Develop Reference

TabActivity listener with onCreate()

I have a project with two tabs. Tabs are created in the main class. Here I added the tablistener too, to handle the changes between the tabs. Here is one tab's instant:
TabHost tabHost = getTabHost();
tabHost.setOnTabChangedListener(this);
TabHost.TabSpec spec;
Intent intent;
intent = new Intent().setClass(this, Tab1.class);
spec = tabHost.newTabSpec("tab1").setIndicator("",
res.getDrawable(R.drawable.ic_tab_tab1))
.setContent(intent);
tabHost.addTab(spec);
The listener method:
public void onTabChanged(String tabName) {
if (tabName.equals("tab1")){
tab1.load();
}
}
And similar for the second tab too. My question is, if the onCreate() methods run only once in the Tab1 and Tab2 classes, how can I "force" the main class to show the corresponding Activity after the tab changes? I receive NullPointerException
The tabs' classes are something like this:
public class Tab1 extends Activity{
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.tab1);
load();
}
public void load(){
//....
}
}

onCreate() method calls only once when your Activity first time loaded.
If you want to perform any functionality on each time you view your Activity, put that functionality in onResume() method.

Activity in TabHost

I use a TabHost.
The below code to call AActivity.
intent = new Intent().setClass(this, AActivity.class);
spec = tabHost.newTabSpec("A").setIndicator("A", res.getDrawable(R.drawable.icon)).setContent(intent);
tabHost.addTab(spec);
And it is in the tab.
But in AActivity I call BActivity.
The BActivity will open new page, but not in the tab.
How to let it on the tab frame?
AActivity use below code to call BActivity:
it = new Intent(this, BActivity.class);
startActivity(it);

If you want to open multiple activity in Tab then on Place of activity use Activity group for par tab and switch view in this activity group for open multiple Activity in single tab
you can take some help from this tutorial

You need to change the current selected tab. There's a method called setCurrentTabByTag(String tag) in the TabHost class that will do that, just pass the tag name of your tab (which in your case is B), or you can use the setCurrentTab(int index) and pass the tab index.
Example. Usually I have a MainActivity class, which is my TabActivity. Inside of this class, I will create all tabs that I need on the onCreate method.
First I set some static int with the tabs indexes.
// Tab index.
public static int FIRST_TAB = 0;
public static int SECOND_TAB = 1;
Later, I create my tabs in the onCreate method.
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Setting the content view.
setContentView(R.layout.main);
// Getting the TabHost object.
mTabHost = getTabHost();
// Declaring the Intent object for the tabs.
Intent intent;
// Creating the First tab.
intent = new Intent().setClass(this, MyFirstActivity.class);
addTab(mTabHost, "First", FIRST_TAB, intent)
// Creating the Second tab.
intent = new Intent().setClass(this, MySecondActivity.class);
addTab(mTabHost, "Second", SECOND_TAB, intent);
// Setting the current tab.
switchTab(FIRST_TAB);
}
public void addTab(TabHost host, String title, String tag, Intent intent) {
TabHost.TabSpec spec = host.newTabSpec(tag);
spec.setContent(intent);
spec.setIndicator(title);
host.addTab(spec);
}
And last the method that will change the current tab.
public void switchTab(int index) {
mTabHost.setCurrentTab(index);
}
Later, inside of the MyFirstActivity you can call the MainActivity swichTab method and pass the index of the tab to change it.
You can retrieve the MainActivity calling the getParent() method of the Activity class.
MainActivity parent = (MainActivity)getParent();

In the tab activity class where the tabhost is created, implement the following method.
public void switchTab(int tab){
tabHost.setCurrentTab(tab);
}
In AActivity/BActivity implement the following method and call it on any event(that you need):
public void switchTabInActivity(long indexTabToSwitchTo){
TabActivity tabActivity;
tabActivity = (TabActivity) this.getParent();
tabActivity.switchTab(indexTabToSwitchTo);
}
Here TabActivity is the class where tabhost is created

Fire action on other activity within TabHost? (Android)

