Activity返回数据给上一个Activity

代码

• kotlin:

​​FirstReturnActivity :​​

class FirstReturnActivity : AppCompatActivity() {
    private lateinit var firstBinding: ActivityReturndataFirstBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        firstBinding = ActivityReturndataFirstBinding.inflate(layoutInflater)
        setContentView(firstBinding.root)

        firstBinding.firstGotoSecond.setOnClickListener {
            val intent = Intent(this, SecondReturnActivity::class.java)
            startActivityForResult(intent, 1)
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        when(requestCode){
            1->if (resultCode== RESULT_OK){
                val returnedData=data?.getStringExtra("data_return")
                Toast.makeText(this,returnedData,Toast.LENGTH_SHORT).show()
            }
        }
    }
}

​​SecondReturnActivity:​​

class SecondReturnActivity: AppCompatActivity() {
    private lateinit var secondBinding: ActivityReturndataSecondBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        secondBinding= ActivityReturndataSecondBinding.inflate(layoutInflater)
        setContentView(secondBinding.root)

        secondBinding.secondReturn.setOnClickListener {
            val intent= Intent()
            intent.putExtra("data_return","Hello MainActivity")
            setResult(RESULT_OK,intent)
            finish()
        }
    }

    override fun onBackPressed() {
        val intent=Intent()
        intent.putExtra("data_return","Hello MainActivity")
        setResult(RESULT_OK,intent)
        finish()
    }
}

• Layout:

​​两个布局各加一个按钮​​

效果: