I have an Activity which creates a class that does some work. What is the typical Android method of having this class report back to the Activity in order to update the UI?
My activity, which creates the class:
public class MainActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MyClass obj = new MyClass(this);
obj.DoWork();
}
}
The class that does the work, and wants to report back some
public class MyClass(Context context) {
private Context context;
public void DoWork() {
//Do some work with a countdown timer
//Report back some values
}
}
You can create your own interface like this:
public class MainActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MyClass obj = new MyClass(this);
obj.setOnWorkDoneListener(new MyClass.OnWorkDoneListener(){
#Override
public void onDone(Values values) {
//Work done, use values
updateUI(values);
}
});
obj.DoWork();
}
}
public class MyClass(Context context) {
private Context context;
public interface OnWorkDoneListener{
void onDone(Values values);
}
private OnWorkDoneListener listener;
public void setOnWorkDoneListener(OnWorkDoneListener listener){
this.listener = listener;
}
public void DoWork() {
//Do some work with a countdown timer
when(workEnded) listener.onDone(backValues);
}
}
Related
I have a video player app where I need to access the lifecycle of an abstract activity from another class in Android. In my abstract activity, I've tried using LifecycleRegistry, but this is getting me the lifecycle owner not the actually lifecycle of the abstract class. How can I access the lifecycle of an abstract activity from another class?
Here is my abstract activity:
abstract public class MainActivity extends AppCompatActivity {
private LifecycleRegistry lifecycleRegistry;
VideoPlayer videoPlayer;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
lifecycleRegistry = new LifecycleRegistry(this);
lifecycleRegistry.setCurrentState(Lifecycle.State.CREATED);
setContentView(R.layout.activity_main);
videoPlayer = new VideoPlayer();
playVideo();
}
public void playVideo(){
videoPlayer.init();
//calls function in VideoPlayer class
}
#Override
protected void onResume() {
super.onResume();
lifecycleRegistry.setCurrentState(Lifecycle.State.RESUMED);
}
#Override
protected void onDestroy() {
super.onDestroy();
lifecycleRegistry.setCurrentState(Lifecycle.State.DESTROYED);
}
}
Here is the class where I need to get the lifecycle of my abstract MainActivity:
public class VideoPlayer {
public void init() {
playVideo();
}
public void playVideo() {
//async call happens here, I need getLifeCycle() from MainActivity
}
}
Don't know a know about the context of you feature, but you You can do smth
public class VideoPlayer {
private Lifecycle mLifecycle;
public VideoPlayer(Lifecycle lifecycle) {
mLifecycle = lifecycle;
}
public void init() {
playVideo();
}
public void playVideo() {
//you have mLifecycle now
}
}
In Activity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...
videoPlayer = new VideoPlayer(getLifecycle());
}
I try to implement a timer using Work Manager.
"Timer button was hit" is appear in logcat, but nothing comes from worker. What I do wrong?
This is my ViewModel class:
public class MainViewModel extends ViewModel {
public static final String LOG_TAG = "MainActivity";
private final WorkManager workManager;
public MainViewModel(WorkManager workManager) {
this.workManager = workManager;
}
public void count() {
Log.d(LOG_TAG, "Timer button was hit!");
OneTimeWorkRequest request = new OneTimeWorkRequest.Builder(MainWorker.class).build();
workManager.beginUniqueWork("count-work", ExistingWorkPolicy.APPEND, request).enqueue();
}
}
This is my worker. Nothing appear in logcat from here. I don't know why.
public class MainWorker extends Worker {
public MainWorker(#NonNull Context context, #NonNull WorkerParameters workerParams) {
super(context, workerParams);
Log.d(MainViewModel.LOG_TAG, "Created");
}
#NonNull
#Override
public Result doWork() {
Log.d(MainViewModel.LOG_TAG, "Work start");
return Result.success();
}
}
This is my activity:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MainViewModel viewModel = new MainViewModel(WorkManager.getInstance(this));
ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.setMainViewModel(viewModel);
}
}
ViewModels are not initialized the way you did. If you have to pass something to ViewModel constructor, you should probably consider using ViewModelProvider.Factory().
You can make your own ViewModelProvider.Factory()
Refer this, https://medium.com/koderlabs/viewmodel-with-viewmodelprovider-factory-the-creator-of-viewmodel-8fabfec1aa4f#:~:text=And%20it%20is%20because%20you,it%20will%20create%20your%20ViewModel.
How can I start getdata() method to another class. I want to show the output to a `ListView which is in another Java class.
tab1Background.java
public class tab1Background extends Activity{
ListView lv;
lv = (ListView) findViewById(R.id.lv);
//some code here
public void getdata() {
//some code here
}
}
tab1report.java i want to start the getdata() activity to show data in listview
public class tab1report extends Fragment {
//some code here
}
public class tab1report extends Fragment {
public void startSomething()
{
((tab1Background) getActivity()).getdata();
}
}
You could use callback method.
public class tab1report extends Fragment {
Callback callback;
public interface Callback {
void call();
}
onAttach(Context context) {
callback = (Callback) context;
}
onStart() {
// Some code here
callback.call();
}
}
public class tab1Background extends Activity implements tab1report.Callback {
ListView lv;
lv = (ListView) findViewById(R.id.lv);
//some code here
public void getdata() {
//some code here
}
public void call() {
getdate();
}
}
This will ensure that the functionality is passed back to the activity.
I'm trying using ReferenceQueue to check Activity if the activity is destory,Whether this activity is recycled.