I am currently in an Android project where our main view is a TabActivity and each tab is a separate Activity. One is a MapActivity and the other two are ordinary Activities.
First note that I think we must have each tab as separate activities, as there is too much code in the separate activities to just have the TabHost switch the content view on a tab change and have all of the code in the same class. Anyways, back to the problem.
One of the tabs include a button, which when pressed should make the TabActivity switch to the MapActivity and animate the map to a specific location.
The tutorial found on http://joshclemm.com/blog/?p=86 shows how to do it if the TabHost contains a mapview and a listview. If an item in the ListView is clicked, the TabHost switches to the mapview and animates to that location (those coordinates). This is exactly what i need to do when the button in the separate activity is pressed.
The MainView.java is created as follows:
public class MainView extends TabActivity implements OnTabChangeListener{
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Resources res = getResources(); // Resource object to get Drawables
TabHost tabHost = getTabHost(); // The activity TabHost
TabHost.TabSpec spec; // Resusable TabSpec for each tab
Intent intent; // Reusable Intent for each tab
intent = new Intent().setClass(this, MapGUI.class);
spec = tabHost.newTabSpec("map").setIndicator("Map",
res.getDrawable(R.drawable.ic_tab_menu_item))
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, MissionView.class);
spec = tabHost.newTabSpec("mission").setIndicator("Mission",
res.getDrawable(R.drawable.ic_tab_menu_item))
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, SIPView.class);
spec = tabHost.newTabSpec("call").setIndicator("Call",
res.getDrawable(R.drawable.ic_tab_menu_item))
.setContent(intent);
tabHost.addTab(spec);
The MissionView.java is as follows:
public class MissionView extends Activity implements Observer{
MissionController mc;
private TextView missionheader, missiondescription, missionaddress,
missiontime, missioninjuries;
private Button changedesc, gotoadress;
private String[] mission;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.missiontablayout);
missionheader = (TextView)findViewById(R.id.missionheader2);
missiondescription = (TextView)findViewById(R.id.missiondescription2);
missionaddress = (TextView)findViewById(R.id.missionaddress2);
missiontime = (TextView)findViewById(R.id.missiontime2);
missioninjuries = (TextView)findViewById(R.id.missioninjuries2);
changedesc = (Button)findViewById(R.id.gotoaddress);
changedesc.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// DO SOMETHING HERE?
}
});
mc = new MissionController(MissionView.this);
}
public void update(Observable observable, Object data) {
if(data instanceof String[]){
mission = (String[]) data;
updateView(mission);
}
}
public void updateView(String[] missiontext){
missionheader.setText(missiontext[0]);
missiondescription.setText(missiontext[1]);
missionaddress.setText(missiontext[2]);
missiontime.setText(missiontext[3]);
missioninjuries.setText(missiontext[4]);
}
}
Anyone know how i could achieve this?
Note that the code supplied above has no implementation to actually draw to the actual location, but the question still remains, how do I make a button pressed in one activity to switch tab in the TabHost and fire a change on that tab activity?

changing tabs in a TabHostcan easily be done with setCurrentTab(int)
http://developer.android.com/reference/android/widget/TabHost.html#setCurrentTab(int)
Sending events to other Activities can simply be achieved by sending a broadcast intent and receiving/handling it in the other Activity.
Alternatively you could save static references to all your tab Activities (ugly...) and call methods directly.

Place the below line on button click where you want to switch to the Map activity
((MainView) getParent()).setTabMap();
and in MainView create the following function
public void setTabMap()
{
//as Map activity is your first tab so pass 0 as index
getTabHost().setCurrentTab(0);
}

