Develop Reference

Select data from one Activity and side by side instant change in Another Activity or fragment in android

Sorry for my bad English.
I have a spinner(with some city list) and a tab layout(say tabA and tabB) in my mainActivity.TabA and TabB have separate fragment. My Question is when I select spinner item from mainActivity then at the same time tab A data will load. Is that possible that we can change data from one class and changes will be made in another class.
Or if you have a better solution then please suggest me.
Thanks in Advance.

You can send data from one activity to another activity using intends. Like this:
Intent intent = new Intent(this, destinationActivity.class);
intent.putExtra("key", "value");
startActivity(intent);
This will send the value to destinationActivity assigned to a variable key.
In your destinationActivity, you can get the value of key and write your code accordingly. Like this:
String key= getIntent().getExtras().getString("key");
Here, value will be stored in key variable.
Hop this helps :)

You can do this by means of a interface. When you need to change the value of class B just call a interface(that is implemented in class B) from current class A and do whatever you want.

How do I pass data from an EditText in one Activity to a TextView in another activity without switching to the second activity?

I want to send a string variable that is entered into an EditText on ActivityOne to pass the data and be displayed as a TextView on ActivityThree. However, I am having problems as the only solutions to do this that I can find cause the activity to switch to ActivityThree while doing this. I want to avoid this or maybe even send the data to ActivityThree and switch to ActivityTwo all on the click of a button. Any help or redirection to a current solution would be greatly appreciated.

If you want to send data from ActivityOne to ActivityThree by avoiding ActivityTwo then save that data in a static variable then use that variable in ActivityThree to set TextView data.

You can simply do this using SharedPreferences.
Setting EditText values in Preference from ActivityOne:
// EditText
EditText editText = (EditText) findViewById(R.id.editText);
SharedPreferences.Editor editor = getSharedPreferences("Your_Preference_Name", MODE_PRIVATE).edit();
editor.putString("KEY_VALUE", editText.getText().toString());
editor.commit();
In ActivityThree, retrieve value from Preference:
SharedPreferences prefs = getSharedPreferences("Your_Preference_Name", MODE_PRIVATE);
String editTextValue = prefs.getString("KEY_VALUE", null);
// TextView
TextView textView = (TextView) findViewById(R.id.textView);
textView.setText(editTextValue);
Hope this will help~

Please use a global variable in Application class and set it's value in ActivityOne and read the same value from ActivityThree.Global variables are available to entire project Activities.

The best way is using input extra. Do this in Activity one
Intent i = new Intent(ActivityOne.this, ActivityThree.class);
i.putExtra("label", "label_text");
startActivity(i);
Then receive the string in Activity three as such:
EditText input = //intialize it in OnCreate
Intent intent = getIntent();
String data = intent.getExtras().getString("label");
input.setText(data);

There are so many ways to do this.. But it heavily depends on what you plan to do with data and your situation..
If you want to display the data in activity three than you can make data persist and later show it when activity three is created or resumed, now:
1- If you want to display the data in activity three and you want the value to persist only in current session you can use a Global Variable or even Static one, if you define the desired value as a static variable inside your activity three than you can easily access it and use it without any need for the activity to be even created:
public ActivityThree extends Activity {
public static String myValue;
2- If you want to display the data in activity three and you want data to persist even if the app is closed you can use SharedPreferences as described here:
https://developer.android.com/training/basics/data-storage/shared-preferences.html
3- If you want to run a background task in activity three on value getting determined you can use LocalBroadcastManager:
https://www.intertech.com/Blog/using-localbroadcastmanager-in-service-to-activity-communications/

Too many Activities in Android App. Any alternatives?

I am creating my first app. In this app, I have an expandable list with many items. When I select any of these items, I want several paragraphs to be displayed. Do I need to create an Activity for each of these items if text is the only thing I want displayed? I know that there has to be an easier way. I did create it like this at first and it seemed very bulky (30+ activities), so now I have it set up so that when an item is selected, the setContentView opens the corresponding layout with the text that needs to be displayed. This works but there is a catch, whenever I hit the back button, it takes me back to my main activity class and not my expandable list class. I want the user to be able to go back and select something else from the list. Any guidance as to what I need to do would be appreciated.

