带返回值的Intent startActivityForResult()废弃/过时，替代为registerForActivityResult()简介

startActivityForResult()废弃/过时后,我们可以用registerForActivityResult()替代。
代码如下：
FirstAvitvity.class

public class FirstActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ActivityResultLauncher launcher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() {
            @Override
            public void onActivityResult(ActivityResult result) {
                if(resultresult.getResultCode() == Activity.RESULT_OK){
                    Log.d("TAG", result.getData().getStringExtra("data_return"));
                }
            }
        });

        Button button1 = (Button) findViewById(R.id.button_1);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(FirstActivity.this,SecondActivity.class);
                launcher.launch(intent);//启动intent跳转
            }
        });
    }
}

SecondActivity

public class SecondActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        Button button2 = (Button) findViewById(R.id.button_2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent();
                intent.putExtra("data_return","Hello World!");
                setResult(RESULT_OK,intent);
                finish();
            }
        });
    }
}

Kotlin写法如下
FirstAvitvity.class

class FirstActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        val launcher = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) { result ->
            if (result.resultCode == RESULT_OK && result.data != null) {
                result.data?.getStringExtra("data_return")?.let {
                    Log.e("TAG", it)
                }
            }
        }
        
        findViewById<Button>(R.id.button_1).setOnClickListener {
            val intent = Intent(this, SecondAct::class.java)
            launcher.launch(intent)
        }
    }
}

SecondActivity

class SecondActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_second)

        findViewById<Button>(R.id.button_2).setOnClickListener {
            val intent = Intent()
            intent.putExtra("data_return","Hello World!")
            setResult(RESULT_OK,intent)
            finish()
        }
    }
}