I have an Activity that includes a TextView to display the current status of the app. Besides MainActivity there is another class that is used for checking for updates and then updating the app if appropriate.
This is the important part of the code.
public class MainActivity extends AppCompatActivity {
private TextView status;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
status = findViewById(R.id.status);
new Update().check();
}
public void setStatus(String status) {
this.status.setText(status);
}
}
How can I update the status TextView from within the Update class?
public class Update extends Activity {
public void check(final Context c) {
runOnUiThread(new Runnable() {
#Override
public void run() {
TextView status = findViewById(R.id.status);
status.setText("Checking for updates...");
}
});
// final TextView status = getApplicationContext().findViewById(R.id.status);
// status.setText("Checking for updates");
// Check for updates...
}
public class UpdateApp extends AsyncTask<String,Void,Void> {
private Context context;
public void setContext(Context contextf){
context = contextf;
}
#Override
protected Void doInBackground(String... arg0) {
// Update the app
}
}
}
Attempting to run getApplicationContext().findViewById(R.id.status) crashes the app. When I put it in a try block it still crashes the app - how can that be when I catch a Throwable object? ... that doesn't make sense!!!
Using runOnUiThread the app runs but the status is not updated.
Put the UpdateApp AsynTask in new file.
public class MainActivity extends AppCompatActivity {
private TextView status;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
status = findViewById(R.id.status);
new UpdateApp(status).execute();
}
}
UpdateApp.java
public class UpdateApp extends AsyncTask<String,Void,Void> {
private TextView status;
public UpdateApp(TextView status){
this.status = status;
}
#Override
protected void onPostExecute(String result) {
status.setText("Update complete");
}
#Override
protected void onPreExecute() {
status.setText("Checking for updates...");
}
#Override
protected Void doInBackground(String... arg0) {
// Update the app
}
}
You just don't need another class to make it works, just copy your UpdateApp class inside MainActivity to access your status view.
In case you want your UpdateApp class to be in a different file (witch I recommend, to separate classes responsibility) you'd need a callback: a reference to your activity to update the status view from the AsyncTask class. The way you can make it is using Interfaces. Take a look to this example
MainActivity.java
public class MainActivity extends AppCompatActivity implements CallbackInterface {
private TextView status;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
status = findViewById(R.id.status);
new LoaderClass(this).execute();
}
#Override
public void setStatusText(String text) {
status.setText(text);
}
}
CallbackInterface.java
public interface CallbackInterface {
void setStatusText(String text);
}
LoaderClass.java
public class LoaderClass extends AsyncTask<String, Void, Void> {
private CallbackInterface callbackInterface;
public LoaderClass(CallbackInterface callback) {
callbackInterface = callback;
}
#Override
protected Void doInBackground(String... arg0) {
callbackInterface.setStatusText("Loaded text");
return null;
}
}
If you are in any Activity you can use runonUIthread() like -
runOnUiThread(new Runnable() {
#Override
public void run () {
// do your magic here
}
});
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 am trying to make a button in activity2(settings page), when the button is clicked, then the title of activity1(MainActivity) will change to what I set to. I have been trying to use interface to carry out the function but it gives me a null pointer exception error.
MainActivity
#Override
public void changeActionBarTitle(String editText){
actionTitle = editText;
setTitle(actionTitle);
};
Interface
public interface ActionBarInterface {
void changeActionBarTitle(String editText);
}
Setting page (activity 2)
public class SettingsPage extends AppCompatActivity {
ActionBarInterface actionBarInterface;
Button editCompanyNameButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings_page);
setTitle("Settings");
editCompanyNameButton = findViewById(R.id.editCompanyNameButton);
editCompanyNameButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
actionBarInterface.changeActionBarTitle("test");
}
});
}
}
Thanks.
You can try this code without using the interface
MainActivity:
#Override
protected void onResume() {
setTitle(Main2Activity.title);
super.onResume();
}
activity2:
public class SettingsPage extends AppCompatActivity {
Button editCompanyNameButton;
static String title;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
setTitle("Settings");
editCompanyNameButton = findViewById(R.id.editCompanyNameButton);
editCompanyNameButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
title = "test";
}
});
}
}
It gives a null pointer exception error because actionBarInterface was not initialised.
