android.util.AndroidRuntimeException: requestFeature() must be called before adding content

本文探讨了在Android开发中遇到的请求功能错误,并详细解释了错误的原因及解决方法,特别关注了当使用Android Studio新建的AppCompactActivity时如何避免此类错误。

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 android.util.AndroidRuntimeException: requestFeature() must be called before adding content


但是代码里面request已经在setContentView之前了! 还是报错!



原因:android studio新建activity继承了v7的AppCompactActivity,改为Activity就可以了

### Padding Key in Cryptography and Data Security Usage In the context of cryptography, padding plays an essential role when using block ciphers to ensure that plaintext messages fit into blocks of specific sizes required by encryption algorithms[^2]. Block ciphers operate on fixed-size blocks of data; therefore, if the message does not align perfectly with these block boundaries, additional bytes must be added through padding schemes. Padding keys are not explicitly defined as separate entities but rather refer to how cryptographic operations handle padded input during both encryption and decryption processes. The term might sometimes cause confusion because it is more accurate to discuss padding mechanisms within key management or algorithm-specific contexts instead of treating them as distinct components called “padding keys.” For instance, PKCS#7 (Public-Key Cryptography Standards) defines one popular method for adding padding bits at the end of each block until reaching full length while ensuring easy removal upon decryption without ambiguity regarding original content size[^1]. #### Implementation Example Using Python’s PyCryptodome Library Below demonstrates implementing AES encryption with PKCS7 padding: ```python from Crypto.Cipher import AES from Crypto.Util.Padding import pad, unpad import base64 def encrypt_data(key, data): cipher = AES.new(key, AES.MODE_CBC) ct_bytes = cipher.encrypt(pad(data.encode('utf-8'), AES.block_size)) iv = base64.b64encode(cipher.iv).decode('utf-8') ct = base64.b64encode(ct_bytes).decode('utf-8') return iv, ct def decrypt_data(key, iv, ciphertext): iv = base64.b64decode(iv) ct = base64.b64decode(ciphertext) cipher = AES.new(key, AES.MODE_CBC, iv) pt = unpad(cipher.decrypt(ct), AES.block_size).decode('utf-8') return pt ``` This code snippet shows how to apply proper padding before performing actual encryption steps and remove this extra information after successful decryption has taken place.
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