CODEWITHSUNDEEP
androidmultithreadingjava-threads
Zubair Rasheed
Zubair Rasheed

Reputation: 49

wait() function not working in thread in android studio

Before asking the question let me tell you that I am new in android development. My question is regarding Threads and wait(); function. Right now I am trying to implement the thread which should change the color of text every 3 seconds but the program crashes as soon as I start it. Here is the code.

package care.client_application;

public class MainActivity extends AppCompatActivity {
   Thread Thread3=null; //Coloring thread
   public TextView Warning;

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

      Warning= (TextView) findViewById(R.id.warning);
      UIHandler = new Handler();  //Initialization of handler

      this.Thread3= new Thread(new Thread3());
      this.Thread3.start();
   }

   class Thread3 implements Runnable{
      @Override
      public void run() {
         Warning.setTextColor(Color.rgb(200,200,0));
         wait(3000);
         Warning.setTextColor(Color.rgb(200,0,0));
      }
   }
}

Upvotes: 1

Views: 271

Answers (4)

Mohammed Atif
Mohammed Atif

Reputation: 4513

public class MainActivity extends AppCompatActivity {

    private TextView warningText;
    private final long TIME_TO_CHANGE = 3000;
    private Handler handler = new Handler();
    private int counter = 0;
    private int[] R = {0, 200}, G = {0, 200}, B = {200, 0};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        warningText = (TextView) findViewById(R.id.warning);
        warningText.setTextColor(Color.rgb(0,0,0));
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                updateTextColor();
                handler.postDelayed(this, TIME_TO_CHANGE);
            }
        }, TIME_TO_CHANGE);
    }

    private void updateTextColor(){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                counter = (counter+1)%2;
                warningText.setTextColor(Color.rgb(R[counter],G[counter],B[counter]));
            }
        });
    }

    @Override
    public void onPause(){
        super.onPause();
        handler.removeCallbacksAndRunnables(null);
    }        

}

Use Handlers for tasks that require waiting. Thread.sleep() is not recommended in Android.

Upvotes: 1

Muhammad Saad Rafique
Muhammad Saad Rafique

Reputation: 3189

First, You shouldn't use that it freezes ui and thats not a good approach. Second if you have to do this then you have to use runonuithread as to change ui on run time you have to do this like:

class Thread3 implements Runnable{
      @Override
      public void run() {
         getActivity().runOnUiThread(new Runnable()
        {
            @Override
            public void run()
            {
             Warning.setTextColor(Color.rgb(200,200,0));
            }
        });
         wait(3000);
getActivity().runOnUiThread(new Runnable()
        {
            @Override
            public void run()
            {
             Warning.setTextColor(Color.rgb(200,0,0));
            }
        });

      }

I hope it helps you do let me know if it works. Best of luck.

Upvotes: 0

rafsanahmad007
rafsanahmad007

Reputation: 23881

I want to change the color of text every 3 seconds

Why not use a Handler instead of Thread

private Runnable task = new Runnable () {
    public void run() {
            //update textview color 
            Warning.setTextColor(Color.rgb(200,200,0));
            mHandler.postDelayed(task, 3000);  //repeat task
    }
};

Call it using:

 private Handler mHandler = new Handler();
// call updateTask after 3 seconds
mHandler.postDelayed(task, 3000);

To stop the task:

    @Override
protected void onPause() {
     mHandler.removeCallbacks(task);
     super.onPause();
}

Upvotes: 1

Nikhil Sharma
Nikhil Sharma

Reputation: 603

First of all you can't update any UI component on Run method of thread like your doing 

Warning.setTextColor(Color.rgb(200,200,0)); // this wrong way to do this

Use Handler to perform any UI update

Upvotes: 0

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