Question

For my application I want to create a class where I can log data into a file. Within my app there’s the ability to email me if they’re experiencing a problem and data from this file could potentially help me dissect the issue. Firstly, am I going about this the wrong way? Is there a better way to log exceptions that occur?

The problem is if I attempt to use the log method from another class using:

Logger.log(0,"","","");

It fails to find the file or indeed create the file if it isn’t already created. The code is attached below.

package com.example.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import android.app.Activity;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.text.format.Time;
import android.util.Log;

public class Logger extends Activity {

final static String FileName = "Log";
static FileOutputStream fos;
static FileInputStream fis;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("logger", "oncreate");
    try {
        File f = getFileStreamPath(FileName);
        if (!f.exists()) {
            Log.d("logger", "file doesn't exist");
            fos = openFileOutput(FileName, Context.MODE_APPEND);
            fos.write(("Created on " + Build.TIME + "\nDevice name: "
                    + Build.MODEL + " \nAndroid Version" + Build.VERSION.SDK_INT)
                    .getBytes());
            fos.close();
        }
        fos = openFileOutput(FileName, Context.MODE_APPEND);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

public static void log(int type, String TAG, String msg) {
    Log.d("logger", "file being written");
    Log.println(type, TAG, msg);
    Time now = new Time();
    now.setToNow();
    try {
        fos = new FileOutputStream(FileName);
        fos.write(("\n" + now.toString() + " " + type + " " + TAG + " " + msg).getBytes());
        fos.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

Answer 1

The file name is not suffice to write a file. You need to give a directory when using FileOutputStream unlike when using openFileOutput. Thus if you change this line:

final static String FileName = "Log";

To

final static String FileName = "data/data/com.example.test/files/Log";

This will fix the issue. Finally oncreate is not called when accessing a method within a class. You have to combine the two as follows:

final static String FileName = "data/data/com.example.test/files/Log";
static FileOutputStream fos;

public static void log(int priority, String tag, String msg) {
    Log.println(priority, tag, msg);
    try {
        Time now = new Time();
        now.setToNow();
        File f = new File(FileName);
        if (!f.exists()) {
            Log.i("Logger", "Creating Log file");
            fos = new FileOutputStream(f, true);
            fos.write(("Created on " + now.toString().subSequence(0, 15)
                    + "\nDevice name: " + Build.MODEL
                    + " \nAndroid Version " + Build.VERSION.SDK_INT)
                    .getBytes());
            fos.close();
        }
        fos = new FileOutputStream(f, true);
        Log.d("file", now.toString());
        fos.write(("\n" + now.toString().substring(4, 15) + " " + priority
                + " " + tag + " " + msg).getBytes());
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}