Android中的异步任务处理与UI更新技巧

import android.os.AsyncTask;
import cn.juwatech.utils.MyUtils;

public class MyAsyncTask extends AsyncTask<Void, Void, String> {
    @Override
    protected String doInBackground(Void... voids) {
        // 在这里执行耗时操作
        return MyUtils.doSomeHeavyWork();
    }

    @Override
    protected void onPostExecute(String result) {
        // 在主线程中更新UI
        textView.setText(result);
    }
}

import android.os.Handler;
import cn.juwatech.utils.MyHandler;

public class MyActivity extends AppCompatActivity {
    private TextView textView;
    private Handler handler = new MyHandler(this);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        textView = findViewById(R.id.textview);

        // 启动耗时操作
        new Thread(new Runnable() {
            @Override
            public void run() {
                String result = doSomeHeavyWork();
                handler.obtainMessage(0, result).sendToTarget();
            }
        }).start();
    }

    private String doSomeHeavyWork() {
        // 执行耗时操作
        return "Result from background thread";
    }
}

class MyHandler extends Handler {
    private WeakReference<MyActivity> activity;

    public MyHandler(MyActivity activity) {
        this.activity = new WeakReference<>(activity);
    }

    @Override
    public void handleMessage(Message msg) {
        MyActivity activity = activity.get();
        if (activity != null) {
            activity.textView.setText((String) msg.obj);
        }
    }
}

import android.app.IntentService;
import android.content.Intent;
import cn.juwatech.utils.MyUtils;

public class MyIntentService extends IntentService {

    public MyIntentService() {
        super("MyIntentService");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        // 执行后台任务
        String result = MyUtils.doSomeHeavyWork();
        // 发送结果回主线程
        sendBroadcast(new Intent("com.example.ACTION_SEND_RESULT").putExtra("result", result));
    }
}

import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
import cn.juwatech.utils.MyUtils;

public class RxJavaExample {
    public void executeAsyncTask() {
        Observable.just(1)
                .subscribeOn(Schedulers.io()) // 在IO线程执行
                .map(MyUtils::doSomeHeavyWork) // 执行耗时操作
                .observeOn(AndroidSchedulers.mainThread()) // 回到主线程
                .subscribe(result -> {
                    // 更新UI
                    textView.setText(result);
                }, throwable -> {
                    // 处理错误
                });
    }
}

import kotlinx.coroutines.*

fun updateUIFromBackground() = GlobalScope.launch(Dispatchers.IO) {
    val result = doSomeHeavyWork()
    withContext(Dispatchers.Main) {
        textView.text = result
    }
}

suspend fun doSomeHeavyWork(): String {
    // 执行耗时操作
    return "Result from background thread"
}