Question

我试图从外部SD card内的特定文件夹中获取图片，并尝试在运行应用时将其显示在列表中。没有提供错误，没有任何反应。只是一个空白页面的任何建议。

我正在获取带扩展名的图像列表，但我如何查看图像！

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


        File file = new File("/sdcard/external_sd/folder_name/");

        File imageList[] = file.listFiles();
        ArrayList<Bitmap> images = new ArrayList<Bitmap>();
        for(int i=0;i<imageList.length;i++)
        {
            Log.e("Image: "+i+": path", imageList[i].getAbsolutePath());

            Bitmap b = BitmapFactory.decodeFile(imageList[i].getAbsolutePath());

            images.add(b);

        }
         setListAdapter(new ArrayAdapter(this,
                android.R.layout.simple_list_item_1,imageList));
    }

Answer 1

如果您使用代码加载图片，则会遇到OutOfMemory异常。尝试使用以下方法正确加载图像。之后，您可以填充ListView。

private static final int IMG_BUFFER_LEN = 16384;
// R.drawable.ic_default - default drawable resource, if we cannot load drawable from provided file
// R.dimen.list_icon_size - size in dp of ImageView inside of ListView (for example, 40dp)

private Drawable extractMediaIcon(String filePath) {
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(filePath, options);
    if (options.outWidth < 0 || options.outHeight < 0 || (options.outWidth * options.outHeight == 0)) {
        return context.getResources().getDrawable(R.drawable.ic_default);
    }

    final int targetHeight = dp2px((int) context.getResources().getDimension(R.dimen.list_icon_size));
    final int targetWidth = targetHeight;

    final boolean isScaleByHeight =
        Math.abs(options.outHeight - targetHeight) >= Math.abs(options.outWidth - targetWidth);

    if (options.outHeight * options.outWidth * 2 >= IMG_BUFFER_LEN) {
        // Load, scaling to smallest power of 2 that'll get it <= desired dimensions
        final double sampleSize = isScaleByHeight
                ? options.outHeight / targetHeight
                : options.outWidth / targetWidth;
        options.inSampleSize =
                (int) Math.pow(2d, Math.floor(
                        Math.log(sampleSize) / Math.log(2d)));
    }

    // Do the actual decoding
    options.inJustDecodeBounds = false;
    options.inTempStorage = new byte[IMG_BUFFER_LEN];

    Bitmap bitmap = BitmapFactory.decodeFile(filePath, options);
    if (bitmap == null) {
        return context.getResources().getDrawable(R.drawable.ic_default);
    }

    final double imageFactor = (double) bitmap.getWidth() / bitmap.getHeight();
    final double targetFactor = (double) targetWidth / targetHeight;

    bitmap = Bitmap.createScaledBitmap(
            bitmap,
            targetFactor > imageFactor ? bitmap.getWidth() * targetHeight / bitmap.getHeight() : targetWidth,
            targetFactor > imageFactor ? targetHeight : bitmap.getHeight() * targetWidth / bitmap.getWidth(),
            false);

    return new BitmapDrawable(context.getResources(), bitmap);
}

从外部SD卡文件夹获取图像并将其显示在列表中

1 个答案: