Develop Reference

How to write and constantly update a text file in Android

I have a camera that I am grabbing values pixel-wise and I'd like to write them to a text file. The newest updates for Android 12 requires me to use storage access framework, but the problem is that it isn't dynamic and I need to keep choosing files directory. So, this approach it succesfully creates my files but when writting to it, I need to specifically select the dir it'll save to, which isn't feasible to me, as the temperature is grabbed for every frame and every pixel. My temperature values are in the temperature1 array, I'd like to know how can I add consistently add the values of temperature1 to a text file?
EDIT: I tried doing the following to create a text file using getExternalFilesDir():
private String filename = "myFile.txt";
private String filepath = "myFileDir";
public void onClick(final View view) {
switch (view.getId()){
case R.id.camera_button:
synchronized (mSync) {
if (isTemp) {
tempTureing();
fileContent = "Hello, I am a saved text inside a text file!";
if(!fileContent.equals("")){
File myExternalFile = new File(getExternalFilesDir(filepath), filename);
FileOutputStream fos = null;
try{
fos = new FileOutputStream(myExternalFile);
fos.write(fileContent.getBytes());
} catch (Exception e) {
e.printStackTrace();
}
Log.e("TAG", "file: "+myExternalFile);
}
isTemp = false;
//Log.e(TAG, "isCorrect:" + mUVCCamera.isCorrect());
} else {
stopTemp();
isTemp = true;
}
}
break;
I can actually go all the way to the path /storage/emulated/0/Android/data/com.MyApp.app/files/myFileDir/ but strangely there is no such file as myFile.txt inside this directory, how come??

Working Solution:
public void WriteToFile(String fileName, String content){
File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS);
File newDir = new File(path + "/" + fileName);
try{
if (!newDir.exists()) {
newDir.mkdir();
}
FileOutputStream writer = new FileOutputStream(new File(path, filename));
writer.write(content.getBytes());
writer.close();
Log.e("TAG", "Wrote to file: "+fileName);
} catch (IOException e) {
e.printStackTrace();
}
}

How can I make custom folder (App folder's) in android 11

Im facing a problem when creating app custom folder. like
com.app and storage/.hideFolder etc.
by using some of approaches below android 11 (SDK API 30) device
it's working fine but in android 11. not able to make it im using an approach which is shown below
public static String root= Environment.getExternalStorageDirectory().toString();
public static final String app_hided_folder ="/.HidedAPPTop/";
public static final String app_showing_folder ="/APPTop/";
public static final String draft_app_folder= app_hided_folder +"Draft/";
public static void make_directry(String path,Context context) {
File dir = new File(path);
if (!dir.exists())
Toast.makeText(context,
(dir.mkdirs() ? "Directory has been created" : "Directory not created"),
Toast.LENGTH_SHORT).show();
else
Toast.makeText(context, "Directory exists", Toast.LENGTH_SHORT).show();
}
Function calling
make_directry(Variables.app_hided_folder,getContext());
Manifest
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
…
android:requestLegacyExternalStorage="true"
…
>
2nd question
public static String root=
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS
).toString();
uri is a video path that I got from response of picker.
File video_file = new File(uri.getPath());
Log.d(Variables.tag + " new path", video_file.getAbsolutePath());
Functions.copyFile(video_file,
new File(Variables.gallery_resize_video));
Function calling of copyFile
public static void copyFile(File sourceFile, File destFile) throws IOException {
if (!destFile.getParentFile().exists())
destFile.getParentFile().mkdirs();
if (!destFile.exists()) {
destFile.createNewFile();
}
FileChannel source = null;
FileChannel destination = null;
try {
source = new FileInputStream(sourceFile).getChannel();
destination = new FileOutputStream(destFile).getChannel();
destination.transferFrom(source, 0, source.size());
} finally {
if (source != null) {
source.close();
}
if (destination != null) {
destination.close();
}
}
}
ERROR : new path:
/storage/emulated/0/Download/STop/MP4_20210128_225711.mp4
System.err:
java.io.FileNotFoundException:
/storage/emulated/0/Download/.HidedTop/gallery_resize_video.mp4:
open failed: EACCES (Permission denied)
And app crashes at destination =
new FileOutputStream(destFile).getChannel();

By using below snippet my problem is solved.
Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM)
the .getExternalStoragePublicDirectory() is deprecated.

