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Hello students and this the holy grail we're going to go ahead and create another Android application.



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So let's just click on this.



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Start in your Android studio project and for the application and just they've here at sixty six dash



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of line capability of line capability.



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And you can specify the company domain package name and the project location and then click on next.



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And here to this minimum STK as the API 16 Android 4.1 jelly bean.



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And then click on next and here choose empty activity next.



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And here are just a click and finish.



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So here let's actually connect our application to the firebase.



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So now at the top just click on Tools and Firebrace And then here click on realtime database and click



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on Save and retrieve data.



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And first just you just need to click on Connect to firebase so you can see here this starting connect



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dialog.



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And here you can just see that we have actually created a new project.



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So if you want to actually create a new firebase project app 66 offline capability.



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So in this tutorial I will actually let you know about the offline capability of fireplace.



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So let's create a new project and then you can specify the country or region and then click on our connect



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to firebase.



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So here we can see that it says connecting our two firebase.



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So it's going to take some time in order to connect that application to the firebase.



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So we should actually wait a little bit here and now as you can see here it says firebase project create



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it and connect it locally to my real app.



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And here you can see that it says connected.



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So now we should do the second step and it says at the real time database to your app.



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So just click on the spot in here and here just accept changes.



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So now as you can see here it can actually make our application ready for using their real time database.



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And here are first of all it's actually the go inside this activity underline main the example.



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And now let's actually collapse this assistance here.



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This firebase assistant and here are essentially agitatedly to this hello world takes you here to get



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it.



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And now first let's actually write a text view or a text field so distasteful.



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Here say this takes viewless for folder.



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Just drag this plain text here and put it here inside this relatively out.



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And now let's write a button instead.



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We just want to just select and drag it here below this text field.



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And put it here.



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So now let's let's actually select this edit takes here.



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And for the editors step in here EDT data this actually deletes So here as you can see we have this



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dialogue and it says update usages as well.



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So here you can just click on yes.



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And for the name attribute here just delete this value and then person enter key on your keyboard and



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select the spot.



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And for the ideas they've been here between send data and sent it up and the person into a general keyword



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and then are here for the text that should be that have this button just typed in here sent data to



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set and then person entelechy on your keyboard.



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So let's actually go inside.



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Our main activity that have a file Let's actually just declare these objects here.



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So now the first one is actually an edit text so EDT data semicolon.



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And the second one is actually a button.



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So between and data semicolon and here inside is uncreate Meffert It's actually to initialize these



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variables.



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So it is the data assignment operator and you literally just create this object.



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First we need to cast this object to an edit text object find view by ID or that Id that EDT data.



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And then at the end of your statements you need to put a semi-colon.



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And here we need to actually to initialize our part in PTEN send data assignment operator and he'll



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essentially cast this object to our putten object find view by id Artaud ID dot between send data.



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So as you can see here it cannot actually recognize our IDs so let's actually go inside our activity



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underlaid minute example here and here as you can see I actually made a mistake.



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And here we need to put PTEN sent data.



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So here I just need to press on until she on my keyboard.



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So let's go back to her domain activity class so PTEN sent data and then I need to press put a semicolon



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at the end of my statement.



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So he'll actually make the Spartan disobedience and date hot button our listeners with the clicks of



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the users to send data that said unclick listener new view that unclick listener.



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So here Enceladus uncle Anklage method we can actually put our own logic so here first of all this actually



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creates somebody else inside.



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Our main activity class.



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So the first one is our Firebrace firebase database and the name of my valuable is database semi-colon.



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So as you can see here I'm just declaring my variable here right.



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I'm not initializing my variable.



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I'm just declaring here.



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Now let's actually declare another variable of type database reference and the name of the variable



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is they have a reference.



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So now let's actually initialize our variables here inside our uncreate Smurfette.



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So here I can say a database right.



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Assignment operator firebase database that get instance semicolon and then lets actually initialize



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our database reference.



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So database reference assignment operator database that gets reference semi-colon.



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Right.



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So now I want to talk about offline capability.



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So what do you mean by offline capability.



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So the offline capability is going to actually enable your application to actually interact with a database



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of when the internet connection is actually gone.



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Right.



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So for example it's actually let me just put these lines of code here.



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And when we run our project and it will make more sense.



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So first of all I just need to type in here database here.



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I'm referring to the name of this valuable database that says persistence enabled and this method actually



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accepts a boolean variable.



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So of here we just need to pass a boolean value right.



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So here I can say true because I want to enable the offline capability of the firebase for my application



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I need to pass the value true for this method.



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So a database that says persistence enabled truth.



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And here I can say that database reference that cheap sinked true.



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So these are the two lines of code that we should put here in order to actually enable the offline capability



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and that's all.



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So that was actually sent this actually just set a value for our node.



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So now I can just type in here database reference dots set value.



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And here I can say for example some value some value right.



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And now let's actually run our project just a click and run app here and now it's actually a little



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bit here.



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Here we need to choose one of these devices one of these virtual devices.



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And then I just click on OK.



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So as you can see here our application crashed.



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Right.



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So let's go to Android studio and here able to show you why our application crashed.



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First of all in order to see of why your application crashed at the bottom you just need to click on



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this android monitor here.



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Right.



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And here you can see what's going on here.



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Let's actually make this area just bigger and you just need to look at these codes.



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You can look at these texts that are in red.



