Android: Intent Switching / Reusing

Recently found this interesting problem in a project where I was using the Intent flag FLAG_ACTIVITY_REORDER_TO_FRONT which is awesome to reuse the same activity kinda of like a cyclic activity switcher, the one issue with this is that if you press back on an activity you have to wait till the activities onDestroy is called. That can be annoying from a UI stand point.

The solution is a combination of flags. The following line fixes the problem.

myIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK|Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);

The reason for this it checks the reorder first and reuse or starts a new activity if it needs too.

Notes on iPhone:Safari ComboBox in an app

One of the things lacking in the iphone is the combobox much like the one available to you when using safari on the iPhone. I decided to implement this functionality into my app, it's not perfect and could still use some more work to be as good as the one in Safari.

Here's a photo of the results. Without the pickerup
Heres one with the picker.

Okay the first thing your going to want is the picture for the drop down.
The basic implementation from a top level perspective is a UITextField that is not enabled. This is a simple approach that will get you what you want but could be better. The following creates the combobox in a given cell, this can be made more generic by making cell into a generic (id*) or (uiview*).


//params
//string default string to show if a user preference isn't already choosen
//field the UITextField you want to assign if you want to save it.
//cell the view you will add the textfield and button to
//action a selector for the uibutton
//fieldstring the user define string which may be empty so i pass it with the default string
- (void)comboboxwith:(NSString*)string withview:(UITextField*)field oncell:(UITableViewCell*)cell withSel:(SEL)action forfield:(NSString*)fieldstring{
//textfield creation
//basic reason for using UITextField it allows you to add a subview to the left or right
//of the text field
field =[[CustomTextField alloc] initWithFrame:CGRectMake(5, 3, self.tableView.frame.size.width-10, 38)];
field.borderStyle = UITextBorderStyleRoundedRect;
field.text = (fieldstring == nil || [fieldstring compare:@""] == 0) ? string : fieldstring;
field.font = [UIFont fontWithName:@"Helvetica" size:24.0];
field.autoresizingMask = UIViewAutoresizingFlexibleWidth;

//add the down arrow for list view
UIImageView *imgview = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"downarrow.png"]];
field.rightView = imgview;
field.rightViewMode = UITextFieldViewModeAlways;
[imgview release];
field.enabled=NO;
[cell addSubview:field];

//uibutton creation on top of uitextfield, plain transparent button that listens to touchs.
UIButton *bnt = [UIButton buttonWithType:UIButtonTypeCustom];
bnt.frame = CGRectMake(5, 3, self.tableView.frame.size.width-10, 38);
bnt.autoresizingMask = UIViewAutoresizingFlexibleWidth;
bnt.backgroundColor = [UIColor clearColor];
[bnt addTarget:self action:action forControlEvents:UIControlEventTouchUpInside];
[cell addSubview:bnt];
}

As for loading the UIPickerView on selection of the combobox, the selector handles to loading of the uipickerview and toolbar with the done button as to exit from the uipickerview. As follows:


//load a uipicker with states, you can give the picker a tag, and a default state if
//loaded from a preference or something.
- (void)selectstate:(id)sender{
[self pickerwith:@"States" withId:0 withdefault:state];
[self adddone];
}

//this loads the uitoolbar and changes its location so that the done button is displayed
//above the uipickerview
- (void)adddone{
UIBarButtonItem *done = [[[UIBarButtonItem alloc]
initWithTitle:@"Done"
style:UIBarButtonItemStyleDone
target:self action:@selector(done:)] autorelease];
UIBarButtonItem *flex = [[[UIBarButtonItem alloc]
initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace
target:self action:nil] autorelease];
self.navigationController.toolbar.barStyle=UIBarStyleBlackTranslucent;
[self.navigationController.toolbar setFrame:CGRectMake(0,self.parentViewController.view.window.frame.size.height-(216+40), 320, 40)];
self.navigationController.toolbar.hidden = NO;
self.toolbarItems = [[[NSArray alloc] initWithObjects:flex, done, nil] autorelease];
}

//creates the actual picker
- (void)pickerwith:(NSString*)string withId:(int)tag withdefault:(NSString*)defaultstring{
//loads the array from a plist file
NSString *bPath = [[NSBundle mainBundle] resourcePath];
NSString *plistFile = [bPath stringByAppendingPathComponent:@"Root.plist"];
NSDictionary *settingsDictionary = [NSDictionary dictionaryWithContentsOfFile:plistFile];
selectionarray = [settingsDictionary objectForKey:string];
[selectionarray retain];