JDK 7: Existing file gets empty on new File("path/to/file.html");

I'm using JDK 7. I've got a class with a method that creates a html-file using PrintStream. Another method in the same class is supposed to use the created file and do stuff with it. The problem is that once i use new File("path/to/file.html), the file lenght is reduced to 0. My code:
public class CreatePDFServiceImpl {
private final PrintStream printStream;
public CreatePDFServiceImpl() throws IOException {
printStream = new PrintStream("/mnt/test.html", "UTF-8");
}
public void createHtmlFile() throws IncorporationException {
try {
StringBuilder html = new StringBuilder();
HtmlFragments htmlFragments = new HtmlFragments();
html.append(htmlFragments.getHtmlTop())
.append(htmlFragments.getHeading())
.append(htmlFragments.buildBody())
.append(htmlFragments.buildFooter());
printStream.print(html.toString());
} finally {
if(printStream != null) {
printStream.close();
}
}
}
This next method is supposed to use the html file created in "createHtmlFile()":
public void convertHtmlToPdf() {
PrintStream out = null;
try {
File file = new File("/mnt/test.html");
/** this code added just for debug **/
if (file.createNewFile()){
System.out.println("File is created!");
} else {
System.out.println("File already exists. size: " + file.length());
}
/* PDF generation commented out. */
//out = new PrintStream("/mnt/testfs.pdf", "UTF-8");
//defaultFileWriter.writeFile(file, out, iTextRenderer);
} catch (IOException e) {
throw new IncorporationException("Could not save pdf file", e);
} finally {
if(out != null) {
out.close();
}
}
My junit integration test class:
#Category(IntegrationTest.class)
public class CreatePDFServiceIntegrationTest {
private static CreatePDFServiceImpl createPDFService;
#BeforeClass
public static void init() throws IOException {
createPDFService = new CreatePDFServiceImpl();
}
#Test
public void testCreateHtmlFile() throws IncorporationException {
createPDFService.createHtmlFile();
File createdFile = new File("/mnt/test.html");
System.out.println("createdFile.length() = " + createdFile.length());
Assert.assertTrue(createdFile.length() > 1);
}
#Test
public void testCreatePDF() throws Exception {
File fileThatShouldExist = new File("/mnt/testfs.pdf");
createPDFService.convertHtml2Pdf();
Assert.assertTrue(fileThatShouldExist.exists());
}
}
The first test passes, output:
"createdFile.length() = 3440".
I checked the file system, there is the file. size 3,44kb.
Second test fails, output from CreatePDFServiceImpl:
"File already exists. size: 0"
Looking in the file system, the file now is actually 0 bytes.
I'm stumped. The new File("path") should only create a reference to that file and not empty it?

I doubt there's an error in File.createNewFile(). I don't yet fully grasp in which order you run your code, but are you aware that this sets the file size to zero?
out = new PrintStream("/mnt/testfs.pdf", "UTF-8");
From the PrintStream(File file) Javadoc:
file - The file to use as the destination of this print stream. If the
file exists, then it will be truncated to zero size; otherwise, a new
file will be created. The output will be written to the file and is
buffered.
I think that's the culprit - but in your code that line is commented out. Am I right you have run your tests with that line commented in?

Cannot create directory but files

Here are things I have done:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
and
public void createMyFolder(){
File directory = new File(Environment.getExternalStorageDirectory().getPath() + "/myfolder/");
directory.mkdir(); //I had also tried mkdirs()
File file= new File(Environment.getExternalStorageDirectory().getPath() + "/t1.dat");
try {
file.createNewFile();
} catch (IOException e) {}
}
I tested 3 devices and one of them threw exception:
java.io.IOException: Cannot create dir /mnt/sdcard/myfolder
t1.dat was created successfully in /mnt/sdcard/ but myfolder was not.
The device is Xperia Ion with Android version 4.0.4. What's wrong about it and how can I fix it?
Edit: I had tried to create folders by some applications, like File Manager.
And they also failed to create although the sdcard is writable and readable.
I think my phone has some "protections" which do not allow me to create folders in sd card.
But it's funny that my phone allows me to create files instead.
public boolean isExternalStorageWritable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
return false;
}
/* Checks if external storage is available to at least read */
public boolean isExternalStorageReadable() {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state) ||
Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
return true;
}
return false;
}

Replace Environment.getExternalStorageDirectory() with directory and also "/myfolder" will be "/myfolder"
public void createMyFolder(){
File directory = new File(Environment.getExternalStorageDirectory().getPath() + "/myfolder");
directory.mkdir(); //I had also tried mkdirs()
File file= new File(directory.getPath() + "/t1.dat");
try {
file.createNewFile();
} catch (IOException e) {}
}

