I've already searched for similar threads, but I couldn't find any solution to my problem.
Here is my main Activity:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mt);
ScrollView sv = new ScrollView(this);
LinearLayout ll = new LinearLayout(this);
ll.setOrientation(LinearLayout.VERTICAL);
sv.addView(ll);
RelativeLayout layout = (RelativeLayout)findViewById(R.layout.activity_mt);
//layout.addView(ll);
layout.addView(sv);
setContentView(layout);
I also added id to my xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:id="#+id/activity_mt"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context=".MtActivity" >
But whenever I try to run my app, it crashes. Where is the problem?
Change
RelativeLayout layout = (RelativeLayout)findViewById(R.layout.activity_mt)
with
RelativeLayout layout = (RelativeLayout)findViewById(R.id.activity_mt)
findViewById looks up for an value into R.id, not in R.layout
You got confused with R.id.activity_mt and R.layout.activity_mtbecause you named them same. Just replace the line
RelativeLayout layout = (RelativeLayout)findViewById(R.layout.activity_mt)
with
RelativeLayout layout = (RelativeLayout)findViewById(R.id.activity_mt)
Previously, it was storing null in layout, that is why is was throwing nullpointerexception. But after doing it, everything will be cool.
Related
I'm following the accepted answer to this question:
ArrayList<EditText> myEditTextList = new ArrayList<EditText>();
for( int i = 0; i < myLayout.getChildCount(); i++ )
if( myLayout.getChildAt( i ) instanceof EditText )
myEditTextList.add( (EditText) myLayout.getChildAt( i ) );
How do you get myLayout, what does it actually represent? In my app I define linear_layout in activitymain.xml but can't seem to get it in MainActivity.java (I tried using R but it didn't work). I'm new to Android development and could really use some high level guidance.
Let Linear Layout be the root of your xml:
<LinearLayout android:id="#+id/my_layout" >
//your views goes here
</LinearLayout>
Then in your Activity you'll have to initialize the view once your layout gets inflated like this
LinearLayout myLayout = (LinearLayout) findViewById(R.id.my_layout);
Hope this helps.
You need to use myLayout as your root layout in your layout.xml file
the myLayout maybe a FrameLayout, LinearLayout, RelativeLayout or ConstraintLayout layout
SAMPLE CODE
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/myLayout"
android:orientation="vertical">
<!-- add your view here-->
</LinearLayout>
Now do findViewById in side your actvity
public class MyActivity extends AppCompatActivity {
LinearLayout myLayout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
myLayout = findViewById(R.id.myLayout);
}
}
You can try below code to get a reference of your LinearLayout in Java code.
LinearLayout myLayout=(LinearLayout) findViewById(R.id.your_linear_layout_id)
assuming your actiivtymain.xml looks like this
<?xml version="1.0" encoding="utf-8"?>
<SomeLayout
android:id="#+id/some_id"
...>
<EditText
...
/>
<EditText
...
/>
.
.
.
</SomeLayout>
mLayout you are referring is the parent of all your edit texts. It may not be the root of your layout but if you want to get a Java instance of it, you need to give it an id. and get the instance by using the code given by #Nilesh Rathod. One more thing to remember is to call the method findViewById(R.id.my_layout); only after setContentView(R.layout.activitymain);.
I've looked over several SO questions and a couple tutorials.
I have tracked the problem, I think, to the context. The solution appears to possibly be editing my xml file, but nothing I find regarding this helps to remedy my problem.
In my main activity with onCreate I try to acquire a reference of my only text view object. This returns a null reference. How do I obtain a valid reference to the textview which I manually placed? I don't know if I have even added this text view correctly; should I have added it via code or something?