//if picker is not nil close a previous picker
if(picker != nil){
[self done:self];
}

//create picker
picker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, self.parentViewController.view.window.frame.size.height-216, 320, 216)];
picker.delegate=self;
picker.dataSource=self;
picker.showsSelectionIndicator=YES;
picker.autoresizingMask = UIViewAutoresizingFlexibleWidth;

//if defaultstring is defined load the picker at that index.
if(defaultstring != nil ){
NSInteger ind = [selectionarray indexOfObject:defaultstring];
[picker selectRow:ind inComponent:0 animated:NO];
}

//since we are inside a tableview disable scrolling
//better response from picker
self.tableView.scrollEnabled=NO;
picker.tag = tag;
[self.view.window addSubview:picker];
}

//remove picker and toolbar should put toolbar back in place if needed.
//reload data
- (void)done:(id)sender{
self.navigationController.toolbar.hidden = YES;
self.toolbarItems = nil;
[picker removeFromSuperview];
[picker release];
picker=nil;
self.tableView.scrollEnabled=NO;
[self.tableView reloadData];
}

As for the UIPickerView delegates I am not going to cover as you can look that up elsewhere.

A better approach to this problem would be to use a uiview subclass, and put a uitextlabel on the left side and a uiimageview on the right side, do the same as above with the loading of the pictures and adding this view as a subview to the parent view.

Once you do that you have the combobox look without any functionality to do that you have two approaches, the first is implement touchesdidbegin and touchdidend, I could be wrong on function names this is more for future proofing, then use this to determine if your uiview has been touch properly and load up the picker as above. Another apporach is to implement the uiview subclass a a UIControl subclass which allows you to use the following:

-(void) addtarget:self withselector:action forEvent:UIEventType

this makes it a uibutton basicly and its a lot simpler to work around. Once you have it loading up the Picker all you have to do is in the didSelectRow delegate method for the UIPickerView is tell the UITextLabel to show the text currently selected.

I hope this was convient, and informational. The last thing I have to say is for further improvement the next view button should also be implemented.

Notes on Android SDK:PreferenceActivity, XML Preferences and using them

Okay so today I was trying to get preferences to work with my app. Now for those of us who have developed on iPhone we are aware that we can setup a plist for settings that will be show up in the settings application on the iphone. This is find and dandy but do we want our users to have to go to the settings application only to change a few settings in our app. No of course.

Well the android has a similiar functionality, that creates a setting page quickly. The beauty of it is that you can load it into your app quite easily. There is some documentation on this widely available, the following website provides a great tutorial on setting up the ui.

http://androidguys.com
the article in question is What's Your Preference in three parts.

The one thing that it doesn't cover is how to use the application settings throughout the app. Anyway asuming you are using the above tutorial to set up user preferences.

the folllowing line of code will recover the settings.


SharedPreferences mprefs = PreferenceManager.getDefaultSharedPreferences(this);

and then you can read them like so.

CharSequence[] names = getResources().getTextArray(R.array.questiontypes);
for(int i=0; i
Log.v(TAG, mprefs.getBoolean(names[i].toString(), true) + "");
}

if you want to alter them from somewhere other than the settings page. you need
a SharedPreferences.editor from the above. Then just do some thing like the following.

meditprefs.putInt(key,value);
meditprefs.commit()
//the above is very important it savs until this line is called and changes are ignored
its like
[[NSUserDefaults standardUserDefaults] synchronize];

Notes on Android SDK: TabHost, Tabs and Activities

Okay so I was doing some more playing around after reading some of the guidelines. Anyway I used two approaches to using to switching between different views in my application going to post above as its useful depending on needs.


the first one is on tabhost, which allows you to switch between different views easily with the tab being pressed, for iPhone Developers its the equiavelent of TabBar Controller, but requires more work to get going specifically if you set it up via the xml view.


import android.widget.TabHost.TabSpec;
import android.widget.TabHost;
import android.app.TabActivity;

//first note is if you want to use a TabHost extend TabActivity instead of Activity
public class Maestro extends TabActivity {

public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
addTabs();
}

private void addTabs(){
Resources resources = getResources();

//since your using the TabActivity you can simply call this method to
//set up the tabhost make sure to call setup()
TabHost tabs = getTabHost();
tabs.setup();

