Develop Reference

Get screenshot of current foreground app on Android having root priviliges

I'm developing an application that is installed on the system partition and I would like to know if it's possible to get a screenshot of the current foreground application from a service. Of course, the application being any third party app.
I'm not interested in security issues or anything related to that matter. I only want to get a snapshot of the current foreground third party app.
Note: I'm aware of the /system/bin/screencap solution but I'm looking for a more elegant alternative that does everything programmatically.

The method that I'm going to describe below will let you to programmatically take screen shots of whatever app it's in the foreground from a background process.
I am assuming that you have a rooted device.
I this case you can use the uiautomator framework to get the job done.
This framework has a been created to automate black box testing of apps on android, but it will suite this purpose as well.
We are going to use the method
takeScreenshot(File storePath, float scale, int quality)
This goes in the service class:
File f = new File(context.getApplicationInfo().dataDir, "test.jar");
//this command will start uiautomator
String cmd = String.format("uiautomator runtest %s -c com.mypacket.Test", f.getAbsoluteFile());
Process p = doCmds(cmd);
if(null != p)
{
p.waitFor();
}
else
{
Log.e(TAG, "starting the test FAILED");
}
private Process doCmds(String cmds)
{
try
{
Process su = Runtime.getRuntime().exec("su");
DataOutputStream os = new DataOutputStream(su.getOutputStream());
os.writeBytes(cmds + "\n");
os.writeBytes("exit\n");
os.flush();
os.close();
return su;
}
catch(Exception e)
{
e.printStackTrace();
Log.e(TAG, "doCmds FAILED");
return null;
}
}
This is the class for uiautomator:
public class Test extends UiAutomatorTestCase
{
public void testDemo()
{
UiDevice dev = UiDevice.getInstance();
File f = new File(Environment.getExternalStorageDirectory().getAbsolutePath());
dev.takeScreenshot(f, 1.0, 100);
}
}
It's best if you create a background thread in which uiautomator will run, that way it will not run onto the ui thread. (the Service runs on the ui thread).
uiatuomator doesn't know about or have a android context.
Once uiautomator gets the control you will be able to call inside it android methods that do not take a context parameter or belong to the context class.
If you need to communicate between uiautomator and the service (or other android components) you can use LocalSocket.
This will allow communication in both ways.

Months have passed since I asked this question but just now had the time to add this feature. The way to do this is simply by calling screencap -p <file_name_absolute_path> and then grabbing the file. Next is the code I used:
private class WorkerTask extends AsyncTask<String, String, File> {
#Override
protected File doInBackground(String... params) {
File screenshotFile = new File(Environment.getExternalStorageDirectory().getPath(), SCREENSHOT_FILE_NAME);
try {
Process screencap = Runtime.getRuntime().exec("screencap -p " + screenshotFile.getAbsolutePath());
screencap.waitFor();
return screenshotFile;
} catch (IOException ioe) {
ioe.printStackTrace();
} catch (InterruptedException ie) {
ie.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(File screenshot_file) {
// Do something with the file.
}
}
Remember to add the <uses-permission android:name="android.permission.READ_FRAME_BUFFER" /> permission to the manifest. Otherwise screenshot.png will be blank.
This is much simpler than what Goran stated and is what I finally used.
Note: It only worked for me when the app is installed on the system partition.

Is it possible to get the last few lines of a logcat on a button click?

