ok, brand new to android studio and kotlin (not programming in general)
installed Android Studio, set up a couple of hardware profiles (and enabled dev mode).
Here is my issue:
Simple app, 'every time you click the button, the number above doubles.'
in the first_fragment.xml file, I rename the ID to 'textDisplayedValue'
in the MainActivity.kt file, I create 2 variables originalValue and newValue.
When I try to set the originalValue to the value in textDisplayedValue, I get an 'Unresolved reference' error
Code
Log
In addition, when I launch the debugger, the 'ok' button is disabled. I assume that is due to the code errors so correct me if I am wrong.
Thanks in advance for the help.
Layout File
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".FirstFragment">
<TextView
android:id="#+id/textDisplayedValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="1"
android:textAppearance="#style/TextAppearance.AppCompat.Large"
app:layout_constraintBottom_toTopOf="#id/button_first"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/button_first"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/next"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#id/textDisplayedValue" />
</androidx.constraintlayout.widget.ConstraintLayout>
binding.fab.setOnClickListener { view ->
val originalValue = 1
val newValue = originalValue * 2
textDisplayedValue = newValue.toString()
Snackbar.make(view, "Value $originalValue changed to $newValue", Snackbar.LENGTH_LONG).show()
}
Try this
Comment the not working code
From the toolbar select
A. Build -> clean project
B. After that Build -> rebuild project
Uncomment the not working code and do this
val originalValue = binding.textDisplayedValue. text() .toString().toLong()
val newValue = originalValue * 2
I have quite a complex problem to do with Android views. I am creating a paint application, and I have two views: a transparent background view and the pixel art board.
For both views, I want the height and width to be calculated off of the distance between view A and B:
Instead of calculating the distance between these two views, I simply 'constraint' a view in the middle like so, and then extract its height by using its measuredHeight property (and yes, you could also calculate the distance between view A and B in the code, but my problem still remains when I try that):
Now, here's the XML code:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/fragment_background_color_daynight"
tools:context=".activities.canvas.CanvasActivity">
<View
android:id="#+id/activityCanvas_topView"
android:layout_width="match_parent"
android:layout_height="90dp"
android:background="#color/fragment_background_color_daynight"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<com.therealbluepandabear.pixapencil.customviews.colorswitcherview.ColorSwitcherView
android:id="#+id/activityCanvas_colorSwitcherView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginEnd="16dp"
app:isPrimarySelected="false"
app:layout_constraintBottom_toBottomOf="#+id/activityCanvas_colorPickerRecyclerView"
app:layout_constraintEnd_toEndOf="#+id/activityCanvas_topView"
app:layout_constraintTop_toTopOf="#+id/activityCanvas_colorPickerRecyclerView"
app:primaryColor="#android:color/holo_green_dark"
app:secondaryColor="#color/black" />
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/activityCanvas_colorPickerRecyclerView"
android:layout_width="0dp"
android:layout_height="50dp"
android:layout_marginStart="16dp"
android:layout_marginEnd="16dp"
android:orientation="horizontal"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
app:layout_constraintBottom_toBottomOf="#+id/activityCanvas_topView"
app:layout_constraintEnd_toStartOf="#+id/activityCanvas_colorSwitcherView"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="#+id/activityCanvas_primaryFragmentHost"
tools:listitem="#layout/color_picker_layout" />
<FrameLayout
android:id="#+id/activityCanvas_distanceContainer"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="#+id/activityCanvas_tabLayout"
app:layout_constraintEnd_toEndOf="#+id/activityCanvas_primaryFragmentHost"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/activityCanvas_topView" />
<com.google.android.material.card.MaterialCardView
android:id="#+id/fragmentOuterCanvas_canvasFragmentHostCardViewParent"
style="#style/activityCanvas_canvasFragmentHostCardViewParent_style"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:elevation="1dp"
app:layout_constraintBottom_toTopOf="#+id/activityCanvas_tabLayout"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/activityCanvas_topView">
<!-- At runtime, the width and height will be calculated -->
<com.therealbluepandabear.pixapencil.customviews.transparentbackgroundview.TransparentBackgroundView
android:id="#+id/activityCanvas_transparentBackgroundView"
android:layout_width="0dp"
android:layout_height="0dp" />
</com.google.android.material.card.MaterialCardView>
<com.google.android.material.tabs.TabLayout
android:id="#+id/activityCanvas_tabLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:tabStripEnabled="false"
app:layout_constraintBottom_toTopOf="#+id/activityCanvas_viewPager2"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent">
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/activityCanvas_tab_tools_str" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/activityCanvas_tab_filters_str" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/activityCanvas_tab_color_palettes_str" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/activityCanvas_tab_brushes_str" />
</com.google.android.material.tabs.TabLayout>
<androidx.viewpager2.widget.ViewPager2
android:id="#+id/activityCanvas_viewPager2"
android:layout_width="0dp"
android:layout_height="110dp"
app:layout_constraintBottom_toBottomOf="#+id/activityCanvas_primaryFragmentHost"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:id="#+id/activityCanvas_coordinatorLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent" />
<FrameLayout
android:id="#+id/activityCanvas_primaryFragmentHost"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
Of course, when it comes to calculating, I thought it would be best practise to utilize AndroidX's OneShotPreDrawListener, like so:
OneShotPreDrawListener.add(binding.root) {
binding.activityCanvasTransparentBackgroundView!!.setViewWidth(binding.activityCanvasDistanceContainer!!.measuredHeight)
binding.activityCanvasTransparentBackgroundView!!.setViewHeight(binding.activityCanvasDistanceContainer!!.measuredHeight)
}
Now, for some reason, the result looks like so:
Why is this the case!
