无法使用android程序从我的手机读取文本文件

Question

It may be a silly question..but I am getting irritated with this.

The main problem is..I have written code to read a text file from external storage.

In my computer, I installed a software called MEMU like blustaks.

in menu software, my program is giving good results...but when I am installing that app in my mobile (cool pad note 3 lite) it's showing "unfortunately app is stopped".

I installed in another mobile "Moto E" but in that mobile also I faced the same problem.

In system software, it is giving outputs..please anyone help me...where is the problem...(the system software is Samsung)

my code is////

    signal_number=1;samples=3600;shifting=180;
    File sdCard = Environment.getExternalStorageDirectory();
    String filename ;
    File dir = new File(sdCard.getAbsolutePath());
                    sample_tenSec = FileData.getData(dir, filename, signal_number,samples,shifting);

////////////////////////java code is///////////////////////

    public class FileData {
public static Number[] getData(File dir , String filename, int signalNumber,int samples,int shifting)
{
    File file = null;
    Number[] result = new Number[samples];

    try    //Get the text file
    {
        file = new File(dir+"/"+filename);
        //file=new File("/storage//3483-14D9//ppg.txt");
        if(file.exists())
        {System.out.println("File Exists");}
        else
        {System.out.println("File Does not Exist");}
    }
    catch(Exception e1)
    {
        System.out.println("File not found.");
    }

    // Read from File
    int start = (signalNumber-1)*(int)(shifting) +1;
    int end = (start + (int) (samples)) - 1;
    int i=1,k=0;

    try
    {
        BufferedReader br = new BufferedReader(new FileReader(file));
        String line;
        while ((line = br.readLine()) != null && i<=end)
        {
            if(i>=start)
            {
                try
                { result[k++]= (Double.parseDouble(line.toString())); }
                catch (NumberFormatException discardNonIntegers)
                { discardNonIntegers.printStackTrace(); }
            }
            i++;
        }
        br.close();
    }
    catch (Exception e)
    {
        System.out.println("File not reading problem.");
        //System.out.println(e.getMessage());
    }
    return result;
}

}

Answer 1

Without seeing the code that you are using, it is hard to pinpoint what the problem is. Just reading the paragraph you wrote, I would guess that you are having a problem with permissions. Remember, you need to not only include static permissions in your manifest, but also runtime permissions as well.

Add permissions like these to your manifest if you need to read and write:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Also, you need to implement runtime permissions. All the info you need can be found here:

https://developer.android.com/training/permissions/requesting.html