Android:如何获取所有带照片的文件夹？

Question

我想做一个画廊。我知道如何获取所有照片并在 GridView 中显示它们。但是有人可以解释如何获取和显示文件夹(带照片)吗？

启动我的 apk 文件后出现错误。请查看我的 xml 文件，这里可能有问题？？？ GridView .xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
    <GridView
        android:id="@+id/gridView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="top"
        android:layout_marginBottom="-10dp"
        android:layout_marginLeft="-10dp"
        android:layout_marginRight="-10dp"
        android:layout_marginTop="-10dp"
        android:horizontalSpacing="-15dp"
        android:numColumns="3"
        android:padding="0dp"
        android:verticalSpacing="-15dp" >
    </GridView>
    </LinearLayout>

和grid_item:

<ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:layout_marginRight="2dp"
        android:layout_marginTop="2dp"

        android:gravity="center"
        android:scaleType="center"
         />

Answer 1

编辑: 我已经为您拼凑了一个工作示例。它是这样工作的:

它将在一个目录中开始(在下面的示例中，/storage/sdcard/DCIM/)。如果目录包含任何图像，它们将被显示。如果它包含任何子目录，它将检查它们是否包含图像或它们自己的子目录。如果他们这样做，将显示一个文件夹图标。单击文件夹图标将打开文件夹，并显示其中包含的图像/子目录。

请注意，这只是为了让您大致了解如何实现它——您仍需要对这段代码进行一些处理以提高效率，尤其是在内存使用方面，但我已经在我的模拟器上运行它，代码运行正常。

在您的 Activity 中

public class MainActivity extends Activity implements OnItemClickListener {

    List<GridViewItem> gridItems;


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

        setGridAdapter("/storage/sdcard/DCIM/");
    }


    /**
     * This will create our GridViewItems and set the adapter
     * 
     * @param path
     *            The directory in which to search for images
     */
    private void setGridAdapter(String path) {
        // Create a new grid adapter
        gridItems = createGridItems(path);
        MyGridAdapter adapter = new MyGridAdapter(this, gridItems);

        // Set the grid adapter
        GridView gridView = (GridView) findViewById(R.id.gridView);
        gridView.setAdapter(adapter);

        // Set the onClickListener
        gridView.setOnItemClickListener(this);
    }


    /**
     * Go through the specified directory, and create items to display in our
     * GridView
     */
    private List<GridViewItem> createGridItems(String directoryPath) {
        List<GridViewItem> items = new ArrayList<GridViewItem>();

        // List all the items within the folder.
        File[] files = new File(directoryPath).listFiles(new ImageFileFilter());
        for (File file : files) {

            // Add the directories containing images or sub-directories
            if (file.isDirectory()
                && file.listFiles(new ImageFileFilter()).length > 0) {

                items.add(new GridViewItem(file.getAbsolutePath(), true, null));
            }
            // Add the images
            else {
                Bitmap image = BitmapHelper.decodeBitmapFromFile(file.getAbsolutePath(),
                                                                 50,
                                                                 50);
                items.add(new GridViewItem(file.getAbsolutePath(), false, image));
            }
        }

        return items;
    }


    /**
     * Checks the file to see if it has a compatible extension.
     */
    private boolean isImageFile(String filePath) {
        if (filePath.endsWith(".jpg") || filePath.endsWith(".png"))
        // Add other formats as desired
        {
            return true;
        }
        return false;
    }


    @Override
    public void
            onItemClick(AdapterView<?> parent, View view, int position, long id) {

        if (gridItems.get(position).isDirectory()) {
            setGridAdapter(gridItems.get(position).getPath());
        }
        else {
            // Display the image
        }

    }

    /**
     * This can be used to filter files.
     */
    private class ImageFileFilter implements FileFilter {

        @Override
        public boolean accept(File file) {
            if (file.isDirectory()) {
                return true;
            }
            else if (isImageFile(file.getAbsolutePath())) {
                return true;
            }
            return false;
        }
    }

}

然后你需要创建适配器，它应该扩展 BaseAdapter，看起来像这样。

public class MyGridAdapter extends BaseAdapter {

    LayoutInflater inflater;
    List<GridViewItem> items;


    public MyGridAdapter(Context context, List<GridViewItem> items) {
        this.items = items;
        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }


    @Override
    public int getCount() {
        return items.size();
    }


    @Override
    public Object getItem(int position) {
        return items.get(position);
    }


    @Override
    public long getItemId(int position) {
        return position;
    }


    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null) {
            convertView = inflater.inflate(R.layout.grid_item, null);
        }

        TextView text = (TextView) convertView.findViewById(R.id.textView);
        text.setText(items.get(position).getPath());

        ImageView imageView = (ImageView) convertView.findViewById(R.id.imageView);
        Bitmap image = items.get(position).getImage();

        if (image != null){
            imageView.setImageBitmap(image);
        }
        else {
            // If no image is provided, display a folder icon.
            imageView.setImageResource(R.drawable.your_folder_icon);
        }

        return convertView;
    }

}

并且您需要创建一个代表每个网格项的类

public class GridViewItem {

    private String path;
    private boolean isDirectory;
    private Bitmap image;


    public GridViewItem(String path, boolean isDirectory, Bitmap image) {
        this.path = path;
        this.isDirectory = isDirectory;
        this.image = image;
    }


    public String getPath() {
        return path;
    }


    public boolean isDirectory() {
        return isDirectory;
    }


    public Bitmap getImage() {
        return image;
    }
}

处理图像的类

public abstract class BitmapHelper {

    public static Bitmap decodeBitmapFromFile(String imagePath,
                                              int reqWidth,
                                              int reqHeight) {

        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeFile(imagePath, options);

        // Calculate inSampleSize
        options.inSampleSize = calculateSampleSize(options, reqWidth, reqHeight);

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(imagePath, options);
    }


    private static int calculateSampleSize(BitmapFactory.Options options,
                                           int reqHeight,
                                           int reqWidth) {

        // Raw height and width of image
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;

        if (height > reqHeight || width > reqWidth) {

            final int halfHeight = height / 2;
            final int halfWidth = width / 2;

            // Calculate the largest inSampleSize value that is a power of 2 and
            // keeps both
            // height and width larger than the requested height and width.
            while ((halfHeight / inSampleSize) > reqHeight
                   && (halfWidth / inSampleSize) > reqWidth) {
                inSampleSize *= 2;
            }
        }

        return inSampleSize;

    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/gridView"
    android:numColumns="auto_fit"
    android:gravity="center"
    android:columnWidth="150dp"
    android:stretchMode="columnWidth"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
</GridView>

grid_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:padding="5dp" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:scaleType="centerCrop"
        android:src="@drawable/andrew_salgado" >
    </ImageView>

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="20dp"
        android:layout_alignParentBottom="true"
        android:alpha="0.8"
        android:background="#000000" >

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:ellipsize="start"
            android:singleLine="true"
            android:textColor="#FFFFFF" />

    </RelativeLayout>

</RelativeLayout>