The application may be doing too much work on its main thread

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        final AssetManager assetManager = getAssets();
        try {
			// for assets folder add empty string
                        String[] filelist = assetManager.list("");
                        // for assets/subFolderInAssets add only subfolder name
                        String[] filelistInSubfolder = assetManager.list("subFolderInAssets");
			if (filelist == null) {
			    // dir does not exist or is not a directory
			} else {
			    for (int i=0; i<filelist.length; i++) {
			        // Get filename of file or directory
			        String filename = filelist[i];
			    }
			}
                     
                        // if(filelistInSubfolder == null) ............  

		} catch (IOException e) {
			e.printStackTrace();
		}
     }

Boolean canWrite =	Environment.getExternalStorageDirectory().canWrite() ;
if(canWrite){
File f = new File(Environment.getExternalStorageDirectory()
                        + File.separator + "my_image.jpg")
f.createNewFile();
}else{

}

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

package cz.okhelp.timer;

import java.util.Timer;
import java.util.TimerTask;

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

public class TimerActivity extends Activity {
TextView hTextView;
@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        hTextView = (TextView)findViewById(R.id.idTextView);
        MyTimerTask myTask = new MyTimerTask();
        Timer myTimer = new Timer();
//        public void schedule (TimerTask task, long delay, long period) 
//        Schedule a task for repeated fixed-delay execution after a specific delay.
//
//        Parameters
//        task  the task to schedule. 
//        delay  amount of time in milliseconds before first execution. 
//        period  amount of time in milliseconds between subsequent executions. 

        myTimer.schedule(myTask, 3000, 1500);        
        
    }
class MyTimerTask extends TimerTask {
	  public void run() {
		  // ERROR
		 hTextView.setText("Impossible");
		 // how update TextView in link below  
                 // //android.okhelp.cz/timer-task-timertask-run-cancel-android-example/
                 
	    System.out.println("");
	  }
	}


}

// warnning
private List list = new ArrayList();

// ok /put type of added object
private List<String> list = new ArrayList<String>();

<application android:label="@string/app_name" android:icon="@drawable/icon">
    <activity android:name="MyActivity"
              android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>