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And here it says fatal exception made.



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So Maine means actually in the forget.



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The main freight.



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And as you can see it says here you can actually find the cause of this error.



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It says jobs that landed at runtime exception.



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So this is the type of this exception run pump exception is actually an exception that occurred when



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you actually when you are running your application.



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Right.



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So when we tried to run our application this error occurred and here as you can see it says 66 of brain



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capability has stopped.



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And here it says Unable to start activity component info.



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So these are the info overnight activity.



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And here is actually scroll to the left.



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And here it says let's scroll to the right as you can see here it says come that Google that firebase



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that database that database acception.



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So this is actually on our database exception.



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And here it says calls to set persistence enabled must be made before any other uses of file based database



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instance.



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So here you can see that it says that V must actually call the said persistence in a belt method or



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before any other usage of firebase database instance.



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So what does this mean.



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So this actually is just go to our codes here.



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As you can see inside our uncreate Smurfette.



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First of all we actually initialized our database instance right.



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And then we actually called this method.



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So this is not right as the here.



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It says that first we should call this method before any other usage of firebase database instance.



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So here let me actually show you this area.



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Again let me show you these texts.



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It says this method must be made before any other usage of firebase database is this.



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So now as you can see it is actually just caught this line of code here.



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So if you are using a match just hold the common key on your keyboard and then press on the letter X



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key on your keyboard.



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And if you are using a Windows machine just hold the control key on your keyboard and then press on



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the letter X key on your keyboard in order to cut this line of code and put it here before this line



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of code here before using the firebase database instance.



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So here I can just paste it here right.



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And in this way as you can see we are actually using this method before using the firebase database



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instance.



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So again we are going to have a problem.



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So but now it's actually on our project and then I'm going to actually let you know what is this.



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Right.



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We may actually encounter another problem.



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So let's run our project again.



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Let me show you the emulator here.



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So again our application crashed.



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So let's see why this time our application crashed again.



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We should go to the Android studio and then click on this android monitor at the bottom.



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And here let me make this area just bigger.



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And here again we should look at these lines of code that are in red.



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And here again it says we have actually our runtime exception.



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And now let me actually scroll to the right and here it says Java the land dot null pointer exception.



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So it says attempt to invoke virtual Meffert void com that Google that firebase that database that firebase



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database that says set persistence enabled boolean on a null object reference as you can see here you



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are calling a method on a null object reference.



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So this is actually an exception.



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So let me show you why this error occurs.



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As you can see here in line number 19 we declared are valuable which is of type firebase database in



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here.



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Right.



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And the name of our valuable is database.



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As you can see here.



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I didn't initialize this variable.



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I just declared this variable.



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And inside our uncreate method before I initialize this variable.



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As you can see here I use this method.



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So in line number 44 I use I actually I actually initialize the Smurfette But in line number 52 are



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used this method.



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So this database here is actually not.



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And if you are calling the sniffer said persistence enabled we are calling this Nefert on a null object.



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This these are valuable database.



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As you can see is not quite because in line number 44 we just initialized it.



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And before this line of code here as you can see here we did it initialize.



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So now in line number for it is if to this database where the event is actually null and you're calling



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the Smurfette on a null object on a null variable.



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So it is going to actually cause an error and our application is going to crash.



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So in order to solve this problem I can just delete this database here and here I can say firebase database



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dot get instance that sets persistence enable true.



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Right.



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So in this way it is much more better.



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So now it's actually our project again.



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Now let me show you the emulator.



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Now as you can see here no errors occurred here.



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And that application is actually running on this emulator.



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So let me show you the web browser here and now I just need to go to as you can see here you just need



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to put this you are in here and then click on go to console.



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And here you should click on this app 5:54 dash of line capability here.



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So this is our project right.



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Just click on it and then click on database and click on rules.



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Just click on this rules tab here and here let's again change these rules so just delete these exclamation



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marks and put an equal operator here and again just delete this exclamation mark and put an equal operator



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and then click and publish.



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So now it's going to actually publish the rules as you can see here.



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And here again just click on the state bar tab here.



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And now this is our note right.



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So here I want to actually just tell the wife right off.



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Right.



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As you can see here my wife is actually on now.



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You want to turn my wife off.



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So now as you can see here my wife is now turned off.



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Right.



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So now let me show you the emulator and now let's actually just click on the spot and send data to server.



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As you can see here I just clicked on this button and now I'm able to actually turn my phone on.



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So now I turn to my wife right on.



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Right.



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And now as you can see here this values some value here is actually here.



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Right.



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So if you have noticed here I actually first turned to my wife right off and then I clicked on the spot



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in and when I turned my wife on again this value is actually sent to the server and we can see the value



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here.



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And that's the offline capability of Firebrace.



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And this is I think the best feature of the file by spackled.



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So this is very nice.



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So if I go back to android studio by just putting two lines of code we did manage to use the offline



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capability as you can see here.



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We did manage to use the offline capability and we could actually use it for our great applications.



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Right.



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So now here I just I'm just sending this value some value so I can actually change this value to the



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value of the EDT date hot that just text that to strike.



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I could actually send the value of this and it takes to the server.



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So I think that's enough for this tutorial.



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And if you have any questions about the of line capability of the firebase or please post the discussion



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in the course and then I'll do my best to answer all of your questions.



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Thank you very much for watching and I'll see you in the next story or.