java如何在类a扩展类B扩展活动时正确使用findViewById

Question

在Android中，我有一个类a扩展了类B，类B扩展了ActionBarActivity。类设置内容视图。由于某些原因，我无法从类B访问视图元素。如何访问视图元素（例如：TextView）？当我尝试在类B中使用findViewById时，它总是空的

public class A extends B {
    @Override
    protected void onCreate(Bundle savedInstanceState)  {
        setContentView(R.layout.activity_main);
        super.onCreate(savedInstanceState);
    }
}

public class B extends ActionBarActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        TextView myTextView = (TextView) findViewById(R.id.myTextView);
        // myTextView is null
    }
}

Answer 1

你在向后继承东西。B类从不设置ContentView

我想这就是你想要的：

public class A extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState)  {
    setContentView(R.layout.activity_main);
    super.onCreate(savedInstanceState);
    }
}

public class B extends A {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // A called setContentView(), so now we can find views by id.
        TextView myTextView = (TextView) findViewById(R.id.myTextView);
        // myTextView now is not null.