Develop Reference

How Do I Change the onClick() Behavior of a Button?

I'm really not sure where to go with this question because I don't necessarily know how possible it is. I'm still somewhat new to Android Studio and coding overall, but I know enough to be dangerous (perhaps that's my problem - I may be thinking too grandiose for a beginner) but this is what I'm looking to do.
I have a single page app with several buttons. I'm creating an app that is essentially a score counter for an NFL game, and the section where my choices for scoring methods looks as follows:
The above section is a Horizontal LinearLayout with 2 Nested LinearLayouts for the 4 scoring buttons on each side. The vertical toggle buttons are already set to change the text on the bottom button from Fieldgoal to Safety and vice-versa depending on the True/False of the toggle for each side.
teamOneToggleButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton compoundButton, boolean isChecked) {
if (isChecked) {
teamTwoToggleButton.setChecked(false);
teamOneSafety.setText("SAFETY");
teamTwoSafety.setText("FIELDGOAL");
} else {
teamTwoToggleButton.setChecked(true);
teamTwoSafety.setText("SAFETY");
teamOneSafety.setText("FIELDGOAL");
} } });
I have that part figured out, but since a Safety scores as 2 points and a fieldgoal scores as 3 points, I need to be able to change the onClick behavior.
I was hoping that there was a Java function that would let me set a new onClick activity much like I can setText, setColor, setAlignment, set(whatever), but I can't find anything close.
I've also played around with trying to define a string based on a .getText() from the button itself, but my application crashes every time.
If anyone has any ideas my full code is here on my Github.

If I understand your question you want to change the OnClickListener.
Currently you define it in your XML:
android:onClick="touchdownClickTeamOne" //This is not recommended practice, now you know.
You should do this in your Java code instead:
Button teamOneTouchDown = findViewById(R.id.team_one_off_td);
teamOneTouchDown.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// Do stuff
}
});
Now you know how to redefine any button's OnClickListener.
I'm not sure how to set it up in a way to programmatically do "this" if the button displays 'Safety' and do "that" if the button displays 'Fieldgoal'.
Currently you use this method:
public void fieldgoalClickTeamOne (View v) {
scoreTeamOne = scoreTeamOne + 3;
displayForTeamOne(scoreTeamOne);
}
We know the View v is a Button and that's Buttons are TextViews, so let's check the text:
public void fieldgoalClickTeamOne (View v) {
TextView textView = (TextView) v; // Could cast to Button, makes no difference here
if (textView.getText().toString().equals("SAFETY") {
// Do this
} else {
// Do that
}
}
PS I'm happy to see a beginner following coding conventions, your code is very easy to read. I have a few pointers.
First you should take a moment to learn the difference between if, else if, and else. Your AdapterView should only have on if statement and many else ifs.
Second you should take some time to learn about generic coding practices and/or reusability (this concept is a little tricky). Back to your AdapterViews, you only need one OnItemSelectedListener:
OnItemSelectedListener onItemSelectedListener = new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
final ImageView imageView;
if (adapterView.getId() == R.id.teamOneSpinner)
imageView = (ImageView) findViewById(R.id.team_one_spinner_team_logo);
else
imageView = (ImageView) findViewById(R.id.team_two_spinner_team_logo);
String s=((TextView)view).getText().toString();
if(s.equals("Arizona Cardinals"))
imageView.setImageResource(R.drawable.arizona_cardinals);
else if(s.equals("Atlanta Falcons"))
imageView.setImageResource(R.drawable.atlanta_falcons));
else if(s.equals("Baltimore Ravens"))
//etc, etc
Viola, one listener for multiple spinners. Set it like so:
teamOneSpinner.setOnItemSelectedListener(onItemSelectedListener);
teamTwoSpinner.setOnItemSelectedListener(onItemSelectedListener);
See how much writing I saved you! Many of your methods are repetitive, you can remove 80% of your code with these techniques.

Horizontal Scroll View working unexpectedly

I am trying to create a calculator. I am working in the latest Android Studio. Like in calculators, all new tokes(numbers, operators) should be shown in the right and if the field is larger than the display, it should scroll to the latest token. I have already browsed and found a way to do the same.
The code for the same is:
private void scrollRight() {
horizontalScrollView = (HorizontalScrollView) findViewById(R.id.horizontalScrollView);
ViewTreeObserver viewTreeObserver = horizontalScrollView.getViewTreeObserver();
viewTreeObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
#Override
public void onGlobalLayout() {
horizontalScrollView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
horizontalScrollView.scrollTo(entry.getWidth(), 0);
}
});
}
scrollRight is called by a onClick event which checks if a token is entered and calls this.
Everything is working perfectly, i.e. on every new token the scroll bar is scrolling to the end. But if I try to scroll to the beginning manually, it no longer works. After this every time a new token is pressed, the scroll bar first moves to the end and then back to the beginning.
The only option that remains is to restart the program. I tried debugging the OnGlobalLayout function but the debugger loses all frames while stepping out from the function, so it is difficult to know what exactly is making the scroll bar go to the beginning.
GIF to show the problem:
Please Help!

