public void actionPerformed(ActionEvent e) {
	Object obj = e.getSource();
	Field field = mainpanel.field;
	if(obj == one_step_button){//一世代ずつ進める
	    if(!spending_time)
		field.nextTime();	    
	}
	if(obj == time_step_button){//時間を流す
	    if(time_step_button.isSelected()){		
		time_step_button.setText("Stop");
		spending_time = true;

	    }
	    else{
		time_step_button.setText("Start");
		spending_time = false;
	    }
	}
	if(obj == clear_button){//クリアする
	    for(int y = 0; y < field.ROW;y++){
		for(int x = 0; x < field.COL;x++){		    
		    field.cells[y][x].die();
		}
	    }
	}
    }