Develop Reference

How to implement Image gallery with single image representing file in image directory

I am trying to implement a feature like Instagram or WhatsApp, where the thumbnail of a single image that exists in a folder in android, is shown on top of a list item, more like a sample of what kinds of image are in the folder.
Help me to understand this feature.

How I implemented it. It might not be the best though, but it works.
I fetched the URIs of all the images using MediaStore, you can learn how to use it here.
The First step was done in a background thread to prevent it from blocking the UI thread.
I sorted out the images I got, grouping them in a List<Image>, which would represent a single directory.
I then added the List<Image> into a List<List<Image>>, which served as the overall images that were fetched and have their total size which I used later to track the number of images in the directory.
The code is below.
#Override
public void run() {
Uri storageUri;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
storageUri = MediaStore.Images.Media.getContentUri(MediaStore.VOLUME_EXTERNAL);
} else {
storageUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
}
// the queries to the MediaStore API (The image details or metadata I need
String[] projection = {
MediaStore.Images.Media._ID,
MediaStore.Images.Media.BUCKET_DISPLAY_NAME,
MediaStore.Images.Media.SIZE,
MediaStore.Images.Media.DISPLAY_NAME};
// now query the MediaStore API using ContentResolver
Cursor imgCursor = getApplicationContext().getContentResolver().query(storageUri, projection, null, null, null);
int bucketId = imgCursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID);
int imgSize = imgCursor.getColumnIndexOrThrow(MediaStore.Images.Media.SIZE);
int name = imgCursor.getColumnIndexOrThrow(MediaStore.Images.Media.DISPLAY_NAME);
int bucketName = imgCursor.getColumnIndexOrThrow(MediaStore.Images.Media.BUCKET_DISPLAY_NAME);
// directoryDictionary is a temporary list of directory names that was found, while querying the MediaStore API
List<String> directoryDictionary = new ArrayList<>();
// generalList is just a list that would represent a general image list, where all images can be found. Just like Whatsapp
List<Image> generalList = new ArrayList<>();
while (imgCursor.moveToNext()) {
long id = imgCursor.getLong(bucketId);
int size = imgCursor.getInt(imgSize);
String fileName = imgCursor.getString(name);
String folderName = imgCursor.getString(bucketName);
// As recommended by the Android developers doc
Uri contentUri = ContentUris.withAppendedId(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, id);
// a single image
Image currentImage = new Image(contentUri, size, fileName, folderName);
// add all images to the general image list, but modifying the directory name
Image genImage = new Image(contentUri, size, fileName, "All Media");
generalList.add(genImage);
int directoryIndex = CollectionUtils.linearSearch(directoryDictionary, folderName);
// if search result (directoryIndex) passes this test, then it means that there is
// no such directory in list of directory names
if (directoryIndex < 0) {
imageDirectoryList.add(new ArrayList<>());
directoryDictionary.add(folderName);
directoryIndex = CollectionUtils.linearSearch(directoryDictionary, folderName);
if (directoryIndex >= 0)
imageDirectoryList.get(directoryIndex).add(currentImage);
} else {
imageDirectoryList.get(directoryIndex).add(currentImage);
}
}
//...then add it if the image list of folder is > 2
if (imageDirectoryList.size() > 2) imageDirectoryList.add(0, generalList);
imgCursor.close();
runOnUiThread(() -> {
// imageAdapter is the RecyclerView's list Adapter.
// notifyDataSetChanged() must be call to refresh list.
imageAdapter.notifyDataSetChanged();
// doViewUpdate was just used to turn on and off the visibility of some views
doViewUpdate();
});
}

DocumentsContract's buildChildDocumentsUriUsingTree(uri, DocumentsContract.getTreeDocumentId(uri)); returns parent Uri tree

I am trying to use DocumentsContract to traverse a directory recursively using the following method.
void traverseDirectoryEntries(Uri rootUri) {
ContentResolver contentResolver = activityMain.getContentResolver();
Uri childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(
rootUri, DocumentsContract.getTreeDocumentId(rootUri));
List<Uri> dirNodes = new LinkedList<>();
dirNodes.add(childrenUri);
while (!dirNodes.isEmpty()) {
childrenUri = dirNodes.remove(0); // get the item from top
try (Cursor cursor = contentResolver.query(childrenUri, new String[]{
DocumentsContract.Document.COLUMN_DOCUMENT_ID,
DocumentsContract.Document.COLUMN_DISPLAY_NAME,
DocumentsContract.Document.COLUMN_MIME_TYPE},
null, null, null)) {
if (cursor != null) {
while (cursor.moveToNext()) {
final String docId = cursor.getString(0);
final String name = cursor.getString(1);
final String mime = cursor.getString(2);
if (isDirectory(mime)) {
final Uri newNode = DocumentsContract.buildChildDocumentsUriUsingTree(
rootUri, docId);
traverseDirectoryEntries(newNode);
}
}
}
}
}
}
// Util method to check if the mime type is a directory
private static boolean isDirectory(String mimeType) {
return DocumentsContract.Document.MIME_TYPE_DIR.equals(mimeType);
}
Unfortunately, this does not work. It goes through the same root directory over and over despite the directory passed in being a child of the root. The line final Uri newNode = DocumentsContract.buildChildDocumentsUriUsingTree(rootUri, docId); returns a Uri with the child directory attached at the end. That works fine. The problem is the follwing line: Uri childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(rootUri, DocumentsContract.getTreeDocumentId(rootUri)); where rootUri is the newNode. I get the same childrenUri; the one I got from rootUri. Is this a bug? Did I make a mistake? Is the docId wrong? I tried getDocumentId(rootUri), but that throws an error because the id it returns is not a tree. It is almost like getTreeDocumentId(rootUri) is returning what getRootId(rootUri) should be returning. Is there a way to fix this?
The rootUri was obtained via ACTION_OPEN_DOCUMENT_TREE. I am running this on Android Pie. I left some code out where I am building a tree structure from the data.

