Develop Reference

Programmatically add an ImageView to Layout

I'm trying to add a bunch of ImageView on my UI using a loop, the problem is that I have no Idea if the ImageView is being added or not because when I run the app it just gives me a blank white screen.
for(int i = 0; i < jsonArray.length(); i++) {
Log.d("test", "ok"); //the loop works btw
poster.setId(i);
JSONObject jsonObject = jsonArray.getJSONObject(i);
ImageView poster = new ImageView(getApplicationContext());
poster.setBackgroundResource(R.drawable.myPoster);
RelativeLayout.LayoutParams posterParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT,
RelativeLayout.LayoutParams.WRAP_CONTENT
);
posterParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
posterParams.addRule(RelativeLayout.CENTER_VERTICAL);
posterParams.width = 160; //is this DP?
posterParams.height = 220;
relativeLayout.addView(poster, posterParams);
}
Any suggestion is welcome.
EDIT
I added another piece of code just to test if a widget will be added without using a loop:
//test
LinearLayout layout = new LinearLayout(this);
Button btn = new Button(this);
btn.setText("this is a button");
btn.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT));
layout.addView(btn);
And I still get the same result, just blank.

First of all, you are giving exactly the same parameter to each ImageView this causes all your ImageView lays on Like STACK only the last one will be visible to you. You may use ScrollView to see if the ImageViews actually added to your root layout
Secondly, set layout parameters to your dynamic ImageViews not your root layout.
Update
How to use ScrollView,
First of all, your XML should contain ScollView and a child (LinearLayout in our case but you can choose any layout depending on your use case) for placing your ImageView
<ScrollView>
<LinearLayout
android:id = "imageViewPlaceHolder">
</LinearLayout>
</ScrollView>
Secondly, in your Java code, you should find an inner layout to add views as follows
LinearLayout placeHolder = findViewById(R.id.imageViewPlaceHolder);
Then you are ready to add ImageViews into placeHolder since your placeHolder wrapped with ScrollView it will create a scroll dynamically if the content height goes beyond the dedicated height.
placeHolder.addView(yourImageView);
Adding everything from Java
HorizontalScrollView hsv = new HorizontalScrollView(context);
hsv.setLayoutParams(yourLayoutParams);
LinearLayout myPlaceHolder = new LinearLayout(context);
myPlaceHolder.setLayoutParams(yourLayoutParamsForLinearLayout);
myPlaceHolder.addView(yourDesiredImageView);
hsv.addView(myPlaceHolder);
yourRootLayout.addView(hsv);
Hope it makes sense, feel free to ask any clarification

try this:
listView = (ListView) findViewById(R.id.lv_info);
ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, text);
listView.addHeaderView(creatHeader(getString(R.string.abuot_email),getResources().getString(R.string.email_info)));
listView.addHeaderView(creatHeader(getString(R.string.about_phone),getResources().getString(R.string.admin_phone_num)));
listView.addHeaderView(creatHeader(getString(R.string.about_copyright), getResources().getString(R.string.copyright_info)));
listView.addHeaderView(creatHeader(getString(R.string.about_version),getResources().getString(R.string.version_info)));
listView.setAdapter(adapter);
Method creatHeader:
public View creatHeader(String title, String text) {
View v = getLayoutInflater().inflate(R.layout.lv_item_header_info, null);
((TextView) v.findViewById(R.id.tvTitle)).setText(title);
((TextView) v.findViewById(R.id.tvText)).setText(text);
return v;
}
Layout file for items:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="#dimen/activity_vertical_margin">
<TextView
android:id="#+id/tvTitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="ssss"
android:textAppearance="?android:attr/textAppearanceListItemSmall"
android:gravity="center_vertical"/>
<TextView
android:id="#+id/tvText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="sssssssss"
android:gravity="center_vertical"/>
</LinearLayout>

