The code is here:
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
Button push_me,secondButton;
TextView textView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
textView = findViewById(R.id.textView);
push_me = findViewById(R.id.push_me);
secondButton = findViewById(R.id.secondButton);
push_me.setOnClickListener(this);
secondButton.setOnClickListener(this);
}
#Override
public void onClick(View v) {
switch (v.getId())
{
case R.id.push_me:
textView.setText(R.string.Someone_pushed);
break;
case R.id.secondButton:
textView.setText(R.string.hello_android);
break;
}
}
if I take out the break (the two breaks down in the program) the program isn't working properly but I can not understand why.
From the "case" label that applies onwards, your code is executed until the switch block is ended (with a }), or until it is left with break (or, depending on context, return, throw, continue, possibly some other things I'm forgetting right now). That's just how it works in Java (and many other C-influenced programming languages).
This behavior is somewhat similar to that of labels and goto instructions, which predate "modern" structured programming. As those have fallen completely out of use unless you have to write Assembly by hand, this behavior is not intuitive for most programmers today, but it lives on as one of those weird traditions, similar to the 80-character line limit which goes all the way back to punchcards.
Related
The example on https://developers.google.com/cast/cast_2nd-screen_app_tutorial shows a onDestroy method which calls unregisterMediaRouteProvider. This causes the MediaRouter.Callback.onRouteUnselected method to get called which in turn ends the session. This leads to the app getting disconnected from the chromecast device and the MediaRouteButton stops being blue. Below is the onDestroy method from the example:
#Override
protected void onDestroy() {
MediaRouteHelper.unregisterMediaRouteProvider(mCastContext);
mCastContext.dispose();
super.onDestroy();
}
So my question is, what is the proper way to handle screen rotation when using the chromecast device from an app?
You can try using isFinishing() method of Activity to figure out if onDestroy is called due to application really "finishing" or is called for other reasons. Another option is to handle orientation change yourself.
You can see the guidelines for handling setup/destruction of the Chromecast (such as when orientation change is happening) on https://developers.google.com/cast/docs/android_sender
The relevant sections of code are the following ones:
#Override
protected void onResume() {
super.onResume();
mMediaRouter.addCallback(mMediaRouteSelector, mMediaRouterCallback,
MediaRouter.CALLBACK_FLAG_REQUEST_DISCOVERY);
}
#Override
protected void onPause() {
if (isFinishing()) {
mMediaRouter.removeCallback(mMediaRouterCallback);
}
super.onPause();
}
And also the following code:
#Override
protected void onStart() {
super.onStart();
mMediaRouter.addCallback(mMediaRouteSelector, mMediaRouterCallback,
MediaRouter.CALLBACK_FLAG_REQUEST_DISCOVERY);
}
#Override
protected void onStop() {
mMediaRouter.removeCallback(mMediaRouterCallback);
super.onStop();
}
It is also a good idea to have a boolean value in your program, for instance "wasLaunched" or "isConnected" to keep track of whether the connection to the chromecast is active or not. I use this variable in my code to check if I can send messages to the receiver or not. Then simply remember to save this variable and restore it when there is an orientation change on the device. This works for me in my chromecast enabled app. The code for saving/restoring my variable, so it survices orientation change is shown below:
protected void onSaveInstanceState(Bundle bundle) {
if (bundle!=null)
{
bundle.putBoolean("wasLaunched", wasLaunched);
}
super.onSaveInstanceState(bundle);
}
protected void onRestoreInstanceState(Bundle savedInstanceState) {
if (savedInstanceState!=null)
{
wasLaunched = savedInstanceState.getBoolean("wasLaunched");
}
super.onRestoreInstanceState(savedInstanceState);
};
Of course you can also put other stuff in your bundle that needs to survive an orientation change. I am not using the onDestroy override you describe there, nor is it mentioned in the google documentation I link to. But I use the teardown() method described in that document I link to for cleaning up, but this only happens when I close the connection, because I dont want to close the connection to the chromecast upon orientation change.
Here's a failing test:
#RunWith(RobolectricTestRunner.class)
public class FailTest {
#Test
public void heightAndWidth_shouldNotBeZero() {
TestActivity testActivity = Robolectric.buildActivity(TestActivity.class).create().resume().visible().get();
View contentView = testActivity.findViewById(69);
Assertions.assertThat(contentView.getWidth()).isNotZero();
Assertions.assertThat(contentView.getHeight()).isNotZero();
}
private static class TestActivity extends Activity {
#Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout contentView = new LinearLayout(this);
contentView.setId(69);
contentView.setLayoutParams(new LayoutParams(666, 666));
setContentView(contentView);
}
}
}
As you can see, I'm calling the visible() method on the ActivityController and driving the Activity lifecycle the correct way. Quoting the documentation:
Wait, What's This visible() Nonsense?
Turns out that in a real Android app, the view hierarchy of an
Activity is not attached to the Window until sometime after onCreate()
is called. Until this happens, the Activity's views do not report as
visible. This means you can't click on them (amongst other unexpected
behavior). The Activity's hierarchy is attached to the Window on a
device or emulator after onPostResume() on the Activity. Rather than
make assumptions about when the visibility should be updated,
Robolectric puts the power in the developer's hands when writing
tests.
So when do you call it? Whenever you're interacting with the views
inside the Activity. Methods like Robolectric.clickOn() require that
the view is visible and properly attached in order to function. You
should call visible() after create().
