I made an android app for learning Java.
Now i like to write objects from a list with objects to a file.
like ...
private List<MyObjects> objects = new ArrayList<MyObjects>();
MyObjects is a extra class and implements "Serializable".
To write the objects in a file i use also a extra class.
Now my problem.
With the below Line i get a FileNotFoundException.
fos = new FileOutputStream(fileName);
When i change this Line with this Line ...
fos = ctx.openFileOutput(fileName, Context.MODE_PRIVATE);
... looks like good but after endig the code i can't find the file in data/data/myPakage/files/.
The file is not exist.
I read the last 4 days a lot of sites and tutorials about that but i can't find my mistake.
Please help my.
I don't need a solved code but a link to the right side or a pointer in my mistaken code is fine.
Sorry for my english. Is not my first language.
I am not sure with code parts you need to get a good overview. If you need more, please tell me.
Here parts of my main site
package com.example.myProject;
import android.os.Bundle;
import android.app.FragmentTransaction;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
public class ActivityMain extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout_calc);
TabAdapter = new TabPagerAdapter(getSupportFragmentManager());
}
}
Here parts of my fragment site
package com.example.myProject;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
public class Fragment_1 extends Fragment implements OnClickListener {
private Button btnOFF;
private List<Numbers> number = new ArrayList<Numbers>();
private View fragment_1;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
this.fragment_1 = inflater.inflate(R.layout.fragment_layout, container, false);
this.btnOFF = (Button)elementary.findViewById(R.id.id_btnOFF_Elementary);
this.btnOFF.setOnClickListener(this);
this.number.add(new Numbers());
// Here i try to get my data back from the file.
// Every time i get the information; The file not exist
// Perhaps the "containsAll" are wrong. But this is in the moment not my problem.
this.number.containsAll(StreamControl.importNumbers(this.getActivity()));
return fragment_1;
}
#Override
public void onClick(View buttonView) {
if (buttonView == this.btnOFF) {
// Here i try to export data over extra class -- see below
// I put in my List with objects calls "number" and information
// for "Context" i hope.
StreamControl.exportNumbers(number, this.getActivity());
}
}
}
Parts of my class Numbers
package com.example.myProject;
import java.io.Serializable;
public class Numbers implements Serializable {
private static final long serialVersionUID = -5384438724532423282L;
.
.
.
}
Here the code from the file "in" and "out"
package com.example.myProject;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
public class StreamControl {
public static void exportNumbers(List<Numbers> number, Context ctx) {
String fileName = "MyCacheFile.ser";
File cacheFile = new File(fileName);
FileOutputStream fos = null;
try {
// With this line is it not working everytime.
// File not found exception
// But to make my own file with "createNewFile()" is not working
// in data/data i have just read permission.
fos = new FileOutputStream(cacheFile);
// If i use this line i have less problems.
// All Informations "i used Toast on a lot of places" was god.
// But after it, it was nowhere a file to found.
//fos = ctx.openFileOutput(fileName, Context.MODE_PRIVATE);
ObjectOutputStream oos = null;
try {
oos = new ObjectOutputStream(fos);
oos.writeInt(number.size());
for (int i =0; i < number.size(); i++) {
oos.writeObject(new Numbers(((Numbers)number.get(i)).getNumbers()));
}
}
catch (IOException e1) { e1.printStackTrace(); }
finally {
try {
if (oos != null) { oos.close(); }
}
catch (IOException ex) { }
}
}
catch (FileNotFoundException e2) { e2.printStackTrace(); }
finally {
try {
if (fos != null) { fos.close(); }
}
catch (IOException ex) { ex.printStackTrace(); }
}
}
public static List<Numbers> importNumbers(Context ctx) {
String fileName = "MyCacheFile.ser";
int count = 0;
List<Numbers> number = new ArrayList<Numbers>();
FileInputStream fis = null;
try {
fis = new FileInputStream(fileName);
ObjectInputStream ois = null;
try {
ois = new ObjectInputStream(fis);
count = ois.readInt();
for (int i = 0; i < count; i++) {
number.add(new Numbers(((Numbers) ois.readObject()).getNumbers()));
}
}
catch (IOException ex) { ex.printStackTrace(); }
catch (ClassNotFoundException ex) { ex.printStackTrace(); }
finally {
try {
if (ois != null) { ois.close(); }
}
catch (IOException ex) { ex.printStackTrace(); }
}
}
catch (FileNotFoundException ex) { ex.printStackTrace(); }
finally {
try {
if (fis != null) { fis.close(); }
}
catch (IOException ex) { ex.printStackTrace(); }
}
return number;
}
}
So, i hope that's are enough information.
