Develop Reference

How can I ask the user to select the app he wants to use to open a file?

I'm trying to make my own file manager for android.
I am wondering how I could asks the user to choose the application he wants to use open a file. like when you are opening a .doc file and you have a bunch of .doc file readers. How would I be able to retrieve the list of apps that the user can use to read/open a file?

Try this code
Uri uri = Uri.parse("Your file name: //"+file.getAbsolutePath());
Intent intent = new Intent();
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setAction(Intent.ACTION_VIEW);
String type = "application/msword";
intent.setDataAndType(Uri.fromFile(file), type);
startActivity(intent);

You should use implicit intent for your purpose. Below is the sample code for giving options to play a video file
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse("https://youtu.be/jxoG_Y6dvU8"), "video/*");
startActivity(Intent.createChooser(intent, "Complete action using"));
I hope it will help you out. For further details you may refer android official documentation as mentioned in below link
https://developer.android.com/training/basics/intents/sending.html#AppChooser

I think you can try this
Intent in= new Intent(Intent.ACTION_MAIN);
in.setComponent(new ComponentName("com.package.address","com.package.address.MainActivity"));
startActivity(in);

how to show app list to open a file

I'm trying to give the user an overview over the apps which can be used to open the selected file. The following code doesn't work properly:
String ext = MimeTypeMap.getFileExtensionFromUrl(file2open);
String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(ext);
Intent intent = new Intent();
intent.setAction(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse(file2open), mime);
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
startActivity(intent);
If a .txt-file is selected, a list with two apps is shown. But no one of them is the right one. If a .pdf-file is selected, on my phone, a pdf-reader will be launched but only the app. The file is not getting opened. How can I show a list with all apps installed on the device to make the user select one, for example, if a file name doesn't contain an extension?

Solved: It was
intent.setDataAndType(Uri.fromFile(f), mime);
Instead of
intent.setDataAndType(Uri.parse(file2open), mime);

Allow user to chose application for open file

In application user can download file and open it after download completed.
I can open window for choosing application something like this:
Intent intent = new Intent();
intent.setAction(android.content.Intent.ACTION_VIEW);
Uri uri = Uri.parse("file://" + path);
intent.setDataAndType(uri,"image/*");
context.startActivity(intent);
But here "image/*" is hard-coded. In my application user can download files with different extensions (txt, gif, png, doc, .etc).
Of course I can do something like this:
if(fileExt.equels("png") || fileExt.equels("jpg") || fileExt.equels("gif") )
intent.setDataAndType(uri,"image/*");
But then i need to write code for all extensions =/
So, can you suggest better way to filter this file extensions?

You can use activity chooser: (of course you need to provide MIME type as image/* so that only applications which can handle images will appear in the activity chooser.
Intent chooser = Intent.createChooser(intent, title);
// Verify the intent will resolve to at least one activity
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(chooser);
}

How to open the My Files folder in Android Programatically (using Intent)?

I am using the below code which opens up the Gallery, Music Player, Dropbox and Contacts, i want the My Files folder to get open programatically, please let me know if there are any specific intent parameters i need to pass to get the File Manager open.
if it is not possible through intent then please give me a snippet or an hint to open the My Files folder programatically.
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("*/*");
Intent i = Intent.createChooser(intent, "View Default File Manager");
startActivityForResult(i, CHOOSE_FILE_REQUESTCODE);
Thanks.

You can use this code to file the files.
int PICKFILE_RESULT_CODE=1;
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("file/*");
startActivityForResult(intent,PICKFILE_RESULT_CODE);
this will help you to browse the files from your storage.

Its best that you include a library in your project which handles this scenario.
This worked for me:
This library shows the list of third-party apps. It also has its own file browser for selecting files.

Bad thing is, most Android distributions may or may not ship with a file manager, and even so, may be not with the one which handles CHOOSE_FILE_REQUESTCODE.
So, you are left to create your own file picker activity. Luckily there are many ready made ones available:
http://code.google.com/p/android-filechooser/
https://developers.inkfilepicker.com/docs/android/

If you want to open samsung My Files application try this below code.
Intent intent = new Intent("com.sec.android.app.myfiles.PICK_DATA");
intent.putExtra("CONTENT_TYPE", "*/*");
startActivityForResult(intent, CHOOSE_FILE_REQUESTCODE);

You have to specifically mention the package name of the explorer application. Please find the example below to open a specific folder in ES Explorer.
public void openfolderInexplorer(String path){
Intent intent = this.getPackageManager().getLaunchIntentForPackage("com.estrongs.android.pop");
if (intent != null) {
// If the application is avilable
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
Uri uri = Uri.parse(path);
intent.setDataAndType(uri, "resource/folder");
this.startActivity(intent);
} else {
// Play store to install app
intent = new Intent(Intent.ACTION_VIEW);
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
intent.setData(Uri.parse("market://details?id=" +
"com.estrongs.android.pop"));
this.startActivity(intent);
}

try this below code. if any file manager available , then it will pop up in a form of menu to choose appropriate for the user.
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("file/*");
startActivityForResult(intent, CHOOSE_FILE_REQUESTCODE);

Display Applications that can handle a particular filetype

So, I have the file path of a file in an application & I want to give the user the ability to select from all applications on the phone that can handle/open that file type and then open the file in that applicaton. How do I do this? - performs a similar function to a file manager.

First you have to pick the type of Intent you want. This code picks applications that can send the data through SMS/email/etc utilizing ACTION_SEND.
Intent intent = new Intent(Intent.ACTION_SEND);
Next you need to use putExtra to get the file/message to the Intent.
Uri uri = Uri.fromFile(new File(myFile));
intent.putExtra(Intent.EXTRA_STREAM, uri);
Finally you create a chooser.
Intent chooser = Intent.createChooser(intent, "A Custom Message");
startActivity(chooser);