查询SD卡下某个文件夹的图片

List lt = new ArrayList<>();
private ListView lv;
private ArrayAdapter adapter;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_li_xian);

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        adapter = new ArrayAdapter(LiXian.this,android.R.layout.simple_list_item_1);
         adapter.addAll( getImagePathFromSD());
        lv.setAdapter(adapter);
    }
});

}

  private List getImagePathFromSD() {
    // 图片列表
    List imagePathList = new ArrayList();
    // 得到sd卡内image文件夹的路径   File.separator(/)
    String filePath = Environment.getExternalStorageDirectory().toString() + File.separator
            + "imageLru";
    // 得到该路径文件夹下所有的文件
    File fileAll = new File(filePath);
    File[] files = fileAll.listFiles();
    // 将所有的文件存入ArrayList中,并过滤所有图片格式的文件
    for (int i = 0; i < files.length; i++) {
        File file = files[i];
        if (checkIsImageFile(file.getPath())) {
            imagePathList.add(file.getPath());
        }
    }
    // 返回得到的图片列表
    return imagePathList;
}
  private boolean checkIsImageFile(String fName) {
      boolean isImageFile = false;
      // 获取扩展名
      String FileEnd = fName.substring(fName.lastIndexOf(".") + 1,
              fName.length()).toLowerCase();
      if (FileEnd.equals("jpg") || FileEnd.equals("png") || FileEnd.equals("gif")
              || FileEnd.equals("jpeg")|| FileEnd.equals("bmp") ) {
          isImageFile = true;
      } else {
          isImageFile = false;
      }
      return isImageFile;
  }