Relationship between Tabs - android

I want to create application with two Tabs, like follow:
MainClass:
private TabHost tabHost;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
tabHost = (TabHost)findViewById(android.R.id.tabhost);
TabSpec firstTabSpec = tabHost.newTabSpec("tid1");
TabSpec secondTabSpec = tabHost.newTabSpec("tid2");
firstTabSpec.setIndicator("First Tab Name").setContent(new Intent(this,MainTab.class));
secondTabSpec.setIndicator("Second Tab Name").setContent(new Intent(this,ResultTab.class));
tabHost.addTab(firstTabSpec);
tabHost.addTab(secondTabSpec);
}
public TabHost getTabHost() {
return tabHost;
}
FirstTab:
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.maintab);
}
SecondTab:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.resulttab);
}
On First tab i have some buttons, with who i calculate some mathematic operations. A want to display result on SecondTab when calculating is finished.
First problem:
I do not know, how can I send data (String) from FirstTab to SecondTab.
I tray:
creating self parameter in Tab class,
setOnTabChangedList
and some similar
but without results.
Second problem (small for now :) ):
When I selected some parameters (my buttons, list, ...) on FirstTab and change view to SelectTab, and return to FirstTab selected parameters are gone.
Anyone help me?

You can send strings with intents. For example:
Intent intent = new Intent().setClass(this, Secondtabclass.class);
intent.putExtra("mykey", "string to send");
startActivity(intent);
And then on the recieving activity you do:
String recievedString = this.getIntent().getStringExtra("mykey");
You could save the state of your list and whatever you like if you override OnResume and OnPause methods. On pause gets called every time your activity loses focus, and on resume gets called every time your activity resumes focus. Like this:
#Override
protected void onResume() {
super.onResume();
//Do stuff
}

Switch between Android tabs using intents

I wish to find out how to switch between tabs using intents.
In my case I'm using the both tabs:
Resources res = getResources();
TabHost tabHost = getTabHost();
TabHost.TabSpec spec;
// Capture tab
spec = tabHost.newTabSpec("capture").setIndicator(null,
res.getDrawable(R.drawable.ic_tab_capture))
.setContent(new Intent(this,CaptureActivity.class));
tabHost.addTab(spec);
// Upload tab
spec = tabHost.newTabSpec("upload").setIndicator(null,
res.getDrawable(R.drawable.ic_tab_capture))
.setContent(new Intent(this,ImageUpload.class));
tabHost.addTab(spec);
To simplify my goal, my CaptureActivity.java includes the following code:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.capture);
Intent intent = new Intent(this, ImageUpload.class);
startActivityForResult(intent, 0);
}
What I'm expecting is, the app should switch instantly to the second tab (ImageUpload activity) which works fine, BUT the tabs themselves disappear. I get the ImageUpload activity as stand-alone page, not within the tab itself.
Any idea what's going wrong there ?

First calling firing ImageUpload.java only fires ImageUpload.class but surely tabhost will disappear.
You need to fire your MainActivity-TabActivity where you added your two tabHost
1.ImageUpload
2.CaptureActivity
which will maintain your TabLayout
call intent like these
Intent i=new Intent(getApplicationContext(),MainActivity.class)//which is your mainActivity-Launcher
i.addFlags(Intent.FLAG_ACTIVITY_BRING_TO_FRONT);
startActivity(i);//will bring MainACtivity to Front
Now Main activity is already running so pointer directly goes to onNewIntent() inside Main Activity
Override onNewIntent() inside MainActivity
=====================================
public class MainActivity extends TabActivty
{
pubilc static TabHost tabhost;
public void onCreate()
{
//where you added your two tab spec
//added them
}
public void onNewIntent(intent)
{
super.onNewIntent(intent);
tabHost.setCurrentTab(1);//1-depends where you want to switch-tabIndexno, I assume Upload is at 2nd position (so "1")
Activity currentActivity=getCurrentActivity();
if(currentActivity instanceof Upload)
{
((upload)currentActivity).onCreate();//watever method you want to call
}
}
}

In the parent activity class where the tabhost is created I implemented a method like the one below:
public void switchTab(int tab){
tabHost.setCurrentTab(tab);
}
Inside of the tab that I would like to be able to switch internally to another tab I created the method below:
public void switchTabInActivity(int indexTabToSwitchTo){
YOURTABHOSTACTIVITY ParentActivity;
ParentActivity = (YOURTABHOSTACTIVITY) this.getParent();
ParentActivity.switchTab(indexTabToSwitchTo);
}
If you would like a good example of this code, you can take a look at my MintTrack project here and here.