Check out topics on 'Getting a Result from an Activity', making use of classes and functions such as Intent, startActivityForResult, onActivityResult.
Android: how to make an activity return results to the activity which calls it?
I am trying to understand better how to create a custom listener with a simple example but I don't know how to start the interface so that it is not null:
public class MainActivity extends AppCompatActivity implements ListenerButton{
TextView helloToOther;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
helloToOther = findViewById(R.id.helloWorldToOtherActivity);
helloToOther.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, ButtonActivity.class));
}
});
}
#Override
public void onClickButton(View view) {
Toast.makeText(this, "Estoy en la primera activity", Toast.LENGTH_SHORT).show();
}
}
This is the second activity:
public class ButtonActivity extends AppCompatActivity {
Button btnInterface;
ListenerButton listenerButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_button);
btnInterface = findViewById(R.id.button_activity__btn__button_interface);
setUpButtonInterface();
}
private void setUpButtonInterface() {
btnInterface.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
listenerButton.onClickButton(v);
}
});
}
}
And there's the interface:
public interface ListenerButton {
void onClickButton(View view);
}
Basically I get a null pointer exception on the second activity because the interface is null, but I don't fall right now as I can start it. Thank you very much.
the reason you are getting a null pointer exception is because you haven't assigned anything to variable listenerButton and therefor it is in fact null!!
you don't need a new interface for that you just need to do this:
public class ButtonActivity extends AppCompatActivity {
Button btnInterface;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_button);
btnInterface = findViewById(R.id.button_activity__btn__button_interface);
setUpButtonInterface();
}
private void setUpButtonInterface() {
btnInterface.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//do whatever you want to do when button is clicked!
}
});
}
}
if you want to define whatever you want to do when button is clicked you need a class and not an interface:
public class ButtonListener implements View.OnClickListener{
#Override
public void onClick(View v) {
//do whatever you want to do when button is clicked!
}
}
and then in your activity do this:
public class ButtonActivity extends AppCompatActivity {
Button btnInterface;
ListenerButton listenerButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_button);
listenerButton = new ButtonListener();
btnInterface = findViewById(R.id.button_activity__btn__button_interface);
setUpButtonInterface();
}
private void setUpButtonInterface() {
btnInterface.setOnClickListener(listenerButton);
}
}
Create a new file:
MyListener.java:
public interface MyListener {
// you can define any parameter as per your requirement
public void callback(View view, String result);
}
In your activity, implement the interface:
MyActivity.java:
public class MyActivity extends Activity implements MyListener {
#override
public void onCreate(){
MyButton m = new MyButton(this);
}
// method is invoked when MyButton is clicked
#override
public void callback(View view, String result) {
// do your stuff here
}
}
In your custom class, invoke the interface when needed:
MyButton.java:
public class MyButton {
MyListener ml;
// constructor
MyButton(MyListener ml) {
//Setting the listener
this.ml = ml;
}
public void MyLogicToIntimateOthers() {
//Invoke the interface
ml.callback(this, "success");
}
}
I'm doing a quiz and I don't want to write in all of new Activities this method but I can't make it work. I was trying to make another java class to put there all methods but how do that
Hope u gonna help me guys
//Main class
public class MainActivity extends AppCompatActivity {
private Button button;
BubbleEmitterView bubbleEmitter;
Handler handler = new Handler();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
emitBubbles();
bubbleEmitter = findViewById(R.id.bubbleEmitter);
button = findViewById(R.id.startButton);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startQuiz();
}
});
}
public void emitBubbles()
{
handler.postDelayed(new Runnable() {
#Override
public void run() {
//determine the size of the bubbles and the range
int size = new Random().nextInt(81)+20;
bubbleEmitter.emitBubble(size);
emitBubbles();
}
},
//determine the range for the bubbles to appear
new Random().nextInt(301)+100);
}
//question class
public class Question1 extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_question1);
}
}
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);
}
}