Develop Reference

Can't find the findViewById function

I'm an Android newbie working with the Eclipse IDE and the Android SDK. Anyway, I've watched a few tutorials and I can't seem to be able to call the findViewById() function.
I would appreciate if you could instruct me how to use it, if it's a method of a static class or something else.
Thanks, I'm sure this won't be a problem for the more advanced users!
Well the in response to the comments I'm trying to use it in an Activity.
Here's the code in there:
package tk.quiero.test1;
import android.support.v7.app.ActionBarActivity;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Where exactly am I supposed to use it?
Thanks

findViewById is defined in the Activity class, so it sounds like you're trying to call this from outside of the Activity. If so, you should post what exactly you're trying to do because there are ways of doing this, but there's also a high likelihood that there's a cleaner or easier way than resolving UI elements outside of the Activity

public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View view = findViewById(R.id.xxxxx)
}
replace xxxxx with the id that you've defined in your xml...which should look like #+id/xxxxx

How do I make a slide left/right menu in Android?

I'm trying to create a small game on Android and have some questions on a specific section of my game. I'm fairly new to android so please excuse if I don't have a full understanding of certain things.
When clicking "play" I'd like to view slide-able menu that makes it able for the user to swipe left and right to choose a level. Overtime I will be adding few more levels but have 2-3 of them now.
What would be the best way to do this? Is it best to implement a fragment for each "level page" or create entirely new activities?
My project is compatible for Android ver. 2.3.3 and above, so it's automatically included the "appcompat_v7" project. (I don't know if that makes a difference).
I've pasted my code below if needed:
package com.example.snake;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
public class SnakeLevelSelectActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_snake_level_select);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.snake_level_select, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_snake_level_select, container, false);
return rootView;
}
}
}
What I intended to do was create several fragment classes and animate between the fragments when the user swipes. I also have issues understanding on how to use several fragments with the "PlaceHolderFragment" class, since the solutions I've found on SO have been different. This is an entirely question, but would be appreciated if it was answered as well.

What would be the best way to do this? Is it best to implement a fragment for each "level page" or create entirely new activities?
This is exactly what a Fragment is for. What you are looking for is already there and named ViewPager. Using ADT and Eclipse you can even create an Activity with this already implemented. Use the "Navigation type" combobox for that purpose:
You can also choose "Action Bar Tabs (with ViewPager)", which will enable Tabs in the ActionBar and make sure that you can switch to different Fragments using both the swipe gesture as well as the tabs.

Android now has this built-in in the SDK.
They call it the Navigation Drawer.
Look up the documentation it contains sample project, it is very easy to implement.

Creating a basic Android Project now adds a Fragment Layout?

This is weird. I had recently gotten into Android programming. I made a fresh install but when I create a new project there is this new option called Fragment Layout Name at the very end of the page where you specify your Activity name. I haven't had this happen before but when I open my main activity this is what I get. Also half of it is filled with errors according to Android. Is there anyway I can go back and avoid this?
package com.example.quizactivity;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}

Do as follows, this works for me..
Step-1:
Right Click on your Project -> Properties -> Android -> In Library panel, remove appcompat_v7 library, Apply and Ok
Step-2:
In Project goto res -> values -> style.xml
In line <style name="AppBaseTheme" parent="Theme.AppCompat.Light"> change parent value from Theme.AppCompat.Light to android:Theme.Light
Step-3:
In Project goto res -> values-v11 -> style.xml
In line <style name="AppBaseTheme" parent="Theme.AppCompat.Light"> change parent value from Theme.AppCompat.Light to android:Theme.Holo.Light
Step-4:
In Project goto res -> values-v14 -> style.xml
In line <style name="AppBaseTheme" parent="Theme.AppCompat.Light.DarkActionBar"> change parent value from Theme.AppCompat.Light.DarkActionBar to android:Theme.Holo.Light.DarkActionBar
Step-5:
In Project goto menu -> main.xml remove these lines in menu tag:
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.test.MainActivity"
and in item tag change this line from app:showAsAction="never" to android:showAsAction="never"
In project, goto res -> layout -> delete fragment.xml
Step-6:
In MainActivity extends Activity not ActionBarActivity and finally your MainActivity.java after remove unnecessary code, looks like this:
package com.example.test;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Enjoy:)

When creating a new project Select Minimum SDK version as upper or higher as u can . and then u will get rid of app compact .
I have chosen Miminum SDK 4.0 and get rid of it .

