‚boolean android.os.Handler.postDelayed (java.lang.Runnable, long)‘ auf einer Null-Objekt Referenz

Question

Ich habe einen Timer in einer anderen Klasse Haupttätigkeit erstellt. Wenn ich den Code ausführen, erhalte ich den folgenden Fehler:

java.lang.NullPointerException: Versuch, virtuelle Methode 'boolean android.os.Handler.postDelayed (java.lang.Runnable, lang)' auf einem Null-Objekt-Verweis aufzurufen

Researching es legt nahe, dass der Handler jedoch nicht in meinem Code initialisiert wird, ist es (wenn ich diesen Code in der mainactivity verwenden fädeln es funktioniert gut)

Kann jemand bieten alle Hinweise, wo im gehend falsch?

Hauptaktivität:

public class MainActivity extends AppCompatActivity { 

private ListView listView; 
TextView timertxt; //this 
public static TextView hourtext;//this2 
int time; //this 




@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    timertxt = (TextView) findViewById(R.id.timertxt);//this 
    hourtext = (TextView) findViewById(R.id.SessionTimerTxt);//this 2 
    final Timer timer; 



    final Button generate = (Button) findViewById(R.id.Generate); 
    generate.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 
      DatabaseAccess myDatabaseHelper = new DatabaseAccess(MainActivity.this); 
      myDatabaseHelper.open(); 
      Cursor d = myDatabaseHelper.getRProgram(); 
      if (d.moveToFirst()) ; 
      DisplayProgram(d); 

      myDatabaseHelper.close(); 

      Timer timer = new Timer(); 
      timer.count(); 
      //the abpove two lines r causing it to crash prob cos timer class is trying to change text on UI 


     } 

     public void DisplayProgram(Cursor d) { 
      TextView result2 = (TextView) findViewById(R.id.result2); 
      result2.setText("\n" + d.getString(1)+ " " + (d.getLong(2)*1000)); 
      time = (d.getInt(2)*1000); 


      TextView dbtime = (TextView) findViewById(R.id.dbtimeproof); 
      dbtime.setText (String.valueOf (time)); 

      final MyCount counter = new MyCount(time,1000);//this 
      counter.start(); 

      Button TButton = (Button) findViewById(R.id.tbutton); 
      TButton.setOnClickListener(new View.OnClickListener() { 
       @Override 
       public void onClick(View view) { 

        //counter.start(); 

       } 
      }); 

     } 

    }); 

} 


// count down timer is an abstract class, so extend it and fill in methods 
public class MyCount extends CountDownTimer { //all below here 

    public MyCount(long millisInFuture, long countDownInterval) { 
     super(millisInFuture, countDownInterval); 
    } 

    @Override 
    public void onFinish() { 
     // it's done 
     timertxt.setText("Done!"); 


    } 

    @Override 
    public void onTick(long millisUntilFinished) { 
     timertxt.setText("Left: " + millisUntilFinished/1000); 

     final String ifvaluest = timertxt.getText().toString(); 

     //if hour timer is greater than 1 sec then process below else skip below 

     if (ifvaluest.equals("Left: 1")){ 


      DatabaseAccess myDatabaseHelper = new DatabaseAccess(MainActivity.this); 
      myDatabaseHelper.open(); 
      Cursor d = myDatabaseHelper.getRProgram(); 
      if (d.moveToFirst()) ; 
      DisplayProgram(d); 

      myDatabaseHelper.close();}} 

     public void DisplayProgram(Cursor d) { 
      TextView result2 = (TextView) findViewById(R.id.result2); 
      result2.setText("\n" + d.getString(1)+ " " + (d.getLong(2)*1000)); 
      time = (d.getInt(2)*1000); 


      TextView dbtime = (TextView) findViewById(R.id.dbtimeproof); 
      dbtime.setText (String.valueOf (time)); 

      final MyCount counter = new MyCount(time,1000);//this 
      counter.start(); 



     } 
    } 


} 

Heres die Timer-Klasse:

public class Timer extends AppCompatActivity { 

//TextView hourtext; 
private int elapsedTime;// used to hold elapsed time 
public Handler handler; 
private int interval = 60000;//millisecs count 





@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    //hourtext = (TextView) findViewById(R.id.SessionTimerTxt); 
    elapsedTime = 0; 
    handler = new Handler();//initialise the handler 
    count(); 



}//starts the count 


    public void count() { 
     runOnUiThread(new Runnable() { 
      @Override 
      public void run() { 


     elapsedTime++; //increase the counter 
     MainActivity.hourtext.setText(String.valueOf(elapsedTime)); 
     handler.postDelayed(runnable, interval); // call the runnable 
      } 
     }); 


