小编Kao*_*aos的帖子

我有一个叫做MainActivity.java的AsyncTask类来调用一个类.最后一个类findViewById()在执行时返回此错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View <mypackage>.MainActivity.findViewById(int)' on a null object reference

我不明白如何ImageView在完成工作R.layout.activity_main之后编辑定位AsyncTask.

MainActivity.java

public class MainActivity extends Activity {

    public MainActivity() {}

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        new Connection().execute();
    }

}

Connection.java

public class Connection extends AsyncTask<String, Void, String> {
    public String result;

    //I know, this isn't correct, how can i do?
    public MainActivity MainActivity;

    @Override
    protected String doInBackground(String... arg0) {
        // …