I just using intent to Main2Activity.class:
switch (v.getId()){
case R.id.btn_turn_two:
Intent intent=new Intent(MainActivity.this,Main2Activity.class);
startActivity(intent);
break;
default:
break;
}
when I press to return MainActivity.class, the Main2Acitivity.class will be destroyed, so I using registerActivityLifecycleCallbacks watch activity in application,
public class MainApplication extends Application{
private watche watche;
#Override
public void onCreate() {
super.onCreate();
watche=new watche(this,getApplicationContext());
}
this class is check the Activity is destoryed.
public class watche {
KeyRefrence ref;
private Context context;
private final Set<String> retainedKeys = new CopyOnWriteArraySet<>();
private final ReferenceQueue<Object> referenceQueue=new ReferenceQueue<>();
public watche(Application application, Context context){
application.registerActivityLifecycleCallbacks(lifecycleCallbacks);
this.context=context;
}
Application.ActivityLifecycleCallbacks lifecycleCallbacks=new Application.ActivityLifecycleCallbacks() {
#Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
}
#Override
public void onActivityStarted(Activity activity) {
}
#Override
public void onActivityResumed(Activity activity) {
}
#Override
public void onActivityPaused(Activity activity) {
}
#Override
public void onActivityStopped(Activity activity) {
}
#Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
}
#Override
public void onActivityDestroyed(Activity activity) {
//weakrefrence to this activity
String key = UUID.randomUUID().toString();
retainedKeys.add(key);
final KeyRefrence weakReference=new KeyRefrence(activity,key,activity.getPackageName(),referenceQueue);
final MyAyTask myAyTask=new MyAyTask(weakReference,activity,context);
myAyTask.doInBackground(null);
}
};
public class MyAyTask extends AsyncTask {
private Activity activity;
private KeyRefrence keyRefrence;
private Context context;
public MyAyTask(KeyRefrence keyRefrence, Activity activity,Context context){
this.activity=activity;
this.context=context;
this.keyRefrence=keyRefrence;
}
#Override
protected void onPostExecute(Object o) {
super.onPostExecute(o);
}
#Override
protected Object doInBackground(Object[] objects) {
gc();
ref=(KeyRefrence)referenceQueue.poll();
if (ref==null){
Log.d(TAG, "onActivityDestroyed:Acitivty is not destory");
}
else if (ref!=null){
Log.d(TAG, "doInBackground: "+ref);
}
return null;
}
}
I have create KeyReference implement WeakReference,and I didn't do anything in Main2Activity.class, I just press the phone return,I check the gc,is working ,but the referencequeue always empty, I'm sure the Activity is destoryed.
I am developing an Android app and thus, I have a MainActivity class. Inside of that MainActivity class, I have a method, let's call it doSomething():
public class MainActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void doSomething(){
// bla bla bla
}
}
I also have a different class (with different layout) that is called OtherActivity. I want to use the doSomething method inside it:
public class OtherActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.other_activity_layout);
// Let's use doSomething()
}
}
I tried this:
public class OtherActivity extends AppCompatActivity {
MainActivity main;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.other_activity_layout);
// Let's use doSomething()
MainActivity main = new MainActivity();
main.doSomething();
}
}
But it does not work. I also tried to make OtherActivity to extend the MainActivity, doing the following:
public class OtherActivity extends MainActivity{
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.other_activity_layout);
// Let's use doSomething()
super.doSomething();
}
}
But it does not allow me to initialize the layout...
How can I do?
Thanks in advance.
To communicate between to Activity Broadcast is the best way, and for the same application, we can use local broadcast using LocalBroadcastManager.
First, we should register one broadcast in MainActivity,
public class MainActivity1 extends AppCompatActivity {
public static final String INTENT_FILTER = "do_some_action";
public static final String INTENT_BUNDLE_VALUE = "value1";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main1);
LocalBroadcastManager.getInstance(this).registerReceiver(
mChangeListener, new IntentFilter(INTENT_FILTER));
}
#Override
protected void onDestroy() {
super.onDestroy();
LocalBroadcastManager.getInstance(this).unregisterReceiver(mChangeListener);
}
private BroadcastReceiver mChangeListener = new BroadcastReceiver() {
#Override
public void onReceive(Context context, Intent intentData) {
// you can do anything here
if (intentData != null && intentData.hasExtra(INTENT_BUNDLE_VALUE)) {
String value = intentData.getStringExtra(INTENT_BUNDLE_VALUE);
doSomeAction(value);
}
}
};
private void doSomeAction(String value) {
}
}
Then to do some action in MainActivity from OtherActivity, we can send Local broadcast from OtherActivity it will reach the receiver of Which we register in MainActivity,
public class OtherActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_other);
// You can call MainActivity to do some actions
Intent intent = new Intent(MainActivity1.INTENT_FILTER);
intent.putExtra(MainActivity1.INTENT_BUNDLE_VALUE, "Any string or any value");
LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
}
Done!!!.
Something like this should do the trick, I'm going to make a static navigator to handle your navigation logic. If you are opposed to static methods you could also make them on your Application object to make it easier to manage dependencies, I'm just making it static for simplicity.
//Making this fully static for simplicity, this is fine for a small app
//you can make it a singleton on the application class for more flexibility
public class Navigator {
//static member vars that determine navigation
// pass in Context if needed for navigation purposes
public static void doSomething(Context context){
// bla bla bla
}
}
public class MainActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity_layout);
}
private void doSomething() {
Navigator.doSomething(this);
}
}
public class OtherActivity extends AppCompatActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.other_activity_layout);
}
private void doSomething() {
Navigator.doSomething(this);
}
}