Enabling an ImageButton from another activity

Question

In my main screen I have an ImageButton which is disabled in the xml file for the main activity. After some other activities are executed I return to the main screen (using finish()) and I want to find this ImageButton enabled. How can I do this?

Here's what I tried. I wanted to use the name of the ImageButton (btn_grand) as in the following, but it does not work because btn_grand is null:

    public void Exit(View view){
    //enable image buttons on the main screen
    finish();
    DataTrak dt = new DataTrak();
    this.setContentView(R.layout.activity_main);
    dt.btn_grand.setEnabled(true);
    dt.btn_grand.setClickable(true);
}

DataTrak is the name of the main activity. The layout file for DataTrak is activity_main.xml. Exit is executed when I click on a button and it belongs to another activity (the current activity).

Could you please help?

Answer 1

You never want to instantiate an Activity this way

DataTrak dt = new DataTrak();

they are not like a normal Java class. Only do it with startActivity(). What you could do is pass an extra to the Activity and check it there. Something like

Intent i = new Intent(v.getContext(), DataTrak.class);
i.putExtra("someKey", true);  // where someKey is any key you want to use 
startActivity(i);

Then in onCreate() or onResume() of your DataTrak Activity (depending on if you have finished it) check that value

Intent i = getIntent();
boolean enable = i.getBooleanExtra("someKey", false);  // false for default value
btn_grand.setEnabled(enable);  // if you passed the value it will enable else is disabled