Monday, 14 July 2014

How To Use startActivityForResult() in android



The next logical step in learning the Android development is to look at how can you call or invoke one activity from another and get back data from the called activity back to the calling activity. For simplicity sake, let us name the first calling activity as parent activity and the invoked activity as the child activity.

For simplicity sake, I use an explicit intent for invoking the child activity. For simple invocation without expecting any data back, we use the method startActivity(). However, when we want a result to be returned by the child activity, we need to call it by the method startActivityForResult(). When the child activity finishes with the job, it should set the data in an intent and call the method setResult(resultcode, intent) to return the data through the intent.

The parent activity should have overridden the method onActivityResult(…) in order to be able to get the data and act upon it. 

NOTE: for successful execution of this sequence of events, the child activity should call finish() aftersetResult(..) in order to give back the handle to the parent activity.

In summary, here are the methods to implement in the parent activity:
  • 1.  startActivtyForResult(..)
  • 2.  onActivityResult(…)

The child Activity should complete the work as usual and finally call:
  • 1.  setResult(…)
  • 2.  finish()

The startActivity() is not only used for migration and it also can carry data within..,

Intent intent = new Intent(1stActivity.this, 2ndActivity.class);
//here putExtra() method is used for carry some data
intent.putExtra("data_name", actual_data);

Now directly we can forward the data from one activity to another activity.

But if you wants to redirect to the 1st activity from the 2nd activity with data of 2nd activity we can use number of technology in Android like

  • Preference,
  • with the help of Bean,
  • startActivityForResult()

The Best & Simple way is to use startActivityForResult() method

Step-1 :

(In your 1st Activity class)
Use the syntax below When you want to move from the 1st Activity to the 2nd Activity

 use startActivityForResult() instead of using startActivity()

Intent intent= new Intent(1stActivity.this, 2ndActivity.class);
startActivityForResult(intent, 1);

//here we are passing two arguments the 1st one is Intent & the 2nd one is integer value for specification.

Step-2 :

(In your 2nd Activity class)

Use the Syntax below When you want to pass your data to the 1st Activity from the 2nd Activity

Intent i=new Intent();
setResult(1, i);
//here we are passing two arguments the 1st one is Intent & the 2nd one is integer value for specification.

Step-3 :

(In your 1st Activity class)

// override the onActivityResult() method

protected void onActivityResult(int requestCode, int resultCode, Intent data) 
super.onActivityResult(requestCode, resultCode, data);
//check with the int code specification 
//(in above activity we are using the integer value of "1")
if (requestCode == 1) 
if (null != data) 
String lst_of_sr = data.getStringExtra("data_name");
Toast.makeText(getApplicationContext(), lst_of_sr  Toast.LENGTH_LONG).show();
 Now you can back to the 1st activity with the data of 2nd activity.

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