I have a scenario where I have created library project in which I am loading the layout as well defining the method which I want to call from the Application project.
public class LibraryActivity {
public LibraryActivity() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.barchart_layout);
bindViews();
}
public void bindViews() {
bChart = (BarChart)findViewById(R.id.barchart);
}
public void setData(int count, float range) {
//definition of the method
// I have to user bChart view here
System.out.println("part 1 "+bChart); <---- this is null
}
Now I have successfully created the AAR project and I want to use this setData from the other project.
So when I run this From the other project By using below code
Intent in = new Intent(MainActivity.this,LibraryActivity.class);
startActivity(in);
LibraryActivity barChartCallBack = new LibraryActivity();
LibraryActivity.setData(15,25);
I got the null pointer on the bChart because my method setData got call first before oncreate so findviewbyid gives me null for the bChart.
You are setting the data on a completely different LibraryActivity object. First you tell the system with the intent to start one, then you start another one that does not get displayed, but you use it to call setData.
Read up on the android developer site:
https://developer.android.com/training/basics/firstapp/starting-activity.html
Basically you need to pass the data via extras in with the intent.
For a Bluetooth library I want to call a startActivityForResult to enable Bluetooth. I want to do this in my own library project. The problem is that sartActivityForResult only works for Activities, my library is not an activity, of course my project using this library project is having an activity. I tried two things
1.
Had my library to extend Activity, so I am creating the object like a normal POJO. Hence when calling startActivityForResult it throws a null pointer.
2.
Tried to get my Activity to pass it into the constructor of my library object. I am not able to to get an activity object, only context but that doesn't help.
What can I do?
EDIT: Some Code
I have the following class in my library project:
public class mylib
{
public mylib()
{
// Do some bluetooth setup thing here
// figure out that bluetooth is not enabled so try to enable it now
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
onActivityResult()
{
// Report back that BT is enabled now
}
}
Then I have of course my Android application using this library project in onCreate() I do something like this
public class Myactivity() extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
// do all the normal stuff
mylib pojo = new mylib(); // This creates a POJO which needs to startActivityForResults(...), see above code
}
}
The two options I mentioned above
I don't see how I can convince mylib to call startActivityForResult doing
public class mylib extends Activity
doesn't seem to do the trick.
I could overload my constructor of mylib to pass in the activity object, I have no idea how to create the activity object.
Hope that makes it a bit clearer.
You can create a constructor of your java class which has parameter of type Activity like below,
public class MyClass
{
private Activity activity;
public MyClass ( Activity activity )
{
this.activity = activity;
}
}
Now you can use this activity variable to call startAcvitiyForResult from your Java class.
I have creted a program that has 3 Activities: MainActivity, UpgradeActivity and UpgradesActivity.
Main Activity contains a timer and it also contains an instance of a Vehicle class.
public class MainActivity extends Activity {
TextView vehicleSpeed, vehicleName, vehicleDistance, vehicleLocation,
vehicleStatus, vehicleNews, vehicleInfo, vehicleMoney;
ProgressBar vehicleFuel;
public static Vehicle vehicle;
boolean launched;
public static PartType selectedType;
Handler handler = new Handler();
I have a button in MainActivity, that when pressed will take me to a page where i can select which part of the vehicle i wish to upgrade. For example i select: Engine. The engine Button takes me to the Upgrade Activity. In this activity i can buy the upgrade which should be applied to the vehicle in MainActivity. For the purpose of this question, lets say it set vehicles speed to +3.
My question is in regards to how to access the vehicle instance inside the MainActivity from the UpgradeActivity. I've tried making the instance static but that didn't work. How do i gain access and how can i change the vehicles variables from the other activities.
Here is where i am making the instance:
#Override
protected void onCreate(Bundle savedInstanceState) {
this.selectedType = PartType.Antenna;
this.launched = false;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
vehicle = new Vehicle();
vehicle.setupCar();
Here is where i am accessing the variable in Upgrades, it call the upgrade function inside of the Vehicle Class:
buyUp1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
MainActivity.vehicle.upgradeEngine(MainActivity.vehicle.engineLvl + 1);
Intent activityChangeIntent = new Intent(UpgradesActivity.this, MainActivity.class);
UpgradesActivity.this.startActivity(activityChangeIntent);
}
});
And this is the function within the Vehicle Class:
public void upgradeEngine(int lvl) {
engineLvl += 3;
engine = parts.getEngine(lvl);
}
The vehicle Stores an integer called: EngineLvl. This determines what level the cars engine is. The level is incremented by +3 everytime the engine is updated.