I looking forward
When you use Context.openFileOutput you create a file in internal storage and you can't check that directory.
Take a look at this to save a file to external storage
Related
Im creating a weight tracking app where the user inputs their weight clicks a save button and then the weight is saved. There is also a load button that loads all the previous inputs. The problem I'am having is that once load is clicked it does load up the weights on the screen but it does it all in one line other than a separate line for each.
I have checked the text file and all the weights are stored in a line each so there's no problem in the function that stores the inputs.
Here is the code for the `weight tracker
package com.example.workouttracker;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
public class WeightTracking extends AppCompatActivity {
private static final String FILE_NAME = "WeightTracking.txt";
EditText mEditText;
EditText mEditText2;
private Button button_back_home;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_weight_tracking);
mEditText = findViewById(R.id.weight);
mEditText2 = findViewById(R.id.weight2);
button_back_home=(Button) findViewById(R.id.button_back_home);
button_back_home.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
homePage();
}
private void homePage(){
startActivity(new Intent(getApplicationContext(),MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
}
});
}
public void save(View v) {
String text = mEditText.getText().toString();
FileOutputStream fos = null;
try {
fos = openFileOutput(FILE_NAME, MODE_APPEND);
fos.write((text + "kg's\n").getBytes());
mEditText.getText().clear();
Toast.makeText(this, "Saved to " + getFilesDir() + "/" + FILE_NAME,
Toast.LENGTH_LONG).show();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fos != null) {
try {
fos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public void load(View v) {
FileInputStream fis = null;
try {
fis = openFileInput(FILE_NAME);
InputStreamReader isr = new InputStreamReader(fis);
BufferedReader br = new BufferedReader(isr);
StringBuilder sb = new StringBuilder();
String text;
while ((text = br.readLine()) != null) {
sb.append(text);
sb.append('\n');
}
mEditText2.setText(sb.toString());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
Someone know's how to get it to load each weight line by line?
Thanks
`
can you please check your xml file, if you have added property android:inputType="textMultiLine" on the edittext
Try changing your code like this:
String sb = "";
String text;
while ((text = br.readLine()) != null) {
sb = sb + text + "\n";
}
As a newbie to Android programming, I have attached four files to the assets folder of my library.
You can see the attached image.
I want to access these files through the Android library using the below code (if I don't use this code in Android library, it runs without an error when I use it in MainActivity).
public void copy_weights() {
try {
AssetManager assetFiles = getAssets();
String[] files = assetFiles.list("");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (NullPointerException e) {
e.printStackTrace(); //catch the error in this line
} catch (Exception e) {
e.printStackTrace();
}
}
but this code give me the error:
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.AssetManager android.Context.getAssets' on a null object refrence
I tried other methods like direct accessing via home:///android_asset/7.cfg but it can't access the files too.
EDIT 1
I call the copy_weights() in mainActivity like below
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
final new_class newClass=new new_class();
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final Button button =(Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
TextView textView=(TextView) findViewById(R.id.textView);
newClass.copy_weights();
}
});
}
EDIT 2
new_class code
package com.example.mylittlelibrary;
import android.content.res.AssetManager;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.dnn.Net;
import org.opencv.imgcodecs.Imgcodecs;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.File;
public class new_class extends AppCompatActivity {
private boolean opencv_sucessfully_included;
private static int BUFFER_SIZE = 1024;
public new_class() { }
private static void copyAssetFiles(InputStream in, OutputStream out) {
try {
byte[] buffer = new byte[BUFFER_SIZE];
int read;
while ((read = in.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
in.close();
in = null;
out.flush();
out.close();
out = null;
} catch (IOException e) {
e.printStackTrace();
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
public void copy_weights() {
try {
AssetManager assetFiles = getAssets();
// MyHtmlFiles is the name of folder from inside our assets folder
String[] files = assetFiles.list("");
// Initialize streams
InputStream in = null;
OutputStream out = null;
for (int i = 0; i < files.length; i++) {
File file = new File(Environment.getExternalStorageDirectory() + "/" + files[i]);
if (!file.exists()) {
in = assetFiles.open(files[i]);
out = new FileOutputStream(Environment.getExternalStorageDirectory() + "/" + files[i]);
copyAssetFiles(in, out);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (NullPointerException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
}
You can't initialize an Activity like that. If you need a reference to a Context (such as with getAssets()) you should pass it to the class.