I don't know what is appcompat v_7 and why is it being add in every time when i create a new project ?

this code is about the default code of MainActivity.java
having problem to understand and also there is a another thing that is the fragmentaion_main.xml file which is likely another buden instead of activity_main.xml why it so ?
package com.example.onehello;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}

What is appcompat_v7?
It is the support library added for backwards compatibility. Android has many versions and each new version brings many changes to the API. So, for the older versions of Android to be compatible with the code written for the newer versions, the appcompat_v7 library is helpful.
Why is it being added every time I create a new project?
I assume that you are using Eclipse IDE for the development. Ideally, it would suffice to create one appcompat_v7 folder and make all the projects link to that folder for support library. But, there seems to be some bug in Eclipse. It creates a new appcompat_v7 folder each time a new project is created.
'fragment_main.xml' is like another burden?
Fragment class was introduced in Android API 11. It is useful in creating different layouts for tablets and phones. It is more of a good support to take advantage of the bigger screens on tablets. If you want to develop your application for a smart phone only, you need not even worry about it. So, it's more of an advantage than a burden.
For more reading on fragments, go to http://developer.android.com/reference/android/app/Fragment.html

This appears after installation "Android Support Library":
https://developer.android.com/tools/support-library/features.html

Fragments and Activities -- where do I put my application logic?

I have created my view how I want it to look. It has 1 images, an input box, and a button. I will want to load another activity when the button is clicked. I am confused why there are fragments and activities. I am new to the Android world (coming from iOS).
My understanding is that Activities are similar to ViewControllers, but I am not sure I understand what a fragment is.
Where do I put the event handling?
package com.phppointofsale.phppointofsale;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
public class StoreUrlActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_store_url);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new StoreUrlFragement()).commit();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.store_url, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class StoreUrlFragement extends Fragment {
public StoreUrlFragement() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_store_url,
container, false);
return rootView;
}
}
}

Firstly I would recommend reading this Fragments . Pay particular attention to the created fragment section, which includes the fragment life-cycle diagram. Second download and compile this Sample App,the effective navigation app will help you understand how different fragments work in tandem, and even implements a action bar.
To answer your question more or less a fragment can be thought of as a separate class. Once you call upon that particular fragment you can call functions from within that class.
Fragment Case-Switch
This is some sample code to show you what I mean.
public Fragment getItem(int i){
switch (i) {
case 0:
// The first section of the app is the most interesting -- it offers
// a launchpad into the other demonstrations in this example application.
return new LaunchpadSectionFragment();
case 1:
return new BluetoothClass();
default:
// The GPS section of the app .
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
fragment.setArguments(args);
return fragment;
}
}
In this case each fragment for me represented a class, which was implemented in a separate tab and each tab had a separate functionality. One of the key advantages of fragments is you can run separate activities without first letting one activity complete.
Furthermore each fragment is an extension of the java.lang.Object library. So it has all those functions + additional ones. I would read this as well. Lastly it would be a good idea to have separate xml files for each fragment then you can display that separately when a fragment is invoked.
Some more code
Each fragment will/could have this
public void onActivityCreated(Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
// Do stuff on creation. This is usually where you add the bulk of your code. Like clickListners
View rootview = inflater.inflate(R.layout.xml_the_fragment_uses container,false);
rootview.findViewById(R.id.your_id).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Do something
}
});
}
public void onStart(){
super.onStart();
Toast.makeText(getActivity(), "Fragment started",Toast.LENGTH_SHORT).show();
}
public void onResume(){
super.onStart();
Toast.makeText(getActivity(), "Fragment Resumed",Toast.LENGTH_SHORT).show();
}
public void onStop(){
super.onStart();
Toast.makeText(getActivity(), "Fragment Stoped",Toast.LENGTH_SHORT).show();
disableBT();
}
Remember these functions are from the fragment life-cycle I mentioned earlier.
Hopefully that gave you some idea on fragments. Also remember to read this as a lot of functionality uses the v7 app compat library. Including the fragment manager.