I did some debugging, and when I log the height of view C, I get the following:
This is wrong. So, as an experiment, I added a GlobalLayoutListener to detect when exactly the view's constraints get resolved:
binding.activityCanvasDistanceContainer?.viewTreeObserver?.addOnGlobalLayoutListener( object : ViewTreeObserver.OnGlobalLayoutListener {
override fun onGlobalLayout() {
Log.d("M_LOG", binding.activityCanvasDistanceContainer?.measuredHeight.toString())
}
})
Result:
So, after the first couple of times it's 438, until after the 4th/5th time it shoots up to 1000.
I am really confused why this is happening, as I want to run the event when the constraints have been fully resolved and calculated, but using OneShotPreDrawListener (or any other alternative) is just running the event when the view has been drawn, but not yet when it has been positioned properly.
I am confused what to do. How can I run an event when the view's constraints have been fully calculated?
Edit for Chetichamp:
I have debugged this and I think I can reproduce this error and tell you in what scenario it occurs and in which scenario it does not.
Basically in my app, prior to activity creation, I have a fragment called NewProjectFragment, which looks like so:
Here's the code for when the 'Done' button is pressed:
binding.fragmentNewCanvasDoneButton.setOnClickListener {
checkForTitleError()
checkForWidthError()
checkForHeightError()
if (!invalidTitle && !invalidWidth && !invalidHeight) {
try {
val title =
binding.fragmentNewCanvasProjectTitleTextInputEditText.text.toString()
val widthValue: Int =
binding.fragmentNewCanvasWidthTextInputEditText.text.toString().toInt()
val heightValue: Int =
binding.fragmentNewCanvasHeightTextInputEditText.text.toString().toInt()
if (widthValue + heightValue >= 2000 && (requireActivity() as MainActivity).showLargeCanvasSizeWarning) {
val frameLayout: FrameLayout =
this#setOnClickListeners.activity?.layoutInflater?.inflate(
R.layout.dont_show_large_canvas_warning_again_checkbox,
requireView().findViewById(android.R.id.content),
false
)
as FrameLayout
val checkBox = frameLayout.getChildAt(0) as MaterialCheckBox
requireActivity().showDialog(
getString(R.string.generic_warning_in_code_str),
getString(R.string.dialog_large_canvas_warning_text_in_code_str),
getString(R.string.dialog_large_canvas_warning_positive_button_text_in_code_str),
{ _, _ ->
if (checkBox.isChecked) {
(requireActivity() as MainActivity).showLargeCanvasSizeWarning =
false
with((requireActivity() as MainActivity).sharedPreferenceObject.edit()) {
putBoolean(
StringConstants.Identifiers.SHARED_PREFERENCE_SHOW_LARGE_CANVAS_SIZE_WARNING_IDENTIFIER,
(requireActivity() as MainActivity).showLargeCanvasSizeWarning
)
apply()
}
}
caller.onDoneButtonPressed(
title,
widthValue,
heightValue,
paramSpotLightInProgress
)
},
getString(R.string.dialog_unsaved_changes_negative_button_text_in_code_str),
{ _, _ ->
},
frameLayout
)
} else {
caller.onDoneButtonPressed(
title,
widthValue,
heightValue,
paramSpotLightInProgress
)
}
} catch (exception: Exception) {
HapticFeedbackWrapper.performHapticFeedback(binding.fragmentNewCanvasDoneButton)
}
} else {
HapticFeedbackWrapper.performHapticFeedback(binding.fragmentNewCanvasDoneButton)
}
}
As you can see, it has a listener, so the code for the listener, which is in MainActivity, is like so (maybe this is causing the issue? and I just don't need a listener like this? I don't know if you think this is why I get the issue):
fun MainActivity.extendedOnDoneButtonPressed(projectTitle: String, width: Int, height: Int, spotLightInProgress: Boolean) {
startActivity(
Intent(this, CanvasActivity::class.java)
.putExtra(StringConstants.Extras.PROJECT_TITLE_EXTRA, projectTitle)
.putExtra(StringConstants.Extras.WIDTH_EXTRA, width)
.putExtra(StringConstants.Extras.HEIGHT_EXTRA, height)
