Develop Reference

Issues when fetching data/Json/file from assets manager on Android 10

Below is my code for reading Json file from assets, It works on every other device except Pixel 3 XL which android version is 10.This device returning null from assets
StringBuilder builder = new StringBuilder();
BufferedReader reader = null;
try {
reader = new BufferedReader( newInputStreamReader( MyApp.getAppInstance().getAssets().open(fileName)));
// do reading, usually loop until end of file reading
String mLine;
builder = new StringBuilder();
while ((mLine = reader.readLine()) != null) {
builder.append(mLine);
}
} catch (IOException e) {
//log the exception
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {}
}
}
return builder.toString();
}

Make sure you have given the required permission in manifest
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
and for Android 10 issue try using
android:requestLegacyExternalStorage="true"
inside your application tag

Getting current scheduler information for Android app using Android Studio

I'm trying to get the current scheduler information from the path "/sys/block/sda/queue/scheduler" to be output in my application. However, it doesn't seem to return anything, not sure what I am doing wrong here?\
private String getScheduler() {
StringBuffer sb = new StringBuffer();
String file = "/sys/block/sda/queue/scheduler"; // Gets governor for big cores
if (new File(file).exists()) {
try {
BufferedReader br = new BufferedReader(new FileReader(new File(file)));
String aLine;
while ((aLine = br.readLine()) != null)
sb.append(aLine + "\n");
if (br != null)
br.close();
}
catch (IOException e) {
e.printStackTrace();
}
}
if (sb.toString().length() == 0) {
return "File not available";
}
return sb.toString();
}
It always return the string "File not available". I know this should work as I did the same thing for returning the current scaling governor. Do I need to request for root permissions within this app, even though my phone is already rooted?
Any help is greatly appreciated! Thank you so much!

on android how to find the original file if got a hard link

in the app when receiving an intent which was created from other app and has a file path, it can access the file's content using the file path.
the question is if that path (call it as 'link-path') is a 'hard link' to the original file, is it possible to find the original file through this 'link-path'?
Searched and find some post like:
https://unix.stackexchange.com/questions/122333/how-to-tell-which-file-is-original-if-hard-link-is-created
they show some unix shell command. Not sure if there is some android file system support for this, anyone having suggestion?

You can use this code I made, based on this post. It will return the target path of any path. If path is not a symbolic link, it will return itself. If path doesn't exist it returns null.
public static String findLinkTarget(String path) {
try {
Process findTarget = Runtime.getRuntime().exec("readlink -f " + path);
BufferedReader br = new BufferedReader(new InputStreamReader(findTarget.getInputStream()));
return br.readLine();
} catch (IOException e) {
Log.w(TAG, "Couldn't find target file for link: " + path, e);
}
}
The code wasn't tested, but I tested the command on Termux and it worked.
EDIT: Try calling getCanonicalPath() on your file, I think it resolves the symlink.

find a way by comparing the inode, in api >21 android has Os to get it, otherwise using the command "ls -i" to get the inode. One issue though, tested on api<=18 the "ls -i" does not return any thing (tested on emulator), in that case maybe fallback to compare the file's size and timestamp.
static String getFileInode(File file) {
String inode = "-1";
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
StructStat st = null;
try {
ParcelFileDescriptor pfd = ParcelFileDescriptor.open(file,
ParcelFileDescriptor.parseMode("r"));
st = Os.fstat (pfd.getFileDescriptor());
if (st != null) {
inode = ""+st.st_ino;
}
} catch (Exception e) {
Log.e(TAG, "fstat() failed”+ e.getMessage());
}
} else {
BufferedReader reader = null;
try {
Process process = Runtime.getRuntime().exec(("ls -il " + path));
reader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
int read;
char[] buffer = new char[4096];
StringBuffer output = new StringBuffer();
while ((read = reader.read(buffer)) > 0) {
output.append(buffer, 0, read);
}
process.waitFor();
String ret = output.toString();
if (!TextUtils.isEmpty(ret)) {
ret = ret.trim();
String[] splitArr = ret.split("\\s+");
if (splitArr.length>0) {
inode = splitArr[0];
}
}
} catch(Exception e) {
Log.e(TAG, "!!! Runtime.getRuntime().exec() exception, cmd:”+cmd);
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {}
}
}
}
return inode;
}