Here are both my onCreate and XML.
protected void onCreate(Bundle savedInstanceState) {
Log.i("[DEBUG]", "main activity - started");
super.onCreate(savedInstanceState);
s_textView = (TextView)findViewById(R.id.textView);
m_GLView = new MyGLSurfaceView(this);
setContentView(m_GLView);
s_textView = (TextView)findViewById(R.id.textView);
Log.i("[DEBUG]", "main activity - finished");
}
I have also tried the following line s_textView = (TextView)m_GLView.findViewById(R.id.textView);
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity">
<merge>
<com.example.a2_1039652.a2_cooper.MyGLSurfaceView />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/textView"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"
android:textSize="20dp" />
</merge>
</RelativeLayout>
I only have added this <com.example.a2_1039652.a2_cooper.MyGLSurfaceView /> line because it was the solution for a similar problem. It hasn't appeared to change anything about my application.
try this
protected void onCreate(Bundle savedInstanceState) {
Log.i("[DEBUG]", "main activity - started");
super.onCreate(savedInstanceState);
m_GLView = new MyGLSurfaceView(this);
setContentView(m_GLView);
RelativeLayout layout = (RelativeLayout)LayoutInflater.from(this).inflate(R.layout.activity_main,null);
s_textView = (TextView) layout.findViewById(R.id.textView);
Log.i("[DEBUG]", "main activity - finished");
}
So after a few hours of rest I was able to come up with the correct string of words to find a SO question with a solution. The solution was found in the question itself found here: Drawing Android UI on top of GLSurfaceView
I am unclear of whether there is an answer to my question. However for an end result I needed a text view, and now I have one which I can set text on. This is how I did it.
I removed the text view I manually placed. Here is the subsequent activity_main.xml file:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity">
</RelativeLayout>
It is unclear to me how much of that configuration data is needed. Though I removed as much as I could find to be removable.
Next I, for the most part, just took the code line for line from that other SO question. This is what I have for my onCreate method.
protected void onCreate(Bundle savedInstanceState) {
Log.i("[DEBUG]", "main activity - started");
super.onCreate(savedInstanceState);
m_GLView = new MyGLSurfaceView(this);
rl = new RelativeLayout(this);
rl.addView(m_GLView);
tv = new TextView(this);
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
lp.addRule(RelativeLayout.CENTER_HORIZONTAL);
lp.addRule(RelativeLayout.CENTER_VERTICAL);
tv.setLayoutParams(lp);
tv.setBackgroundColor(0xFFFFFFFF);
rl.addView(tv);
s_textView = tv;
setContentView(rl);
Log.i("[DEBUG]", "main activity - finished");
}
For now I will mark this as the solution. If someone comes along and provides an answer for how to properly obtain a reference - for a manually added TextView when the app is using a GLSurfaceView - then I will mark it as the answer, so long as it works.
I tried making an app using this tutorial (example 2). I created a navigation drawer activity.
My main fragment xml (added card):
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:card="http://schemas.android.com/apk/res-auto"
android:layout_width="fill_parent"
android:layout_height="fill_parent" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
tools:context=".MainActivity$PlaceholderFragment"
android:id="#+id/mainfragment">
<ScrollView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/scrollView" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/abovecards">
<it.gmariotti.cardslib.library.view.CardListView
android:id="#+id/myList"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
card:list_card_layout_resourceID="#layout/list_card_thumbnail_layout"
style="#style/list_card.thumbnail"/>
</LinearLayout>
</ScrollView>
</RelativeLayout>
In my main activity activity I added:
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
cardthingy();
}
public void cardthingy(){
int listImages[] = new int[]{R.mipmap.ic_launcher, R.mipmap.ic_launcher1,
R.mipmap.ic_launcher, R.mipmap.ic_launcher1, R.mipmap.ic_launcher};
ArrayList<Card> cards = new ArrayList<Card>();
for (int i = 0; i<5; i++) {
// Create a Card
Card card = new Card(this.getActivity());
// Create a CardHeader
CardHeader header = new CardHeader(this.getActivity());
// Add Header to card
header.setTitle("Test: " + i);
card.setTitle("Some text here");
card.addCardHeader(header);
CardThumbnail thumb = new CardThumbnail(this.getActivity());
thumb.setDrawableResource(listImages[i]);
card.addCardThumbnail(thumb);
cards.add(card);
}
CardArrayAdapter mCardArrayAdapter = new CardArrayAdapter(this.getActivity(), cards);
CardListView listView = (CardListView) getActivity().findViewById(R.id.myList);
if (listView != null) {
listView.setAdapter(mCardArrayAdapter);
//this I tried from googling possible solutions
FrameLayout mainy = (FrameLayout) getActivity().findViewById(R.id.container);
mainy.setLayoutParams(new DrawerLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
RelativeLayout fragy = (RelativeLayout) getActivity().findViewById(R.id.mainfragment);
fragy.setLayoutParams(new FrameLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
ScrollView feed = (ScrollView) getActivity().findViewById(R.id.scrollView);
feed.setLayoutParams(new RelativeLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
LinearLayout rLGreen = (LinearLayout) getActivity().findViewById(R.id.abovecards);
rLGreen.setLayoutParams(new FrameLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
listView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
}
}
The problem is that it is showing a scrollable screen that only fills up space of 1 card instead of the whole screen:
As you can see in my xml and java, I've tried some things to fix this, but unfortunately I'm out of ideas.