It seems as though I'm doing all I need to do. So why am I getting no height/width?
There is no layout pass in Robolectric, hence the view dimensions are always zero.
https://github.com/robolectric/robolectric/issues/819
I've been reading about AsyncTasks and Hanlders and Loopers but I still can't figure out where I'm going wrong in my code. I'm trying to run code that will look over a Tic Tac Toe grid and determine the best move for the computer. I want this code to run in the background 'cause it can take some time and then I can update the UI level with a textbox that says something like "I'm Thinking". I've tried this a bunch of different ways, none with success.
private class PostTask extends AsyncTask<String, Integer, String> {
private Board _b;
private Welcome.Player _opp;
private int _depth;
#Override
protected void onPreExecute() {
super.onPreExecute();
}
protected void SetVars(Board b, Player p, int depth){
_b = b;
_opp = p;
_depth = depth;
}
#Override
protected String doInBackground(String... params) {
Looper.prepare();
try{
_bestMove = _b.GetBestMove(_opp,_depth);
}
catch(Exception err){
_bestMove = -1;
}
return "All done";
}
#Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if(_bestMove == -1){
TextView tv = (TextView) findViewById(R.id.tv_Score);
tv.setText("Had and error, couldn't make a move.");
}
FollowUpComputerMove(this);
}
The above code will work for exactly 5 moves and then it crashes. When I watch in the debugger I see new theads being created named Thread<#> AsyncTask #1. Once I get to five of those AsyncTasks it goes back to try and grab the first AsyncTask and crashes. When it crashes I'm shown the ThreadPoolExecutor.class file.
I've also read that I shouldn't be using both the AsyncTask and the Looper objects together so I've tried taking the Loooper.prepare() statement out, but then my AsyncTask fails immediately with the error message:
Can't create handler inside thread that has not called Looper.prepare() - AsyncTask inside a dialog
I've read repeatedly that you shouldn't be trying to update the UI from an AsyncTask and that often the above error is because of that, but GetBestMove isn't updating the UI thread. When I trace through to see where the error comes, it fails when calling a constructor saying it can't find the class.
Can anyone point me in the right direction? My end goal is to use one main thread and only one background thread, and just keep re-using the background thread whenever the computer needs to make a move. I know that the recursive method GetBestMove works when I run this program in a single-thread manner. But the screen freezes for too long on some moves as the method is being run. Thank you so much.
-NifflerX
Apologies for answering my own question, but the issue I was facing had nothing to do with recursion. The class I was calling was extending the class Activity, and while trying to call that from an AsyncTask the program was erroring out. When I removed the extends Activity from the class definition it started working again. Sorry for the post.
-NifflerX
I'm completely new to Java and Android..
While using actionbarsherlock, I'm having a problem that I can't solve.
My app has around 8 Activities in total, and each of them has the SAME action bar,
using ABS.
So I was wondering if there is a way to keep the whole ABS part in 1 class,
and then call it in other activities when needed. Or else, I would have to write the same code in each activity to reach the same action bar, which really doesn't look correct.
I remember before using ABS, I had to use a separate row in XML then inflate it in other activities when needed. But this whole ABS project seems too vast for a newbie like me and I'm
really getting confused.. can any one help me clarify? Thanks in advance.
Use a base class which sets up the action bar.
public abstract class BaseActivity extends SherlockFragmentActivity {
#Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ActionBar ab = getSupportActionBar();
ab.whatever....
}
}
And then in your activities...
public class MySweetActivity extends BaseActivity {
#Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.whatever);
}
}
I am coding a javafx program and i need to create and use my own Stage based (Javafx.Stage) dialog box for showing messages and confirmations. I have written all the necessary code by now but i have a problem:
A dialog box must stop execution of rest of the code until a respond is given like "yes" or "no" or "retry". When i use my dialog box like "DialogBox.ShowMessage", a stage appears with message and buttons. But, as you may think, the rest of the code continues to execute. How can i get around this? When i create the stage, it must stop the other threads or the thread that it depends on. I have searched through internet and here, but i can not find exact solution. One idea is using "javafx.event.EventDispatcher" or "javafx.event.EventDispatchChain" but i couldn't figure out how to use them. And another idea is using "java.awt.EventQueue". And here is somthing that can help: I have a control of stage show and hide events and showing or hiding eventhandlers. I think som sort of thread queue can be used in one of these spesific sections.
I hope i clarified the situation enough. Briefly, ı need to manage threads while using another stage with my own code.
Thank you.
About execution suspending there is a Jira issue for it http://javafx-jira.kenai.com/browse/RT-19783.
As a workaround, I have no idea how to use EventDispatcher and EventDispatchChain to overcome this problem but you can send the EventHandlers as parameter. For instance,
public static void ShowMessage(final EventHandler<ActionEvent> okAction, final EventHandler<ActionEvent> cancelAction){
// Define and add buttons to the "view" and show message
btnOk.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent event) {
okAction.handle(null);
}
});
btnCancel.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent event) {
cancelAction.handle(null);
}
});
}
and use it as,
DialogBox.ShowMessage(
new EventHandler<ActionEvent>() {
#Override public void handle(ActionEvent arg0) {
// Do stuff when "ok" clicked.
},
new EventHandler<ActionEvent>() {
#Override public void handle(ActionEvent arg0) {
// Do stuff when "cancel" clicked.
});
I agree with this is a kind of "winding" way however.
Siteye hoş geldin ve kolay gelsin.