Question

我正在尝试在下载文件时更新进度条，但是在我的服务任务中，我无权访问UI。这意味着我无法使用findViewByID找到ProgressBar元素来更新ProgressBar。这是相关代码：

MainActivity：


import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.view.View;

public class MainActivity extends AppCompatActivity {

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

    public void startService(View view) {
        startService(new Intent(getBaseContext(), MyService.class));
    }
    public void stopService(View view) {
        stopService(new Intent(getBaseContext(), MyService.class));
    }
}

MyService类：

package com.example.services;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.widget.ProgressBar;
import android.widget.Toast;
import java.net.MalformedURLException;
import java.net.URL;
import android.os.AsyncTask;
import android.util.Log;
import java.util.Timer;
import java.util.TimerTask;

public class MyService extends Service {
    int counter = 0;
    static final int UPDATE_INTERVAL = 1000;
    private Timer timer = new Timer();

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Toast.makeText(this, "Service Started", Toast.LENGTH_LONG).show();
        doSomethingRepeatedly();


        try {
            new DoBackgroundTask().execute(
                    new URL("http://www.amazon.com/somefiles.pdf"),
                    new URL("http://www.wrox.com/somefiles.pdf"),
                    new URL("http://www.google.com/somefiles.pdf"),
                    new URL("http://www.learn2develop.net/somefiles.pdf"));
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        return START_STICKY;
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        if (timer != null){
            timer.cancel();
        }
        Toast.makeText(this, "Service Destroyed", Toast.LENGTH_LONG).show();
    }

    private void doSomethingRepeatedly() {
        timer.scheduleAtFixedRate(new TimerTask() {
            public void run() {
                Log.d("MyService", String.valueOf(++counter));

            }
        }, 0, UPDATE_INTERVAL);
    }

    private class DoBackgroundTask extends AsyncTask<URL, Integer, Long> {
        protected Long doInBackground(URL... urls) {
            int count = urls.length;
            long totalBytesDownloaded = 0;
            for (int i = 0; i < count; i++) {
                totalBytesDownloaded += DownloadFile(urls[i]);
                publishProgress((int) (((i + 1) / (float) count) * 100));
            }
            return totalBytesDownloaded;
        }
        protected void onProgressUpdate(Integer... progress) {
            Log.d("Downloading files", String.valueOf(progress[0]) + "% downloaded");
            Toast.makeText(getBaseContext(),
                    String.valueOf(progress[0]) + "% downloaded-"+counter,
                    Toast.LENGTH_LONG).show();
        }

        protected void onPostExecute(Long result) {
            Toast.makeText(getBaseContext(), "Downloaded " + result + " bytes",
                    Toast.LENGTH_LONG).show();
            //stopSelf();
        }
    }

    private int DownloadFile(URL url) {
        try {
            //---simulate taking some time to download a file---
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //---return an arbitrary number representing
        // the size of the file downloaded---
        return 100;
    }
}

基本上，我想通过使用MyService类中的bytesDownloaded变量来更新MainActivity中的ProgressBar，但是我不确定如何在MainActivity中处理Async调用。如果可能的话。

谢谢！

使用服务时更新ProgressBar的进度？

0 个答案: