Develop Reference

Dump input device file using getevent tool on Android

I have a rooted Android 7 phone and I would like to dump unix input event files. Using adb I could do it using the following command:
adb shell getevent -t /dev/input/event7 > recorded_touch_events.txt
This will dump the event7 file into recorded_touch_events.txt. But this only works when the phone is connected by usb cable with the PC. Using Android I can dump files with the following code:
th = new Thread(new Runnable(){
private Process exec;
#Override
public void run() {
try {
exec = Runtime.getRuntime().exec(new String[]{"su","-c","getevent -t /dev/input/event7"});
InputStreamReader is = new InputStreamReader(
exec.getInputStream());
String s;
BufferedReader br = new BufferedReader(is);
while(((s = br.readLine()) != null) && run){
// write line to text file
}
is.close();
exec.destroy();
} catch (IOException e) {
e.printStackTrace();
}
}
In this way, I could store every read line in a text file.
Are there other approaches (probably faster ones) for directly dumping the event file?

getevent is used to print input events out in human readable form. For example during interactive debug session. You do not need to use getevent for just dumping or any other computer processing task. Just open and read the input file. The event record format is very simple.

Certainly No, you are doing it right.

How to change DNS in android 4.x+ using internal linux commands within app?

I have been working on this small project in college about changing the default DNS of wifi network to a custom DNS like Google, OpenDNS, Metacert, etc.
I know I have to write a shellscript inside the app's code that would edit the hosts file in the filesystem.
The problem is I have no idea where to start from. I have researched on google for some time and I couldn't figure anything.
If anyone knows about it, please guide me. Please tell me the name of the file to be edited, its location, what commands are required and how to run those commands' combination as a shellscript on a click of a button on the UI of app.
EDIT : I'm stuck only at this. Any help will be greatly appreciated.

I'm not sure about which files you would have to edit but this should give you the tools you need to do that.
The first thing you need to do is root the phone if you haven't already. If it's not rooted, you'll run into an issue like: Working Directory : null environment when running Process.Builder on android
There are a lot of guides available for that online. Install SuperSU as well. In order to run shell commands or scripts you should look at the ProcessBuilder class in Android:
http://developer.android.com/reference/java/lang/ProcessBuilder.html
I've given some sample code below to help you along the way. You could execute this in an OnClick() for a button.
/**
* Runs the shell command.
*
* #param command an array of Strings. command[0] contains the name of the
* shell command. command[1]... contains parameters.
*
* #return the text outputted by the command to stderr or stdout
*/
String runCmd(String[] command, boolean readOutput,
boolean waitForExit) {
ProcessBuilder probuilder = new ProcessBuilder()
.command(command)
.redirectErrorStream(true);
String output = "";
Process process;
// Log.d("MyShellCommand", "Executing " + command[0]);
try {
process = probuilder.start();
} catch(IOException e) {
return e.getMessage();
}
if (readOutput) {
InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
try {
while ((line = br.readLine()) != null) {
// Log.d("MyShellCommand", "Read a line: " + line);
output += line + "\n";
}
} catch(IOException e) {
output = e.getMessage();
}
}

How to read logcat written through my application in all android os

I need to capture all the logs written through my application. I know from Jetllybean OS we can read need only our application log. But when I tried by using command "logcat -d" using exec method by application and I did not get any data.
Please help me on this.
Thanks,
Saravanakumar

This is the example that I was playing around with before that will generate a log text file in local storage:
private static String generateLogcatLogCommond = "logcat -d > /sdcard/IssueReport/log.txt";
public static String generateLogcatLog() throws InterruptedException {
try {
File issueReport = new File(Environment.getExternalStorageDirectory(), "IssueReport");
if (!issueReport.exists())
issueReport.mkdir();
File logFile = new File(issueReport,"log.txt");
logFile.createNewFile();
Process process = Runtime.getRuntime().exec("/system/bin/sh -");
DataOutputStream os = new DataOutputStream(process.getOutputStream());
os.writeBytes(generateLogcatLogCommond);
logLocation = "/sdcard/IssueReport/log.txt";
Log.d("Client", logLocation);
} catch (IOException e) {
e.printStackTrace();
}
return logLocation;
}
What the above code is doing is using 'sh' to run 'logcat -d' command and save it as a file locally. This will get ALL the logcat log. For you, you can change that to 'logcat -s ""' and it will save all logcat log of your application to a file.

Android memory error

I cannot understand why this keeps crashing with a memory error:
server = new URL("http://-link cannot be supplied-");
BufferedReader reader2 = read(server);
line = reader2.readLine();
StringBuilder bigString = new StringBuilder("");
while(line!=null) {
bigString.append(line);
reader2.readLine();
}
the file is not -that- big 7000 odd lines # 240,031 bytes on disk.
Basically what i need to do is to tell wether the file contains a small string (a postcode) the file is basically a list of postcodes.
What is the best way to read this in? as obviously what i am doing is not working at all :D

Your while loop never ends!
while(line!=null) {
bigString.append(line);
line = reader2.readLine();
}
should work.

Problem finding/reading a file

I'm trying to develop a small application, where I was given a JSON file, and I have to extract data from it. As I understood a JSON object takes a string argument, thus I'm trying to access a file and write the data from it to a string.
I've placed that file in a "JSON file" folder, and when I try to read the file, it throws me a file not found exception.
I've tried several ways to find a path to that file, but every attempt was for vain.
It might be that I'm extracting the path wrong, or might be something else, please help me.
Thanks in advance.
here is the code of finding the path:
try
{
path = Environment.getRootDirectory().getCanonicalPath();
}
catch (IOException e)
{
e.printStackTrace(); //To change body of catch statement use File | Settings | File Templates.
}
File jFile = new File(path + /"JSON file/gallery.json");
here is the code for reading from a file :
String str ="";
try
{
BufferedReader in = new BufferedReader(new FileReader(jFile));
while ((str += in.readLine()) != null)
{
}
in.close();
}
catch (IOException e)
{
e.getMessage();
}
return str;
Here more specification:
I want to take the data from the file in order to do that : JSONObject(jString).
when I extract the path of json file I create a file with the path and pass it to the function that reads from the file, and there it throws me a file not found exception, when I try to read from it.
The file does exists in the folder (even visually - I've tried to attach an image but the site won't let me, because I'm new user)
I've tried to open the file through the windows address bar by typing the path like that:
C:\Users\Marat\IdeaProjects\MyTask\JSON file\gallery.json and it opens it.

if you store it in the assets folder you can access it by using
InputStream is = context.getResources().getAssets().open("sample.json");
You can then convert it to a String
public static String inputStreamAsString(InputStream stream)
throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(stream));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
br.close();
return sb.toString();
}

EDIT
You need to put the file in the device, if it is on your computer, it is not accessible from your device. There are some ways to do that, and one of them is to put it in the res/ dir of your application. Please refer to the documentation to see how to do that.
Debug it. I'm pretty sure it will be very easy to find. To start with, look for the following:
Print the path before you create the file, e.g. Log.d("SomeTag", path + "/JSON file/gallery.json")
Observe the full exception details. Maybe there is another problem.
Explore the folders and see if the file exists (in eclipse: window -> show view -> other -> android -> file explorer.
You will probably observe the problem and be able to fix it. If not, post here a question with more details, including the results of those trials.
BTW, GetgetRootDirectory() returns the root directory of android, that's not what you want (you don't have RW permissions there) you probably want to get the applcation directory, you can see how to get it here, in the question I asked a few month ago. But since you didn't give us those details, it will be hard to help you more then that.