Try
horizontalScrollView.post(new Runnable() {
#Override
public void run() {
horizontalScrollView.fullScroll(View.FOCUS_RIGHT);
}
});
And call findViewById only once in onCreate.

Call a method when fragment is visible to user

I need execute a method when the fragment is visible (to the user).
Example:
I have 2 buttons (button 1 and button 2) ,
2 fragments(fragment 1 and fragment 2)
and the method loadImages() inside the class fragment 2.
when I press "button2" I want to replace fragment 1 by fragment 2
and then after the fragment 2 is visible (to the user) call loadImages().
I tried to use onResume() in the fragment class but it calls the method before the fragment is visible and it makes some delay to the transition.
I tried setUserVisibleHint() too and did not work.
A good example is the Instagram app. when you click on profile it loads the profile activity first and then import all the images.
I hope someone can help me. I will appreciate your help so much. Thank you.

Use the ViewTreeObserver callbacks:
#Override
public void onViewCreated(View v, Bundle savedInstanceState) {
super.onViewCreated(v, savedInstanceState);
final View view = v;
// Add a callback to be invoked when the view is drawn
view.getViewTreeObserver().addOnDrawListener(new ViewTreeObserver.OnDrawListener() {
#Override
public void onDraw() {
// Immediately detach the listener so it only is called once
view.getViewTreeObserver().removeOnDrawListener(this);
// You're visible! Do your stuff.
loadImages();
}
});
}

I'm a little confused by what you are trying to do. It sounds like the images are loading too fast for you... so does that mean that you have the images ready to display? And that is a bad thing?
My guess (and this is just a guess) is that Instagram does not have the profile pictures in memory, so they have to make an API call to retrieve them, which is why they show up on a delay. If the same is the case for you, consider starting an AsyncTask in the onResume method of the fragment. Do whatever loading you need to do for the images in the background, and then make the images appear in the onPostExecute callback on the main thread. Make sure you only start the task if the images are not already loaded.
However, if you already have the images loaded in memory, and you just want a delay before they appear to the user, then you can do a postDelayed method on Handler. Something like this:
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
loadImages();
}
}, 1000);
Edit
As kcoppock points out, the handler code is pretty bad. I meant it to be a quick example, but it is so wrong I should not have included it in the first place. A more complete answer would be:
private Handler handler;
public void onResume(){
super.onResume();
if(handler == null){
handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
loadImages();
}
}, 1000);
}
}
public void onDestroyView(){
super.onDestroyView();
handler.removeCallbacksAndMessages(null);
handler = null;
}

Use the onActivityCreated() callBck

Android animation only shows the last ArrayList element

I have 5 TextView fields that are meant to display a String and change the text every 10 seconds.
In order to make the change I have an AsyncTask that grabs the next 5 messages (doInBackground) and passes them to onPostExecute to be displayed in the UI.
When I display the messages without an animation, everything works perfectly fine and the messages rotate every 10 seconds via a new AsyncTask every time.
Now, when I attempt to use a simple fade-in/out animation on the TextViews, I can see all of them fading out and then back in with a placeholder string however the actual text messages I want to display are only displayed in the last TextView.
The AsyncTask is an inner-class of my MainActivity.java.
I have implemented an AnimationListener in MainActivity.java and due to that the objects below in onPostExecute ((TextView) mNextTextView & (String) mNextMessageToDisplay) are also declared as global variables in the main class.
Here's AsyncTask's onPostExecute:
protected void onPostExecute(List<String> mFiveMessagesToDisplay) {
super.onPostExecute(mFiveMessagesToDisplay);
for (int mTextViewCounter = 0; mTextViewCounter < 5; mTextViewCounter++) {
// Prepare the next TextView and message to use
mNextTextViewToUse = mTextViewArrayList.get(mTextViewCounter);
mNextMessageToDisplay = mFiveMessagesToDisplay.get(mTextViewCounter);
// Post and animate the message changes in the TextView
mNextTextViewToUse.startAnimation(mFadeOutAnimation);
}
}
And my AnimationListener:
private AnimationListener mFadeOutAnimListener = new AnimationListener() {
public void onAnimationStart(Animation animation) {}
public void onAnimationRepeat(Animation animation) {}
public void onAnimationEnd(Animation animation) {
mNextTextViewToUse.setVisibility(View.INVISIBLE);
mNextTextViewToUse.setText(mNextMessageToDisplay);
mNextTextViewToUse.setVisibility(View.VISIBLE);
mNextTextViewToUse.startAnimation(mFadeInAnimation);
}
}
As you can see, my setText() method is applied on the mNextTextViewToUse object with the contents of mNextMessageToDisplay, which are as mentioned before both global variables in the main class.
Both ArrayLists, the one containing the messages and the other containing the correct, I have iterated over both and printed the contents - everything is in its place.
Reminding again that if I use setText() with the same TextView and String objects under onPostExecute, everything works perfectly fine just without the animation.
Many thanks in advance!