//tabspec defines the attributes of the tab
TabSpec tab;
//this creates a new tabspec with an id of quiz
tab = tabs.newTabSpec("Quiz");
//this sets the intent/ activity of the tab when pressed
tab.setContent(new Intent(this, Quiz.class));
//this sets the name displayed and the image if you add one
//tab.setIndicator("Quiz");
tab.setIndicator("Quiz",resources.getDrawable(R.drawable.quiz));
//then you add the tab to the tab view
tabs.addTab(tab);

tab = tabs.newTabSpec("Practice");
tab.setContent(new Intent(this, Practice.class));
tab.setIndicator("Practice",resources.getDrawable(R.drawable.practice));
tabs.addTab(tab);

tab = tabs.newTabSpec("Settings");
tab.setContent(new Intent(this, Settings.class));
tab.setIndicator("Settings",resources.getDrawable(R.drawable.settings));
tabs.addTab(tab);

//sets the current tab
tabs.setCurrentTab(0);
//add the tabhost to the main content view
setContentView(tabs);
}


now of course you need to make sure that the classes you have set above to be invoked by the tabhost are all activities of some sort depending on your application, and make sure you add them as activites in your Application Manifest.

this is simple just add the following xml to your manifest file. where Settings is the name of your classes.

\>activity label="Settings" name="Settings">
\>\activity>

Now the last thing to note is that these are the basic of using the tabhost, using the above methods you can easily setup a tab bar and get your other views up and running, now if you want to use xml to set up tabhost there are strict requirements in setting it up.

here is what you need for the tabhost via xml

you need a tabhost
with a tabwidget
with a framelayout

according to sources there seems to be a naming convention as well, but in my opinion its too much of a hassle especially if your app only needs the tabhost as the main controller.


Next instead of using the tabhost lets use the menu list that you get when you press menu. The benefits of this is you get more room in your app. this is quite simple with a few options.

well first to get an options menu use the following.

public boolean onCreateOptionsMenu(Menu menu){
//add(groupid, itemid, order, itemname)
menu.add(0, 1, 0, "Quiz").setIcon(R.drawable.quiz);
menu.add(0, 2, 0, "Settings").setIcon(R.drawable.settings);
menu.add(0, 3, 0, "Practice").setIcon(R.drawable.practice);
return true;
}

public boolean onOptionsItemSelected(MenuItem item){
switch(item.getid()){
case 1:{
startactivity(new Intent(this,Quiz.class));
return true;
}
case 2:{
startactivity(new Intent(this,Settings.class));
return true;
}
case 3:{
startactivity(new Intent(this,Practice.class));
return true;
}
}
return false;
}


now that is the simple way that simply starts a new activity when you click on one of the menu items. Now to get back you click on the back button on the phone. As you can imagine that is annoying so you have to thinking about the design of app before you consider something like this. For instance if you want to bring up a settings page the above would be nice as you can get rid of a button from the main ui. then simply press back after changing your settings.

But if your going to try and use this as a navigation controller like a tab bar then make sure you add the following after each start activity.
finsh();

that closes the current activity before going to the next one. this gets rid of the tabhost and give you the same benefits, also by doing this the menu is dynamic unlike the tabhost. I mean why would you allow a user to choose the quiz when you are in the quiz already.

Notes on Android SDK: Dynamic TableLayouts, adding Views and TableRows

So I currently playing around with making dynamic tables on the Android platform. I want to port my iPhone applications to the other mobile platforms. Am going to be looking into Palm Pre as well soon enough. Anyway while doing this I was trying to create a Dynamic Table, instead of relying on the XML view.

now the code to adding something to a TableLayout is quite simple.


//set the content view from an XML file
setContentView(R.layout.main);

//first get the TableLayOut from the xml file that you previous loaded
TableLayout table = (TableLayout) findViewById(R.id.TableLayout01);

//set the columns to resize so that the row gets the full length of the screen
table.setColumnStretchable(0, true);
table.setColumnCollapsed(1, true);

//useful for getting a resource by name
int resID = getResources().getIdentifier("filename", "drawable", "com.yourcompany.yourApp");

//now create a view you want to add to the tableLayout
//in this case a ImageView
ImageView img = new ImageView(activity);
img.setImageResource(ResID);

//set the height to 100 and width to the width of the parent
img.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, 100));

//finally add to the tableLayout view
table.addView(img);



its quite simple, but now replace adding the ImageView to the Table with adding a TableRow to the Table which may have any number of views within. A TableRow is simply a LinearLayout.


