《第一行代码Android》_is attempting to register while current state is r-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_42589381/article/details/135340987

本文讲述了在Android应用中，从使用startActivityForResult()到registerForActivityResult()的迁移过程中，开发者需要注意在onCreate()生命周期阶段正确注册结果接收器，以避免试图在非STARTED状态时注册的错误。

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2.3.5返回数据给上一个活动

startActivityForResult()启用，使用registerForActivityResult()代替，

报错：“is attempting to register while current state is RESUMED. LifecycleOwners must call register before they are STARTED”需要将registerForActivityResult()写在onCreate()中，表示在生命周期STARTED之前调用

public class FirstActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityResultLauncher<Intent> intentActivityResultLauncher = registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), new ActivityResultCallback<ActivityResult>() {
            @Override
            public void onActivityResult(ActivityResult result)
            {
                int resultCode = result.getResultCode();
                if(resultCode==RESULT_OK)
                {
                    String returnData = result.getData().getStringExtra("data_return");
                    Log.d("FirstActivity",returnData);
                }
            }
        });

        setContentView(R.layout.first_layout);

        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);
                intentActivityResultLauncher.launch(intent);
            }
        });
    }