；
}
公共void onLoaderReset（加载器光标）{
适配器.swapCursor（空）；
}
私有类ImageCursorAdapter扩展了CursorAdapter{
私人停车场平面布置；
私有上下文；
公共图像游标适配器（上下文，游标c）{
超级（上下文，c）；
mContext=上下文；
mLayoutInflater=LayoutInflater.from（上下文）；
}
@凌驾
公共void bindView（视图、上下文上下文、光标）{
ImageView newView=（ImageView）view.findViewById（R.layout.grid_项）；
String imagePath=cursor.getString（cursor.getColumnIndexOrThrow（MediaStore.Images.Thumbnails._ID））；
if（imagePath！=null&&imagePath.length（）！=0&&newView！=null）{
设置可见性（ImageView.VISIBLE）；
}
}
@凌驾
公共视图newView（上下文上下文、光标、视图组父对象）{
视图v=MLAYOUTINGER.充气（R.layout.grid_项，父项，false）；
返回v；
}
}

项目的布局文件如下所示：

photo_item.xml：

<?xml version="1.0" encoding="UTF-8"?>
<GridView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/photo_item"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="24dp"
android:padding="6dp" />

<?xml version="1.0" encoding="utf-8"?>
<ImageView
 xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/grid_item"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="24dp"
android:padding="6dp"

/>

grid_item.xml：

<?xml version="1.0" encoding="UTF-8"?>
<GridView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/photo_item"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="24dp"
android:padding="6dp" />

<?xml version="1.0" encoding="utf-8"?>
<ImageView
 xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/grid_item"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="24dp"
android:padding="6dp"

/>

---

在bindView中，您实际上没有将imageView的可绘制设置为任何内容。您获取一个图像路径，验证它是否为真实路径，然后忽略它：）使用该路径获取可绘制的图像！然后将imageView的可绘制设置为该图像。

尝试以下代码

sdcard.java

public class Sdcard extends Activity {

//  Cursor used to access the results from querying for images on the SD card.

private Cursor cursor;

 // Column index for the Thumbnails Image IDs.

private int columnIndex;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sdcard);

    // Set up an array of the Thumbnail Image ID column we want
    String[] projection = {MediaStore.Images.Thumbnails._ID};
    // Create the cursor pointing to the SDCard
    cursor = managedQuery( MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI,
            projection, // Which columns to return
            null,       // Return all rows
            null,
            MediaStore.Images.Thumbnails.IMAGE_ID);
    // Get the column index of the Thumbnails Image ID
    columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);

    GridView sdcardImages = (GridView) findViewById(R.id.gridView1);
    sdcardImages.setAdapter(new ImageAdapter(this));


}

private class ImageAdapter extends BaseAdapter {

    private Context context;

    public ImageAdapter(Context localContext) {
        context = localContext;
    }

    public int getCount() {
        return cursor.getCount();
    }
    public Object getItem(int position) {
        return position;
    }
    public long getItemId(int position) {
        return position;
    }
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView picturesView;
        if (convertView == null) {
            picturesView = new ImageView(context);
            // Move cursor to current position
            cursor.moveToPosition(position);
            // Get the current value for the requested column
            int imageID = cursor.getInt(columnIndex);
            // Set the content of the image based on the provided URI
            picturesView.setImageURI(Uri.withAppendedPath(
                    MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID));
            picturesView.setScaleType(ImageView.ScaleType.FIT_XY);
            picturesView.setPadding(10, 10, 10, 10);
            picturesView.setLayoutParams(new GridView.LayoutParams(100, 100));
        }
        else {
            picturesView = (ImageView)convertView;
        }
        return picturesView;
    }
}

}