//set the content view from an XML file
setContentView(R.layout.main);

//first get the TableLayOut from the xml file that you previous loaded
TableLayout table = (TableLayout) findViewById(R.id.TableLayout01);

//set the columns to resize so that the row gets the full length of the screen
table.setColumnStretchable(0, true);
table.setColumnCollapsed(1, true);

//useful for getting a resource by name
int resID = getResources().getIdentifier("filename", "drawable", "com.yourcompany.yourApp");

TableRow row = new TableRow(this);

//the tablerow is suppose to use this layout params always according to sdk guidelines
row.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.WRAP_CONTENT);

//now create a view you want to add to the tablerow
//in this case a ImageView
ImageView img = new ImageView(this);
img.setImageResource(ResID);

//set the height to 100 and width to the width of the parent
img.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, 100));

//add the ImageView to the row
row.addView(img);

//finally add to the tableLayout view
table.addView(row);

now if you have tried the above could nothing should come up, that's because certain views have their own LayoutParams class.

so what you need to do to make the above code work is change the following line.

row.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.WRAP_CONTENT));

with

row.setLayoutParams( new TableRow.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));

the basic thing is make sure to check your using the right LayoutParams with a given class, because if your not the platform won't know what to do with that layout.

Anyway though it was worthing mentioning cause it took me a while to figure it out.

Notes on iPhone:MapKit, CFNetwork, and Push Notifications Part 1

This is my first tutorial so for those of you here looking for tips and hints bear with me as I get the hang of this.

Alright the first thing I am going to cover is how we can use Push Notifications to keep track of downloads of our app. I am also going to be using MapKit as a means of allowing users to see where others who have used our app are located. It isn't going to look pretty but hopefully the code with help you.

Am hoping to make this a library so that I can just kinda plug it in to any other application I make in the future.

So first step, Lets open up xcode and start a new tab bar applications.

why tab bar?

1. we want one of the screens to be a map

2. we want to display stats of our app.

We are going to handle the view before any code.

Okay first thing we are going to want to do is add a few IBOutlets for UILabels in the first view controller. You could also use a table or any other means you want to display the statistics. Just make sure to incorporate a quick way to change stats.

Note make sure to connect them properly.

Here is what mine looks like: MainWindow.xib

so what do these terms mean:

(removed Installed but was too lazy to change pic)

Open how many people actually opened the app

Removed how many people deleted the app

Reinstalled how many people reinstalled and open the app again.

This is what my FirstViewController.h looks like

#import "UIKit/UIKit.h"

@interface FirstViewController : UIViewController {

IBOutlet UILabel *opened;

IBOutlet UILabel *removed;

IBOutlet UILabel *reinstalled;

}

@property (nonatomic,retain) IBOutlet UILabel *opened;

@property (nonatomic,retain) IBOutlet UILabel *removed;

@property (nonatomic,retain) IBOutlet UILabel *reinstalled;

@end

FirstViewController.m make sure to synthesize and dealloc

#import "FirstViewController.h"

@implementation FirstViewController

@synthesize opened;

@synthesize removed;

@synthesize reinstalled;

- (void)dealloc {

[opened dealloc];

[removed dealloc];

[reinstalled dealloc];

[super dealloc];

}

@end

Now for the map.

First add the MapKit Framework to the project.

Create a subclass of UIViewController name it whatever, but for the sake of understanding name it something like map.h/m

As always you can create any subviews programmatically or through IB, am using the simple way IB. Don't forget to connect everything in IB. Also change the SecondView in the tab bar to the map.xib or simply rename to map.xib and alter. Last make sure you change the class of UIViewController in TabBarController.

Map.xib:

#import "UIKit/UIKit.h"

#import "MapKit/MapKit.h"

@interface Map : UIViewController {

IBOutlet MKMapView *map;

}

@property (nonatomic,retain) IBOutlet MKMapView *map;

@end

#import "Map.h"

@implementation Map

@synthesize map;

- (void)viewDidLoad{

//enable location on the map

[mapview setShowsUserLocation:YES];

[super viewDidLoad];

}

- (void)dealloc {

[map dealloc];

[super dealloc];

}

@end

now the last step on the initial step up is to register the device with your server and apple's push notification service as well. We are going to be registering as a Badge notification. The reason we are doing this is because if you do not actually send notifications you can't keep track of number of times your app gets removed, and for that matter reinstalled.

first step is to register with APN. To do this we simply call

[[UIApplicatio sharedApplication] registerForRemoteNotificationTypes:UIRemoteNotificationTypeBadge];

but we also need to implement the callback delegates

- (void)application:(UIApplication *)app didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)devToken;