Android textView.setText() throws exception

I'm trying to create an app where I can put several times the same kind of layout in a LinearLayout.
The layout just has a TextView and i'm trying to use setText but this line of code doesn't seems to work.
I don't know how many layout I must add to the LinearLayout because it depends of how many drones (I have one layout/drone) the user will have upload to the app, so I made a function that read the text to put in the TextView from a SharedPreference and that also read the number of drones (so the number of layouts) in another SharedPreferences.
The TextView i'im putting the string in is from a layout named dronelayoutmain.
I tried sending just "test" in the setText, but it crashes anyway, so I think that android just can't find my TextView, but I don't really know why.
So here is the function I call in OnCreate that is supposed to add one layout for each drone I have
public void affichagedrone(){
LinearLayout mlineairelayout = (LinearLayout)
findViewById(R.id.lineaireLayout);
LinearLayout.LayoutParams params = new
LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
Context mContext;
mContext = getApplicationContext();
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
SharedPreferences droneprefs = mContext.getSharedPreferences("dronepref", MODE_PRIVATE);
SharedPreferences applimaindata = mContext.getSharedPreferences("applimaindata", MODE_PRIVATE);
int nbdrone = applimaindata.getInt(String.valueOf(emplacementNbDrone),1);
String string;
TextView textViewnomConstructeurDrone;
if (nbdrone !=0) {
for(int i=0;i<nbdrone;i++) {
textViewnomConstructeurDrone = (TextView) findViewById(R.id.textViewNomConstructeur);
string = droneprefs.getString(String.valueOf(i),"Fail");
textViewnomConstructeurDrone.setText(string);
final View rowView = inflater.inflate(R.layout.dronelayoutmain, null);
// Add the new row before the add field button.
mlineairelayout.addView(rowView);
}
}
}
And here is the layout i'm trying to put in the LinearLayout.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="120dp"
>
<TextView
android:id="#+id/textViewNomConstructeur"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="5dp"
android:text="#string/adddrone"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
The function is supposed to check in applimaindata the number of layout to add, and then, in the for(), is supposed to set the Text of the TextView from the droneprefs file and then add the Layout to the main LinearLayout

If this TextView belongs in the newly inflated layout, you must find it after the layout is inflated:
for(int i = 0; i < nbdrone; i++) {
final View rowView = inflater.inflate(R.layout.dronelayoutmain, null);
textViewnomConstructeurDrone = rowView.findViewById(R.id.textViewNomConstructeur);
string = droneprefs.getString(String.valueOf(i),"Fail");
textViewnomConstructeurDrone.setText(string);
mlineairelayout.addView(rowView);
}

Dynamically adding buttons to scroll view

I would like some help with dynamically adding buttons to a ScrollView. I've got it working with a LinearLayout but obviously I can only add so many buttons before they no longer appear on screen. My code is below with an attached image of its current state.
I tried changing every occurrence of LinearLayout with ScrollView in the code but when I ran it, I got an error that stated something along the lines of ScrollViews can only have 1 direct child.
I'm not sure how to make it work, so if someone could give me some guidance on how to do it, I would be very grateful.
My XML Code:
<RelativeLayout 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"
<LinearLayout
android:id="#+id/mainLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_below="#id/imageTextView"
android:layout_centerHorizontal="true">
</LinearLayout>
</RelativeLayout>
My Java Code (where I'm dynamically creating the buttons):
public class Main5Activity extends AppCompatActivity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main5);
LinearLayout layout = (LinearLayout) findViewById(R.id.mainLayout);
for (int i = 0; i < 6; i++)
{
LinearLayout row = new LinearLayout(this);
row.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
for (int j = 0; j < 4; j++)
{
final Button btnTag = new Button(this);
btnTag.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
btnTag.setText("" + (j + 1 + (i * 4)));
btnTag.setId(j + 1 + (i * 4));
row.addView(btnTag);
}
layout.addView(row);
}
}
}
Image of the current layout.

Yes ScrollView can only have 1 child, and often it is the ViewGroup like LinearLayout, RelativeLayout, etc.
You need to wrap your LinearLayout with a ScrollView, like this:
<ScrollView>
<LinearLayout
android:id="#+id/mainLayout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_below="#id/imageTextView"
android:layout_centerHorizontal="true"/>
</ScrollView>
Or you can change your topmost RelativeLayout into ScrollView if it has only one child.

