Develop Reference

Exception when downloading file from box.com - Android

I am trying to download a file using the Box android SDK. The problem seems to be with the destinationFile parameter. The box.com call is checking whether the destinationFile exists - but why? I get java.io.FileNotFoundException.
destinationFile = new File(getFilesDir(), "myfile.crs");
// destinationFile = new File(getFilesDir(),"/");
try {
BoxDownload fileDownload = mFileApi.getDownloadRequest(destinationFile, fileID)
// Optional: Set a listener to track download progress.
.setProgressListener(new ProgressListener() {
#Override
public void onProgressChanged(long numBytes, long totalBytes) {
// Update a progress bar, etc.
}
})
.send();
} catch (BoxException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

To do All the checks
Log.i(getClass().getName(),"Does File exists:"+(destinationFile.exists()?"Yes":"No"));
Log.i(getClass().getName(),"Is it A file:"+(destinationFile.isFile()?"Yes":"No"));
Log.i(getClass().getName(),"Is it Writable:"+(destinationFile.canWrite()?"Yes":"No"));
Log.i(getClass().getName(),"Is it A Readable:"+(destinationFile.canRead()?"Yes":"No"));
Log.i(getClass().getName(),"Path:"+destinationFile.getAbsolutePath());
you are most likely to found file does not exists then do this before using it.
if(!destinationFile.exists()){
try {
destinationFile.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}

The answer was to create a new File. Then call .createNewFile() on the File instance. Then call all of the code I posted except to put run it in the background. That's why I was asking here - I was wondering if I was doing something incorrect for Android and I was. Box networking operations need to be done on a thread.
Too bad they never show this for downloading a file. Too bad there's not one example of downloading a file with the Android DSK on the web.

Android - where can I see the request url that is generated when setDataSource(..) is called?

I am trying to add headers to my setDataSource() method. Is there any way I could see the request itself that is sent ? I need to do this because I'd like to confirm if the url generated by setDataSource method is correctly formed. I don't however see any apis in the MediaPlayer class that can help me do this. Any direction or a solution would be most appreciated.

For non-file media source, the framework handle it by MediaHTTPConnection which is a hide API. You can change its field VERBOSE to true to see the printed log.
Since it's not exported, we can't use it directly. The following code might helpful, but I am not sure if it works. Run it before setDataSource().
try {
Class mediaServiceClass = Class.forName("android.media.MediaHTTPConnection");
Field field = mediaServiceClass.getDeclaredField("VERBOSE");
field.setAccessible(true);
Field modifiersField = Field.class.getDeclaredField("modifiers");
modifiersField.setAccessible(true);
modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);
field.setBoolean(null, true);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
You can refer here to see the detail implementation of MediaHTTPConnection.

TransactionTooLargeException in UsbHost mode

I'm using usb-serial-for-android library and I am getting some strange results. After 2.5 hours of continuous communicating with the serial port and reading and writing successfully, I get this exception:
exception in UsbManager.openDevice
android.os.TransactionTooLargeException
at android.os.BinderProxy.transact(Native Method)
at android.hardware.usb.IUsbManager$Stub$Proxy.openDevice(IUsbManager.java:339)
at android.hardware.usb.UsbManager.openDevice(UsbManager.java:255)
at com.hoho.android.usbserial.driver.UsbSerialProber$1.probe(UsbSerialProber.java:63)
at com.hoho.android.usbserial.driver.UsbSerialProber.probeSingleDevice(UsbSerialProber.java:174)
But when i force close my app and then restart it, everything is fine and my app can communicate with the port again.
It maybe useful to mention that before the exception , I get this exception:
java.io.FileNotFoundException: /sdcard/log.txt: open failed: EMFILE (Too many open files)
at libcore.io.IoBridge.open(IoBridge.java:406)
at java.io.FileOutputStream.<init>(FileOutputStream.java:88)
at java.io.FileWriter.<init>(FileWriter.java:58)
at org.example.myapp.util.L.log(L.java:32)
I use class L for logging purposes:
public class L {
public synchronized void log(String message){
File logFile = new File("sdcard/log.txt");
if (!logFile.exists())
{
try
{
logFile.createNewFile();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
//BufferedWriter for performance, true to set append to file flag
BufferedWriter buf = new BufferedWriter(new FileWriter(logFile, true));
buf.append(new Date(DateProvider.getInstance().getCurrentDateAsMillisecs()).toString()+": "+message);
buf.newLine();
buf.close();
}
catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
It seems that some kind of buffer or cache is getting filled and prevents communicating with the device.
How can I get rid of the exception?
Update:
Writing to log file never fails even though I'm getting the exception. It only affects communicating with usb device.

You are opening too many files.
Problems I have found:
- You never close logFile
- You open the file in the log function, a static File would be better and could be initialized in a log_init(); function.
Or, make logFile an object variable and initialize it in the constructor.
I think solving these will solve your problem.

Can you not use getFilesDir() to pass the directory path while creating file

public class L {
public static File logFile = new File("sdcard/log.txt");
public synchronized void log(String message){
....
Everytime you call new File you request a file resource from the system. As you keep doing it the system will complain that you opened too many files. To avoid this, request the file only once.

Blank File is saved when using screencap programatically in Android

code snippet
void takeSnapShot()
{
Process process = null;
try
{
process = Runtime.getRuntime().exec("/system/bin/screencap -p /sdcard/snapshot/test_2.png" );
try
{
process.waitFor();
} catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
I am gettin an empty file saved whereas If i use the same command through adb shell, i get my screen captured.
Any help will be appreciatable

Edit: my previous answer was mistaken, any app can use the screen capture command.
It might be a permission issue. Are you sure you have permission to write to sdcard?
Check this post, which covers your topic:
How to run android system app without root permisson?

I solved this by adding the following permission to my Manifest.
<uses-permission
android:name="android.permission.READ_FRAME_BUFFER"
tools:ignore="ProtectedPermissions"/>
NOTE: This is a protected permission, my application is a system app and also signed using the platform key.

How to prevent android app from crashing when a file has not been found using openFileInput

I want to react to a situation that no file has been found using FileInputStream. When i ran an app that loads a file that doesn't exist it opens an android popup with force close. I would like to react to the situation by changing a text in a text view and saying that the file has not been found. i tried changing the exceptions to change a text view and show that a file has not been found and the app still crashes.
Here is the piece of code:
FileInputStream fis = null;
String collected = null;
try {
fis = openFileInput("test");
byte[] dataArray = new byte[fis.available()];
while (fis.read(dataArray) != -1){
collected = new String(dataArray);
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
try {
fis.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
tv.setText(collected);

To ensure that an Android application does not force-close, your options are: a) do not do anything that will cause an exception, b) catch your exception with your own try/catch block, c) install an application level uncaught exception handler. Option a is not too feasible, c is not very helpful, and based on your code snippet you seem to be trying b -- however there appears to be another exception that you're not catching with this. The contents of logcat will tell you what exception, and the stack trace will lead to a point in your code which needs the try/catch.