startActivityForResult 替代方案

startActivityForResult() 方法用于返回数据给上一个 Activity。

但这个方法已经被废弃了很久，现在 Google 使用 registerForActivityResult() 方法来实现此功能。

registerForActivityResult() 实现

使用 registerForActivityResult() 写法，实现 SecondActivity 返回数据给 FirstActivity

FirstActivity 代码

class FirstActivity : AppCompatActivity() {

    private val requestDataLauncher =
        registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
            if (result.resultCode == RESULT_OK) {
                val data = result.data?.getStringExtra("data")
                Log.d("FirstActivity", "data =${data}")
            }
        }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = FirstLayoutBinding.inflate(layoutInflater)
        setContentView(binding.root)
        val button = binding.button1
        button.setOnClickListener {
            val intent = Intent(this, SecondActivity::class.java) 
            requestDataLauncher.launch(intent) //调用 launch 方法，该方法接收 输入类型 I
        }
    }
}

SecondActivity 代码

class SecondActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_second)
        val binding = ActivitySecondBinding.inflate(layoutInflater)
        setContentView(binding.root)
        val button2 = binding.button2
        button2.setOnClickListener() {
            val intent = Intent()
          	intent.putExtra("data","register")
            setResult(RESULT_OK, intent)
            finish()
        }
    }
}