Develop Reference

android kotlin click listener loses its "click methods" after some time

Hi I'm implementing click listeners in the following way but after some time the methods and variables inside the listener's closure get the wrong values or something. Let me explain the implementation of the listener a little better a for loop creates the listener for a set of image views then later in the program the for loop is called a second time and it resets the listener methods and variables to different values. Everything works great for about 30 minutes but then for some reason, the listener's methods and variables start having the wrong values. Has anybody ever heard of this behavior or can tell me where I've gone wrong with the code? Keep in mind that the listener I'm about to paste here is just a small piece of a 1014 line class. I'm hoping somebody can spot How I'm implementing the listener wrongly and can give me some advice on how to "reset" the listener so that it's variables and values stay over time. Hopefully you can read the code without putting it in an editor but feel free to copy it for readability's sake Here is the code for the image view listener with comments.
//image views are held in an array
//set an image view in its imageview container
imgArr0[slotId1].invalidate()
imgArr0[slotId1].setImageDrawable(null)
//drw is not defined in this example
imgArr0[slotId1].setImageDrawable(drw)
/*if video or image id is set to image then set a listener for the image
*/
/*slotId1 is not defined in this example but it is simply a counter to iterate over the ImageView array
*/
if (videoOrImageId0[slotId1] == "image") {
//null any listeners that might be attached to the image view
imgArr0[slotId1].setOnClickListener(null)
//set or reset the listener
imgArr0[slotId1].setOnClickListener() {
`enter code here`//if the current config is portrait then set a new image image
if (currentConfig0 == "portrait0") {
act0.lrgImage0.invalidate()
act0.lrgImage0.setImageDrawable(null)
/*drw is not defined in this example but works fine in the production script
*/
act0.lrgImage0.setImageDrawable(drw)
}
--calmchess
ccc tv application with problem.
(https://i.stack.imgur.com/PjdbN.jpg)![enter image description here](https://i.stack.imgur.com/FaMnc.

I was able to partially solve this question by destroying all the image views and their associated click listeners then rebuilding those... However I don't consider this issue completely solved so if anybody can provide a better solution I'd love to hear it because rebuilding the images every few minutes has to be using a lot of unnecessary hardware resources.
--calmchess

TextView.setMaxLines not working?

In my app I have a screen where I display some text and then a photo. The text is variable in length (sometimes none at all, sometimes a lot), so I wanted to have it set up so the text never takes up more than a few lines (but can be scrolled) leaving enough room for the image below.
My view component for this part is created programatically, and I've adjusted the code to have the following (currently in my text-setting method, but the same thing happens if it's in the initial view-create code)
public void SetDescription(String description)
{
mTxtDescription.setText(Html.fromHtml(description));
mTxtDescription.setClickable(true);
mTxtDescription.setMaxLines(5);
mTxtDescription.setLines(5); //this makes no difference either!
mTxtDescription.setSingleLine(false);
mTxtDescription.setScrollbarFadingEnabled(true);
mTxtDescription.setScrollBarStyle(VERTICAL);
mTxtDescription.setMovementMethod(ScrollingMovementMethod.getInstance());
mTxtDescription.invalidate(); //adding this made no difference...
}
However it doesn't work- long text still fills the whole screen and the image has vanished due to being pushed down to a height of 0. How can I get the text to never be more than 5 lines?

Try removing the call to setSingleLine. And use setInputType(InputType.TYPE_TEXT_FLAG_MULTI_LINE). It'd also put this call before the setMaxLines and setLines call to be sure.
Note: setLines overrides the settings of setMaxLines and setMinLines.
The TextView has many issues surrounding the various calls to how it should display multiple, ellipses, etc.

The setSingleLine(false) seemes to reset the setMaxLines command. Try to move the setSingleLine command before the setText. That worked for me.

The below code is working fine for me
txt = (TextView)findViewById(R.id.textview);
txt.setMaxLines(5);
txt.setMovementMethod(new ScrollingMovementMethod());
txt.setScrollContainer(true);
txt.setText("Example Text");
txt.setTextColor(Color.WHITE);
txt.setScrollbarFadingEnabled(true);
in xml inside textview
android:scrollbars="vertical"

Simple TextView.setText causes 40% CPU Usage

Running my application causes ~40% CPU usage on my Phone:
final String position = String.format("%02d:%02d:%02d", time.getHours(), time.getMinutes(),
time.getSeconds());
getActivity().runOnUiThread(new Runnable() {
#Override
public void run() {
c.mTxtPosition.setText(position);
...
By commenting out the setText method the CPU Usage drops to the expected level of ~4%. The method is invoked every second and does refresh ImageViews, CustomViews ... without causing the same load excess.
Besides the CPU Usage dalvik constantly reports garbage collecting of about 10-1000 objects just by calling setText().
Creating a tracefile like this:
Debug.startMethodTracing("setText");
c.mTxtPosition.setText(position);
Debug.stopMethodTracing();
traceview lists the following methods as Top 5 by their respective exclusive CPU%:
ViewParent.invalidateChildInParent(16%)
View.requestLayout(11%)
ViewGroup.invalidateChild(9%)
TextView.setText(7%)
toplevel(6%)
Has anybody an explanation for this?