}//ends of the count section 

// Runnable - calls the count() function to continue the sequence 
private Runnable runnable = new Runnable() { 
    @Override 
    public void run() { 
     count(); 
    } 
}; //end runnable section 



} //end of class 

Answer 1

Gerade hatte einen Geistesblitz! Es ist, weil ich den Handler innerhalb des runonui nicht instanziiert habe. Also, um es Arbeit habe ich nur noch den folgenden Code OBEN elapsedtime ++

Handler = new Handler();

Answer 2

Sie nicht AppCompatActivity

public class Timer { 
//TextView hourtext; 
private int elapsedTime; // used to hold elapsed time 
public Handler handler; 
private int interval = 60000; //millisecs count 
private Context ctx; 
Timer(context contxt) { 
    ctx = contxt; 
} 

public void count() { 
    elapsedTime = 0; 
    handler = new Handler(); //initialise the handler 
    count(); 

    ((Activity) ctx).runOnUiThread(new Runnable() { 
    @Override 
    public void run() { 


    elapsedTime++; //increase the counter 
    MainActivity.hourtext.setText(String.valueOf(elapsedTime)); 
    handler.postDelayed(runnable, interval); // call the runnable 
    } 
    }); 


    } //ends of the count section 

// Runnable - calls the count() function to continue the sequence 
private Runnable runnable = new Runnable() { 
    @Override 
    public void run() { 
    count(); 
    } 
}; //end runnable section 



} //end of class 

Ihre MainActivity.java als

public class MainActivity extends AppCompatActivity { 

private ListView listView; 
TextView timertxt; //this 
public static TextView hourtext; //this2 
int time; //this 




@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    timertxt = (TextView) findViewById(R.id.timertxt); //this 
    hourtext = (TextView) findViewById(R.id.SessionTimerTxt); //this 2 
    final Timer timer; 



    final Button generate = (Button) findViewById(R.id.Generate); 
    generate.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View view) { 
    DatabaseAccess myDatabaseHelper = new DatabaseAccess(MainActivity.this); 
    myDatabaseHelper.open(); 
    Cursor d = myDatabaseHelper.getRProgram(); 
    if (d.moveToFirst()); 
    DisplayProgram(d); 

    myDatabaseHelper.close(); 

    Timer timer = new Timer(MainActivity.this); 
    timer.count(); 
    //the above two lines r causing it to crash prob cos timer class is trying to change text on UI 


    } 

    public void DisplayProgram(Cursor d) { 
    TextView result2 = (TextView) findViewById(R.id.result2); 
    result2.setText("\n" + d.getString(1) + " " + (d.getLong(2) * 1000)); 
    time = (d.getInt(2) * 1000); 


    TextView dbtime = (TextView) findViewById(R.id.dbtimeproof); 
    dbtime.setText(String.valueOf(time)); 

    final MyCount counter = new MyCount(time, 1000); //this 
    counter.start(); 

    Button TButton = (Button) findViewById(R.id.tbutton); 
    TButton.setOnClickListener(new View.OnClickListener() { 
    @Override 
    public void onClick(View view) { 

     //counter.start(); 

    } 
    }); 

    } 

    }); 

} 


// count down timer is an abstract class, so extend it and fill in methods 
public class MyCount extends CountDownTimer { //all below here 

    public MyCount(long millisInFuture, long countDownInterval) { 
    super(millisInFuture, countDownInterval); 
    } 

    @Override 
    public void onFinish() { 
    // it's done 
    timertxt.setText("Done!"); 


    } 

    @Override 
    public void onTick(long millisUntilFinished) { 
    timertxt.setText("Left: " + millisUntilFinished/1000); 

    final String ifvaluest = timertxt.getText().toString(); 

    //if hour timer is greater than 1 sec then process below else skip below 

    if (ifvaluest.equals("Left: 1")) { 


    DatabaseAccess myDatabaseHelper = new DatabaseAccess(MainActivity.this); 
    myDatabaseHelper.open(); 
    Cursor d = myDatabaseHelper.getRProgram(); 
    if (d.moveToFirst()); 
    DisplayProgram(d); 

    myDatabaseHelper.close(); 
    } 
    } 

    public void DisplayProgram(Cursor d) { 
    TextView result2 = (TextView) findViewById(R.id.result2); 
    result2.setText("\n" + d.getString(1) + " " + (d.getLong(2) * 1000)); 
    time = (d.getInt(2) * 1000); 


    TextView dbtime = (TextView) findViewById(R.id.dbtimeproof); 
    dbtime.setText(String.valueOf(time)); 

    final MyCount counter = new MyCount(time, 1000); //this 
    counter.start(); 



    } 
} 


}