android - 从 SD 卡中获取多个图像以显示在 Coverflow 中

Question

如何让多个图像显示在此封面流中。我收到空指针异常和其他问题。如何在不知道 SD 卡上有多少图像的情况下从 SD 卡加载图像？图片数量不固定。通过使用此代码，我能够毫无问题地显示一张图片:

i.setImageBitmap(BitmapFactory.decodeFile("/mnt/sdcard/pic03.png"));

它加载了一张图片，一张从 SD 卡指定的图片，并将所有 coverflow 图像制作为同一张图片，pic03.png，大约一打相同的图片填充了 coverflow。太好了，但是我想加载 SD 卡上的所有图像。所以每张图片都填满了 coverflow 的每个部分，而不是一张相同的图片填满了所有部分。

完全迷失在这里并尝试这样做并从 Logcat 得到空指针异常并且想知道为什么？有谁知道如何让它工作？

下面是我正在使用的代码，可以给你一些想法: 请注意，当从 SD 卡上的指定地址加载一张图像时它确实有效。至少那部分效果很好，但是多张图片？

// added this code inside the onCreate method to load the cursor with images only if the IS_PRIVATE column
// in the sqlite database is equal to the integer 1 

String[] img = { MediaStore.Images.Media._ID };
imagecursor = managedQuery(
MediaStore.Images.Media.EXTERNAL_CONTENT_URI, img,
MediaStore.Images.Media.IS_PRIVATE + "='" + 1 +"'",null, MediaStore.Images.Media._ID + "");
image_column_index = imagecursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);
count = imagecursor.getCount();

//-------------------------------------------------------------------
// ImageAdapter class is a nested class inside of the CoverFlowExample class

public class ImageAdapter extends BaseAdapter {
int mGalleryItemBackground;
private Context mContext;
private FileInputStream fis;

// originally earlier version of this app loaded images from the R.drawable folder like this

private Integer[] mImageIds = {

  //  R.drawable.pic01,
  //  R.drawable.pic02,
  //  R.drawable.pic03,
  //  R.drawable.pic04,
  //  R.drawable.pic05,
  //  R.drawable.pic06,
  //  R.drawable.pic07,
  //  R.drawable.pic08,
  //  R.drawable.pic09
};

//---------------------------------------------------------------------
// getView() method that is in the ImageAdapter class that extends the BaseAdapter class
// this class is a nested class inside the CoverFlowExample class that extends Activity.
// the CoverFlowExample class is used to implement the coverflow part of the app as an Activity

public View getView(int position, View convertView, ViewGroup parent) {
  // to load from resources like SD card
  ImageView i = new ImageView(mContext);

 // use for single image -->  i.setImageBitmap(BitmapFactory.decodeFile("/mnt/sdcard/pic03.png"));

 image_column_index = imagecursor.getColumnIndexOrThrowMediaStore.Images.Media.DATA);
 imagecursor.moveToPosition(position);

 int id = imagecursor.getInt(image_column_index);
 i.setImageURIUri.withAppendedPathMediaStore         .Images.Media.EXTERNAL_CONTENT_URI, ""+ id));

 // image from R.drawable use -->  i.setImageResource(mImageIds[position]);
 i.setLayoutParams(new CoverFlow.LayoutParams(130, 130));
 i.setScaleType(ImageView.ScaleType.MATRIX);            
 return i;

  // return mImages[position];  <-- not using this as im am not getting image from R.drawable
}

Answer 1

问题似乎是 String[] img = { MediaStore.Images.Media._ID } 这是 imagecursor 中包含的唯一列，而您尝试获取 DATA 列，imagecursor.getColumnIndexOrThrowMediaStore.Images.Media.DATA)