I would suggest creating string resources for each item you would like to display, then creating one activity with a TextView. Then, instead of creating new intents for each activity, create an intent that goes to the new activity, and add an extra that contains the text for the TextView. For example:
Activity1:
myButton.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
Intent intent = new Intent(this, ParagraphView.class);
intent.putExtra("textData", getResources().getString(R.string.myText));
getBaseContext().startActivity(intent);
}
});
In the onCreate of the viewer, add this to get your TextView:
Intent intent = getIntent();
String textData = intent.getStringExtra("text");
Now, we need to write the text into the TextView:
TextView tv = (TextView) findViewById(R.id.myTextView);
tv.setText(textData);
All you have to to is set up your string resources and button click listeners. You may consider this easier than having lots of activities (it's definitely easier to manage entries this way) but does require a bit of setup.
Edit: Thanks to #ianhanniballake for pointing out a much better way (I don't even know what I was thinking at the time...)
Edit2: Wow, I REALLY messed up my code. (Hopefully) Fixed now

How can I setText() (TextView) when the TextView is in another layout?

My app has 2 layouts (main layout) and (preference (prefs) layout).
When the MainActivity loads, I set setContentView(R.layout.main); - main layout
I need to then set text for a TextView in the preference layout, but it never gets set.
LayoutInflater factory = getLayoutInflater();
View inflate = factory.inflate(R.layout.prefs, null);
TextView eSerial = (TextView) inflate.findViewById(R.id.editTextSerial);
mSerial = "Test";
eSerial.setText(mSerial);
The way I get to the preference page is with a menu and then the page loads up with no change to TextView
I have searched and not found an answer yet.
Please help.
Thank you.

When the menu kicks off your prefs activity, you can populate the view with the values. user1853479 points out one way of doing this, which is to add the values to an intent. Assuming you want to store these prefs for future runs, you can also set any that for that specific run and save them in your local store. Another method is to create a singleton to store your settings, load it when your app starts, modify and save as needed, and access it from any of your activities.

Short answer: You can't do this.
Long answer:
If you are launching the preference page yourself, you must be creating an Intent to do so. Call putExtra() to store your text inside that intent. In your PreferenceActivity, call getIntent().getStringExtra() to get the text, then put it in your TextView.

Changing a textview in a separate activity in android

I have a log in page that pulls information from a data base, I then want to use this some of this information to populate different textviews on a new page/activity. I can get a textview to change on the activity where I have my submit button, but when I try to change the textview on my second activity, it just crashed (The application has stopped unexpectedly).
Here's my code for changing the textview (where txtID is my textview on a separate activity)
TextView test2 = (TextView) findViewById(R.id.txtID);
test2.setText(test);
my xml for seperate activity
<TextView android:text="TextView" android:id="#+id/txtID"
android:layout_width="wrap_content" android:layout_height="wrap_content"></TextView>
Oh, I'm using a tableview for my login page, then tabs for my the rest of my pages. I'm pretty new to this, so sorry if this is something simple, but any help would be greatly appreciated!! :-)

You don't want to directly touch the UI elements of another Activity. You can make use of bundles to pass information back and forth. Here is an example:
Say we have Activity A, and it has some information as a String it wants to pass to become the text of a TextView in Activity B.
//Setup our test data
String test = "Some text";
//Setup the bundle that will be passed
Bundle b = new Bundle();
b.putString("Some Key", test);
//Setup the Intent that will start the next Activity
Intent nextActivity = new Intent(this, ActivityB.class);
//Assumes this references this instance of Activity A
nextActivity.putExtras(b);
this.startActivity(nextActivity);
So now in the onCreate method for Activity B, we can get that String and assign it as the text to the TextView like you have
public void onCreate(Bundled savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main); //Setup some layout, set to your own
String test = getIntent().getExtras().getString("Some Key");
TextView test2 = (TextView) findViewById(R.id.txtID);
test2.setText(test);
}

I'd probably let each separate Activity take care of its own display, and not try to have Activity 1 directly update the display of Activity 2, which is kind of what it looks like you were doing.
The Notepad Tutorial demonstrates an application with two Activities, where one Activity calls another, passing in data. (Take a look at onListItemClick in Notepadv3.) You could maybe follow this model to pass data from Activity 1 to Activity 2, where Activity 2 then takes care of its proper display, using the data it received.
If you're still having problems (like your application crashing), then please post the complete minimal code necessary to replicate your problem. Note the Notepad Tutorial and the Hello, World Tutorial include steps for debugging, which might help you isolate the exact problem.

Andy... If you try to directly touch a UI widget in another activity, your app will crash. Been there, done that accidentally. Instead, consider passing an immutable stateful object between the activities. This can be done using startActivityForResult for instance. I have some sample code here.