java - 我可以在 finish() 上传递额外的 Intent 吗？

Question

我想知道，是否可以将信息发送到调用 finish() 后返回的 Activity ？

例如，我有一个 Activity SendMessageActivity.class，它允许用户向其提要发布消息。将消息保存到服务器后，我调用 finish()。我应该用新的 Intent 启动我的 MainActivity.class 吗？或者生命周期开发直接完成 SendMessageActivity.class 更好？

我不认为开始一项新 Activity 有什么意义，因为关闭当前 Activity 总是会让您返回到 MainActivity.class。完成当前 Activity 后如何发送额外的字符串？

Answer 1

使用onActivityResult。

这可能会帮助您理解onActivityResult。

通过使用 startActivityForResult(Intent intent, int requestCode)您可以启动另一个 Activity ，然后在 onActivityResult() 中接收该 Activity 的结果方法。所以onActivityResult()是从您启动另一个 Activity 的地方开始。

onActivityResult(int requestCode, int resultCode, Intent data)检查这里的参数。请求代码用于从您获得结果的位置进行过滤。这样您就可以使用它们的 requestCode 来识别不同的数据!

示例

 public class MainActivity extends Activity {

        // Use a unique request code for each use case 
        private static final int REQUEST_CODE_EXAMPLE = 0x9988; 

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

            // Create an Intent to start AnotherActivity
            final Intent intent = new Intent(this, AnotherActivity.class);

            // Start AnotherActivity with the request code
            startActivityForResult(intent, REQUEST_CODE_EXAMPLE);
        }

        //-------- When a result is returned from another Activity onActivityResult is called.--------- //
        @Override
        public void onActivityResult(int requestCode, int resultCode, Intent data) {
            super.onActivityResult(requestCode, resultCode, data);

            // First we need to check if the requestCode matches the one we used.
            if(requestCode == REQUEST_CODE_EXAMPLE) {

                // The resultCode is set by the AnotherActivity
                // By convention RESULT_OK means that what ever
                // AnotherActivity did was successful
                if(resultCode == Activity.RESULT_OK) {
                    // Get the result from the returned Intent
                    final String result = data.getStringExtra(AnotherActivity.EXTRA_DATA);

                    // Use the data - in this case, display it in a Toast.
                    Toast.makeText(this, "Result: " + result, Toast.LENGTH_LONG).show();
                } else {
                    // AnotherActivity was not successful. No data to retrieve.
                }
            }
        }
    }

AnotherActivity <- 这是我们用来发送数据到MainActivity的那个

public class AnotherActivity extends Activity {

        // Constant used to identify data sent between Activities.
        public static final String EXTRA_DATA = "EXTRA_DATA";

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

            final View button = findViewById(R.id.button);
            // When this button is clicked we want to return a result
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    // Create a new Intent as container for the result
                    final Intent data = new Intent();

                    // Add the required data to be returned to the MainActivity
                    data.putExtra(EXTRA_DATA, "Some interesting data!");

                    // Set the resultCode to Activity.RESULT_OK to 
                    // indicate a success and attach the Intent
                    // which contains our result data
                    setResult(Activity.RESULT_OK, data); 

                    // With finish() we close the AnotherActivity to 
                    // return to MainActivity
                    finish();
                }
            });
        }

        @Override
        public void onBackPressed() {
            // When the user hits the back button set the resultCode 
            // to Activity.RESULT_CANCELED to indicate a failure
            setResult(Activity.RESULT_CANCELED);
            super.onBackPressed();
        }
    }

注意:现在 checkin MainActivity你startActivityForResult在那里您指定 REQUEST_CODE 。假设您想调用三个不同的 Activity 来获取结果..所以有三个 startActivityForResult使用三个不同的 REQUEST_CODE 进行调用。 REQUEST_CODE 只是您在 Activity 中指定的唯一键，用于唯一标识您的 startActivityForResult来电。

一旦您从这些 Activity 收到数据，您就可以检查 REQUEST_CODE 是什么，然后您就知道啊哈这个结果来自此 Activity 。

这就像你给你的爱人发了一封带有彩色封面的邮件，并要求他们用同样的封面回复。然后，如果您收到他们的回信，您就知道是谁给您寄来的。哇哦；)