The problem is that the engine level never changes. Even if i make the Vehicle instance and all of the variables within vehicle STATIC;
MAINACTIVITY:
Vehicle
Button to UpgradesActivity
UPGRADESACTIVITY:
Button to UpgradeActivity
UPGRADEACTIVITY:
Change vehicle enginelvl Int
Button back to MainActivity
Main>Upgrades>Upgrade
Thank you for your time
Hard to say what is wrong without seeing the code, but I would advise you to use the Intent extras to move your data between activities. You will need to make your Vehicle class implement Parcelable (there is an example of how to implement Parcelable on that page, and countless others on the net). You pass your object as extra to the intent launching your UpgradeActivity like this :
Intent upgradeIntent = new Intent(this, UpgradeActivity.class);
upgradeIntent.putExtra("com.example.model.Vehicle", yourVehicleObject);
startActivityForResult(upgradeIntent, UPGRADE_CAR_REQUEST_CODE);
//UPGRADE_CAR_REQUEST_CODE is a unique private static final int
Then you can retrieve it in your UpgradeActivity onCreate method :
Intent intent = getIntent();
Vehicle vehicleFromLastActivity = intent.getParcelableExtra("com.example.model.Vehicle");
Before going back to your MainActivity you do something like this :
Intent dataIntent = new Intent();
dataIntent.putExtra("com.example.model.Vehicle", yourModifiedVehicleObject);
setResult(RESULT_OK, dataIntent);
finish();
Then finally in MainActivity you need to handle the result, it is done like this :
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode) {
case UPGRADE_CAR_REQUEST_CODE:
if(resultCode == android.app.Activity.RESULT_OK) {
Vehicle modifiedObject = data.getParcelableExtra("com.example.model.Vehicle");
// Now you can use that object which is coming from UpgradeActivity
}
}
}
Of course this could cause issues if your Vehicle class takes a lot of memory. You could then consider passing only the relevant information through the Intent to rebuild the object in the UpgradeVehicle Activity, for example only the id & name.
There are three different cases:
1) A user launches an app, navigates in it, pressed home and click on the app icon again to launch our app again.
2) A user launches an app, navigates in it, presses home, chooses recent and click on the app to launch our app again.
3) A user launches an app, navigates in it, click something in the app (TextView with a link), which calls another app (as example Email) and user clicks back button, which bring us back to our app.
I know about flag "clearTaskOnLaunch" flag, it solves case #1.
I know about about flag "excludeFromRecents", it solves case #2 (may be not the most user friendly solution, but it works).
What about case #3? I have a workaround right now. However, I will have to put it on all activities which can be lead to another app. I wonder, whether there is better way to solve it (without handling it in all such activities).
This should be handled on the Application level.
For API level 14, you can register an ActivityLifeCycleCallback in your Application class
public void registerActivityLifecycleCallbacks (Application.ActivityLifecycleCallbacks callback)
You can use it, to know on an Application level, which activities are destroyed, paused, resumed etc etc. Whenever, an activity is paused, without a new activity being created/resumed, you should clear the Activity stack, and re-launch your startActivity
If you target SDK versions < 14, you should implement your own method, to know which activities are created/resumed and paused, and do the same whenever an activity is paused, without a new activity being created/resumed
1) define a public static normalPause = true variable in a Class.
2) in onPause method of all of your activities set it false (I am worry. We might not be in a normal pause)
2) in onCreate method of all of your activities set it true (Do not worry. We are in a normal pause)
3) in onResume of all of your Activities:
if(!Utilities.normalPause)
{
this.finish()
}
Enjoy!
It seems a similar question has already been asked. It sounds like the OP came up with a working solution. How do I collapse "child activities"?
EDIT:
Instead of using a button you can use a boolean to tell whether or not you need to collapse back to the main activity. Have your root activity extend from Activity and the child activities extend from CollapsableActivity. To get this to work in all cases I added startOutsideActivity() and startOutsideActivityForResult().
