问题:

I have a class that is currently extending Activity and I have methods like findViewById, ArrayAdapter etc. I want to turn it into an independent class but all the above methods become undefined. What is the problem? Shouldn't importing the classes be enough? For eg, I import android.view.View for findViewById but it still makes no difference. Please advise.

回答1:

you should pass the instance of your Activity to your Second Class on the constructor like this :

In your Activity Instanciate your Class like this :

MyClass instance = new MyClass(this);

And in your second Class , the constructor will be like this :

public class MyClass {  public Activity activity;  //.... other attributes   public MyClass( Activity _activity){     this.activity = _activity; //other initializations...  } }

and then when you want to use the findViewById() method , you can do like this :

EditText txt = (EditText)this.activity.findViewById(R.id.txt);

回答2:

if you want to call any function that belongs to Activity then only thing you need to have is context of the Activity.

eg.

class A extends Activity{  Context ctx; void oncreate(Bundle b) ctx = this;  B bob = new B(ctx); } }

Here is class B.

Class B { B(Activity a) { a.anyFunctionOfActivity(); }  }

回答3:

findViewById is non-static public method of the Activity Class ,so it only be available for a Activity object. Therefore, import android.view.View and android.app.Activity won't make it available. To make it available, you could pass around a Actvity object - usually a this point in your activity. However, notice that you should always update your View in the UI thread.

回答4:

Please try the following:

public static View getLayoutByRes(@LayoutRes int layoutRes,@Nullable ViewGroup viewGroup) {     final LayoutInflater factory = getSystemService(Context.LAYOUT_INFLATER_SERVICE);     return factory.inflate(layoutRes, viewGroup); }  TextView tv = (TextView) getLayoutByRes(R.layout.xxx ,Null).findViewById(R.id.editd);

转载请标明出处:using findviewbyid in a class that does NOT extend Activity in android

文章来源: using findviewbyid in a class that does NOT extend Activity in android

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