I have a method name checkForUpdate() in UpdateActivity.java. It looks like this:
#NonNull
#SuppressWarnings("deprecation")
protected String checkForUpdate(int curVersionCode) {
HttpClient httpclient = new DefaultHttpClient();
...
}
I am trying to call it from anotherActivity. So I'm trying to use code like this:
private void callFromAnotherActivity() {
UpdateActivity updateApp = new UpdateActivity();
String result = updateApp.checkForUpdate(...);
}
so when I type updateApp. then a list of the methods of UpdateActivity.java appears but there is no checkForUpdate() method. Why?
so when I type updateApp. then a list of the methods of UpdateActivity.java appears but there is no checkForUpdate() method. Why?
This is because your method is not public and probably you haven't import the UpdateActivity.
Please be noted that you can't create an Activity by calling the following:
UpdateActivity updateApp = new UpdateActivity();
You need to use something like this:
// context is your activity context.
Intent updateApp = new Intent(context, UpdateActivity.class);
context.startActivity(updateApp);
My suggestion:
You need to move the checkForUpdate method from UpdateActivity and make it as an util. So, other activity using the method won't be dependent and coupled with UpdateActivity. Localize the method to an utility class something like this:
public class UpdateUtil {
...
#NonNull
#SuppressWarnings("deprecation")
public static String checkForUpdate(int curVersionCode) {
HttpClient httpclient = new DefaultHttpClient();
...
}
}
and then use the method with:
UpdateUtil.checkForUpdate(1);
If you can't move the code (e.g, you don't have ownership of the code), you can do these things:
Make the checkForUpdate as static method
Use EventBus to tell the UpdateActivity to do the update.
You should not create an instance of the activity class. It is wrong. Activity has ui and lifecycle and activity is started by startActivity(intent)
Check here : call a method in another Activity
Related
I have an Activity-class with a method called getPacketNames() that returned the names of some installed packages.
private ArrayList<CharSequence> getPackageNames(){
ArrayList<CharSequence> packageNames = new ArrayList<>();
List<PackageInfo> packagesInfos = getPackageManager().getInstalledPackages(0);
for(PackageInfo packageInfo: packagesInfos){
if(!isSystemApp(packageInfo)){
packageNames.add(packageInfo.packageName);
}
}
return packageNames;
}
I want to make it easy for someone else to call this method from another class. However, in order to do so, they would have to create an instance of the activity. This seems cumbersome, and not correct.
Is thee any way I can create this method outside of an Activity? When I create a separate class and copy-paste the method it does not work, because getPackageManager().getInstalledPackages(0) seems to need to be in an activity.
You should't attempt to do that. Instead create a UtilityClass and make your getPackageNames() as static method.
public final class MyUtils {
public static ArrayList<CharSequence> getPackageNames(final Context context){
ArrayList<CharSequence> packageNames = new ArrayList<>();
List<PackageInfo> packagesInfos = context.getPackageManager().getInstalledPackages(0);
for(PackageInfo packageInfo: packagesInfos){
if(!isSystemApp(packageInfo)){
packageNames.add(packageInfo.packageName);
}
}
return packageNames;
}
private static boolean isSystemApp(...){
...
}
}
Then from the Activity, you can access it as follows:
MyUtils.getPackageNames(this);
Sagar's answer is correct and you should follow that. If you are going to create a util class don't forget to add a private constructor, so that your util class will not be instantiated.
For a "hacky" and bad solution, you can always define your method as public static in your activity class and call it from elsewhere with YourActivity.methodname. But this approach will fail especially if you experiment with Don't Keep Activities option.
I am trying to initialize a class that calls another class that uses AsyncTask. I am using GetDataFromDB gDataFromDB = new GetDataFromDB() but that does not initialize the class, it just gives me access to any static methods in the class. So what do I do to get the onCreate method to run? I have tried using intent but keep getting an error because this is a static class
public class FacadeDataFromDB extends Activity {
static ArrayList<HashMap<String, String>> visitorsList;
private static FacadeDataFromDB dataFromDB;
static boolean accessDB = false;
private FacadeDataFromDB() {
}
public static void initInstance() {
}
public static FacadeDataFromDB getInstance() {
if (dataFromDB == null) {
// Create the instance
dataFromDB = new FacadeDataFromDB();
}
return dataFromDB;
}
public static void setData() {
if (!accessDB) {
GetDataFromDB gDataFromDB = new GetDataFromDB();
accessDB = true;
}
// visitorsList = gDataFromDB.returnInfoFromDB();
}
public static ArrayList<HashMap<String, String>> getVisitorForDay() {
// TODO Auto-generated method stub
setData();
return visitorsList;
}
}
GetDataFromDB is the other class that I am calling. The current class is a static class and uses a singleton because I only want one initialization of the class the gets data from the db. If you have more questions or want me to post code let me know. Thanks
It seems to me that your two classes FacadeDataFromDB GetDataFromDB should not inherit Activity
Activities are made for GUI and user-interaction (I don't see any in your example) and their life-cycle is managed by the framework : you never create them manually with new.