You are abusing this well known void traverseDirectoryEntries(Uri rootUri) function.
You think it is recursive but it is not.
Remove the recursive call and instead add 'newNode' to the list.
// traverseDirectoryEntries(newNode);
dirNodes.add(newNode);
Then you make use of the list.
Then original code is restored.
Who changed it without telling so?
Of course you can adapt this function to make it recursiv.
Nice exercise ;-).

Import multiple .csv file into android sqlite database

I am now trying to import csv files from a certain directory in sd card from an android device. Recently, I can successfully import a single csv files. However, I have no ideas on how to get the list of all csv files and then using a loop to import the csv file one by one.
This is the my code for importing single csv:
button_import_csv.setOnClickListener(new View.OnClickListener(){
public void onClick(View v){
DatabaseHelper helper = new DatabaseHelper(getApplicationContext());
SQLiteDatabase db = helper.getWritableDatabase();
try{
FileReader file = new FileReader("/sdcard/downloadedfolder/A1/adv_sales_order.csv");
BufferedReader buffer = new BufferedReader(file);
ContentValues contentValues=new ContentValues();
String line = "";
String tableName ="adv_sales_order";
db.beginTransaction();
while ((line = buffer.readLine()) != null) {
String[] str = line.split("\t");
contentValues.put("order_date", str[0]);
contentValues.put("cust_code", str[1]);
contentValues.put("customer_ref_no", str[2]);
contentValues.put("line_no", str[3]);
contentValues.put("item_code", str[4]);
contentValues.put("tran_code", str[5]);
contentValues.put("order_qty", str[6]);
db.insert(tableName, null, contentValues);
}
db.setTransactionSuccessful();
db.endTransaction();
}catch (IOException e){
}
}
});
The columns for different csv fileS are not the same.(For example,some may has 4 columns named A,B,C,D and the other one may has columns named as C,D,E,F) Besides hard coding all columns for each csv file, are there any possible ways?
Can anyone tell me any solution???Thank you.

There are two possibilities I can think of...
First: If you are in control of the filenames then give them names with a sequential numeric aspect, e.g., file1.csv, file2.csv etc You can then simply use a for loop to build the filenames and process them. Example...
// Lets say you have 5 files named file1.csv thru file5.csv
for(int i = 1; i < 6; i++) {
String filename = "file" + i + ".csv";
// Process the file which has the above filename
}
Second: Get all of the files in the directory using the listFiles() method. Example...
// This code assumes you have a File object for the directory called dir
File[] files = dir.listFiles();
for(int i = 0; i < files.length; i++) {
String filename = files[i].getAbsolutePath();
if (filename.endsWith(".csv")) {
// Process the file which has the above filename
}
}
I'm not sure if either of the code blocks above are perfect but basically they both simply use a for loop. There are other ways but those are the most straight-forward.
EDIT:
Some csv files use the first line to describe the column names. In some ways this is a bit like a schema of a dataset. Example (using comma-separated values)...
A,B,C,D
valueA,valueB,valueC,valueD
...
Using this approach means you can get access to the column names by reading the first line and splitting it to make an array. You can then use a for loop to put the ContentValues. Try the following...
// Read the first line separately and split to get the column names
line = buffer.readLine();
String[] cols = line.split("\t");
db.beginTransaction();
while ((line = buffer.readLine()) != null) {
String[] str = line.split("\t");
for (int i = 0; i < cols.length; i++) {
contentValues.put(cols[i], str[i]);
}
db.insert(tableName, null, contentValues);
}
db.setTransactionSuccessful();
db.endTransaction();
BTW I notice you're splitting on "\t" so make sure your column names on the first line are tab-delimited (obviously).

