android 将相册图片存到app

在Android应用中将相册中的图片保存到应用私有存储目录中，可以按照以下步骤进行：

1.请求权限：

在AndroidManifest.xml中添加读取和写入外部存储的权限：

     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
     

对于Android 6.0（API级别23）及以上版本，还需要在运行时请求这些权限。

2.选择图片：

使用Intent打开相册选择图片：

     Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
     startActivityForResult(intent, REQUEST_CODE_PICK_IMAGE);
     

3.处理选择结果：

在onActivityResult方法中处理选择结果：

     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
         super.onActivityResult(requestCode, resultCode, data);
         if (requestCode == REQUEST_CODE_PICK_IMAGE && resultCode == RESULT_OK && data != null) {
             Uri selectedImageUri = data.getData();
             saveImageToAppDirectory(selectedImageUri);
         }
     }
     

4.保存图片到应用私有目录：

使用ContentResolver获取图片数据并保存到应用私有目录：

     private void saveImageToAppDirectory(Uri imageUri) {
         try {
             // 获取输入流
             InputStream inputStream = getContentResolver().openInputStream(imageUri);
             // 创建文件名
             String fileName = System.currentTimeMillis() + ".jpg";
             // 获取应用私有目录
             File appDir = new File(getFilesDir(), "images");
             if (!appDir.exists()) {
                 appDir.mkdir();
             }
             // 创建文件
             File file = new File(appDir, fileName);
             // 获取输出流
             OutputStream outputStream = new FileOutputStream(file);
             // 复制数据
             byte[] buffer = new byte[1024];
             int length;
             while ((length = inputStream.read(buffer)) > 0) {
                 outputStream.write(buffer, 0, length);
             }
             // 关闭流
             inputStream.close();
             outputStream.close();
             // 提示保存成功
             Toast.makeText(this, "图片保存成功", Toast.LENGTH_SHORT).show();
         } catch (IOException e) {
             e.printStackTrace();
             Toast.makeText(this, "图片保存失败", Toast.LENGTH_SHORT).show();
         }
     }
     

5.运行时权限请求：

在选择图片之前检查并请求权限：

     private static final int REQUEST_CODE_PERMISSIONS = 100;

     private boolean checkAndRequestPermissions() {
         List<String> permissionsNeeded = new ArrayList<>();
         final List<String> permissionsList = new ArrayList<>();

         if (ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
             permissionsList.add(Manifest.permission.READ_EXTERNAL_STORAGE);
         }
         if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
             permissionsList.add(Manifest.permission.WRITE_EXTERNAL_STORAGE);
         }

         if (!permissionsList.isEmpty()) {
             if (permissionsList.size() > 0) {
                 permissionsNeeded.addAll(permissionsList);
             }
             ActivityCompat.requestPermissions(this, permissionsList.toArray(new String[permissionsList.size()]), REQUEST_CODE_PERMISSIONS);
             return false;
         }
         return true;
     }

     @Override
     public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
         super.onRequestPermissionsResult(requestCode, permissions, grantResults);
         if (requestCode == REQUEST_CODE_PERMISSIONS) {
             if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                 // 权限已授予，继续选择图片
                 Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                 startActivityForResult(intent, REQUEST_CODE_PICK_IMAGE);
             } else {
                 Toast.makeText(this, "权限被拒绝，无法选择图片", Toast.LENGTH_SHORT).show();
             }
         }
     }