Question

MainActivity.java

public class MainActivity extends AppCompatActivity {

    WebView webView;
//    webView.setWebViewClient

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
//        webView.getSettings().setBlockNetworkLoads(false);
        webView = (WebView) findViewById(R.id.urlWebView);
        webView.loadUrl("https://unsplash.com/images");

        Intent serviceIntent = new Intent();
        webView.setDownloadListener(new DownloadListener() {
            @Override
            public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimetype, long contentLength) {
                    serviceIntent.putExtra("urlToDownload", url);

                    Log.d("Download img", url);
                    Log.d("User Agent", userAgent);
                    Log.d("Content", contentDisposition);
                    Log.d("mimetype", mimetype);
                    Log.d("Content Length", String.valueOf(contentLength));

            }
        });

    }
    
}

downloaderSer.java

package com.example.lab3webview;

import android.app.IntentService;
import android.content.ComponentName;
import android.content.Intent;
import android.os.Environment;
import android.util.Log;
import android.webkit.URLUtil;

import androidx.annotation.Nullable;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;

public class downloaderSer extends IntentService {

    @Override
    public void onCreate() {
        super.onCreate();

    }

    MainActivity mainActivity;
    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     *
     * @param name Used to name the worker thread, important only for debugging.
     */
    public downloaderSer(String name) {
        super(name);

    }

    // Downloader Intent Service
    @Override
    protected void onHandleIntent(Intent intent) {
        String urlToDownload = intent.getExtras().getString("urlToDownload");
        // test  service intent here
        try {
            URL url = new URL(urlToDownload);
            String filename = URLUtil.guessFileName(urlToDownload, null, null);
            InputStream is = url.openStream();
            DataInputStream dis = new DataInputStream(is);
            byte[] buffer = new byte[1024];
            int length;
            FileOutputStream fos = new FileOutputStream(new File(Environment.getExternalStorageDirectory() + "/" + "Download/" + filename));
            while ((length = dis.read(buffer))>0) {
                fos.write(buffer, 0, length); }
        } catch (Exception e) {
            Log.e("Image download", e.toString());
        }
    }

    @Override
    public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }
}

AndroidManifest.xml

 <uses-permission android:name="android.permission.INTERNET" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Lab3WebView"
        android:usesCleartextTraffic="true">

到目前为止，前面提到的java类是我正在编写的代码。现在，我遇到了一个问题，在我的downloaderSer.java类中，它无法从站点成功下载图像，然后将其保存到下载文件中。我花了好几个小时才能弄清楚。我以为，在onHandleIntent方法中，我已成功将MainActivity类的urlToDownload传递到此处。有人可以解释为什么这在逻辑上是错误的吗？

IntentService确实有效，但下载图像失败

0 个答案: