Question

I wanna develop a app manager, and implements function like this: edit different type(with different suffix) opening app, or clear default. Is this possible in Android?

Answer 1

You can use:

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setData(<The URI of the data you want to open>);
intent.setType(<MIME type>); // Optional        
startActivity(intent);

This will show you the appliation choser dialog with the applications that can open the data based on the URI scheme/path and/or the MIME type.

You can also use Intent.ACTION_EDIT instead of Intent.ACTION_VIEW if you want to edit the data.

EDIT: Nothing much to show, to open a TXT file you can use:

File file = new File(Environment.getExternalStorageDirectory(), "test.txt");
Uri uri = Uri.parse("file://" + file.getAbsolutePath());

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setData(uri);        
startActivity(intent);

If there is any application associated with TXT files, the Android OS will prompt you to chose an app, if there is only 1 application capable of opening the specified file type, it will open it using that.