1 publicclass MainActivity extends Activity {
 2 private ImageView image;
 3 private Button btn;
 4 privateint index;
 5 privateint totalCount;
 6 private ArrayList<String> imageSrcs =new ArrayList<String>();
 7     @Override
 8 publicvoid onCreate(Bundle savedInstanceState) {
 9 super.onCreate(savedInstanceState);
10         setContentView(R.layout.main);
11         
12         image = (ImageView)findViewById(R.id.image);
13         btn = (Button)findViewById(R.id.btn);
14         
15 //获取上下文
16         Context ctx = MainActivity.this;
17 //获取ContentResolver对象
18         ContentResolver resolver = ctx.getContentResolver();
19 //获得外部存储卡上的图片缩略图
20         Cursor c = resolver.query(MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, null, null, null, null);
21 //为了for循环性能优化，用一变量存储数据条数
22         totalCount = c.getCount();
23         
24 //将Cursor移动到第一位
25         c.moveToFirst();
26 //将缩略图数据添加到ArrayList中
27 for(int i=0; i<totalCount; i++){
28 int index = c.getColumnIndexOrThrow(MediaStore.Images.Thumbnails.DATA);
29             String src = c.getString(index);
30             imageSrcs.add(src);
31             index = i;
32             c.moveToNext();
33         }
34 //关闭游标
35         c.close();
36         
37 //点击按钮，切换图片
38         btn.setOnClickListener(new OnClickListener(){
39             @Override
40 publicvoid onClick(View v) {
41                 String src = imageSrcs.get(index);
42                 image.setImageURI(Uri.parse(src));
43                 index ++;
44 if(index == totalCount){
45                     index =0;
46                 }
47             }
48         });
49     }
50 }