CODEWITHSUNDEEP
javaandroidclassandroid-activitynullpointerexception
baharsan
baharsan

Reputation: 181

How to Call Method in Activity From Other Class not Activity in Android?

I have 2 class in my project, first extend activity and other extend other class. please help how to call the method in main activity from other class not activity? here my code :

  1. Extend Activity Class

    public class Isign extends Activity {
private static final String TAG         = "Sample::Activity";

public Isign() {
    Log.i(TAG, "Instantiated new " + this.getClass());
}   
@Override
protected void onCreate(Bundle savedInstanceState) {
    Log.i(TAG, "onCreate");
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    super.onCreate(savedInstanceState);
    a = new IsignView(this);

LinearLayout lv = new LinearLayout(this);
lv.setOrientation(LinearLayout.VERTICAL);
LinearLayout.LayoutParams textViewParams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);

tv = new TextView(this);
tv.setTextSize(20);
tv.setText("RESULT : ");
tv.setLayoutParams(textViewParams);
lv.addView(tv);
lv.addView(a);

setContentView(lv);} 

public void update_kom(String d){
    Log.i("asd", "asd");
    tv.setText("");
    tv.setText("RESULT : " + d);
}

  2. Not Extend Activity Class

    public class IsignView  extends IsignCvViewBase  {
public IsignView(Context context) {
super(context);

try {

} catch (IOException e) {
    e.printStackTrace();
    Log.e(TAG, "Failed to load cascade. Exception thrown: " + e);
}
}

By the way I Have used this way to call method from main activity :

new Isign().update_kom("bottle");

and i get this error LogCat :

07-05 06:52:22.290: E/AndroidRuntime(2708): FATAL EXCEPTION: Thread-12
07-05 06:52:22.290: E/AndroidRuntime(2708): java.lang.NullPointerException
07-05 06:52:22.290: E/AndroidRuntime(2708): at 
org.baharsan.isign.Isign.update_kom(Isign.java:86)     
07-05 06:52:22.290: E/AndroidRuntime(2708): at 
org.baharsan.isign.view.IsignView.processFrame(IsignView.java:353)
07-05 06:52:22.290: E/AndroidRuntime(2708): at 
org.baharsan.isign.cv.IsignCvViewBase.run(IsignCvViewBase.java:101)
07-05 06:52:22.290: E/AndroidRuntime(2708): at 
org.baharsan.isign.view.IsignView.run(IsignView.java:557)
07-05 06:52:22.290: E/AndroidRuntime(2708): at  
java.lang.Thread.run(Thread.java:1019)

Thank you for your Response, i am sorry if this question repeated while i can't find similiar question like my problem. other problem just show me how to call method in other class from main activity but this question is opposite. "how to call method in main activity from other class?"

thank you so much :)

Upvotes: 0

Views: 4402

Answers (3)

dmon
dmon

Reputation: 30168

While RSenApps' answer works, it's not the best idea to make a View work only inside a certain activity. Instead, declare an interface in your View. Then have the Activity implement that interface and give it to the View, either via the constructor or in a setter. The View can just call the method on the instance of the interface when whatever event you are interested in happens.

Also, note that you can never, ever, call new on an Activity yourself, Activities are always managed by the framework.

Upvotes: 2

H4F
H4F

Reputation: 131

call the "WantedActivity" by writeing this in the "CallActivity" 

public class CallActivity extends Activity {
    //The Activity we wnt to call
    private WantedActivity stringname;

stringname is used to deal with the WantedActivity . also you can remove private

Upvotes: 0

Ryan S
Ryan S

Reputation: 4567

Easiest way is to pass reference of the activity to your other class instead of Context. For example

public IsignView(Isign activityReference) {
super((Context) activityReference);
activityReference.update_kom("bottle");
try {

} catch (IOException e) {
    e.printStackTrace();
    Log.e(TAG, "Failed to load cascade. Exception thrown: " + e);
}
}

Upvotes: 1

Related Questions