如果我尝试启动服务，为什么会收到 InstantiationException?

Why do I get an InstantiationException if I try to start a service?(如果我尝试启动服务，为什么会收到 InstantiationException?)

问题描述

可能重复:
Android RuntimeException: 无法实例化服务

我整天都在尝试解决以下问题，但似乎没有任何效果.

I have been trying to fix the following problem all day but nothing seems to work.

我有一个小部件，它通过 IntentService 更新它的视图.但是在尝试启动此服务时，我不断收到 InstantiationException.下面是错误的堆栈跟踪和我用来启动服务的代码.我不相信我需要发布服务的代码，因为它甚至从未启动，但如果有人不这么认为，我当然会这样做.

I have a widget which gets it's views updated via an IntentService. But i keep getting an InstantiationException when trying to start this service. Below is the stack trace of the error and the code i use to launch the service. I don't believe i need to post the code of the service as it is never even started, but if someone thinks otherwise i will of course do so.

堆栈跟踪

05-30 13:58:47.150: ERROR/AndroidRuntime(1163): FATAL EXCEPTION: main
05-30 13:58:47.150: ERROR/AndroidRuntime(1163): java.lang.RuntimeException: Unable to instantiate service syrligt.cashtrack.widgets.StatisticsWidgetUpdateService: java.lang.InstantiationException: syrligt.cashtrack.widgets.StatisticsWidgetUpdateService
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:1904)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.app.ActivityThread.access$2500(ActivityThread.java:117)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:982)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.os.Looper.loop(Looper.java:123)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.app.ActivityThread.main(ActivityThread.java:3647)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at java.lang.reflect.Method.invokeNative(Native Method)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at java.lang.reflect.Method.invoke(Method.java:507)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at dalvik.system.NativeStart.main(Native Method)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163): Caused by: java.lang.InstantiationException: syrligt.cashtrack.widgets.StatisticsWidgetUpdateService
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at java.lang.Class.newInstanceImpl(Native Method)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at java.lang.Class.newInstance(Class.java:1409)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:1901)
05-30 13:58:47.150: ERROR/AndroidRuntime(1163):     ... 10 more

小部件代码

 public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
     for(int i = 0; i<appWidgetIds.length ; i++){
         Intent intent = new Intent(context,StatisticsWidgetUpdateService.class);
         intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]);
         context.startService(intent);
     }
 }

服务代码

public class StatisticsWidgetUpdateService extends IntentService {

public StatisticsWidgetUpdateService(String name) {
    super(name);
}

@Override
protected void onHandleIntent(Intent intent) {
    AppWidgetManager appWidgetManager=AppWidgetManager.getInstance(this);
    int appWidgetId = intent.getExtras().getInt(AppWidgetManager.EXTRA_APPWIDGET_ID);
    CashDB cdb = new CashDB(this);
    cdb.open();

    RemoteViews updatedViews = new RemoteViews(getPackageName(), R.layout.statistics_widget);
    updatedViews.removeAllViews(R.id.list);
    PendingIntent pendingIntent = null;
    Cursor c = null;
    Intent i = null;
    SharedPreferences sp = getSharedPreferences(Preferences.PREFERENCES, 0);

    double incomeAmount = cdb.sumTransactions(null, new TimeFrame(sp.getInt(Preferences.DEFAULT_TIME_FRAME, TimeFrame.ALL_TIME)), 1);
    double expenseAmount = Math.abs(cdb.sumTransactions(null, new TimeFrame(sp.getInt(Preferences.DEFAULT_TIME_FRAME, TimeFrame.ALL_TIME)), -1));

    int value = StatisticsWidgetConfig.getConfig(this, appWidgetId);
    c = cdb.fetchCategoriesWithSums(new TimeFrame(sp.getInt(Preferences.DEFAULT_TIME_FRAME, TimeFrame.ALL_TIME)), value, 3);

