Android下的Gallery显示技术分析(一)

Android下使用的比较频繁的用来导航的控件就是Gallery了，这里我们回顾一下如何使得我们的Gallery控件显示一些特效，扩充原有系统Gallery的展现。

设计目标：

扩充系统Gallery功能，使得Gallery能够显示选中效果。

设计思路：

设计2组图片，并且绘制时根据item是否选中来绘制；

步骤：

1. 扩充构造函数，添加参数：context、两组resource，并且根据传入的resource分别创建2组view；
2. override getView方法，并且在其中根据是否选中来返回不同的内容；

代码比较简单：

public class GalleryAdapter extends BaseAdapter {private Context context;private View[] views;private View[] views_f;public GalleryAdapter(Context context, int[] resources, int[] resources_f) {super();this.context = context;createViews(resources, resources_f);}private void createViews(int[] resources, int[] resources_f) {views = new View[resources.length];views_f = new View[resources_f.length];for (int i = 0; i < resources.length; i++) {views[i] = createView(resources[i]);}for (int i = 0; i < resources_f.length; i++) {views_f[i] = createView(resources_f[i]);}}private View createView(int resourceId) {Bitmap bm = BitmapFactory.decodeResource(context.getResources(), resourceId);ImageView v = new ImageView(context);v.setImageBitmap(bm);LayoutParams params = new LayoutParams(bm.getWidth(), bm.getHeight());v.setLayoutParams(params);return v;}@Overridepublic int getCount() {return views.length;}@Overridepublic Object getItem(int position) {return views[position];}@Overridepublic long getItemId(int position) {return position;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {Gallery gly = (Gallery) parent;if (position == gly.getSelectedItemPosition())return views_f[position];return views[position];}}