PhoneGap 3.1 Android copy audio file from www folder to SD card

Here is the problem. I got an app that download audio files to the phone then play it back. All works without problem. But the little problem is - the customer wants to have something that play straight away when the other files are being download.
So I put an short audio in the www/files/ folder. That works without any issue with iOS. I just reference it (from media player) as
document.addEventListener('deviceready' , function()
{
var media = new Media('files/default.m4a' , function()
{
// this success call back never works!
});
setTimeout(function()
{
media.play();
},100);
});
Now the problem is Android. Got a FileError.NOT_FOUND_ERR error. Looking at LogCat (From Android studio)
The path become
/mnt/sdcard/files/default.m4a
It seems that Android couldn't handle a relative path like iOS (strange enough all the images or template are relative path in the js app. And they all work fine).
Been searching up and down a solution how do I copy just that one audio file to the sd card. no luck so far. The problem is I couldn't correctly find the absolute path to the original file. There are lots of example out there which is total BS. They hardcoded the path in! Android can be anything, in the emulator is /mnt/sdcard/ on my test device turns into /external/sdcard0
And that just from (java):
String path = Environment.getExternalStorageDirectory().getAbsolutePath();
I seen tons and tons of people got the same problem. But the solution out there are pretty out date. Or not really solve the first problem (which is finding out where is the original file in the first place). There must be one problem many people face right?
Thanks in advance.
P.S. I also try this
this.getClass().getPackage().getName();
call from inside the onCreate method. That only got me partial but not the absolute path.
UPDATE
Here is the complete working code (for PhoneGap 3.1)
package YOUR_PACKAGE_NAME;
import android.os.Bundle;
import org.apache.cordova.*;
/* for the other two plugins */
import java.io.*;
import android.os.Environment;
import android.util.Log;
import android.content.res.AssetManager;
public class YourAppName extends CordovaActivity
{
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
super.init();
this.CopyAssets();
super.loadUrl(Config.getStartUrl());
}
private void CopyAssets() {
AssetManager assetManager = getAssets();
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open(FILE_YOU_WANT_TO_COPY_IN_WWW);
out = new FileOutputStream(Environment.getExternalStorageDirectory()
.toString()
+ WHERE_YOU_WANT_TO_PUT_IT_PLUS_NAME);
this.copyFile(in, out);
in.close();
in = null;
out.flush();
out.close();
out = null;
} catch (Exception e) {
Log.e("tag", e.getMessage());
}
}
private void copyFile(InputStream in, OutputStream out) throws IOException {
byte[] buffer = new byte[1024];
int read;
while ((read = in.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
}
}

Try this :
public class testsample extends DroidGap {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set by <content src="index.html" /> in config.xml
CopyAssets();
super.setIntegerProperty("loadUrlTimeoutValue", 6000);
super.loadUrl(Config.getStartUrl());
}
private void CopyAssets() {
AssetManager assetManager = getAssets();
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open("www/img/logo.png"); // if files resides
// inside the "Files"
// directory itself
// "www/img/logo.png" is path of assets/www folder
out = new FileOutputStream(Environment
.getExternalStorageDirectory().toString()
+ "/"
+ "logo.png");
copyFile(in, out);
in.close();
in = null;
out.flush();
out.close();
out = null;
} catch (Exception e) {
Log.e("tag", e.getMessage());
}
}
private void copyFile(InputStream in, OutputStream out) throws IOException {
byte[] buffer = new byte[1024];
int read;
while ((read = in.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
}
}
Do't Forget to Add Permission on AndroidManifest.xml
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

A cleaner option is to install the org.apache.cordova.file-transfer plugin and transfer the file from "file:///android_asset/www/song.mp3" to /YourApp/song.mp3
cordova plugin add org.apache.cordova.file#1.1.0
cordova plugin add org.apache.cordova.file-transfer
And then:
// Assumes variable fileURL contains a valid URL to a path on the device,
// for example, cdvfile://localhost/persistent/path/to/downloads/
var fileTransfer = new FileTransfer();
var uri = encodeURI("http://some.server.com/download.php");
fileTransfer.download(
uri,
fileURL,
function(entry) {
console.log("download complete: " + entry.toURL());
},
function(error) {
console.log("download error source " + error.source);
console.log("download error target " + error.target);
console.log("upload error code" + error.code);
},
false,
{
//headers: {
// "Authorization": "Basic dGVzdHVzZXJuYW1lOnRlc3RwYXNzd29yZA=="
//}
}
);
More info here:
https://github.com/apache/cordova-plugin-file-transfer/blob/master/doc/index.md
This way you only wave to worry about your javascript