Your issue is that the loops finishes by the time the animation ends, that's why you see only the last message.
Lets say that mNextTextViewToUse points to TextView1. You start a fade out animation for this TextView. By the time the animation ends, mNextTextViewToUse points to a different textView object (because the loop continue to run while the fade out animation is playing) so when onAnimationEnd is being called (by the fade out animation of TextView1) mNextTextView points to TextView5, and basically you are setting the text to this text view only.
There are several ways to solve this / implement what you need, personally I would probably create my own TextView class (extending TextView of course) and I'll add a public method called setTextAnimated (String newText). It will look something like:
public void setTextAnimated (String newText) {
mNextText = newText;
startAnimation(mFadeOutAnim);
}
where your onAnimationEnd callback will simple call setText(mNextText) and then will start fade-in animation.
Using this you will avoid another issue - that if you use the same animation object on different views - they will share the same timeline and interpolator. The result is that if View1 start a fade out animation that should take 200ms, and View 5 starts the same animation after 140ms, View5 will immediately "jump" to the same alpha value that View1 is.

I found the solution!
I ended up completely removing the FOR loop logic and using recursion which raises a Boolean flag once it has used all 5 available TextViews.
The method that gets the next TextView and String message and execute the animated setText():
public void updateTextView(List<String> mMessages) {
mNextTextViewToUse = mTextViewArrayList.get(mCurrentMessageIndex);
mNextMessageToDisplay = mMessages.get(mCurrentMessageIndex);
mNextTextViewToUse.startAnimation(mFadeOutAnimation);
if (mCurrentMessageIndex == 4) {
mStopMessageDisplayRepeat = true;
} else {
mCurrentMessageIndex++;
}
}
The Runnable that calls the method above, while the recursion stop Boolean is false:
public Runnable mUpdateTextViewRunnable = new Runnable() {
final static int POSTDELAY_INTERVAL = 600;
#Override
public void run() {
updateTextView(mFiveMessages);
if (! mStopMessageDisplayRepeat) {
mMessageDisplayRepeatHandler.postDelayed(mUpdateTextViewRunnable, POSTDELAY_INTERVAL);
}
}
};
Execute the Runnable:
public void startTextViewRunnableRepeat() {
mUpdateTextViewRunnable.run();
}
This is how my AsyncTask's onPostExecute() looks like:
#Override
protected void onPostExecute(List<String> mFiveMessagesToDisplay) {
super.onPostExecute(mFiveMessagesToDisplay);
mFiveMessages = mFiveMessagesToDisplay;
startTextViewRunnableRepeat();
}

Android execute when multiple tasks are done

I'm working on an app that downloads information from my server after an NFC card has been detected.
When a card is detected, I start
- an Asynctask to download some data from my server
- an animation of a popup appearing on the screen
After both the asynctask and the animation are done, I want to start a method that displays the downloaded data in the popup.
What is the correct way to trigger this new method? It can only start when both conditions are met.

In the async task you use to download data add the onPostExecute method to remove the animation popup and show the downloaded data as well like this :
protected void onPostExecute(Long result) {
//put code to disable animation popup
//code for displaying downloaded data popup
}
For more info check out http://developer.android.com/reference/android/os/AsyncTask.html

you Animation object has the method setAnimationLister. It takes as parameter a Class Object that implements the interface Animation.AnimationListener . This interface requires three methods to be implemented:
#Override
public void onAnimationStart(Animation animation) {
}
#Override
public void onAnimationEnd(Animation animation) {
}
#Override
public void onAnimationRepeat(Animation animation) {
}
The onAnimationEnd is triggered when the animation ends. If I have not misunderstood you, this is what you need
EDIT:
you could have two booleans value, boolean animationFinished = false, downloadFinished = false; When onPostExecute is called put downloadFinished to true and call yourMethod.
When onAnimationEnd is triggered animationFinished = true and call yourMethod. yourMethod should start like:
if (!animationFinished || !downloadFinished)
return;