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2018-08-10
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摘要：本文将带你了解Android应用开发之Android根据文件路径加载指定文件，希望本文对大家学Android有所帮助
本文将带你了解Android应用开发之Android根据文件路径加载指定文件，希望本文对大家学Android有所帮助
Android根据指定的文件路径加载指定文件格式（图片格式 png, gif,jpg jpeg）的文件相关信息的列表。
如图：
代码：
Java代码 <span style="background-color: #ffffff;">public class Util { /**** * 计算文件大小 * * @param length * @return */ public static String ShowLongFileSzie(Long length) { if (length >= 1048576) { return (length / 1048576) + "MB"; } else if (length >= 1024) { return (length / 1024) + "KB"; } else if (length < 1024) { return length + "B"; } else { return "0KB"; } } /*** * * 更具路径得到该路径下的全部图片信息 * @return */ public static List<AddFileInfo> getSDPathFrom() { // 图片列表 List<AddFileInfo> imagePathList = new ArrayList<AddFileInfo>(); // 得到sd卡内image文件夹的路径 String filePath = Environment.getExternalStorageDirectory().toString() + File.separator+"BigNoxHD/cache/"; //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 (checkIsFile(file.getPath())) { String time = new SimpleDateFormat("yyyy-MM-dd") .format(new Date(file.lastModified())); AddFileInfo info=new AddFileInfo(file.getName(), Util.ShowLongFileSzie(file.length()), time, file.getAbsolutePath()); imagePathList.add(info); } } // 返回得到的图片列表 return imagePathList; } /**** * 验证文件格式 * @param fName * @return */ public static boolean checkIsFile(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") ) { isImageFile = true; } else { isImageFile = false; } return isImageFile; } /**** * 根据文件路径获取图片 * 其中w和h你需要转换的大小 * @param path * @param w * @param h * @return */ public static Bitmap convertToBitmap(String path, int w, int h) { BitmapFactory.Options opts = new BitmapFactory.Options(); // 设置为ture只获取图片大小 opts.inJustDecodeBounds = true; opts.inPreferredConfig = Bitmap.Config.ARGB_8888; // 返回为空 BitmapFactory.decodeFile(path, opts); int width = opts.outWidth; int height = opts.outHeight; float scaleWidth = 0.f, scaleHeight = 0.f; if (width > w || height > h) { // 缩放 scaleWidth = ((float) width) / w; scaleHeight = ((float) height) / h; } opts.inJustDecodeBounds = false; float scale = Math.max(scaleWidth, scaleHeight); opts.inSampleSize = (int)scale; WeakReference<Bitmap> weak = new WeakReference<Bitmap>(BitmapFactory.decodeFile(path, opts)); return Bitmap.createScaledBitmap(weak.get(), w, h, true); } }</span> public class Util {
/****
* 计算文件大小
*
* @param length
* @return
*/
public static String ShowLongFileSzie(Long length) {
if (length >= 1048576) {
return (length / 1048576) + "MB";
} else if (length >= 1024) {
return (length / 1024) + "KB";
} else if (length < 1024) {
return length + "B";
} else {
return "0KB";
}
}
/***
*
* 更具路径得到该路径下的全部图片信息
* @return
*/
public static List<AddFileInfo> getSDPathFrom() {
// 图片列表
List<AddFileInfo> imagePathList = new ArrayList<AddFileInfo>();
// 得到sd卡内image文件夹的路径
String filePath = Environment.getExternalStorageDirectory().toString() + File.separator+"BigNoxHD/cache/";
//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 (checkIsFile(file.getPath())) {
String time = new SimpleDateFormat("yyyy-MM-dd")
.format(new Date(file.lastModified()));
AddFileInfo info=new AddFileInfo(file.getName(), Util.ShowLongFileSzie(file.length()), time, file.getAbsolutePath());
imagePathList.add(info);
}
}
// 返回得到的图片列表
return imagePathList;
}
/****
* 验证文件格式
* @param fName
* @return
*/
public static boolean checkIsFile(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") ) {
isImageFile = true;
} else {
isImageFile = false;
}
return isImageFile;
}
/****
* 根据文件路径获取图片
* 其中w和h你需要转换的大小
* @param path
* @param w
* @param h
* @return
*/
public static Bitmap convertToBitmap(String path, int w, int h) {
BitmapFactory.Options opts = new BitmapFactory.Options();
// 设置为ture只获取图片大小
opts.inJustDecodeBounds = true;
opts.inPreferredConfig = Bitmap.Config.ARGB_8888;
// 返回为空