I noticed this myself a while ago, I think the problem is that every time you call setText, the size of the textbox can change, thus requiring the entire screen to go through relayout (expensive).
I haven't tried this myself yet, but if your textbox is simple and can be made to be a relatively fixed size, maybe try to subclass TextView and create a view that does not resize itself on setText, but rather just draws whatever it can into the existing area? That would save a lot of time.
Perhaps theres already a flag to setText that can make it do this, but I'm not aware of it, though I haven't searched closely.

In my case, I update a TextView from touch event, which cause a lot of updating The solution was to change the TextView layout_width & layout_height to fixed sized.

some possible improvements :
try using a handler which updates the textview every 0.5 seconds instead of a thread that does it.
make the runnable a final constant object instead of craeting a new one every second.
consider checking that the time has changed (newTimeInMs-LastPublishedTimeInMs>=1000) before telling the textview to update itself.
instead of String.format , try using StringBuilder . however , you won't enjoy the locale solution that the String.format gives (for example , for arabic digits) .

In my case it was this property of TextView:
android:ellipsize="marquee"
Removing it speeded up setting text.

If you look at the source code of setText method you can see that it does a lot of heavy lifting - there is measuring, drawing and object allocations, all of which run on the main thread.
You can use the new PrecomputedText API in order to do all of this on the background thread and make setText faster.
You can use the following working example using kotlin & coroutines
private fun TextView.setTextAsync(text: String) {
val textView = this
lifecycleScope.launch {
val params = TextViewCompat.getTextMetricsParams(textView)
val precomputedText = withContext(Dispatchers.Default) {
PrecomputedTextCompat.create(text, params)
}
TextViewCompat.setPrecomputedText(textView, precomputedText)
}
}
For more details you can read an article about it on my blog
https://androidexplained.github.io/android/ui/2020/10/21/improving-textview-settext-performance.html

java Runtime exception

TextView txtOtherMatches = (TextView) dialog.findViewById(R.id.txtOtherMatches);
txtOtherMatches.setText("Other Matches");
i m getting this error while running application and i m just assigning simple text to Textview at run time .....
java.lang.NullPointerException

Make sure your TextView in the xml has exactly the same id: android:id="#+id/txtOtherMatches"
Check that you don't have more than one res/layout folder (e.g., layout-normal, layout-large or layout-land) and, if you do, make sure that your TextView is present in the layourt corresponding to your device/emulator
Check that it was added to the current View (most probably, through some ViewGroup)
If everything else fails, clean the Eclipse project and rebuild

txtOtherMatches is probably null because it doesn't exist in the current view.When you use findViewById the view must be in the "contentview" you've set with setContentView, or added later tot the view. You can't find any "random" view that has an ID somewhere, it must actually be "present" in your current view.
If the view is NOT in the xml you're using already, but somewhere else in one of your xmls, you must use an inflater to get the View, and add it with View.add()

It would be helpfull if you provide a few more lines before that one.
But my guess is Nanne is right.
Try to add a safety check:
(this wouldn't change the code flow)
if(txtOtherMatches == null) {
throw new NullPointerException("darn, the R.id.txtOtherMatches is not in the dialog")
}
(on the other hand Nanne mistakenly mentions 'current view' while I'm sure he meant the 'dialog' view.
Put some more meat if you need further assistance ;)

TextView.setText() followed by TextView.invalidate() doesn't update text in view

I have no idea why this doesn't work. The TextView is defined from an tag in the view. The base TextView doesn't have text set and I want to set it in the View on display.
I have tried placing the below in onCreate and onStart but it doesn't seem to work. The last two lines are just for debugging. I can verify that the header does get the text. The thing is, the TextView doesn't actually get updated. Any ideas?
TextView header=(TextView) findViewById(R.id.acheader);
header.setText(R.string.accounts);
header.invalidate();
header=(TextView) findViewById(R.id.acheader);
String blah=(String) header.getText();

Try again removing the text in 4th line
header=(TextView) findViewById(R.id.acheader);

header.invalidate() is not needed.
Instead of String blah = (String) header.getText() try
String blah = heager.getText().toString();
And why are you verifying a "setText()" on text view using code? Why can't you check the
actual output?
The above code might not work the way you are trying to use it, because the redraw of text view is handled by the framework and generally it tries to group item updates (Dirty rectangles to be specific) and update them all at once. It may do it well after your function exits, Try to validate visually, thats the best way.