ファイルサイズ検証用コード

MainActivity.java

public class MainActivity extends Activity {

  private static final int REQUEST_CODE_GALLERY = 0;
  
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        Button btnCallGallary = new Button(this);
        btnCallGallary.setText("ギャラリーを開く");
        btnCallGallary.setOnClickListener(new OnClickListener() {
      @Override
      public void onClick(View v) {
        Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
        intent.setType("image/*");
        startActivityForResult(intent, 0);
      }
    });
        
        setContentView(btnCallGallary);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
      super.onActivityResult(requestCode, resultCode, data);
      
      if(requestCode == REQUEST_CODE_GALLERY && resultCode == RESULT_OK) {
        Uri imageUri = data.getData();
        
        // ギャラリーのカーソルを作成
        ContentResolver contentResolver = getContentResolver();
        String[] filePathColumn = { MediaStore.Images.Media.DATA, MediaStore.Images.Media._ID };
        Cursor cursor = contentResolver.query(imageUri, filePathColumn, null, null, null);

        cursor.moveToFirst();

        // ファイルパスを取得
        int dataColumnIndex = cursor.getColumnIndex(MediaStore.Images.Media.DATA);
        String filePath = cursor.getString(dataColumnIndex);

        Toast.makeText(this, "filePath -> " + filePath + "\nfileSize -> " + new File(filePath).length(), Toast.LENGTH_LONG).show();
      }
    }
    
}