- (void)application:(UIApplication *)app didFailToRegisterForRemoteNotificationsWithError:(NSError *)err;

put all this in the AppDelegate.m

#import "AppTrackerAppDelegate.h"

@implementation AppTrackerAppDelegate

@synthesize window;

@synthesize tabBarController;

- (void)applicationDidFinishLaunching:(UIApplication *)application {

[[UIApplication sharedApplication] registerForRemoteNotificationTypes:UIRemoteNotificationTypeBadge];

[window addSubview:tabBarController.view];

}

- (void)sendProviderDeviceToken:(const void*)devToken{

}

//Delegate methods that tell you if you succeeded.

- (void)application:(UIApplication *)app didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)devToken {

const void *devTokenBytes = [devToken bytes];

self.registered = YES;

[self sendProviderDeviceToken:devTokenBytes]; // custom method

}

- (void)application:(UIApplication *)app didFailToRegisterForRemoteNotificationsWithError:(NSError *)err {

NSLog(@"Error in registration. Error: %@", err);

}

@end

so now your wondering what goes in the sendProviderDeviceTokern. Well it depends on how you plan to implement your server, if you implement a low level server then something like BSD Sockets or CFNetwork is what you want to use. If you are using a php script then something NSUrl is what you want to use. In this case I want to learn CFNetwork so that what am using. CFNetwork has a few different connection type am using CFSocket API's.

#include "CFNetwork/CFNetwork.h"

#include "sys/socket.h"

#include "netinet/in.h"

#include "arpa/inet.h"

#define PORT 2048

#define IPADDR "127.0.0.1"

//this is the callback method that gets called when

//client opens up the connection to the server

//if you were using more than one callback type you would need

//to check before continuing but since we only

//used the connect callback there was no need.

void ConnectCallBack(CFSocketRef socket, CFSocketCallBackType type,

CFDataRef address, const void *data, void *info){

//gets the native socket its a BSD socket so

//all normal BSD socket methods work

//like send you need to close the socket

CFSocketNativeHandle sock = CFSocketGetNative(socket);

send(sock, info, sizeof(info)+1, 0);

close(sock);

}

//this will open up a socket to our server

//we use the connectcallback to know when the socket actually connects

//once connected you need to have ConnectCallBack write the

//devToken to the server.

- (void)sendProviderDeviceToken:(const void*)devToken{

//socket reference and context, which get past around in the callback method

CFSocketRef sock;

CFSocketContext context = { 0, &devToken, NULL, NULL, NULL };

//open socket with default allocator its a TCP socket in ipv_4

sock = CFSocketCreate(NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketConnectCallBack, (CFSocketCallBack)ConnectCallBack, &context);

//if can't create socket fail to send devtoken

if(sock == NULL){

NSLog(@"error");

}

else {

//put the address of your server and port

//port define above as well as ip address

struct sockaddr_in addr;

memset(&addr, 0, sizeof(addr));

addr.sin_len = sizeof(addr);

addr.sin_family = AF_INET;

addr.sin_port = htons(PORT);

addr.sin_addr.s_addr = inet_addr(IPADDR);

//create reference and connect to server

CFDataRef connectAddr = CFDataCreate(NULL, (unsigned char *)&addr, sizeof(addr));

CFSocketConnectToAddress(sock, connectAddr, -1);

//run the socket through run loop,

//if connects callback method is called

CFRunLoopSourceRef sourceRef = CFSocketCreateRunLoopSource(kCFAllocatorDefault, sock, 0);

CFRunLoopAddSource(CFRunLoopGetCurrent(), sourceRef, kCFRunLoopCommonModes);

CFRelease(sourceRef);

CFRunLoopRun();

}

}

ways to improve codebase make sure to include reachability checking. I hope this was helpful or interesting in some way. That handles the basics of getting the app running with the desired views. Look forward to server for push notification implementation and getting the actual data you want display. Ending with getting your location when you open the app and sending it to the server. Also more about JSON for both push notifications, and map points.

Welcome

This is my first post so welcome all to my Blog. A little about myself, I am a freelance iPhone Developer/Software Developer. This blog will for the most part serve as a means of allowing me to create reference material for myself and others who find themselves in the same boat. I will also be posting about encounters with new technology, as well tutorials.

Also please post comments on errors I may have left, or simply not notice. All other comments welcome too.