📚 04-活动与生命周期

4.1 生命周期回调

class MainActivity: AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) }
    override fun onStart() { super.onStart() }
    override fun onResume() { super.onResume() }
    override fun onPause() { super.onPause() }
    override fun onStop() { super.onStop() }
    override fun onDestroy() { super.onDestroy() }
}

4.2 状态保存与恢复

override fun onSaveInstanceState(outState: Bundle) {
    outState.putString("key", "value")
    super.onSaveInstanceState(outState)
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val restored = savedInstanceState?.getString("key")
}

4.3 Activity 结果 API

private val pick = registerForActivityResult(ActivityResultContracts.GetContent()) { uri ->
    // 处理返回的 uri
}

fun pickImage() { pick.launch("image/*") }