How can I send data to ble device from second or third activity of the same program

Question

I can send data from the first activity but on repeating the same procedure on the second activity to send data to ble device is not successful. How can I send data from second activity?

Answer 1

use this to save

Intent intent = new Intent(FirstScreen.this, SecondScreen.class)
    intent .putExtra(strName, keyIdentifer );

use this to get

String newString;
if (savedInstanceState == null) {
    Bundle extras = getIntent().getExtras();
    if(extras == null) {
        newString= null;
    } else {
        newString= extras.getString("STRING_I_NEED");
    }
} else {
    newString= (String) savedInstanceState.getSerializable("STRING_I_NEED");
}

Answer 2

If you just want to send data to the next activity, use Intent intent = new Intent(FirstActivity.this, SecondActivity.class) intent.putExtra("id_for_value", value); startActivity(intent);

And recover it with

  value= getIntent().getExtras().getString("id_for_value");//if it is a string

OR

If you want to send data back from the Second activity back to the Previous, you have to use start activity for results

Intent intent=new Intent(MainActivity.this,SecondActivity.class);  
startActivityForResult(intent, 2)//where 2 is the request code
finish();

Again in the FirstActivity, overide this

@Override  
   protected void onActivityResult(int requestCode, int resultCode, Intent data)  
   {  
             super.onActivityResult(requestCode, resultCode, data);  
              // check if the request code is same as what is passed  here it is 2  
               if(requestCode==2)  
                     {  
                        String result=data.getStringExtra("ResultId");   

                     }  
 }  

And in your PreviousActivity, you pass the data like this

Intent intent=new Intent();  
intent.putExtra("ResultId",message);  
setResult(2,intent);  
finish();