.putExtra(StringConstants.Extras.SPOTLIGHT_IN_PROGRESS_EXTRA, spotLightInProgress)
)
}
Now, what I come to the conclusion is that all of this extra work is causing a delay, because when you simply tap on a pre-existing project, we can see that the intent is much simpler:
fun MainActivity.extendedOnCreationTapped(param: PixelArt) {
startActivity(
Intent(this, CanvasActivity::class.java)
.putExtra(StringConstants.Extras.INDEX_EXTRA, pixelArtData.indexOf(param))
.putExtra(StringConstants.Extras.PROJECT_TITLE_EXTRA, param.title))
}
With a simple intent like so, the problem doesn't get reproduced, and it sizes properly.
What I relaized is that the work done in NewProject fragment is causing a delay, and when I simply scrap out the work and perfom a simple intent, the problem is 'fixed'. I don't know how to fix this but hopefully it can help with finding a solution.
Debugging even further
When I debug the issue even further, I notice something strange. The measuredHeight of the root layout jumps up by one thousand:
This is not observed when the creation is tapped with the simple intent. I am lost for words as to how strange this bug is, I've never seen this in my life.
There is something going on with your code that is touching your views that is causing the multiple layouts. Without that code being posted, it is impossible to say what.
To help you with debugging, set the one shot to the following:
OneShotPreDrawListener.add(binding.root) {
Log.d("Applog", "OneShot")
binding.activityCanvasTransparentBackgroundView.layoutParams.width =
binding.activityCanvasDistanceContainer.measuredWidth
binding.activityCanvasTransparentBackgroundView.layoutParams.height =
binding.activityCanvasDistanceContainer.measuredHeight
binding.activityCanvasTransparentBackgroundView.requestLayout()
}
In my test, when placing this in the onCreateView() function of a fragment, "OneShot" is logged just once and the size of the view is adjusted as you say it should be. (btw, requestLayout() was required in this test.)
I would take a look at any other code that touches your views to see if something else is triggering the multiple calls: maybe setWidth() or setHeight().
I will add that I have noticed in the past that ConstraintLayout will call the global layout listener multiple times. Usually, I would say, the listener is removed on the first call, so this behavior would not be noticed.
Instead of the global layout listener or the predraw listener, you could try a layout listener:
binding.root.doOnLayout {
// Your code here
}
or
binding.root.doOnNextLayout {
// Your code here
}
doOnNextLayout is guaranteed to be called only once, while doOnLayout may be called multiple times.
Wow guys.
I finally found a solution, after 12 hours of nonstop debugging, almost going clinically insane, and logging and destroying my codebase.
I realized that the keyboard from the NewProjectFragment was cutting the view, causing the bug. Holy moly... I am ecstatic that I finally found why this is happening but at the same time shocked how I didn't discover this before!
The solution was to add the following to the activity:
<activity
android:name="com.therealbluepandabear.pixapencil.activities.canvas.CanvasActivity"
android:windowSoftInputMode="stateHidden" // this
android:hardwareAccelerated="true"
android:exported="false" />
Prior to this, the windowSoftInputMode was adjustResize -- causing the bug.
I have 2 button and 1 textview in my layout. I had just trained, but saw some bugs. When users starts the cronometer they can unlimited click on the start button how can i fix it ?
I'm really newbie in the android development. Can you give advices for me, while i was watching my udemy lesson, i could catch the codes and basics. After that, when i try to build some basic projects for improve my skills, it gets hard. I have many syntax errors. I know what to do, but I'm confusing the order.