Try changing
LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT
to
LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.MATCH_PARENT
Ok. The solution was pretty simple. The problem was fixed by removing the scrollview from the xml
<ScrollView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="#+id/scrollView" >
</ScrollView>
The card list view automatically becomes scrollable after a certain amount of items.
And the following lines weren't necessary any more:
//this I tried from googling possible solutions
FrameLayout mainy = (FrameLayout) getActivity().findViewById(R.id.container);
mainy.setLayoutParams(new DrawerLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
RelativeLayout fragy = (RelativeLayout) getActivity().findViewById(R.id.mainfragment);
fragy.setLayoutParams(new FrameLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
ScrollView feed = (ScrollView) getActivity().findViewById(R.id.scrollView);
feed.setLayoutParams(new RelativeLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
LinearLayout rLGreen = (LinearLayout) getActivity().findViewById(R.id.abovecards);
rLGreen.setLayoutParams(new FrameLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
listView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT));
I just started android and I tried below questions to get this answer before posting it here:
Android - Adding layout at runtime to main layout
Add button to a layout programmatically
Dynamically adding a child to LinearLayout with getting each child's position
And I am still not able to add a button to linear layout :(
Below is the code for activity, please let me know where I am wrong:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout layout = (LinearLayout) View.inflate(this, R.layout.activity_main, null);
Button btn = new Button(this);
btn.setId(123);
btn.setText("Welcome to WI FI World");
layout.addView(btn);
}
And xml looks like below:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</LinearLayout>
Try assigning an id to your layout then add the button to the layout.
Im pretty sure those 2 layouts are not the same, so you are infact adding a button to a layout that is never displayed.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LinearLayout layout = (LinearLayout) findViewById(R.id.lnr_main);
Button btn = new Button(this);
btn.setId(123);
btn.setText("Welcome to WI FI World");
layout.addView(btn);
}
With Layout assigned an id
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/lnr_main"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</LinearLayout>
Take the Id for LinearLayout in XML and in jave code use that id of LinearLayout from XML
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/linear" >
</LinearLayout>
In onCreate():
LinearLayout linear=(LinearLayout)findViewById(R.id.linear);
//Select widgets
linear.addView()
Give an id to your linearLayout.
Then in your code
LinearLayout layout = (LinearLayout)findViewById(R.id.given_id);
Keep the rest the same, should work.
I'm trying to add a bunch of TextViews at runtime to a scrollview but I get The specified child already has a parent. You must call removeView on the child's parent first.
main.xml
<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
</LinearLayout>
</ScrollView>
testapp
#Override
public void onCreate(Bundle savedInstanceState) {
TextView[] data;
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
View layout = findViewById(R.id.layout);
.......................................
data = new TextView[10];
for (int i = 0; i < 10; i++) {
data[i] = new TextView(this);
data[i].setText("data = " + i);
((ViewGroup) layout).addView(data[i]);
}
setContentView(layout);
}
You cannot use setContentView() twice in a single Activity like this. That's the problem.
Look at this answer here:
A view can only have a single parent. The view that you are adding (I am guessing re-using) is already part of another view hierarchy. If you really want to reuse it (I would suggest you probably don't) then you have to detach it from its parent in its existing view hierarchy.
I think the problem is of layout variable.
it already has a parent ScrollView view as per XML now when you are using this setContentView(layout); so this try to add layout in different parent ..