Helper for sending ACTION_IMAGE_CAPTURE intent and retrieve its results. Handles all low level operations

ImageCaptureHelper.java

//MIT License
//Copyright (c) 2015 Karol Wrótniak, Droids On Roids
package pl.droidsonroids.imagehelpers;

import java.io.File;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import android.app.Activity;
import android.content.ActivityNotFoundException;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.database.Cursor;
import android.net.Uri;
import android.os.Environment;
import android.provider.MediaStore;
import android.provider.MediaStore.Images.ImageColumns;
import android.provider.MediaStore.MediaColumns;

/**
 * Helper for sending ACTION_IMAGE_CAPTURE intent and retrieve its results. Handles all low level operations
 * <br>
 * Usage:<br>
 * <ol>
 * <li>Launch camera app by calling {@link #launchCameraApp(int, Activity, String)}, save resulting Uri, handle (or ignore) exceptions.</li>
 * <li>In your onActivityResult(int requestCode, int resultCode, Intent data) call {@link #retrievePhotoResult(Activity, String) ) }. You may want to inform user if photo cannot be read despite the result is RESULT_OK.</li>
 * </ol> 
 * @author koral--
 *
 */
public class ImageCaptureHelper
{
	private ImageCaptureHelper ()
	{}

	private static final String[] PROJECTION = new String[] { MediaColumns.DATA };
	private static final ContentValues CONTENT_VALUES = new ContentValues( 1 );
	private static final String PHOTO_SHARED_PREFS_NAME = "photo_shared";
	private static final String PHOTO_URI = "photo_uri";
	/**
	 * Description text inserted into @link{ImageColumns.DESCRIPTION} column 
	 */
	public static final String DESCRIPTION="Photo taken with example application" ;
	static 
	{
		CONTENT_VALUES.put( ImageColumns.DESCRIPTION, DESCRIPTION);
	}
	/**
	 * Tries to obtain File containing taken photo. Perform cleanups if photo was not taken or it is empty.
	 * @param caller caller Activity
	 * @param photoKey key in Shared Preferences for taken image, can be null
	 * @return File containing photo or null if no or empty photo was saved by camera app.
	 */
	public static File retrievePhotoResult ( Activity caller, String photoKey )
	{
		try
		{
			if ( photoKey == null )
			{
				photoKey = PHOTO_URI;
			}
			SharedPreferences prefs = caller.getSharedPreferences( PHOTO_SHARED_PREFS_NAME, Context.MODE_PRIVATE );
			String takenPhotoUriString = prefs.getString( photoKey, null );
			prefs.edit().remove( photoKey ).commit();

			if ( takenPhotoUriString == null )
			{
				return null;
			}

			Uri takenPhotoUri = Uri.parse( takenPhotoUriString );
			ContentResolver cr = caller.getContentResolver();
			File out = new File( getPhotoFilePath( takenPhotoUri, cr ) );
			if ( !out.isFile() || ( out.length() == 0 ) )
			{
				cr.delete( takenPhotoUri, null, null );
			}
			else
			{
				return out;
			}
		}
		catch ( Exception ex )
		{
			// no-op
		}
		return null;
	}

	/**
	 * Tries to create photo placeholder and launch camera app
	 * @param requestCode your unique code that will be returned in onActivityResult
	 * @param caller caller Activity
	 * @param photoKey key in Shared Preferences for taken image, can be null
	 * @throws ActivityNotFoundException if no camera app was found
	 * @throws Exception if there is a problem with create photo eg. SDcard is not mounted. It may be eg. {@link IllegalStateException} or {@link UnsupportedOperationException} depending on {@link ContentResolver}.
	 */
	public static void launchCameraApp ( int requestCode, Activity caller, String photoKey ) throws ActivityNotFoundException, Exception
	{
		if ( photoKey == null )
		{
			photoKey = PHOTO_URI;
		}

		ContentResolver cr = caller.getContentResolver();
		Uri takenPhotoUri = cr.insert( MediaStore.Images.Media.EXTERNAL_CONTENT_URI, CONTENT_VALUES );
		if ( takenPhotoUri == null )
		{
			throw new IllegalStateException( "Photo insertion failed" );
		}
		Intent intent = new Intent( MediaStore.ACTION_IMAGE_CAPTURE );
		intent.putExtra( MediaStore.EXTRA_OUTPUT, getIntentUri( takenPhotoUri, cr ) );
		caller.startActivityForResult( intent, requestCode );

		SharedPreferences prefs = caller.getSharedPreferences( PHOTO_SHARED_PREFS_NAME, Context.MODE_PRIVATE );

		prefs.edit().putString( photoKey, takenPhotoUri.toString() ).commit();
	}

	private static Uri getIntentUri ( Uri takenPhotoUri, ContentResolver cr )
	{
		String path = getPhotoFilePath( takenPhotoUri, cr );
		if ( path == null )
		{
			throw new IllegalStateException( "Photo resolution failed" );
		}
		return Uri.fromFile( new File( path ) );
	}

	private static String getPhotoFilePath ( Uri takenPhotoUri, ContentResolver cr )
	{
		Cursor cursor = cr.query( takenPhotoUri, PROJECTION, null, null, null );
		String res = null;
		if ( cursor != null )
		{
			int dataIdx = cursor.getColumnIndex( MediaColumns.DATA );
			if (dataIdx>=0&&cursor.moveToFirst())
				res = cursor.getString( dataIdx );
			cursor.close();
		}
		return res;
	}

	/**
	 * Dirty hack for API level <8 to get a top-level public external storage directory where Camera photos should be placed.<br>
	 * Empty photo is inserted, path of its parent directory is retrieved and then photo is deleted.<br>
	 * If photo cannot be inserted eg. external storage is not mounted, then "DCIM" folder in root of the external storage is used as a fallback. 
	 * @param cr {@link ContentResolver} used to resolve image Uris
	 * @return path to directory where camera app places photos (may be fallback) 
	 */
	public static String getPhotoDirPath(ContentResolver cr)
	{
		String fallback=Environment.getExternalStorageDirectory()+"/DCIM";
		Uri takenPhotoUri =null;
		String photoFilePath=null;
		try
		{
			takenPhotoUri=cr.insert( MediaStore.Images.Media.EXTERNAL_CONTENT_URI, CONTENT_VALUES );
			if ( takenPhotoUri == null )
				return fallback;
			photoFilePath=getPhotoFilePath( takenPhotoUri, cr );
			cr.delete( takenPhotoUri, null, null );
		}
		catch (Exception ex)
		{
			//igonred
		}
		if (photoFilePath==null)
			return fallback;
		String parent = new File(photoFilePath).getParent();
		Matcher m = Pattern.compile( "/DCIM(/|$)").matcher( parent );
		if (m.find())
			parent= parent.substring( 0, m.end() );

		return parent;
	}	
}