Whats wrong with my Thread()-code?

Question

I have a question regarding an Android application. I want to, later on, create a game and i am currently trying out classes and functions that I need to understand. At the moment im trying to get a grip of how to use threads in a good way, but my application is "force closing" when i touch the button.

For this test application, all have on the screen is one TextView and one button. The button is calling threadStart() when pressed. (onClick in xml) And what i want it to do is to create a thread which increases the variable value by 1 and then report to the UI thread which then update the textview with the new value.

Can someone see what i am doing wrong with this small pice of code?

package com.weldeborn.tc;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.widget.TextView;

public class ThreadCounter extends Activity {

    TextView txtCounter1;

    int value=0;
    final Handler mHandler = new Handler();
    final Runnable mUpdateResults = new Runnable() {
        public void run() {
            updateResult();
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        txtCounter1 = (TextView) findViewById(R.id.counter1);

    }

    protected void threadStart() {
        Thread t = new Thread() {
            public void run() {
                doSomething();
                mHandler.post(mUpdateResults);
            }
        };
        t.start();
    }

    private void doSomething() {
        value = value+1;
    }

    private void updateResult() {
        txtCounter1.setText(value);
    }
}

My code is based on an example from Android Developer: The Common Tasks and how to do them section under the "Handling Expensive Operations in the UI Thread" heading.

I am thankful for any help.

Without LogCat error output you will never be able to debug your programs. Google it, use it. Also if you have XML code, you should use it. — Codemonkey, Mar 04 '11 at 13:23
In the buttonView (in the main.xml file) I use android:onClick="threadStart". I think what it does is to implement a onCliclListener, it has worked for my previous applications. — Weldeborn, Mar 04 '11 at 14:09

score 1 · Accepted Answer · edited May 23 '17 at 10:33

1

setText doesn't work correctly when you pass an integer, directly. Try converting it to String before:

txtCounter1.setText(String.valueOf(value));

Also, check this answer about the usage of threads that need to update the UI.

edited May 23 '17 at 10:33

Community

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answered Mar 04 '11 at 13:32

Alex

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score 0 · Answer 2 · answered Mar 04 '11 at 13:33

0

if threadStart is your onClick the signature needs to be

public void threadStart(View v)

answered Mar 04 '11 at 13:33

Robby Pond

73,164
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Thanks for the quick answers! I haven't manage to fix it yet but I will read the links suggested and also correct the int-String problem that i missed. – Weldeborn Mar 04 '11 at 14:11

Whats wrong with my Thread()-code?

2 Answers2