Java 使用服务下载文件
我正在尝试将下载管理器安装到android,所以当我尝试启动该服务时,它会给我错误信息 在我的清单中,我声明了服务名称,并获得了internet权限和外部存储写入权限 这是主要活动:Java 使用服务下载文件,java,android,Java,Android,我正在尝试将下载管理器安装到android,所以当我尝试启动该服务时,它会给我错误信息 在我的清单中,我声明了服务名称,并获得了internet权限和外部存储写入权限 这是主要活动: public class DownloadLabMyClassActivity extends Activity { Button downloadButton; @Override public void onCreate(Bundle savedInstanceState) {
public class DownloadLabMyClassActivity extends Activity {
Button downloadButton;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downloadButton = (Button) findViewById(R.id.button1);
downloadButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent serviceIntent = new Intent(DownloadLabMyClassActivity.this,DownloadService.class);
startService(serviceIntent);
}
});
}
}
这就是服务
public class DownloadService extends IntentService {
public DownloadService(String name) {
super("");
// TODO Auto-generated constructor stub
}
@Override
protected void onHandleIntent(Intent arg0) {
// TODO Auto-generated method stub
Log.d("service", "onHandleIntent()");
/* try {
URL fileUrl = new URL("http://goo.gl/Mfyya");
HttpURLConnection urlConnection = (HttpURLConnection)fileUrl.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.connect();
File sdcard = Environment.getExternalStorageDirectory();
File file = new File (sdcard, "filename.ext");
FileOutputStream fileoutput = new FileOutputStream (file);
InputStream inputstream = urlConnection.getInputStream();
int totalSize = urlConnection.getContentLength();
int downloadedSize = 0;
byte[] buffer = new byte[1024];
int bufferlength =0;
while ((bufferlength = inputstream.read(buffer)) > 0)
{
fileoutput.write(buffer, 0, bufferlength);
downloadedSize += bufferlength;
//updateProgress(downloadedSize, totalSize);
}
fileoutput.close();
} catch (IOException e) {
Log.d("service", "error");
//e.printStackTrace();
}*/
}
}
这就是错误:
11-20 09:38:21.107: E/AndroidRuntime(1627): FATAL EXCEPTION: main
11-20 09:38:21.107: E/AndroidRuntime(1627): java.lang.RuntimeException: Unable to instantiate service com.test2.lab.DownloadService: java.lang.InstantiationException: can't instantiate class com.test2.lab.DownloadService; no empty constructor
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2237)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.app.ActivityThread.access$1600(ActivityThread.java:123)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1201)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.os.Handler.dispatchMessage(Handler.java:99)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.os.Looper.loop(Looper.java:137)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.app.ActivityThread.main(ActivityThread.java:4424)
11-20 09:38:21.107: E/AndroidRuntime(1627): at java.lang.reflect.Method.invokeNative(Native Method)
11-20 09:38:21.107: E/AndroidRuntime(1627): at java.lang.reflect.Method.invoke(Method.java:511)
11-20 09:38:21.107: E/AndroidRuntime(1627): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
11-20 09:38:21.107: E/AndroidRuntime(1627): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
11-20 09:38:21.107: E/AndroidRuntime(1627): at dalvik.system.NativeStart.main(Native Method)
11-20 09:38:21.107: E/AndroidRuntime(1627): Caused by: java.lang.InstantiationException: can't instantiate class com.test2.lab.DownloadService; no empty constructor
11-20 09:38:21.107: E/AndroidRuntime(1627): at java.lang.Class.newInstanceImpl(Native Method)
11-20 09:38:21.107: E/AndroidRuntime(1627): at java.lang.Class.newInstance(Class.java:1319)
11-20 09:38:21.107: E/AndroidRuntime(1627): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2234)
11-20 09:38:21.107: E/AndroidRuntime(1627): ... 10 more
我的问题是:
- 如何正确启动此服务
- 所需的许可,如果缺少什么
- 如何使用此服务下载多个文件
- 我可以为每个文件实例化此服务并将其添加到它们的列表中,以便将来可以暂停或恢复整个列表或特定服务吗
public DownloadService() {
super("DownloadService");
// TODO Auto-generated constructor stub
}
要将数据传递给服务检查如何添加一个空构造函数?你不能,cz父类需要传递一个字符串值,我必须删除构造函数中的参数并将null传递给super,这是workyes,但不是。你需要一个空构造函数(这基本上就是你得到的错误)这调用了一个超级函数,它使用字符串作为参数。对,但是如果你传递一个字符串值,它仍然会给你同样的错误,如果你保持它为空,它仍然会给你同样的错误,所以我尝试了null,它被工作编辑了,你将需要超级函数调用中的一个参数。超级函数要求一个名称,这不仅仅是为了看起来漂亮。(事实上是的,但这不是你要知道的。父母要求一个名字,如果不给一个名字,那将是不礼貌的)。