Android 每 2 秒更新 UI

Question

我已经搜索并尝试了将近一天的解决方案，但没有任何效果，所以我决定 post 我的代码在这里，希望有人能给我一些帮助，谢谢！

我有一个扩展 ListFragment 的片段。

列表有四项；下面三个，我只是在我的私有ListAdapter class中的getView()方法中设置了他们的图片和文字。对于第一个，我想不断地改变它的画面。我有一个位图数组 promotion_image_array ，其中包含三个位图，我将用作第一项的源。以下是我的getView()的代码和我现在得到的截图：

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHolder holder;
        View myView = convertView;

        System.out.println("in getView");

        if (myView == null) {
            myView = inflater.inflate(R.layout.home_category_item, null);
            holder = new ViewHolder();
            holder.item_image= (ImageView)myView.findViewById(R.id.item_image);
            holder.res_name = (TextView)myView.findViewById(R.id.res_name);


            if(position == 0){
                holder.res_name.setVisibility(View.GONE);
                promotion_image_view = holder.item_image;
                System.out.println("position == 0");
            }
            else if(position == 1) {
                holder.res_name.setText("Food");
                holder.item_image.setBackgroundResource(R.drawable.restaurant_icon);
                System.out.println("position == 1");
            }
            else if(position == 2) {
                holder.res_name.setText("Shop");
                holder.item_image.setBackgroundResource(R.drawable.shop_icon);
                System.out.println("position == 2");
            }
            else if(position == 3) {
                holder.res_name.setText("Groupon");
                holder.item_image.setBackgroundResource(R.drawable.groupon_icon);
                System.out.println("position == 3");
            }
            myView.setTag(holder);
        }
        else {
            // View recycled, no need to inflate
            holder = (ViewHolder) myView.getTag();
        }

        return myView;
    }
}

我尝试使用处理程序和运行nable 在片段的 onCreate() 方法中持续更新第一项的图像。我有一个静态变量 promotion_image_view，我在片段的顶部声明了它，我使用这行代码在我的 getView() 方法中获取第一个项目的实际 ImageView：（来自上面的代码片段）

promotion_image_view = holder.item_image;

然后我尝试在我的运行nable的运行()方法中设置promotion_image_view的背景，下面是我的运行nable的代码和onCreate() 中的处理程序：

      counter = 0;

      mHandler = new MyHandler(this);

      runnable = new Runnable() {
          @Override
          public void run() {
              mHandler.postDelayed(runnable,3000);

              // Repeatedly display three promotion images
              Bitmap[] promotion_image_array = my_global_variables.city_config_object.config_promotion_image_array;
              BitmapDrawable ob = new BitmapDrawable(my_resources, promotion_image_array[counter]);
              if(promotion_image_view != null) {
                  promotion_image_view.setBackground(ob);
                  System.out.println("promotion_image_view != null");
              }
              System.out.format("in run: counter = %d%n", counter);
              counter++;
              if(counter == 3) counter = 0;
          }
      };

      runnable.run();

promotion_image_view != null 和

in run: counter = %d%n,计数器

正确打印（以恒定速率连续打印）并且计数器的值也正确。（0,1,2,0,1,2,0 .....）。但是画面一点变化都没有

非常感谢任何帮助，谢谢！！

********************************* 阅读一些答案后 --- 第一次编辑 ***** ***************************

感谢回答的人，我尝试了notifyDataSetChanged()方法，还是不行；图像未更改，但打印输出看起来正确。

修改后的代码如下：

getView() 方法：

   @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHolder holder;
        View myView = convertView;

        if (myView == null) {
            myView = inflater.inflate(R.layout.home_category_item, null);
            holder = new ViewHolder();
            holder.item_image= (ImageView)myView.findViewById(R.id.item_image);
            holder.res_name = (TextView)myView.findViewById(R.id.res_name);

            if(position == 0){
                holder.res_name.setVisibility(View.GONE);

                Bitmap[] promotion_image_array = my_global_variables.city_config_object.config_promotion_image_array;
                BitmapDrawable ob = new BitmapDrawable(my_resources, promotion_image_array[counter]);
                holder.item_image.setBackground(ob);

                System.out.format("in run: counter = %d%n", counter);
                counter++;
                if(counter == 3) counter = 0;

                System.out.println("in getView: position == 0");
            }
            else if(position == 1) {
                holder.res_name.setText("Food");
                holder.item_image.setBackgroundResource(R.drawable.restaurant_icon);
                System.out.println("position == 1");
            }
            else if(position == 2) {
                holder.res_name.setText("Shop");
                holder.item_image.setBackgroundResource(R.drawable.shop_icon);
                System.out.println("position == 2");
            }
            else if(position == 3) {
                holder.res_name.setText("Groupon");
                holder.item_image.setBackgroundResource(R.drawable.groupon_icon);
                System.out.println("position == 3");
            }
            myView.setTag(holder);
        }
        else {
            // View recycled, no need to inflate
            holder = (ViewHolder) myView.getTag();
        }

        return myView;
    }
}

handler 和运行nable:

      counter = 0;

      mHandler = new MyHandler(this);

      runnable = new Runnable() {
          @Override
          public void run() {
              mHandler.postDelayed(runnable, 3000);
              adapter.notifyDataSetChanged();
          }
      };

      runnable.run();

下面是我认为正确的打印输出：

I/System.out﹕ in 运行: counter = 0