BitmapFactory.decodeFile(path, opts);
int width = opts.outWidth;
int height = opts.outHeight;
float scaleWidth = 0.f, scaleHeight = 0.f;
if (width > w || height > h) {
// 缩放
scaleWidth = ((float) width) / w;
scaleHeight = ((float) height) / h;
}
opts.inJustDecodeBounds = false;
float scale = Math.max(scaleWidth, scaleHeight);
opts.inSampleSize = (int)scale;
WeakReference<Bitmap> weak = new WeakReference<Bitmap>(BitmapFactory.decodeFile(path, opts));
return Bitmap.createScaledBitmap(weak.get(), w, h, true);
}
}
MainActivity.java
Java代码 public class MainActivity extends Activity { private ListView mListview; private List<AddFileInfo> list; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); } private void initView() { // TODO Auto-generated method stub mListview = (ListView) findViewById(R.id.listview); list = Util.getSDPathFrom(); mListview.setAdapter(new Adapter(MainActivity.this)); } class Adapter extends BaseAdapter { private LayoutInflater inflater; private Context context; public Adapter(Context context) { this.context = context; this.inflater = LayoutInflater.from(context); } @Override public int getCount() { return list.size(); } @Override public Object getItem(int position) { return list.get(position); } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (null == convertView) { convertView = inflater.inflate( R.layout.item_mytask_file_listview, null); holder = new ViewHolder(convertView); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } AddFileInfo info = (AddFileInfo) getItem(position); holder.img.setImageBitmap(Util.convertToBitmap(info.getPath(), 99, 99)); holder.tv_name.setText("文件名称：" + info.getName()); holder.size.setText("文件大小：" + info.getSize()); holder.time.setText("文件创建时间：" + info.getTime()); return convertView; } } class ViewHolder { private TextView tv_name; private TextView size; private TextView time; private ImageView img; public ViewHolder(View view) { img = (ImageView) view.findViewById(R.id.img); tv_name = (TextView) view.findViewById(R.id.item_file_name); size = (TextView) view.findViewById(R.id.item_file_size); time = (TextView) view.findViewById(R.id.item_file_time); } } } public class MainActivity extends Activity {
private ListView mListview;
private List<AddFileInfo> list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}
private void initView() {
// TODO Auto-generated method stub
mListview = (ListView) findViewById(R.id.listview);
list = Util.getSDPathFrom();
mListview.setAdapter(new Adapter(MainActivity.this));
}
class Adapter extends BaseAdapter {
private LayoutInflater inflater;
private Context context;
public Adapter(Context context) {
this.context = context;
this.inflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return list.size();
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
if (null == convertView) {
convertView = inflater.inflate(
R.layout.item_mytask_file_listview, null);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
AddFileInfo info = (AddFileInfo) getItem(position);
holder.img.setImageBitmap(Util.convertToBitmap(info.getPath(), 99, 99));
holder.tv_name.setText("文件名称：" + info.getName());
holder.size.setText("文件大小：" + info.getSize());
holder.time.setText("文件创建时间：" + info.getTime());
return convertView;
}
}
class ViewHolder {
private TextView tv_name;
private TextView size;
private TextView time;
private ImageView img;
public ViewHolder(View view) {
img = (ImageView) view.findViewById(R.id.img);
tv_name = (TextView) view.findViewById(R.id.item_file_name);
size = (TextView) view.findViewById(R.id.item_file_size);
time = (TextView) view.findViewById(R.id.item_file_time);
}
}
}
不要忘记在AndroidManifest.xml加权限哦！
Html代码 <!-- SD卡权限 --> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> <!-- SD卡权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
本文由职坐标整理并发布，希望对同学们有所帮助。了解更多详情请关注职坐标移动开发之Android频道！
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