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
public class CollapsableActivity extends Activity {
private boolean returnToRoot;
public static final int COLLAPSE_BACK = -1; // something other than RESULT_CANEL (0)
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
returnToRoot = true;
}
#Override
protected void onStart() {
super.onStart();
returnToRoot = true;
}
#Override
protected void onRestart() {
super.onRestart();
// start collapsing the stack
if (returnToRoot) {
setResult(COLLAPSE_BACK);
finish();
}
}
#Override
public void startActivityForResult(Intent intent, int requestCode) {
super.startActivityForResult(intent, requestCode);
returnToRoot = false;
}
public void startOutsideActivityForResult(Intent intent, int requestCode) {
super.startActivityForResult(intent, requestCode);
returnToRoot = true;
}
#Override
public void startActivity(Intent intent) {
// call startActivityForResult to make sure and catch the collapse condition
super.startActivityForResult(intent, 0);
returnToRoot = false;
}
public void startOutsideActivity(Intent intent) {
super.startActivity(intent);
returnToRoot = true;
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == COLLAPSE_BACK) {
returnToRoot = true;
}
}
}
This worked properly for me in all cases you listed. The only difference is you need to call startOutsideActivity() or startOutsideActivityForResult() when you navigate away from you app. Personally, I think this adds clarity to your intentions. Hope it helps!
I know you don't want to manage it in all activities but you can do this and still handle the code in one place with a super activity
public abstract class BlundellActivity extends Activity {
#Override
public void onPause(){
// Whatever strategy you want
}
}
public class SomeActivity extends BlundellActivity {
// Do whatever you normally want to do
}
public class SomeActivity extends BlundellActivity {
// Do whatever you normally want to do here as well
}
Perhaps, android:noHistory is what you're looking for. If you declare all your activities except StartupActivity with this attribute, then they will be finished as the user navigates away from them and only StartupActivity will appear.
You can try this steps:
use one boolean static flag isFinish in StartupActivity with default false value.
in onCreate() of StartupActivity set isFinish value to false.
write below code in onResume() method of all activities in your project.
if(isFinish)
{
finish();
}
set isFinish value to true when you open any native app like email, browser etc.
or
5 . set isFinish value to true in onBackPress() method whenever you want to close application on back press.
Case 6: if android browser open on clicking on any link then use below code is onPause() method
if(isBrowserRunning("com.android.browser"))
{
isFinish = true;
finish();
}
////////////////
private boolean isBrowserRunning(String processName)
{
ActivityManager manager = (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
String packageName = manager.getRunningTasks(1).get(0).topActivity.getPackageName();
Log.i("LogTest", "Current process package name: " + packageName);
return processName.equalsIgnoreCase(packageName);
}
You can create a sample project to know other browser package name like opera mini, US browser etc.
add below permission in manifest:
<uses-permission
android:name="android.permission.GET_TASKS" />
You can call this.finish() on the onPause() of your Activity, that way the activity will be closed in the three cases.
You need to use bundle and pass appropriate parameter/or parameters from the calling app (i.e. click something in the app (TextView with a link)).
Retrieve the parameter in the called app (Email app).
You can send the name of the activity in the parameter.
Now being in Email app(the called app) Click of back button navigate back to your calling application.
Optionally you can save the state of activity from the caller program, as required.
You need to use Bundle, and Intent to implement this logic.
Code snippet:
In the calling program, we need to store parameters/data required for back button functionality in the called program.
Bundle bndleData = new Bundle();
Use putString(), putInt() methods of Bundle class.
String prefix = getPackageName().toString();
(this prefix can be stored in application level constants.java file as applicable)
bndleData.putString("ParentActivity", this.getLocalClassName());
Also store additional parameters if required
bndleData.putString("paramName", valueofParamName);
bndleData.putInt("IntChannelImage", chImageInt);
Intent intent = new Intent(v.getContext(), AMRChannelPlayer.class);
intent.putExtra(prefix + "bndleChnlData", bndleData);
startActivity(intent);
Caller Program:
Retrive the data, activity nae from bundle and use it in back button implementation:
prefix = getPackageName().toString();
Bundle extras = getIntent().getBundleExtra(prefix + "bndleData");
String parentActivity = extras.getString("ParentActivity");
extras.getString("paramName");
I hope this helps you.
