Question

I am trying to get Shared Preferences in an AsyncTask, but I don’t get it.

How do I have to use context here?

package com.example.wettkampftimerbt;

import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.URL;

import android.content.Context;
import android.content.SharedPreferences;
import android.os.AsyncTask;

public class network extends AsyncTask<URL, String, String> {

    private final String PREFS_NAME = "prefs", W1 = "w1",  W2="w2", W3="w3", W4="w4", 
            W5="w5", W6="w6", W7="w7", SENDBEG="sendbeg", SENDEND="sendend";
    int w1, w2, w3, w4, w5, w6, w7, sendend, sendbeg;

    protected String doInBackground(URL... params) {
        int c2, c3, c4, c5, c6;
        int w0 = 00;
        try {
            w1 = sendbeg;
            c2 = w2;
            c3 = w3;
            c4 = w4;
            c5 = w5;
            c6 = w6;
            w7 = sendend;

            Socket ss = new Socket("192.168.3.100", 4455);
            System.out.println(ss);
            boolean stopData = true;
            System.out.println("lane1 stop send");
            DataOutputStream dos = new DataOutputStream(
                    ss.getOutputStream());
            while (stopData) {
                dos.writeByte(w0);
                dos.writeByte(w1);
                dos.writeByte(c2);
                dos.writeByte(c3);
                dos.writeByte(c4);
                dos.writeByte(c5);
                dos.writeByte(c6);
                dos.writeByte(w7);
                stopData=false;
            }
        } catch (IOException e) {
            System.out.println("IO error" + e);
            e.printStackTrace();
        }

        return "Done";
    }

    public void onPreExecute(){
        Context context = network.this;
        SharedPreferences prefs = context.getSharedPreferences("PREFS_NAME");

        doInBackground();
    }

    public void getPrefs (Context context){         
        w1= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W1, "00"));
        w2= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W2, "00"));
        w3= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W3, "00"));
        w4= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W4, "00"));
        w5= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W5, "00"));
        w6= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W6, "00"));
        w7= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(W7, "00"));
        sendbeg= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(SENDBEG, "00"));
        sendend= Integer.valueOf(context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE).getString(SENDEND, "00"));
    }
}

This is the snippet, my problem is about: I have no errors, except to a nullPointerException (caused by getPrefs(null);?) on Start. Can someone help me?

I already read a lot of context explanations and even the Android developer site I visited, but I don’t get, WHAT context is, and what it exactly does.

EDIT: Thanks for the fast answers, but it still does not work. I put now the whole activity in here, with one sample you gave me, but I get errors now. Is it up to me, or does Eclipse hate me?

EDIT2: I call the doInBackground on my own, because it does not start on HIS own.

EDIT3: Worked around now, it works ^^ I am calling getPrefs from my main activity directly, and then network from getPrefs… fine so far, but: I’m getting this NetworkOnMainThreadException error. What to do now?

Answer 1

Try this:

1) Define a local variable in your Async class(in your case which is network class)

Context context;

2) Create constructor in your Async Task to accept context:

public network(Context context) {
    this.context = context;       
}

3) Now, in onPreExecute() while calling getPrefs, call like this :

getPrefs(context);

4) You can call this class from your MainActivity like this:

network networkObj= new network(MainActivity.this);
networkObj.execute(url);