Android中Bitmap、File与Uri之间的简单记录

String path ;
File file = new File(path)

String path = FileTools.getRealPathFromUri(content,uri);
//自定义方法在下面
 public static String getRealPathFromUri(Context context, Uri uri) {

 if (null == uri) return null; //传入的Uri为空,结束方法

 final String scheme = uri.getScheme(); //得到Uri的scheme

 String realPath = null;

 if (scheme == null)
  realPath = uri.getPath(); //如果scheme为空 
 else if (ContentResolver.SCHEME_FILE.equals(scheme)) {
  realPath = uri.getPath(); //如果得到的scheme以file开头
 } else if (ContentResolver.SCHEME_CONTENT.equals(scheme)) {
  //得到的scheme以content开头
  Cursor cursor = context.getContentResolver().query(uri,
   new String[]{MediaStore.Images.ImageColumns.DATA},
   null, null, null);
  if (null != cursor) {
  if (cursor.moveToFirst()) {
   int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
   if (index > -1) {
   realPath = cursor.getString(index);
   }
  }
  cursor.close(); //必须关闭
  }
 }
 
//经过上面转换得到真实路径之后,判断一下这个路径,如果还是为空的话,说明有可能文件存在于外置sd卡上,不是内置sd卡.
 if (TextUtils.isEmpty(realPath)) {
  if (uri != null) {
  
  String uriString = uri.toString();
  int index = uriString.lastIndexOf("/"); //匹配 / 在一个路径中最后出现位置

  String imageName = uriString.substring(index);
  //通过得到的最后一个位置,然后截取这个位置后面的字符串, 这样就可以得到文件名字了 

  File storageDir;

  storageDir = Environment.getExternalStoragePublicDirectory(
   Environment.DIRECTORY_PICTURES); //查看外部储存卡公共照片的文件

  File file = new File(storageDir, imageName);
  //自己创建成文件,

  if (file.exists()) {
   realPath = file.getAbsolutePath();
  } else {
//  //那么存储在了外置sd卡的应用缓存file中
   storageDir = context.getExternalFilesDir(Environment.DIRECTORY_PICTURES);
   File file1 = new File(storageDir, imageName);
   realPath = file1.getAbsolutePath();
  }
  }
 }
 return realPath;

 

 比如我在android 8.0 上运行的时候
 选择照片之后的Uri : content://media/external/images/media/568344
 进行上面方法转换完之后: /storage/emulated/0/com.appben.appche/browser-photos/1550297407488.jpg
 

 }

https://blog.csdn.net/qq_39949109/article/details/80609472

File file = new File(".\\test1.txt");
File file = new File("D:\\workspace\\test\\test1.txt");
 System.out.println("-----默认相对路径：取得路径不同------");
 System.out.println(file1.getPath());
 System.out.println(file1.getAbsolutePath());
 System.out.println("-----默认绝对路径:取得路径相同------");
 System.out.println(file2.getPath());
 System.out.println(file2.getAbsolutePath());


结果是:
-----默认相对路径：取得路径不同------
.\test1.txt
D:\workspace\test\.\test1.txt
-----默认绝对路径:取得路径相同------
D:\workspace\test\test1.txt
D:\workspace\test\test1.txt


 File file = new File("..\\src\\test1.txt");
 System.out.println(file.getAbsolutePath());
 System.out.println(file.getCanonicalPath());
//得到的结果
D:\workspace\test\..\src\test1.txt
D:\workspace\src\test1.txt

File file = null;
try{
 file = new File(new URI(uri.toString()));
}catch(URISyntaxException e){
 e.printStackTrace();
}

URI uri = file.toURI();

Uri uri = Uri.parse(path);

Bitmap bitmap = BitmapFactory.decodeStream(contentResolver.openInputStream(uri))

Bitmap bitmap = BitmapFactory.decodeFile(file.getPath); //这个file要是真实路径创建的file

//自己创建想要保存的文件的文件对象
BuffferedOutPutStream bos = 
new BufferedOutputStream(new FileOutputStream(file));
bos.flush;
bos.close;