I am trying to get the Logcat (at least last few lines) on a button click but nothing comes up -
view.findViewById(R.id.logdone).setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// Make file name.
String fullName = "userlogs";
// Extract to file.
File file = new File(fullName);
InputStreamReader reader = null;
FileWriter writer = null;
try
{
// get input stream
String cmd = "logcat -d -v time";
Process process = Runtime.getRuntime().exec(cmd);
reader = new InputStreamReader (process.getInputStream());
// write output stream
writer = new FileWriter (file);
char[] buffer = new char[10000];
do
{
int n = reader.read (buffer, 0, buffer.length);
if (n == -1)
break;
writer.write (buffer, 0, n);
} while (true);
reader.close();
writer.close();
}
catch (IOException e)
{
if (writer != null)
try {
writer.close();
} catch (IOException e1) {
}
if (reader != null)
try {
reader.close();
} catch (IOException e1) {
}
e.printStackTrace();
return;
}
}
}
NOTE:
I do have permissions -
<uses-permission android:name="android.permission.READ_LOGS" />
UPDATE:
My most of the content is in Log.d() then Log.v() then Log.e() then Log.i(). But how to get the last event lines on a button click. My purpose is to get those lines and send them via email to the developer.
I am using the popular third party API known as ACRA to send email which is working fine.
I can use StringBuilder to put all my device logs into it and then to send via email.
But I am unable to get.
Any elegant way that works well effectively ?

Given the comment I made about the READ_LOGS permission no longer being granted to non-system apps, I would instead recommend using a MemoryHandler with a standard Java Logger. On a button click, you can push the messages to a target StreamHandler (which you can use to just dump them into the output buffer of your choice).

Is it possible to get the last few lines of a logcat on a button click?
There has never been a documented and supported way for apps to get anything from LogCat. And, as Turix notes, things were locked down further in Android 4.2.
Any elegant way that works well effectively ?
Log the data yourself to a file that you control, rather than (or in addition to) logging the data to LogCat.

Is it possible to update an android app while it is running and then reload it again

This question might have been asked earlier, but could not get any clear answer. I basically do not want and client interactions with the updates and other stuff, all they can see is the app running and they are happy. But for this to do I need some background thread or something that checks the market for a new update and updates it in the behind and after applying the update reboot the app.
P.S. I am totally new to android development so really sorry if I am sounding crazy, but this is my requirement

You can not update (or install) an app without user-interaction, unless
You're a system app (custom ROM)
Your device is rooted and your updater has root privileges.
Further, there is no official API available to check the version of an app available in the Google Play store.
You can achieve some of what you are trying to do by keeping track of the current version outside of Google Play and then prompting to update the user by launching the market link. If you do that from a secondary app, you can even wait for the update to be complete and then re-launch the app.
In practice, you can't do silent installs/updates without user-interaction, and that's a Good Thing (tm), for the reasons that the first couple of commenters have stated.

AFAIK, it is possible if you have root access, the process is like following:
Your app is in /system/app folder (as a system app)
You need following permissions:
android.permission.INSTALL_PACKAGES
android.permission.DELETE_PACKAGES
android.permission.CLEAR_APP_CACHE
android.permission.WRITE_EXTERNAL_STORAGE
android.permission.MOUNT_UNMOUNT_FILESYSTEMS
Your app must be signed with system signature
java -jar signapk.jar platform.x509.pem platform.pk8 helloworld.apk hello.apk
Check for updates in a background thread and download updated .apk file to a temporary place, e.g apk_path
Execute pm install apk_path command programmatically, below is a snippet:
public String silentInstallation(String apkPath)
{
String[] args = { "pm", "install", "-r", apkPath };
ProcessBuilder processBuilder = new ProcessBuilder(args);
Process process = null;
InputStream errIs = null;
InputStream inIs = null;
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int read = -1;
process = processBuilder.start();
errIs = process.getErrorStream();
while ((read = errIs.read()) != -1) {
baos.write(read);
}
baos.write('\n');
inIs = process.getInputStream();
while ((read = inIs.read()) != -1) {
baos.write(read);
}
byte[] data = baos.toByteArray();
result = new String(data);
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (errIs != null) {
errIs.close();
}
if (inIs != null) {
inIs.close();
}
} catch (IOException e) {
e.printStackTrace();
}
if (process != null) {
process.destroy();
}
}
return result;
}
Hope it helps.

execute pipes command in android?