Instead of using multiple solutions you can use a single one that solves all the problems.
Check this answer:
https://stackoverflow.com/a/8576529/327011
With a Broadcast and BroadcastReceivers in each activities of your application you can kill all activities whenever your application goes to background.
UPDATE:
To detect if your application when to background you can use onStop, check this to understand the theory: Activity side-by-side lifecycle
And this is the implementation: https://stackoverflow.com/a/5862048/327011
I think this is all you need :-)
I am new to android so please excuse the newbie question. I have a game I am trying to port from an old Java applet to android. My goal is to get this functional and then post an article on a site like CodeProject (or a better one if there are ones more appropriate). The idea is to show that a person brand new to android development can create an app in a reasonable amount of time.
I am making some progress but have run into a problem. I have the main activity in which the user interacts with. I then created a menu item that in turn starts a second activity (call it child) with a modest number of checkbox's, seekbar's etc to fill in parameters. I can successfully pass the class containing all the options from main to child. But I cannot get the child to pass this data back to the main.
First here is my main code that starts the child activity:
public void addBalls()
{
Intent myIntent = new Intent(this, GameOptions.class);
Bundle b = new Bundle();
b.putSerializable("options", gameParams);
myIntent.putExtras(b);
startActivityForResult(myIntent,STATIC_OPTIONS_VALUE);
}
The data passed to the child (and hopefully back again) is:
public class GameOptionParams implements Serializable
{
private static final long serialVersionUID = 1L;
public int speedBarPosition;
public int vgravityBarPosition;
public int mgravityBarPosition;
public int viscosityBarPosition;
public int restititionBarPosition;
public boolean trace;
public boolean collide;
public boolean mush;
public boolean wrap;
public boolean flicker;
}
And here is the expected return (again in main)
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode)
{
case (STATIC_OPTIONS_VALUE) :
{
if (resultCode == Activity.RESULT_OK)
{
//retrieve intended options
Bundle b = data.getExtras();
gameParams = (GameOptionParams) b.getSerializable("options");
}
break;
}
}
}
The child activity successfully receives the gameParams data. It then interacts with the user to update the values and then I attempt to return it but it does not seem to get sent to main. Here is the child code in the onStop() override.
Maybe this code should not be in the onStop() override but I can't determine where else to place it.
#Override
public void onStop()
{
super.onStop();
//read widget values
gameParams.speedBarPosition = speedBar.GetPosition();
gameParams.vgravityBarPosition = vgravityBar.GetPosition();
gameParams.mgravityBarPosition = mgravityBar.GetPosition();
gameParams.viscosityBarPosition = viscosityBar.GetPosition();
gameParams.restititionBarPosition = restititionBar.GetPosition();
//todo save to persistent
Intent resultIntent = new Intent(this, TiltBall2ImpactActivity.class);
Bundle b = new Bundle();
b.putSerializable("options", gameParams);
resultIntent.putExtras(b);
setResult(Activity.RESULT_OK, resultIntent);
}
Back in the main onActivityResult override I always see requestCode=0, resultCode=0, data=null. I assume this is a typical newbie problem, I have been reading the sdk documentation, user forums etc and have come close to a solution but just not quite there yet. Any help would be appreciated.
Since this is sort of a setting menu for the game, I assume you are going to need these values for more than one activity. If so you extend the android.app.Application class.
In that class you can create attributes to hold your values. In any activity you can call
MyApplication myApp = (MyApplication)getApplicationContext();
where myApp is a singleton. So you will get the values you set from another activity.
You will need to add this code to your application tag in the manifest file for it to work
android:name=".MyApplication"
If you need to keep these values for next startup of the application, you need to use SharedPreferences. This is a good tutorial for that
http://saigeethamn.blogspot.com/2009/10/shared-preferences-android-developer.html
Assuming in your 'child' activity, the user has to press an 'OK' or 'Save' button then put the code to set the gameParams parameters in the button's onClick(...) handler.
Use the default constructor for instantiating the Intent, example...
Intent resultIntent = new Intent();
...then after creating the Bundle and adding gameParams to it and calling setResult(...), simply call finish() to terminate the 'child' activity. There aren't many occasions that I can think of to override onStop() and I suspect you don't want to be using it to attempt returning the Intent.