CODEWITHSUNDEEP
androidandroid-asynctask
Henk Schurink
Henk Schurink

Reputation: 429

AsyncTask has no zero argument constructor

Let's say I have an Android AsyncTask called UpdateInterfaceStatusesTask:

private class UpdateInterfaceStatusesTask extends AsyncTask<Object, Object, Object> {

    public UpdateInterfaceStatusesTask() {
        ;
    }

    protected Object doInBackground(Object... params) {
        View header = ((NavigationView) findViewById(R.id.nav_view)).getHeaderView(0);
        ((TextView) header.findViewById(R.id.nav_head_status)).setText(ServerThread.getInstance().isInterrupted() ? "Offline" : "Online");
        return null;
    }

    @Override protected void onPostExecute(Object param) {
        ;
    }
}

And I want to programatically create a new instance of it:

public void createNewInstance(Class<? extends AsyncTask<?, ?, ?>> clazz) {
    try {
        clazz.newInstance().execute();
    } catch (Exception x) {
        x.printStackTrace();
    }
}

I'm getting the following error:

W/System.err: java.lang.InstantiationException: java.lang.Class<nl.hypothermic.offthegrid.ChatActivity$UpdateInterfaceStatusesTask> has no zero argument constructor
W/System.err:     at java.lang.Class.newInstance(Native Method)
W/System.err:     at nl.hypothermic.offthegrid.tasks.TaskScheduler$1.run(TaskScheduler.java:27)
W/System.err:     at android.os.Handler.handleCallback(Handler.java:790)
W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:99)
W/System.err:     at android.os.Looper.loop(Looper.java:164)
W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:6494)
W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
W/System.err:     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

Anyone have the same problem?

Upvotes: 1

Views: 58

Answers (1)

nsndvd
nsndvd

Reputation: 830

I guess your private class is actually a nested class and you need to make it static in order to use the 0 arguments constructor. Otherwise, there is always at least one argument (always the 1st), which is an instance of the containing class.

Upvotes: 5

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