NullPointerException getting a TextView

I am creating an extremely simple Android application to serve as a proof of concept and a reference for an application I will create in the future.
My goal is to create a ListView, each item containing a TextView and a Button that, when pressed, makes a Toast pop up displaying the content of the TextView.
Here is my code and xml:
main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<ListView
android:layout_height="match_parent"
android:layout_width="match_parent"
android:id="#+id/mainListView1"/>
</LinearLayout>
entry.XML:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center_vertical"
android:orientation="horizontal"
android:id="#+id/entryLayout"
>
<TextView
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:id="#+id/entryTextView1"
android:padding="10dp"
android:textSize="25sp"/>
<ImageButton
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:src="#android:drawable/ic_menu_close_clear_cancel"
android:id="#+id/entryImageButton"
/>
</LinearLayout>
MainActivity.Class
public class MainActivity extends Activity{
/* Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// Set main.xml as user interface layout
setContentView(R.layout.main);
String[] companies = new String[] { "Test1", "Test2", "Test3",
"Test4", "Test4", "Test6", "Test7", "Test8", "Test9", "Test10"};
ArrayList<LinearLayout> views = new ArrayList<LinearLayout>();
for(int x=0; x!= companies.length-1; x++){
LinearLayout layout = (LinearLayout) findViewById(R.id.entryLayout);
TextView text = (TextView) layout.getChildAt(0);
text.setText(companies[x]);
ImageButton button = (ImageButton) layout.getChildAt(1);
button.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View v){
LinearLayout layout = (LinearLayout) v.getParent();
TextView view = (TextView) layout.getChildAt(0);
Toast.makeText(MainActivity.this,view.getText(), Toast.LENGTH_SHORT).show();
}
});
views.add(layout);
}
ListView listView = (ListView) findViewById(R.id.mainListView1);
for(LinearLayout layout: views){
listView.addView(layout);
}
}
I get an Kin the line
TextView text = (TextView) layout.getChildAt(0);
And for the life of me I can't figure out why. This is likely due to my lack of knowledge to how certain functions in the API work.

Your immediate issue is that findViewById looks in the layout you've inflated with setContentView() and since the Views you are trying to inflate aren't in that layout, they return null.
So this line returns null
LinearLayout layout = (LinearLayout) findViewById(R.id.entryLayout);
which causes a NPE at this line as you've noticed
TextView text = (TextView) layout.getChildAt(0);
because layout is null.
The bigger issue is the way you are going about using your ListView. Since you want to use a custom layout for the rows, you should be using a custom Adapter and inflate the appropriate layout there . You can then utilize Adapter's getView() method to set the data in each row as needed.
This tutorial can help you get started on that.
You also may want to watch Google I/O World of ListView
ListView Docs

Android- Adding items dynamically to scrollview

I have been for hours trying to follow various tutorials in order to add items dynamically into a scrollview but nothing seems to be working...
The idea is just to add Strings into a TextView next to a Checkbox, which were done in a separate xml file and I just wanted the list to grow as I keep adding them.
For now, only one String is being added (the last one substitutes the previous one), and in any attempt to try to change that, my app stops working.
Here is the code as it stands:
TableLayout addPlayersTableLayout;
TableRow tableRow1;
ScrollView addPlayersScrollView;
String[] players = new String[]{ "Blah", "Whatever", "Test", "Nipah!"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPlayersTableLayout = (TableLayout)findViewById(R.id.TableLayout1);
tableRow1 =(TableRow)findViewById(R.id.tableRow1);
addPlayersScrollView = (ScrollView)findViewById(R.id.playersScrollView);
insertPlayerInScrollView();
}
Here is the implementation of the function that is supposed to add the items:
(add_player_row.xml is the file where the textview and checkbox that are supposed to be the items were made)
private void insertPlayerInScrollView() {
LayoutInflater inflator = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View newPlayerRow = inflator.inflate(R.layout.add_player_row, null);
TextView newPlayerTextView = (TextView) newPlayerRow.findViewById(R.id.addPlayerTextView);
CheckBox playerCheckBox = (CheckBox)findViewById(R.id.playerCheckBox);
newPlayerTextView.setText(players[1]);
addPlayersTableLayout.addView(newPlayerRow,0);
}
The final line of code is the only way it works at all, even though on most forums and tutorials, people would indicate for me to use the addPlayersScrollView, but if I do so, the app crashes.
So... Any ideas?
Thank you very much!

I'm facing something similar than you. I have a layout like this:
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<TableLayout
android:id="#+id/tableLayoutList"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</ScrollView>
And have my row defined like this (mRowLayout.xml):
<TableRow xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/LinearLayoutRow"
android:layout_width="match_parent"
android:layout_height="match_parent">
<CheckBox
android:id="#+id/checkBoxServEmail"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</TableRow>
And then I use the following code to inflate my row:
private void fillTable(View v, Cursor c) {
TableLayout ll = (TableLayout) v.findViewById(R.id.tableLayoutList);
View mTableRow = null;
int i = 0;
while(!c.isAfterLast()){
i++;
mTableRow = (TableRow) View.inflate(getActivity(), R.layout.mRowLayout, null);
CheckBox cb = (CheckBox)mTableRow.findViewById(R.id.checkBoxServEmail);
cb.setText( c.getString(c.getColumnIndex(Empleado.EMAIL)));
mTableRow.setTag(i);
//add TableRows to TableLayout
ll.addView(mTableRow);
c.moveToNext();
}
}
What I'm trying to do here is inflate my rows dynamically. The cursor have the items that I wanna show from data base. I'm not sure if this can solve your problem. Let me know.