registerForActivityResult()方法的简单理解和使用

最近学到了reGISterForActivityResult,简单理解一下：
1、使用registerForActivityResult为获取到的结果注册结果回调，但其本身不会启动intent跳转
2、registerForActivityResult最后会返回一个ActivityResultLauncher对象用于启动intent跳转
3、registerForActivityResult第一个参数是ActivityResultContracts，除了通用的StartActivityForResult，还有TakePicture（拍照）、RequestPermission（请求单个权限）、PickContact（从通讯录获取联系人）等预定义好的contract
4、第二个参数中的onActivityResult() 方法用于处理获取到的数据结果

深入理解参考以下两篇文章：
https://www.cnblogs.com/–here–gold–you–want/p/14841024.html
http://www.icodebang.com/article/264591

SecondActivity的数据返回给FirstActivity，代码如下：

一、FirstActivity.java

public class FirstActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //该方法要放在onCreate里面，不能放在监听器里        ActivityResultLauncher launcher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() {            @Override            public void onActivityResult(ActivityResult result) {                if(result.getResultCode() == Activity.RESULT_OK){                    Log.d("data_return", 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            }        });    }}

二、SecondActivity.java

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","the data of returning to FirstActivity");                setResult(RESULT_OK,intent);                finish();            }        });    }}

来源地址：https://blog.csdn.net/weixin_50822129/article/details/127644130