I want to display application logs.
On terminal I used this command: adb logcat -s brief *:V|grep "pid"
It's display My Application logs.
pid means application pid which is display in logcat table.
public static String logProc()
{
String value = "";
try
{
String cmd[] = {"logcat","-s","brief","*:V","|","grep",
android.os.Process.myPid()+""};
Process p = Runtime.getRuntime().exec(cmd,null, null);
BufferedReader reader = new BufferedReader(new
InputStreamReader(p.getInputStream()));
String line = reader.readLine();
while (line != null)
{
value += line + "\n";
line = reader.readLine();
}
p.waitFor();
}
catch (IOException e1)
{
e1.printStackTrace();
}
catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return value;
}

Most official Android builds do not come with grep (Edit: more recent releases now do)
You can install busybox if you want extra commands - without root you would have to put it in an alternate location.
You have the additional problem that you are trying to exec() a shell command to connect two programs via pipes, which isn't going to work unless you exec a shell interpreter and give it that command. Or you could set up the pipe yourself and exec both programs.
But since you are writing a program, it would probably be simpler to do your pattern matching in the java code.

How to get the build.prop values?

How do I get the build.prop values that are found in /system/build.prop without root access? How do I edit them?

You can probably consider using SystemProperties.get("someKey") as suggested by #kangear in your application using reflection like:
public String getSystemProperty(String key) {
String value = null;
try {
value = (String) Class.forName("android.os.SystemProperties")
.getMethod("get", String.class).invoke(null, key);
} catch (Exception e) {
e.printStackTrace();
}
return value;
}
And then you can use it any where like:
getSystemProperty("someKey");

Try This
static String GetFromBuildProp(String PropKey) {
Process p;
String propvalue = "";
try {
p = new ProcessBuilder("/system/bin/getprop", PropKey).redirectErrorStream(true).start();
BufferedReader br = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while ((line = br.readLine()) != null) {
propvalue = line;
}
p.destroy();
} catch (IOException e) {
e.printStackTrace();
}
return propvalue;
}

Does System.getProperty() help? As an alternative, you can execute getprop in a Process and retrieve its output.

Such as:
SystemProperties.get("ro.rksdk.version")

use android.os.Build class, see http://developer.android.com/reference/android/os/Build.html, but you can not edit it without root access.

I have checked multiple devices including some Samsung and LG devices as well as a Nexus 4, latest one was the Nvidia Shield Tablet with Android 6.0.
On all devices ll on /system/build.prop gave me this result(of course with varying size and date of build.prop):
-rw-r--r-- root root 3069 2015-10-13 21:48 build.prop
This means that anyone and any app without any permissions can read the file. Root would only be required for writing the non "ro."-values. You could just create a new BufferedReader(new FileReader("/system/build.prop")) and read all lines.
Advantages of this approach:
no need for reflection (SystemProperties.get)
no need to spawn a Process and executing getprop
Disadvantages:
does not contain all system properties (some values e.g. are set at boot only available at runtime)
not handy for getting a specific value compared to SystemProperties.get

On the setting page of your file manager, set home as /system, then you could browse system folders and copy build.prop and paste to sdcard. I'm still trying to root my phone but I have no problem tweaking on the way (no pun).

To read properties using reflection on the hidden API :
static public String getprop(String key){
try { Class c = Class.forName("android.os.SystemProperties");
try { Method method = c.getDeclaredMethod("get", String.class);
try { return (String) method.invoke(null, key);
} catch (IllegalAccessException e) {e.printStackTrace();}
catch (InvocationTargetException e) {e.printStackTrace();}
} catch (NoSuchMethodException e) {e.printStackTrace();}
} catch (ClassNotFoundException e) {e.printStackTrace();}
return null;
}
To edit them (Root required) manually, you should extract them with adb :
adb pull /system/build.prop
Edit them on the computer, then "install" the new build.prop :
adb push build.prop /sdcard/
adb shell
mount -o rw,remount -t rootfs /system
cp /sdcard/build.prop /system/
chmod 644 /system/build.prop
Would be safer to keep an original build.prop copy.