通过活动传递值

// 在源活动中
Intent intent = new Intent(this, TargetActivity.class);
intent.putExtra("key", "value");
startActivity(intent);

// 在目标活动中
Intent intent = getIntent();
String value = intent.getStringExtra("key");

// 在源活动中
SharedPreferences sharedPreferences = getSharedPreferences("MyPrefs", MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString("key", "value");
editor.apply();

// 在目标活动中
SharedPreferences sharedPreferences = getSharedPreferences("MyPrefs", MODE_PRIVATE);
String value = sharedPreferences.getString("key", "default_value");

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putString("key", "value");
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    String value = savedInstanceState.getString("key");
}

int number = intent.getIntExtra("number_key", 0); // 提供默认值0

// 示例：使用AES加密
SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(), "AES");
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] encrypted = cipher.doFinal("sensitive_data".getBytes());