First, remove your AppCompatActivity extension:
public class new_class {
Then change your constructor and add a global variable:
private Context context;
public new_class(Context context) {
this.context = context;
}
You'll notice some of your methods are now in red and unresolved. Just add context. before them. For example
context.getAssets()
Make a new instance of that class by adding a this argument to it:
final new_class newClass = new new_class(this);
Also, you shouldn't put anything before super.onCreate() is called, so move that to go after it.
I am asking here as all other solutions have not worked. I want to read a text file from the web and have this string put into a textview. I am just testing at the moment and the only thing in the text file is the value "223". My app is crashing on start can anyone please help?
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.StringBuilderPrinter;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private TextView textView;
private StringBuilder text = new StringBuilder();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BufferedReader reader = null;
try {
URL url = new URL("http://something.uk/pmt/status.txt");
reader = new BufferedReader(
new InputStreamReader(url.openStream()));
String str;
while ((str = reader.readLine()) != null) {
text.append(str);
text.append('\n');
}
} catch (IOException e) {
Toast.makeText(getApplicationContext(), "Error reading file.", Toast.LENGTH_LONG).show();
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (MalformedURLException e) {
}
catch (IOException e) {
}
}
TextView output = (TextView) findViewById(R.id.textView);
output.setText((CharSequence) text);
}
}
}
STACKTRACE:
https://pastebin.com/YSCB9RBg
Probably because you are using StringBuilder which is not a CharSequence. Use output.setText(text.toString()); instead of output.setText((CharSequence) text);
TextView.setText() expects a CharSequence as an argument. String is a CharSequence, but StringBuilder is not. To get a String you gave to call StringBuilder.toString()
You should look at the crash though. And post it next time you ask a question on stackoverflow.
The crash log you provided clearly states the reason for crash: android.os.NetworkOnMainThreadException. It means that you are trying to do a network operation on the main thread and the Android OS does not let you. It is a rule since Honeycomb. The solution is to use AsyncTask, for example. Here is an article about network ops and AsyncTask.
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.StringBuilderPrinter;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
private TextView textView;
private StringBuilder text = new StringBuilder();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BufferedReader reader = null;
new AsyncTask<Void,Void,Void>(){
#Override
protected Void doInBackground(Void... params) {
try {
URL url = new URL("http://something.uk/pmt/status.txt");
reader = new BufferedReader(
new InputStreamReader(url.openStream()));
String str;
while ((str = reader.readLine()) != null) {
text.append(str);
text.append('\n');
}
} catch (IOException e) {
Toast.makeText(getApplicationContext(), "Error reading file.", Toast.LENGTH_LONG).show();
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (MalformedURLException e) {
}
catch (IOException e) {
}
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
TextView output = (TextView) findViewById(R.id.textView);
output.setText(text.toString());
}
}.execute(null,null,null);
}
}
}
I'm currently developing an android application with makes some user data while running which is saved in two ArrayList. Once the application closes, I need to save the datas on to the internal memory but in my logcat I'm always getting the error IOException file not found.
I'm confused about why it always happen. The following is my code for my activity. Please help me!