What can i do to do get better ?
main_activity.kt
var runnable : Runnable = Runnable { }
var handler : Handler = Handler( )
var number = 0
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//Cronometer have bugs
// User can click the start button for unlimited
}
fun startTime(view: View) {
runnable = object : Runnable {
override fun run() {
number++
textView2.text = "$number"
handler.postDelayed(this,1000)
}
}
handler.post(runnable)
}
fun stopTime(view:View) {
handler.removeCallbacks(runnable)
}
}
```
activity_main.xml
```<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="#+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="90dp"
android:onClick="startTime"
android:text="START"
app:layout_constraintBaseline_toBaselineOf="#+id/button4"
app:layout_constraintStart_toStartOf="parent" />
<Button
android:id="#+id/button4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="49dp"
android:layout_marginTop="88dp"
android:onClick="stopTime"
android:text="STOP"
app:layout_constraintStart_toEndOf="#+id/button3"
app:layout_constraintTop_toBottomOf="#+id/textView2" />
<TextView
android:id="#+id/textView2"
android:layout_width="180dp"
android:layout_height="40dp"
android:layout_marginTop="109dp"
android:gravity="center"
android:text="0"
android:textSize="24sp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
```
Your question is not clear. If you want to prevent the user from clicking on the buttons more than once, you could disable them as soon as a click event is detected. For example, in your startTime method you could add
(view as Button).enabled = false
You need to cast your view to Button because the enabled property is not present in the View class (it comes from the TextView class actually, but Button inherits from it).
Then, you need to enable it again when you click on the stop button. You will need to retrieve a reference to your start button somehow, so you can access and enable it from your stopTime method. I'll leave that as an exercise for you ;).
This seems to work on Android 6 Marshmallow device Xiaomi Redmi 3S.
Seems like an emulator problem, but it isn't really misbehaving in any other sense.
I am a beginner in Android development and don't know much.
I have already confirmed that notifications for my app is ON.
Specs:
API Level : Android 4.4 (KitKat)
Android Studio version: 3.6.4
Emulator: Pixel XL API 28
All I attempted to do was a toast message would pop up telling how many times the button has been clicked.
Here's the MainActivity.kt:
class MainActivity : AppCompatActivity() {
private var greetingCount = 0
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
btnToastMessage.setOnClickListener {
val suffix = when (++greetingCount) {
1 -> "st"
2 -> "nd"
3 -> "rd"
else -> "th"
}
val greetingMsg = "Welcome for the $greetingCount$suffix time(s)!"
Toast.makeText(this#MainActivity, greetingMsg, Toast.LENGTH_LONG).show()
Log.i(".MainActivity", "Clicked Button")
}
}
}
And here's the activity_main.xml file:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:padding="30dp">
<TextView
android:id="#+id/txtHelloWorld"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.314" />
<Button
android:id="#+id/btnToastMessage"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Click Me!"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.49"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/txtHelloWorld"
app:layout_constraintVertical_bias="0.49" />
</androidx.constraintlayout.widget.ConstraintLayout>
Didn't know this could be done, but wiping data and cold-booting the device fixed it.
Following are the steps you can follow (because I too got stuck):
Try restarting and cleaning your emulator device.
OR
You can run the app on your physical (android) device by setting the USB Debugging
option to True.
ConstraintLayout intermittently fails to layout correctly when a view is set from GONE to VISIBLE shortly after an activity is resumed:
<android.support.constraint.ConstraintLayout
android:id="#+id/constraint_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<TextView
android:id="#+id/text1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<TextView
android:id="#+id/text2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintLeft_toRightOf="#id/text1"
app:layout_constraintTop_toTopOf="parent"/>
</android.support.constraint.ConstraintLayout>
override fun onResume() {
super.onResume()
text1.text = ""
text1.visibility = View.GONE
text2.text = ""
text2.visibility = View.GONE
text1.postDelayed({
text1.text = "Hello"
text1.visibility = View.VISIBLE
text2.text = "World"
text2.visibility = View.VISIBLE
}, 100
)
}
Full source code here
Instrumenting the TextView class reveals that the TextView instances are measured correctly but their width is set to 0 when they are laid out.
I wonder if the ConstraintLayout LinearSystem is non-deterministic. Are there maps that are iterated over where the iteration order is undefined? (I've seen this with Cassowary)
I'm looking to your statement in github page:
ConstraintLayout intermittently fails to layout correctly when a view is set from GONE to VISIBLE shortly after an activity is resumed
I've checked out your project and changed 100ms to 1000ms.
Here's the output:
It seems to me, that you expect that the moment you perform textview.setVisibility(View.GONE) you expect the view to be not visible. That's not the way android works. You are merely posting an event to the MessageQueue that would be handled later by Looper, and this 100ms is not enough for human eye to see those changes happening.
This was a bug in the ConstraintLayout fixed in constraint-layout:1.1.0-beta2 https://issuetracker.google.com/issues/65613481