我最近使用我使用媒体查询和媒体库设计的自定义图库对显示图片进行了一些测试…它工作得很好,但我真的需要做一些自定义的事情.
我不希望在媒体商店中扫描或提供图片,因此我希望我的应用扫描目录并创建缩略图并显示这些缩略图.
我发现它真的很薄,找到任何高质量的例子来做到这一点.
任何人都可以帮助一个小例子.
这是我想要做的.
>图片存储在SD卡的目录中.
>使用我的自定义图库,它将扫描此目录,但“不”使用媒体库
>我需要显示目录的内容,但作为缩略图我假设我需要先创建这个缩略图？
>点击一个thumnail将是我的自定义图库中的全屏图像.
我想我只需要一些帮助就可以从目录中获取图片,因为我没有存储整个媒体库,所以我无法使用查询.另一件令我担心的事情是,我需要为这些图像中的每一个创建缩略图(在运行中？)因为显示图像但是尺寸减小我会怀疑性能会非常糟糕.
任何人都可以伸出援助之手吗？
提前致谢
最佳答案 我前一段时间做的完全相同.您必须将图像所在的文件夹名称传递给setBaseFolder.这个方法反过来调用refresh() – 使用FilenameFilter(代码不包括但很容易实现)从该文件夹获取名为orig _…. jpg的所有图像并将其保存在mFileList中.然后我们调用notifyDataSetChanged(),然后调用每个单元格的getView().
现在,在getView()中我们要么从缓存中获取一个缩略图位图,如果我们已经有了它,否则我们制作一个灰色占位符并启动ThumbnailBuilder来创建缩略图.从中获取位图.
我认为你必须稍微更改ThumbnailBuilder,因为我创建了相当大的“缩略图”(500×500),因为我还需要调整大小的图像用于其他目的.此外,当我处理相机拍摄的照片时,有一些东西,根据exif信息旋转图像.但基本上,ThumbnailBuilder只是检查是否已经有缩略图(我的缩略图图像放在同一个文件夹中,但前缀是small_而不是orig_) – 如果缩略图已经存在,我们将其作为Bitmap并完成,否则图像生成.最后,在onPostExecute()中,位图设置为ImageView.
public class PhotoAdapter extends BaseAdapter {
private Context mContext;
private int mCellSize;
private File mFolder;
private File[] mFileList;
private Map<Object, Bitmap> mThumbnails = new HashMap<Object, Bitmap>();
private Set<Object> mCreatingTriggered = new HashSet<Object>(); // flag that creating already triggered
public PhotoAdapter(Context context, int cellSize) {
mContext = context;
mCellSize = cellSize;
}
@Override
public int getCount() {
if (mFolder == null) {
return 0; // don't do this
} else {
return mFileList.length;
}
}
@Override
public Object getItem(int position) {
return mFileList[position];
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView view = (ImageView)convertView;
if (view == null) {
view = new ImageView(mContext);
view.setLayoutParams(new GridView.LayoutParams(mCellSize, mCellSize));
view.setScaleType(ImageView.ScaleType.CENTER_CROP);
view.setPadding(8, 8, 8, 8);
view.setBackgroundColor(0xFFC6CCD3);
}
Object item = getItem(position);
Bitmap bm = mThumbnails.get(item);
if (bm == null) {
view.setImageBitmap(null);
if (!mCreatingTriggered.contains(item)) {
mCreatingTriggered.add(item);
new ThumbnailBuilder(view, (File)item).execute();
}
} else {
view.setImageBitmap(bm);
}
return view;
}
public void setBaseFolder(File baseFolder) {
if (baseFolder == null) return;
if (!baseFolder.equals(mFolder)) {
releaseThumbnails();
mFolder = baseFolder;
}
refresh();
}
public void refresh() {
if (mFolder == null) {
return;
}
mFileList = mFolder.listFiles(EtbApplication.origImageFilenameFilter);
if (mFileList == null) mFileList = new File[0];
notifyDataSetChanged();
}
public void releaseThumbnails() {
for (Bitmap bm : mThumbnails.values()) {
bm.recycle();
}
mThumbnails.clear();
}
// ------------------------------------------------------------------------------------ Asynchronous Thumbnail builder
private class ThumbnailBuilder extends AsyncTask<Void, Integer, Bitmap> {
private ImageView mView;
private File mFile;
public ThumbnailBuilder(ImageView view, File file) {
mView = view;
mFile = file;
}
@Override
protected Bitmap doInBackground(Void... params) {
Log.d("adapter", "make small image and thumbnail");
try {
return createThumbnail(mFile.getAbsolutePath());
} catch (Exception e) {
return null;
}
}
@Override
protected void onPostExecute(Bitmap result) {
if (result != null) {
mView.setImageBitmap(result);
mThumbnails.put(mFile, result);
} else {
mView.setImageResource(R.drawable.ic_launcher);
}
}
/**
* Creates Thumbnail (also rotates according to exif-info)
* @param file
* @return
* @throws IOException
*/
private Bitmap createThumbnail(String file) throws IOException {
File thumbnailFile = new File(file.replace("orig_", "small_"));
// If a small image version already exists, just load it and be done.
if (thumbnailFile.exists()) {
return BitmapFactory.decodeFile(thumbnailFile.getAbsolutePath());
}
// Decode image size
BitmapFactory.Options bounds = new BitmapFactory.Options();
bounds.inJustDecodeBounds = true;
BitmapFactory.decodeFile(file, bounds);
if ((bounds.outWidth == -1) || (bounds.outHeight == -1))
return null;
int w, h;
if (bounds.outWidth > bounds.outHeight) { // Querformat
w = 500;
h = 500 * bounds.outHeight / bounds.outWidth;
} else { // Hochformat
h = 500;
w = 500 * bounds.outWidth / bounds.outHeight;
}
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inSampleSize = 4; // resample -- kleiner aber noch nicht die 500 Pixel, die kommen dann unten
Bitmap resizedBitmap = BitmapFactory.decodeFile(file, opts);
resizedBitmap = Bitmap.createScaledBitmap(resizedBitmap, w, h, true);
ExifInterface exif = new ExifInterface(file);
String orientString = exif.getAttribute(ExifInterface.TAG_ORIENTATION);
int orientation = orientString != null ? Integer.parseInt(orientString) : ExifInterface.ORIENTATION_NORMAL;
int rotationAngle = 0;
if (orientation == ExifInterface.ORIENTATION_ROTATE_90) rotationAngle = 90;
if (orientation == ExifInterface.ORIENTATION_ROTATE_180) rotationAngle = 180;
if (orientation == ExifInterface.ORIENTATION_ROTATE_270) rotationAngle = 270;
Matrix matrix = new Matrix();
matrix.setRotate(rotationAngle, (float) resizedBitmap.getWidth() / 2, (float) resizedBitmap.getHeight() / 2);
Bitmap rotatedBitmap = Bitmap.createBitmap(resizedBitmap, 0, 0, w, h, matrix, true);
resizedBitmap.recycle();
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
rotatedBitmap.compress(Bitmap.CompressFormat.JPEG, 90, bytes);
thumbnailFile.createNewFile();
FileOutputStream fo = new FileOutputStream(thumbnailFile);
fo.write(bytes.toByteArray());
fo.close();
//new File(file).delete(); // Originalbild löschen
return rotatedBitmap;
}
}
}
