Example of method of partial loading and moving basemap in Android development

public class MapMgr {
  public static MapMgr mapMgr = null;
  private int map_num = 28;
  private int b_x = 0;
  private int b_y = 0;
  private int width = 0;
  private int height = 0;
  private Bitmap bmpView = null;
  //create by danielinbiti, the premise is that your picture is indeed larger than the screen. If it is not larger than the screen, just modify the comment line below.  public static void init(int width,int height){
    if(mapMgr==null){
      mapMgr = new MapMgr(width,height);
    }
  }
  public static MapMgr getInstance(){
    return mapMgr;
  }
  public MapMgr(int width,int height){
     = width;
     = height;
    Bitmap bmp = ().getBackGroundBitmap();
    b_x = (()-width)/2;//Make sure the picture is larger than the screen    b_y = (()-height)/2;
    bmpView = (bmp, b_x, b_y, width, height);
  }
  public void logic(){
  }
  public void mapDown(){
    Bitmap bmp = ().getBackGroundBitmap();
    if(b_y+height<()){
      b_y = b_y + ()/map_num;
      if(b_y+height>()){
        b_y = () - height;
      }
    }
    bmpView = (bmp, b_x, b_y, width, height);
  }
  public void mapUp(){
    Bitmap bmp = ().getBackGroundBitmap();
    if(b_y>0){
      b_y = b_y - ()/map_num;
      if(b_y<0){
        b_y = 0;
      }
    }
    bmpView = (bmp, b_x, b_y, width, height);
  }
  public void mapLeft(){
    Bitmap bmp = ().getBackGroundBitmap();
    if(b_x>0){
      b_x = b_x - ()/map_num;
      if(b_x<0){
        b_x = 0;
      }
    }
    bmpView = (bmp, b_x, b_y, width, height);
  }
  public void mapRight(){
    Bitmap bmp = ().getBackGroundBitmap();
    if(b_x+width<()){
      b_x = b_x + ()/map_num;
      if(b_x+width>()){
        b_x = () - width;
      }
    }
    bmpView = (bmp, b_x, b_y, width, height);
  }
  public void draw(Canvas canvas){
    Paint paint = new Paint();
    if(bmpView!=null){
      (bmpView,0, 0, paint);
    }
  }
}

public void onKeyDownDeal(int keyCode){
    if(keyCode==KeyEvent.KEYCODE_DPAD_UP){
      ().mapUp();
    }else if(keyCode==KeyEvent.KEYCODE_DPAD_DOWN){
      ().mapDown();
    }else if(keyCode==KeyEvent.KEYCODE_DPAD_LEFT){
      ().mapLeft();
    }else if(keyCode==KeyEvent.KEYCODE_DPAD_RIGHT){
      ().mapRight();
    }
}