See the android tutorial : https://developer.android.com/guide/components/activities.html and Activity javadoc : https://developer.android.com/reference/android/app/Activity.html.
I'm not sure that you completely understand the Android runtime. You should start Activities using Intent objects, not by creating them with the new keyword as you are. To ensure that your onCreate() method is called within your Activity, you could launch an explicit Intent from some other Activity/Context: Intent intent = new Intent(currentContext, FacadeDataFromDB.class);.
Also, when it comes to Activities, you shouldn't use private constructors. See this post for reasons why.
I just ran into this problem while coding android. If I have a non-static method (It has to be non-static for the code inside to work) in my main class, how am i supposed to call it from within another class, because obviously I can't create another instance of my main class without starting a new instance of the program?
public class MainActivity extends FragmentActivity {
public static String starttime = "";
public static String startdate = "";
public static String endtime = "";
public static String enddate = "";
public static boolean start = false;
}
public void setDateText() {
EditText TextStart = (EditText)findViewById(R.id.txt_start);
TextStart.setText(startdate + " at " + starttime, TextView.BufferType.NORMAL);
EditText TextEnd = (EditText)findViewById(R.id.txt_end);
TextEnd.setText(enddate + " at " + endtime, TextView.BufferType.NORMAL);
}
Any help on how to call the setDateText() method from another class?
Thanks in advance
Normally you can't call a non static method from a static type, so you would do:
MainActivity m = new MainActivity(); // No constructor needed in class def.
m.setDateText();
But, when the program starts, you're not giving your JVM anything to call at the start, so you need to add:
#Override
//the function called when activity is created
public void onCreate(Bundle savedInstanceState) {
//call the create fct. Of the base class
super.onCreate(savedInstanceState);
//load the layout specified in the layout.xml
setContentView(R.layout.main);
MainActivity m = new MainActivity();
m.setDateText();
}
This will be called when the activity is created.
Go to Android - A beginner's guide for more information.
Also watch your syntax, your method def is outside of your class def.
Without knowing which other class is trying to access the MainActivity instance, you will need to pass a reference of this instance to your other objects, probably by passing this into a constructor or method.
For example
public class MainActivity extends FragmentActivity {
public void someMethod() {
SomeClass someClass = new SomeClass(this); // pass this for callbacks
// ~ more
}
}
where SomeClass is a class where you need to call the MainActivity's setDateText method.
I am trying to understand the need for you to call the function from another activity. Your main activity is anyway not on the foreground, so if you call this function from there, date will not be shown. Once you finish the 2nd activity and you will be back to MainActivity, then only you need this function to be called.
If that is so, then you can use startActivityForResult() to start 2nd activity, and then pass the date information back to MainActivity through onActivityResult(). You can call this function in MainActivity itself.
If you have to invoke setDate() at the activity's launch, you can pass the date in the Intent when you launch the activity and pull the date in MainActivity's onCreate method.
If you have to invoke setDate() at a different time other than launch, you can send a broadcast from other activity/component and make MainActivity listen to the Broadcast and pull the date from the intent's data.
I need a class to get the artists, albums and tracks on the device, which I will then use JNI to call upon.
At the moment, in its barebones, the following causes a crash.
public class AndroidMediaLibray extends Activity {
public void getArtists() {
getContentResolver();
}
}
How do I get this to not crash?
The problem you have, is that you need to call getContentResolver() on a Context. If you call it in an Activity, you automatically call it on the Context of the Activity. But you (probably) never really start AndroidMediaLibrary. Please refer to the documentation of activities. If you want to have the DB call in an extra class, you may have a look at the following code. I have created a class with static methods. I just need to pass the context of my given Activity to that class. In your case that class might look like this:
public class AndroidMediaLibrary {
public static List<String> getArtists(Context context){
ArrayList<String> retVal = new ArrayList<String>();
ContentResolver resolver = context.getContentResolver();
// some more stuff here..
return retVal;
}
}
You may call that function from your MainActivity with:
List<String> myValues = DBUtils.someFunction(MainActivity.this);
I'm new to android and I need little help please. I want to pass data from an activity to a framelayout class, so I've implement a callback. On my activity I use an interface and setting the listener like this:
private OnCallStateListener onCallStateListener;
public interface OnCallStateListener{
int Data = 1;
void OnCallState(int wichAction)
}
public void setOnCallStateListener(OnCallStateListener listener){
onCallStateListener = listener;
}
private void dispatchTriggerEvent(int whichHandle){
if(onCallStateListener != null){
onCallStateListener.OnCallState(whichHandle);
}
}
And I use it like:
private onCallDisconnect(){
dispatchTriggerEvent(OnCallStateListener.DATA);
The dispatchTriggerEvent is executed but the problem is that the listener onCallStateListener is always null. what am I missing here?
Thanks!
It is null because you did not create an instance of the class. From what you have here you only have an interface. You would first need to create a class that implements that interface, and then say something like:
OnCallStateListener myVar = new OnCallStateListenerImpl();