Self updating app

TL:DR; version ;)
my app should run without user interaction (autostart etc works)
it should update itself (via apk) without any user interaction
rooted devices are possible
.
problem:
querying a newer apk from a server works
when starting the apk with a (view?) intent, the "install app" prompt pops and needs a user confirmation
How do I solve this without any user interaction?
http://code.google.com/p/auto-update-apk-client/
This seems to be a solution, but there must be better approach.
I already found this: Install Application programmatically on Android
but that doesn't solve my problem.

Solved it! :D
It just works in rooted devices but works perfectly.
Using the unix cmd "pm" (packageManager) allows you to install apks from sdcard, when executing it as root.
Hope this could help some people in the future.
public static void installNewApk()
{
try
{
Runtime.getRuntime().exec(new String[] {"su", "-c", "pm install -r /mnt/internal/Download/fp.apk"});
}
catch (IOException e)
{
System.out.println(e.toString());
System.out.println("no root");
}
}
Required permissions:
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

My suggestion is to use plugin mechanism instad of updating the app. You can dynamically load classes from the Web and run them inside your app without any user interaction. There is a lot of resources spread across the Internet:
How to load a Java class dynamically on android/dalvik?
http://android-developers.blogspot.com/2011/07/custom-class-loading-in-dalvik.html

If su -c doesn't work, try su 0 (only rooted devices can do su!)
The full answer looks like this:
private void installNewApk()
{
String path = mContext.getFilesDir().getAbsolutePath() + "/" + LOCAL_FILENAME;
mQuickLog.logD("Install at: " + path);
ProcessUtils.runProcessNoException(mQuickLog, "su", "0", "pm", "install", "-r", path);
}
With this class defined:
public class ProcessUtils {
Process process;
int errCode;
public ProcessUtils(String ...command) throws IOException, InterruptedException{
ProcessBuilder pb = new ProcessBuilder(command);
this.process = pb.start();
this.errCode = this.process.waitFor();
}
public int getErrCode() {
return errCode;
}
public String getOutput() throws IOException {
InputStream inputStream = process.getInputStream();
InputStream errStream = process.getErrorStream();
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
String line;
StringBuilder sb = new StringBuilder();
while ((line = br.readLine()) != null) {
sb.append(line + System.getProperty("line.separator"));
}
br = new BufferedReader(new InputStreamReader(errStream));
while ((line = br.readLine()) != null) {
sb.append(line + System.getProperty("line.separator"));
}
return sb.toString();
}
public static String runProcess(String ...command) throws IOException, InterruptedException {
ProcessUtils p = new ProcessUtils(command);
if (p.getErrCode() != 0) {
// err
}
return p.getOutput();
}
public static void runProcessNoException(String ...command) {
try {
runProcess(command);
} catch (InterruptedException | IOException e) {
// err
}
}
}

specific android processor details

I have gone through the forums and got a method to get the android processor information as a string! well, it returns lots of information that is irrelevant to a user. I want to get the specific details only like
Processor Name or type
Avilabale cores
Cache size
Processor Version
this is the method I found to get the information! if any one can tell me a way to get specific details please help me! :)
private String getInfo() {
StringBuffer sb = new StringBuffer();
sb.append("abi: ").append(Build.CPU_ABI).append("\n");
if (new File("/proc/cpuinfo").exists()) {
try {
BufferedReader br = new BufferedReader(new FileReader(new File("/proc/cpuinfo")));
String aLine;
while ((aLine = br.readLine()) != null) {
sb.append(aLine + "\n");
}
if (br != null) {
br.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}
and I'm kinda new to android app development so please help me in this! :) ( MY research project )

I'm getting the Processor namefrom the available details. You can change what you want.
while ((aLine = br.readLine()) != null) {
if(aLine.contains("Processor"))
{
String pro=aLine;
Log.v("Processor>>>",pro);
}
sb.append(aLine + "\n");
}