Android: Sorting mp3 files by title in a clickable listview

I am attempting to create a music player app for a Nexus 7 tablet. I am able to retrieve music files from a specific directory as well as information that is associated with them such as title, artist, etc. I have loaded the files's titles into a clickable list view. When the user clicks on a title, it takes them to an activity that plays the associated song. I was attempting to sort the titles alphabetically and ran into a snag. When I sort just the titles, they no longer match with the correct songs. This is to be expected since I only ordered the titles and not the actual files. I attempted to modify the sorting algorithm by doing this:
//will probably only work for Nexus 7
private final static File fileList = new File("/storage/emulated/0/Music/");
private final static File fileNames[] = fileList.listFiles(); //get list of files
public static void sortFiles()
{
int j;
boolean flag = true;
File temp;
MediaMetadataRetriever titleMMR = new MediaMetadataRetriever();
MediaMetadataRetriever titleMMR2 = new MediaMetadataRetriever();
while(flag)
{
flag = false;
for(j = 0; j < fileNames.length - 1; j++)
{
titleMMR.setDataSource(fileNames[j].toString());
titleMMR2.setDataSource(fileNames[j+1].toString());
if(titleMMR.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE).compareToIgnoreCase(titleMMR2.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE)) > 0)
{
temp = fileNames[j];
fileNames[j] = fileNames[j+1]; // swapping
fileNames[j+1] = temp;
flag = true;
}//end if
}//end for
}//end while
}
This is supposed to retrieve the song titles from two files, compare them, and swap the files in the File array if the first comes after the second alphabetically. For some reason, when I run the activity that calls this method, the app crashes. If I remove the + 1 from titleMMR2's data source
titleMMR2.setDataSource(fileNames[j].toString());
the app no longer crashes but the list is not in order. Again this is understandable since it compares the song titles to themselves. I don't know why the + 1 would make the program crash. It is not an array out of bounds error. There are a total of 6 .mp3 files in the directory and they are the only files in that directory. I have also tried using Arrays.sort(fileNames) but that only orders them by their file name and not song title. I also tried this:
Arrays.sort(fileNames, new Comparator<File>(){
public int compare(File f1, File f2)
{
titleMMR.setDataSource(f1.toString());
titleMMR2.setDataSource(f2.toString());
return titleMMR.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE).compareToIgnoreCase(titleMMR2.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE));
} });
That snippet also resulted in a crash. There are no errors in the java code and all appropriate classes have been imported. I'm really at a loss as to what is wrong. Any help will be appreciated and if any new info is needed I will gladly provide it. Thanks in advance.
FIXED
The correct code snip is this:
public static void sortFiles()
{
int j;
boolean flag = true;
File temp;
MediaMetadataRetriever titleMMR = new MediaMetadataRetriever();
MediaMetadataRetriever titleMMR2 = new MediaMetadataRetriever();
while(flag)
{
flag = false;
for(j = 0; j < fileNames.length - 1; j++)
{
titleMMR.setDataSource(fileNames[j].toString());
titleMMR2.setDataSource(fileNames[j+1].toString());
String title1;
String title2;
if(titleMMR.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE) == null)
title1 = fileNames[j].getName();
else
title1 = titleMMR.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE);
if(titleMMR2.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE) == null)
title2 = fileNames[j+1].getName();
else
title2= titleMMR2.extractMetadata(MediaMetadataRetriever.METADATA_KEY_TITLE);
if(title1.compareToIgnoreCase(title2) > 0)
{
temp = fileNames[j];
fileNames[j] = fileNames[j+1]; // swapping
fileNames[j+1] = temp;
flag = true;
}//end if
}//end for
}//end while
}

Recorded Video is not Visible in my other Activity untill I reboot my Tablet Asus Transformer

I have created a Project having many activities. One activity is to record the video, that is working fine. I can see the recorded video in my specified folder without restart my tablet.
But when I try to find all the videos in that folder in some other activity using query, see code below. Then I can't see my recorded video until I restart my tablet. I can see just old recorded videos before starting my tablet. I couldn't understand this strange behavior.
Can anyone put some light on this issue??
Thanks.
private void initVideosId() { // getting the videos id in Video Folder of SD Card
try {
// Here we set up a string array of the thumbnail ID column we want
// to get back
String[] proj = { _ID };
//Querying for the videos in VideoGallery folder of SD card
// Now we create the cursor pointing to the external thumbnail store
_cursor = managedQuery(_contentUri, proj, // Which columns to return
MEDIA_DATA + " like ? ", // WHERE clause; which rows to
// return (all rows)
new String[] { "%VideoGallery%" }, // WHERE clause selection
// arguments (none)
null); // Order-by clause (ascending by name)
int count = _cursor.getCount();
// We now get the column index of the thumbnail id
_columnIndex = _cursor.getColumnIndex(_ID);
// initialize
_videosId = new int[count];
// move position to first element
_cursor.moveToFirst();
for (int i = 0; i < count; i++) {
int id = _cursor.getInt(_columnIndex);
//
_videosId[i] = id;
//
_cursor.moveToNext();
//
}
} catch (Exception ex) {
showToast(ex.getMessage().toString());
}
}

If you stored the file on external storage, you need to use MediaScannerConnection to get the MediaStore to index that file, such as:
MediaScannerConnection.scanFile(
this,
new String[] {file.getAbsolutePath()},
null,
new OnScanCompletedListener() {
#Override
public void onScanCompleted(String path, Uri uri) {
// do something if you want
}
});