Develop Reference

Xamarin Android Sqlite Db browser

I have my first smartphone since one week and try make a App with Xamarin.
I use SQLite with EntityFrameworkCore to store data.
It is work fine, but to debug easier I want use a SQLite browser.
The database file path is 'data/data/{AppName}/Database.db'.
I debug from a physic device by USB, but when I explore the device with Windows Explorer I cannot find the SQLite DB file. The 'data/data' folder is not available. Then I can not use a SQLite browser to see the data.
In this post, the author use a Android emulator and can see 'data/data' folder :
https://blog.xamarin.com/building-android-apps-with-entity-framework/
But I prefer use a real device.
Have you a solution?
A solution from the MikeT, in development store the db file in available folder like this :
public static string DatabasePath
{
get
{
var dbFolder = Android.OS.Environment.GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads).AbsolutePath;
var fileName = "database.db";
var dbFullPath = Path.Combine(dbFolder, fileName);
return dbFullPath;
}
}
In production, copy the db file to a available folder.

One a real device you would, I believe, need to root the device to directly access the data.
However, what you could do is to copy the database file elsewhere e.g. to external storage. In following is the core process that I use:-
try {
FileInputStream fis = new FileInputStream(dbfile);
OutputStream backup = new FileOutputStream(backupfilename);
//byte[] buffer = new byte[32768];
int length;
while((length = fis.read(buffer)) > 0) {
backup.write(buffer, 0, length);
}
backup.flush();
backup.close();
fis.close();
catch (IOException e) {
e.printStackTrace();
confirmaction = false;
}
I use the following to get the pathname for backupfilename:-
File dir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),subdirectory);
this.directory = dir.getPath();
I then add the actual filename (which is user input).
Note! I do checks to determine that EXTERNAL storage is mounted etc.
To get the database path i use:-
String dbfilename = this.getDatabasePath(
DBConstants.DATABASE_NAME).getPath();
dbfile = new File(dbfilename);
This is of course Java, but I'd assume that it could be converted/adapted to suit. The crux of the answer is to get the database file into a place from which you can access it.

Call the ExtractDb method from your activity
public void ExtractDB()
{
var szSqliteFilename = "databasename.db3";
var szSourcePath = new FileManager().GetLocalFilePath(szSqliteFilename);
var szDatabaseBackupPath = Android.OS.Environment.ExternalStorageDirectory.AbsolutePath + "/databasename_Backup.db3";
if (File.Exists(szSourcePath))
{
File.Copy(szSourcePath, szDatabaseBackupPath, true);
Toast.MakeText(this, "Copied", ToastLength.Short).Show();
}
}
Get path to the android device storage as shown below
public class FileManager
{
public string GetLocalFilePath(string filename)
{
string path = System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal);
return Path.Combine(path, filename);
}
}
you need to add the android.permission.WRITE_EXTERNAL_STORAGE permission in your manifest file.

Creating a file unsing openFileOutput() which is visible to other applications

I'm using the openFileOutput() to create a new txt file. I need the file to be visible from other applications (as well as from a PC when the Android device is connected via USB. Ive tried using .setReadable(true); but this does not seem valid. Please advise how I should declare the file is visible / public.
try {
textIncoming.append("saving");
final String STORETEXT = "test.txt";
OutputStreamWriter out = new OutputStreamWriter(openFileOutput(STORETEXT, 0));
out.setReadable(true);
out.write("testing");
out.close();
}
catch (Throwable t) {
textIncoming.append("not saving");
}
Ive changed my program to use getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS), but for some reason it returns a path /storage/emulated/0/Documents, and I cant even find this folder on the device. Ive looked at the files on the android device using ES file explorer but cant find the folder or file I'm trying to create (Plus I want these in an documents folder on the SD card, so it seems that its not giving me a pointer to the SD card at all, and not creating the folder, and not creating the file. Following is my updated code, please advise
String root = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS).toString();
File myDir = new File(root + "/Saved_Receipts");
myDir.mkdirs();
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String fname = "DRcpt-" + n + ".xml";
textIncoming.append(root);
File file = new File(myDir, fname);
if (file.exists()) {
file.delete();
}
try {
FileOutputStream out = new FileOutputStream(file);
out.flush();
out.close();
}
catch (Exception e) {
e.printStackTrace();
}

Save it to sdcard if you want anyone to be able to read it.
This android documentation should tell you what you need to do.
https://developer.android.com/guide/topics/data/data-storage.html#filesExternal

openFileOutput() documentation says:
Open a private file
So the file that it creates won't be visible to other apps, unless you copy it to another directory that is visible. In that case, you have to save your data in what's called "external storage" which is shared with other apps. Use the code at this link.

Where should I have users save the images that they made on my app

My users make custom images on my app and I am unsure what directory I should use when they save. Should I use MediaStore.Images.Media.EXTERNAL_CONTENT_URI?

