Develop Reference

One class for each layout (new page)?

I wast just wondering if the standard practice is to create an activity/fragment class for each layout file (new page).
Example:
MainActivity.java
onCreate(){
setContentView(R.layout.**start_page**)
}
And than when the user clicks a button in the action bar (or some other button on the screen):
onOptionItemSelected() {
switch XX -> case XX: setContentView(R.layout.**next_page**)
}
So could i do the above instead of launching a new activity.java (that contains a new layout.xml) with an intent, or inflating the view with a fragment.java (that also contains a new layout.xml).
I can see that the up/back navigation wouldn't work with the above code, but is that the only reason why you basically have to create two files (.java & .xml) for each new page in your app.

Yes you could do it technically but beware that if you already create an instance of view lets say Button and you change the layout button will be null because button is not located in your View and also it will take time to render again the layout. So it is a best practice to start a new activity or just create a fragment.

You can do that, but every view will be on the given Activity, and the event handlers would be in the same class, which isn't really modular. It could get extremely bloated and you'll have a 2000 line superclass because it handles every single button click in arbitrary functions (or even worse, in a single onClick function).

(Android) Call Fragment from other Package within the Project

So the scenario is
com.example.fragment1.FragmentSample.class
com.example.fragment2.FragmentSample2.class
,,,
com.example.main.MainActivity.class
so when my app start it will create fragmentsample as default and I like to call fragmentsample2 when I press the enter button in fragmentsample... but my code has always error how can i do this?? btw my mainactivity extend on activity... is this wrong like it should be FragmentAcitivity or is it ok?

In my experience, ADT is unhappy (doesn't recognize the R file) when Fragments don't belong to the same package as their Activity, so in your case you would need to move FragmentSample.java & FragmentSample2.java into com.example.main
If that doesn't solve your problem, you need to provide more detail on the error/s you're seeing.

Switching between layouts from the same activity: Possible but recomended?

I want to know why do people keep recommending starting new Activities when you want to display another screen?
Let's say I want to display a screen with a label and an edit_text to ask for username, then another similar screen to ask for age, then another screen to display the data entered and ask for confirmation.
I did this:
main_layout.xml: has a button let's say mainButton, onClick="startRegistration"
name_layout.xml: edittext asking for name
age_layout.xml: edittext asking for age
confirm_layout.xml: display info + button to confirm
and in:
public class MainActivity extends Activity {
onCreate(...) {
...
setContentView(R.layout.main_layout);
}
public void startRegistration(View clickedButton) {
setContentView(R.layout.name_layout);
}
..
}
... and so on, all button handlers are public void methods in main class and each method contains setContentView() with the next layout as parameter.
I have a feeling this is bad programming style, however it works perfectly fine. Is it ok to do this? If not, is there any other easy way? Starting a new activity for such things feels really stupid to me.

Normally you group 'activities' together in an Activity. For you, registration uses multiple screens but are linked to each other. I would suggest using 1 Activity with a ViewFlipper.
Having 1 Activity for all will screw up the navigation for the user. The Back key has to be handled specially. "if back key, set this content, else set this content, etc"

If you code different layouts for the same type of screen then its not really an ideal idea. The better idea is to have the same layout and point to the same layout from the classes where the layouts are the same. In the screen where you want to have an extra/less control or different control then just have unique IDs to such controls.
Refer the controls from their IDs and you will have a single layout file. Writing different layout classes where the controls are same will pave way to code repetition and hence is not an ideal way of coding.

How to structure my android application

I'm very new to Android development, and want to make sure that I'm structuring my application correctly. First, let me explain what is needed.
The application starts off prompting the user for an access code, depending on their response there are two resulting menu's which can appear. One menu has 5 buttons, while the other adds two extra buttons making seven. Each one of those buttons brings me to a different view where more information will be displayed.
I originally starting writing it with one activity and a different XML file for each view. However, the more I have been researching online it seems that I should have a different Activity for each individual view. But now I'm relatively confused how I can prompt the user for input before initializing any of the Activities.
If anyone has any input I'd really appreciate it.
Thanks

You will need to initialize an activity before getting user input. And I think it is common that if you go to a new view that it uses a different class and xml layout. So for each of the new views you could make a new class that extends an activity and then has an xml file related to that view.
So have these 2 files for each new view you show.
Java file:
public class Activity1 extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout1);
}
}
XML file:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/layout1"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
//add any views
</LinearLayout>

Try:
-push activity1 with layout1
-pop inputDialog
-when inputDialog is closed by clicking ok...
-push Activity2 with layout2, proceed with you input from activity1 using extras
...and so on ;)

I have been trying to break up my programs into an activity and a corresponding xml layout for each view. If you have one activity and all those layouts, you have the potential to have a monster block of code in that one activity. I find that breaking it up makes it easier to read and debug.
As for prompting the user before initializing activities, i'm not entirely clear on what you mean. You need to load an activity before anything happens, in your situation it could easily be a simple password acception activity. If you're talking about passing information between activities, you can package data in an intent, and use that to start a new activity. Then in that new activity pull the information out of the intent.

