Android中从活动实例化IntentService时出现Java空指针异常

我正在创建一个应用程序，其中包含一个活动和一个将从此活动调用的意图服务。 Intent服务的目的是将文件从android设备发送到远程服务器。该文件由应用程序创建

问题是：当我试图从活动中创建的方法实例化意图服务时，我得到了一个空指针异常

这是Eclipse显示的错误：

08-07 03:09:18.720: E/AndroidRuntime(1182): FATAL EXCEPTION: main
08-07 03:09:18.720: E/AndroidRuntime(1182): Process: com.viruni.authentication, PID: 1182
08-07 03:09:18.720: E/AndroidRuntime(1182): java.lang.RuntimeException: Unable to instantiate service com.viruni.authentication.DataUploader: java.lang.NullPointerException
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2556)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.app.ActivityThread.access$1800(ActivityThread.java:135)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.os.Handler.dispatchMessage(Handler.java:102)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.os.Looper.loop(Looper.java:136)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.app.ActivityThread.main(ActivityThread.java:5017)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at java.lang.reflect.Method.invokeNative(Native Method)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at java.lang.reflect.Method.invoke(Method.java:515)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at dalvik.system.NativeStart.main(Native Method)
08-07 03:09:18.720: E/AndroidRuntime(1182): Caused by: java.lang.NullPointerException
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.content.ContextWrapper.getContentResolver(ContextWrapper.java:99)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at com.viruni.authentication.DataUploader.<init>(DataUploader.java:25)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at java.lang.Class.newInstanceImpl(Native Method)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at java.lang.Class.newInstance(Class.java:1208)
08-07 03:09:18.720: E/AndroidRuntime(1182):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:2553)
08-07 03:09:18.720: E/AndroidRuntime(1182):     ... 10 more

调用启动意向服务的代码是：

Intent iservice = new Intent(Viewer1.this, DataUploader.class);
startService(iservice);

Viewer1是我要从中调用服务的活动。DataUploader是我试图启动的Intent服务

有人能帮我调试这个错误吗。我确信活动的任何其他部分都没有错误

注意：我正在从我创建的方法调用startService（）方法

这是我的数据上传器类：

public class DataUploader extends IntentService{
    String encoded_string;
    String android_id;

    public DataUploader() {
        super("Empty Constructor");
        android_id = Secure.getString(getContentResolver(),Secure.ANDROID_ID);
    }

    public DataUploader(String name) {
        super("DataUploader");      
    }


    @Override
    protected void onHandleIntent(Intent intent) {
        String filename = intent.getStringExtra("filename");

        Log.d("Testing","File name : " + filename);
        //doFileUpload();
    }

    public int doFileUpload() {
        int serverResponseCode = 0;
        String uploadServerUri = "my_URL string";
        Date d = new Date();
        d.getTime();

        File file = new File(path to the file, "r");
        try {
            HttpClient httpclient = new DefaultHttpClient();

            HttpPost httppost = new HttpPost(uploadServerUri);

            InputStreamEntity reqEntity = new InputStreamEntity(
                    new FileInputStream(file), -1);
            reqEntity.setContentType("binary/octet-stream");
            reqEntity.setChunked(true); // Send in multiple parts if needed
            httppost.setEntity(reqEntity);
            HttpResponse response = httpclient.execute(httppost);
            //Do something with response...

        } catch (Exception e) {
            // show error
        }

        Log.i("FileUpload", "FileUpload: Time : " + d.getTime());
        return 0;

    }


}

---

做一些小的修正

Intent-iservice=newintent（Viewer1.this，DataUploader.class）；

---

这是startService（iservice）

发布您的DataUploader服务代码…同时发布您的完整stacktrace。这里有一个嵌套的“起因”异常。我更喜欢以文字而不是图片的形式发布。我已经试过了。但是没有改变！出现了相同的错误：(

public class DataUploader extends IntentService{
    String encoded_string;
    String android_id;

    public DataUploader() {
        super("Empty Constructor");
        android_id = Secure.getString(getContentResolver(),Secure.ANDROID_ID);
    }

    public DataUploader(String name) {
        super("DataUploader");      
    }


    @Override
    protected void onHandleIntent(Intent intent) {
        String filename = intent.getStringExtra("filename");

        Log.d("Testing","File name : " + filename);
        //doFileUpload();
    }

    public int doFileUpload() {
        int serverResponseCode = 0;
        String uploadServerUri = "my_URL string";
        Date d = new Date();
        d.getTime();

        File file = new File(path to the file, "r");
        try {
            HttpClient httpclient = new DefaultHttpClient();

            HttpPost httppost = new HttpPost(uploadServerUri);

            InputStreamEntity reqEntity = new InputStreamEntity(
                    new FileInputStream(file), -1);
            reqEntity.setContentType("binary/octet-stream");
            reqEntity.setChunked(true); // Send in multiple parts if needed
            httppost.setEntity(reqEntity);
            HttpResponse response = httpclient.execute(httppost);
            //Do something with response...

        } catch (Exception e) {
            // show error
        }

        Log.i("FileUpload", "FileUpload: Time : " + d.getTime());
        return 0;

    }


}