Basically MediaStore.Images.Media.EXTERNAL_CONTENT_URI is part of Content Resolver which allow you to read and write resource from your user device. You need to ask yourself wether it is good to save their image into device. You could save your image in private or public which still decided by you. There is internal and external storage, wether you need all image to be deleted when your app is deleted or you don't want other app access the photo you user created use internal storage otherwise use external storage.Take a look on this link which take you step by step to understand why, which,how to save file into your app.

You can make a directory of your own app in the internal storage of the device and store all the pictures made from your app there.
You can make the directory using
File directory = new File(Environment.getExternalStorageDirectory() + File.separator + "<app name>");
if(!directory.exists){
directory.mkdirs;
}
And then store the pictures in this path
Random generator = new Random();
int n = 10000;
n = generator.nextInt(n);
String name = "<image name>"+n+".jpg";
File pictureFile = new File(directory, name);
pictureFile.createNewFile();
try {
FileOutputStream out = new FileOutputStream(pictureFile);
finalBitmap.compress(Bitmap.CompressFormat.JPEG, 90, out);
out.close();
} catch (Exception e) {
e.printStackTrace();
}

where to write a text file and how to set it up for an sd card

I know this is a popular question but I have looked at all of the other responses and none of them seem to work. What I want to do is write some code to a text file. My first question: is there a way to view that text file without writing code to the console? Second, I dont know where in my phone it goes and I want to see it to help trouble shoot, so if you know how to do that too, it would be great. So now I will give you an overview of what is happening. When I start my program it checks to see if the file exists, if it doesn't it reads a file out of my assets folder and copies that info and sends it to a file into the sd card. If it exits it reads the info from the sd card. Next if I press a button and change numbers and print it to my sd card again then I close it using task managers then when I come back the original information is here. I don't feel like it is being able to find my sd card location. So far I have used.
File outfilepath = Environment.getExternalStorageDirectory();
String FileName = "ExSettings.txt" ;
File outfile = new File(outfilepath.getAbsolutePath()+"/TimeLeft/"+FileName);
File outfilepath = Environment.getExternalStorageDirectory();
String FileName = "ExSettings.txt" ;
File outfile = new File(outfilepath, FileName);
Any Ideas?

This is a function that I wrote which will take in a list array and write to a file line by line.
It will use the path in fileName to make a new folder called myfolder in the root of the SDCard, an inside will be your file of newtextfile.txt.
List<String> File_Contents = new ArrayList<String>();
File_Contents.add("This is line one");
File_Contents.add("This is line two");
File f = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/myfolder/newtextfile.txt");
f.mkDirs();
try {
BufferedWriter out = new BufferedWriter(new FileWriter(f));
for (int x = 0; x < File_Contents.size(); x++) {
out.write(File_Contents.get(x));
out.write(System.getProperty("line.separator"));
}
out.close();
return true;
} catch (Exception e) {
return false;
}

Is this a safe and correct way to save file to internal memory?

I've been using the following code, but intuitively I see it's not too safe. Will it work flawlessly in every device? This code copies to internal memory my main database (100 kB) in the first app run. Thanks for your time.
private void CopyDBtoInternal() {
String path = "/data/data/com.myproject/databases/";
String DB_DESTINATION = "/data/data/com.myproject/databases/sample.db";
// Check if the database exists before copying
boolean initialiseDatabase = (new File(DB_DESTINATION)).exists();
if (initialiseDatabase == false) {
//create folders
File db_folder = new File(path);
db_folder.mkdirs();
AssetManager assetManager = getApplicationContext().getAssets();
try {
InputStream is = assetManager.open("sample.db");
// Copy the database into the destination
OutputStream os = new FileOutputStream(DB_DESTINATION);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer)) > 0){
os.write(buffer, 0, length);
}
os.flush();
os.close();
is.close();
} catch (IOException e) {
e.printStackTrace();
AlertDialog.Builder dialogo = new AlertDialog.Builder(AppGuiaDeBulas.this);
dialogo.setTitle("Alerta");
dialogo.setMessage("It was not possible to save database. Error #001");
dialogo.setNeutralButton("OK", null);
dialogo.show();
}
}
}

Check out this part of the article on writing to storage.
If you're using API Level 8 (Froyo) or greater, use getExternalFilesDir() to open a File that represents the external storage directory where you should save your files. This method takes a type parameter that specifies the type of subdirectory you want, such as DIRECTORY_MUSIC and DIRECTORY_RINGTONES (pass null to receive the root of your application's file directory). This method will create the appropriate directory if necessary. By specifying the type of directory, you ensure that the Android's media scanner will properly categorize your files in the system (for example, ringtones are identified as ringtones and not music). If the user uninstalls your application, this directory and all its contents will be deleted.
If you're using API Level 7 or lower, use getExternalStorageDirectory(), to open a File representing the root of the external storage. You should then write your data in the following directory:
/Android/data//files/
The is your Java-style package name, such as "com.example.android.app". If the user's device is running API Level 8 or greater and they uninstall your application, this directory and all its contents will be deleted.
http://developer.android.com/guide/topics/data/data-storage.html#AccessingExtFiles