    updatedViews.setTextViewText(R.id.balance, StringConversion.formatAmount(incomeAmount - expenseAmount));//balance text
    updatedViews.setViewVisibility(R.id.value_bar, incomeAmount - expenseAmount < 0 ? R.drawable.list_item_value_red_medium : R.drawable.list_item_value_green_medium);//value bar
    updatedViews.setTextViewText(R.id.income, StringConversion.formatAmount(incomeAmount));//income text
    updatedViews.setTextViewText(R.id.expense, StringConversion.formatAmount(expenseAmount));//expense text
    updatedViews.setTextViewText(R.id.popularity, Integer.toString(cdb.fetchAllTransactions(new TimeFrame(sp.getInt(Preferences.DEFAULT_TIME_FRAME, TimeFrame.ALL_TIME)), null, null,null).getCount()));//popularity text

    for(int j = 0; j<c.getCount();j++){

        c.moveToPosition(j);
        RemoteViews statisticsView = new RemoteViews(getPackageName(), R.layout.statistics_widget_list);

        statisticsView.setTextViewText(R.id.name, c.getString(c.getColumnIndexOrThrow(CashDB.CATEGORY_NAME)));//category name
        statisticsView.setImageViewResource(R.id.icon, c.getInt(c.getColumnIndexOrThrow(CashDB.CATEGORY_IMAGE)));//category icon
        statisticsView.setViewVisibility(R.id.starred, c.getInt(c.getColumnIndexOrThrow(CashDB.CATEGORY_STARRED)) == 1 ? View.VISIBLE : View.GONE);//starred icon

        double procent = c.getLong(c.getColumnIndexOrThrow(CashDB.TRANSACTION_SUM));
        procent = procent/(value == -1 ? expenseAmount : incomeAmount);
        procent = Math.abs(procent * 100);

        if((procent%1) < 0.1){
             statisticsView.setTextViewText( R.id.procent, String.format("%.0f%s",procent," %"));//procentage
        }else{
             statisticsView.setTextViewText( R.id.procent, String.format("%.1f%s",procent," %"));//procentage
        }

        Bitmap bmp;
        if(value == -1){
            bmp=BitmapFactory.decodeResource(getResources(), R.drawable.progress_bar_red);
        }else{
            bmp=BitmapFactory.decodeResource(getResources(), R.drawable.progress_bar_green);
        }
        int width=(int) (procent*4.056);  // kankse fuckar upp på andra display storlekar
        if(width<2){
            width=2;
        }
        width = (int) getResources().getDisplayMetrics().density * width;
        int height=10;
        Bitmap resizedbitmap=Bitmap.createScaledBitmap(bmp, width, height, true);
        statisticsView.setImageViewBitmap(R.id.progress_bar, resizedbitmap);//procent bar

        i = new Intent(this, ViewCategory.class);
        i.putExtra(CashDB.CATEGORY_ID, c.getLong(c.getColumnIndexOrThrow(CashDB.CATEGORY_ID)));
        i.setAction("cashtrackViewCategory"+c.getLong(c.getColumnIndexOrThrow(CashDB.CATEGORY_ID)));
        pendingIntent = PendingIntent.getActivity(this, 0, i, PendingIntent.FLAG_UPDATE_CURRENT);
        statisticsView.setOnClickPendingIntent(R.id.statistics_widget_list_layout, pendingIntent);
        updatedViews.addView(R.id.list, statisticsView);

    }

    c.close();
    cdb.close();
    appWidgetManager.updateAppWidget(appWidgetId, updatedViews);
}

}

推荐答案

你的服务需要有一个公共的无参数构造函数.否则，Android 将无法实例化它.

You service needs to have a public no-args constructor. Otherwize, Android will not be able to instantiate it.

所以替换

public StatisticsWidgetUpdateService(String name) {
    super(name);
}

与

public StatisticsWidgetUpdateService() {
    super("SOME NAME");
}

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