如何通过线程更新非 MainActivity 活动？

Question

我想更新一个不是 MainActivity 的 Activity。

所以我通过 MainActivity 中的 onClick 方法启动了第二个 Activity。

现在活动“SecondActivity”在前面。 当我在“MainActivity”中启动一个线程时，如何引用“SecondActivity”来更新他们的 TextViews 等等？

伪代码

 public class activity_MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ThreadSome threadSome= new ThreadSome();
        threadSome.start()
    }
   
   onClick(View View){

   Intent intent = new Intent(this, activity_Second.class);
   startActivity(intent);
   }
}

内线

public class ThreadSome extends Thread {

    @Override
    public void run() {
      //This is what I don't know, so I just write what I want to do.
      // I know the following Code is wrong and not working.

      activity_Second.someTextView.setText("Hi");
    }
}

WeakReference 是最好的方法，还是更好地使用静态 TextView 对象？你会如何解决这个问题？

Answer 1

根据您的描述，我认为您想做一些事情，根据前台活动中执行的某些事件，活动堆栈中会有一些 ui 更改。有一种通过 startActivityForResult() 使用 onActivityResult() 的好方法，但如果这不能直接满足您的要求，那么您可以尝试以下方法：

/**
    UpdateActivity is the activity where some ui update or action will be taken based on event in EventActivity.
**/

public class UpdateActivity extends Activity {

    private BroadcastReceiver mReceiver;
    public static final String ACTION_UPDATE = "com.my.internal.activity.action";

    ...

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update);

        ......

        //Prepared Intent for broadcast receiver
        IntentFilter intentFilter = new IntentFilter(ACTION_UPDATE);
        //registering our receiver
        this.registerReceiver(mReceiver, intentFilter);

        .....
    }

    //This is the receiver section where you need to do the ui update
    mReceiver = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            //extract our message from intent
            String some_msg = intent.getStringExtra("msg_1"); //parameter received if passed in intent when broadcast called.
            //log our message value
            Log.i("Message", some_msg);

            updateActivityUi();
        }
    };

    private void updateActivityUi() {
        // you need to write the code for the update which you want to do after an event done in other activity.
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        //unregister our receiver
        this.unregisterReceiver(this.mReceiver);
    }
}

public class EventActivity extends Activity {

    ...

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_event);

        ......

        //Sending BroadcastReceiver against the action ACTION_UPDATE and it will be received by UpdateActivity.
        if(condition_for_event) {
            Intent i = new Intent(UpdateActivity.ACTION_UPDATE).putExtra("msg_1", "Hey! an event performed here.");
            this.sendBroadcast(i);
        }

        .....
    }

    ....
}

如果它解决了您的问题，请告诉我。