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.text.Html;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.widget.Button;
public class MainActivity extends ActionBarActivity {
public static ArrayList<String> myArrayList=new ArrayList<String>();
public static ArrayList<String> myArrayListwr=new ArrayList<String>();
static int close=1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
close=1;
System.out.println("Oncreate called");
try{
final File dir = new File(getApplicationContext().getFilesDir() + "/file");
if(!(dir.exists()))
{
dir.mkdirs(); //create folders where write files
}
final File file = new File(dir+ "/lines.txt");
if(!(file.exists())) {
file.createNewFile();
}
BufferedReader br = new BufferedReader(new FileReader(file));
if (br.readLine() == null) {
close=0;
}
br.close();
}
catch (IOException exc) { exc.printStackTrace(); }
try {
if(myArrayList.size()==0 && close!=0)
{
System.out.println("retriving data from file lines");
FileInputStream input =openFileInput("lines.txt"); // Open input stream
DataInputStream din = new DataInputStream(input);
int sz = din.readInt(); // Read line count
for (int i=0;i<sz;i++) { // Read lines
String line = din.readUTF();
myArrayList.add(line);
}
din.close();
}
}
catch (IOException exc) { exc.printStackTrace(); }
try {
if(myArrayListwr.size()==0 && close!=0)
{
System.out.println("retriving data from file lineswr");
final File dirwr = new File(getApplicationContext().getFilesDir() + "/file");
if(!dirwr.exists())
dirwr.mkdirs(); //create folders where write files
final File filewr = new File(dirwr+ "/lineswr.txt");
if(!filewr.exists()) {
filewr.createNewFile();
}
FileInputStream inputwr = openFileInput("lineswr.txt"); // Open input stream
DataInputStream dinwr = new DataInputStream(inputwr);
int szwr = dinwr.readInt(); // Read line count
for (int iwr=0;iwr<szwr;iwr++) { // Read lines
String linewr = dinwr.readUTF();
myArrayListwr.add(linewr);
}
dinwr.close();
}
}
catch (IOException exc) { exc.printStackTrace(); }
Button phy = (Button) findViewById(R.id.button3);
Button mat = (Button) findViewById(R.id.button1);
Button bio = (Button) findViewById(R.id.button2);
Button chem = (Button) findViewById(R.id.button4);
}
#Override
public void onBackPressed() {
super.onBackPressed();
try {
if(myArrayList.size()!=0)
{
System.out.println("inside on back pressed saving data to lines");
//Modes: MODE_PRIVATE, MODE_WORLD_READABLE, MODE_WORLD_WRITABLE
String fileName = getApplicationContext().getFilesDir()+"/file/"+ "lines.txt";
FileOutputStream output = openFileOutput("lines.txt",MODE_PRIVATE);
DataOutputStream dout = new DataOutputStream(output);
dout.writeInt(myArrayList.size()); // Save line count
for(String line : myArrayList) // Save lines
dout.writeUTF(line);
dout.flush(); // Flush stream ...
dout.close(); // ... and close.
}
}
catch (IOException exc) { exc.printStackTrace(); }
try {
if(myArrayListwr.size()!=0)
{
System.out.println("inside on back pressed saving data to lineswr");
//Modes: MODE_PRIVATE, MODE_WORLD_READABLE, MODE_WORLD_WRITABLE
String fileNamewr = getApplicationContext().getFilesDir()+"/file/"+ "lineswr.txt";
FileOutputStream outputwr = openFileOutput("lineswr.txt",MODE_PRIVATE);
DataOutputStream doutwr = new DataOutputStream(outputwr);
doutwr.writeInt(myArrayListwr.size()); // Save line count
for(String linewr : myArrayListwr) // Save lines
doutwr.writeUTF(linewr);
doutwr.flush(); // Flush stream ...
doutwr.close(); // ... and close.
}
}
catch (IOException exc) { exc.printStackTrace(); }
Intent intent = new Intent(MainActivity.this, MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.putExtra("EXIT", true);
startActivity(intent);
}
}
I am new here.
I consider myself to have broken past newbie-ism and I am breaking into intermediate programming. I am trying to read from my assets folder, and the problem I am having is that my program keeps catching the exception. Can you help me figure out what I am doing wrong? Here is my code:
package com.example.testone;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.widget.TextView;
public class AssetsTest extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TextView textView = new TextView(this);
setContentView(textView);
AssetManager assetManager = getAssets();
InputStream inputStream = null;
try {
inputStream = getAssets().open("myawesometext.txt");
String text = loadTextFile(inputStream);
textView.setText(text);
} catch (IOException e) {
textView.setText("Couldn't load file");
} finally {
if (inputStream != null)
try {
inputStream.close();
} catch (IOException e) {
textView.setText("Couldn't close file");
}
}
}
public String loadTextFile(InputStream inputStream) throws IOException {
ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
byte[] bytes = new byte[4096];
int len = 0;
while ((len = inputStream.read(bytes)) > 0)
byteStream.write(bytes, 0, len);
return new String(byteStream.toByteArray(), "UTF8");
}
}
I have searched every website including this one, combing over the other similar questions, and could not find an answer that worked for me. Your help would be so greatly appreciated.
Thanks in advance!