Android - Creating a new activity in Eclipse [duplicate]

This question already has answers here:
Best way to add Activity to an Android project in Eclipse?
(8 answers)
Closed 9 years ago.
Easy one.
I've gone through a few guides and tutorials, and they're quite clear on how to start an activity (with intent).
However, how do I create a new activity in Eclipse? I can probably do this by hand, but then I have to modify the R file, which is auto-generated, and add a new xml layout.

Ok. Being a newbie myself I think the above two answers are thinking too much. He's asking very simply how to create a new activity in Eclipse.. I think this is what he wants:
A new Activity in Eclipse is actually a Class.
You would doubleclick 'src' on the left side in the Package Explorer, then highlight your 'com.' name, right click, select 'New' and then select 'Class'. Enter the Name as NewActivity and set the Superclass to android.app.Activity, then hit Finish.
When the NewActivity.java file opens up it should look like this:
package com.example.yourappname;
import android.app.Activity;
public class NewActivity extends Activity {
}
You can leave the Superclass blank and add extends Activity to the code itself if you prefer.
The final step is adding the Activity to your Manifest. So doubleclick AndroidManifest.xml to open it up and then click the 'Application' tab on the bottom. Next to the 'Application Nodes' box, click 'Add'. Highlight 'Activity' (the square box with a capital A) and click 'Ok'. Now look for the 'Attributes for Activity' box and enter a Name for the Activity and precede it by a period. In this example you'd enter '.NewActivity'.
And then you can add your onCreate() code so it looks like this:
public class NewActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_view);
//rest of the code
}
}
main_view would be your main view xml file, main_view.xml, that you would create in your layout directory.
To call the new Activity, your Intent in the code (in a different Activity) to start a new Activity looks something like this:
Intent startNewActivityOpen = new Intent(PresentActivity.this, NewActivity.class);
startActivityForResult(startNewActivityOpen, 0);
And that's it, you have the code to call the new activity and you created it. I hope this helps someone.

I know this is an old question, but I know there are still people with this same question(I did up until today)
If you add a new activity to your manifest file, there's a special link to click on to automatically create the new Activity, complete with the onCreate() method ready to be filled in.
Open the AndroidManifest.xml, and go to the 'Application' tab. Under 'Application Nodes', find and click the 'Add' button. You will likely create a new element at the top level, so select that option, highlight 'Activity', and press OK.
Once you've created the Activity, go to the 'Attributes for Activity' and fill in the name. Once you've filled in the name you want, click on the blue 'Name*' link next to the field. The new file wizard will show up, and all you have to do is press OK.
Voila! New Activity, registered in the manifest and as a ready-to-go Java class.

You create the activity by extending the activity class . Once you have creatd the activity class , You need to add the activity in the androidmanifest file specifying the properties for the activity...
A sample one would be something like this ...
<activity android:name=".JsonActivity" android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
The action here indicates that it is the one that starts first ..
I dont think you need to modify the R.java file ... Once you add these in the android manifest file and save it automatically gets updated. Also the things that u added like the layouts, menus, strings, id's etcc.... in the various xml files also get automatically updated...
Correct me if i am wrong ...

I tried searching for this question on Google and haven't seen this solution yet, so I thought I'd post it here.
In Eclipse, you can click on the "New" button on the toolbar. Under Android, select Android Activity, and run through the wizard. This is the best solution by far, since it lets you set up a layout and an Activity all in one, while also updating the Manifest for you.

How to add New Activity Eclipse step by Step:
Stpe1:Double click on the androidManifest
Step2:on the Menu bar click Aplication
Step3:Scroll down to application node and CLick add button
Step 4:click select Activity and Ok
step 5:clik on the the Texte(Name* Note:make sur u clik on the texte
not into the textbox )
step6:there a new Java Class dialog
## Heading ##write the classe name
## Heading ## check checkbox construct from the super classe and and ok..

There is also the tried and tested method of starting with one of the samples and going from there.
The Hello tutorial is as good a starting point is any, just select the create from existing sample option.
The latest update to the eclipse plugin even includes a tool to rename your package should you change your mind though I haven't used it yet so can't say if it works. (Right click on the package then select Android Tools, Rename Application Package).

It is important to say that if you type the desired name for the new Activity on Name box, a dot must be put before the new name. Otherwise, the window to complete the creation of Java code will not open when you click on names link.