I am trying to run an AndroidApp on my phone. I am able to show my welcome fragment, moreover I can trigger the log-message. Unfortunately I am getting a null pointer exception if I want to change the text value from 'welcome' to 'Neuer Text'. What went wrong? I am quite new to android development.
public class WelcomeFragment extends Fragment implements OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_welcome, container, false);
Button button1 = (Button) view.findViewById(R.id.button1);
button1.setOnClickListener((OnClickListener) this);
return view;
}
#Override
public void onClick(View v) {
//Log.d("JobaApp", "Logtext"); // see LogCat
TextView text1 = (TextView) v.findViewById(R.id.welcome_text);
text1.setText("NeuerText");
}
}
In the onClick(), v is the view item that was clicked, e.g. the button, not the view that is inflated in onCreateView().
You should use getView():
public class WelcomeFragment extends Fragment implements OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_welcome, container, false);
Button button1 = (Button) view.findViewById(R.id.button1);
button1.setOnClickListener((OnClickListener) this);
return view;
}
#Override
public void onClick(View v) {
//Log.d("JobaApp", "Logtext"); // see LogCat
switch (v.getId) {
case R.id.button1:
TextView text1 = (TextView) getView().findViewById(R.id.welcome_text);
text1.setText("NeuerText");
break;
}
}
}
Also, if you don't want that action taking place for every button you may want to consider using a switch statement in your onClick().
You cant get the TextView from the button's onClick passed parameter ("View v"), since this is the actual button's view.
You should do something like:
public class WelcomeFragment extends Fragment implements OnClickListener {
View view;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_welcome, container, false);
Button button1 = (Button) view.findViewById(R.id.button1);
button1.setOnClickListener((OnClickListener) this);
return view;
}
#Override
public void onClick(View v) {
//Log.d("JobaApp", "Logtext"); // see LogCat
TextView text1 = (TextView) view.findViewById(R.id.welcome_text);
text1.setText("NewerText"); //Also fixed typo
}
}
In OnClick(View v) , v is the button that you are clicking on. The TextView does not belong to Button, it belongs to R.layout.fragment_welcome. So you find and initialize the TextView inside onCreateView() of the fragment, and then use it inside onClick();
Some what like this:
public class WelcomeFragment extends Fragment implements OnClickListener {
TextView tv;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_welcome, container, false);
Button button1 = (Button) view.findViewById(R.id.button1);
button1.setOnClickListener((OnClickListener) this);
tv = (TextView) v.findViewById(R.id.welcome_text);
return view;
}
#Override
public void onClick(View v) {
//Log.d("JobaApp", "Logtext"); // see LogCat
tv.setText("NeuerText");
}
}
Related
I am new to Java/android develop and trying to follow instructions from android site but cannot find clear answer to implementing onclicklistener in fragment. Please help me why its keep crashing in runtime when I click.
public class TestFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_mngr_user, container, false);
return v;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDBhelper = new UserBaseHelper(getActivity());
// Capture our button from layout
TextView TextviewShow = (TextView)getActivity().findViewById(R.id.text_show);
// Register of onClick listener with the implementation above
TextviewShow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// do something when the text_show is clicked
displayInfo();
}
});
}
.....
}
try this
use this
TextView TextviewShow = (TextView)v.findViewById(R.id.text_show);
instead of this
TextView TextviewShow = (TextView)getActivity().findViewById(R.id.text_show);
change your code as below
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_mngr_user, container, false);
// Capture our button from layout
TextView TextviewShow = (TextView)v.findViewById(R.id.text_show);
// Register of onClick listener with the implementation above
TextviewShow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// do something when the text_show is clicked
displayInfo();
}
});
return v;
}
Try this
public class TestFragment extends Fragment {
View v;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
v = inflater.inflate(R.layout.fragment_mngr_user, container, false);
return v;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDBhelper = new UserBaseHelper(getActivity());
// Capture our button from layout
TextView TextviewShow = (TextView)v.findViewById(R.id.text_show);
// Register of onClick listener with the implementation above
TextviewShow.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// do something when the text_show is clicked
displayInfo();
}
});
}
.....
}
Move your code from onCreate() method to onCreateView() method and change the following code
From
(TextView)getActivity().findViewById(R.id.text_show);
to
(TextView)v.findViewById(R.id.text_show);
Can someone tell me how to set a button in tabbed fragment layout to open a new activity? If I set a button in a tab then it shows error.
You have to save the inflated view in a variable, then use findViewById on that view to find the textview and button, then at the end, return the inflated view.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_g, container, false);
TextView tv = (TextView) root.findViewById(R.id.textView);
Button btn = (Button) root.findViewById(R.id.button);
//Other code here
return root;
}
You're misunderstanding some very fundamental things, such as writing code after the return statement. You might want to read some starter guides online.
You can use below code
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_complete_registration, container, false);
final TextView tv=(TextView)view.findViewById(R.id.textView);
final Button button=(Button)view.findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//Your required code here
}
});
return view;
}
I am working with Android Studio. I have a fragment on my Activty and I want to hide it when the user clicks on it.
For some reason I can´t just override a function for onclick like in the activties. And everytime I ask google all I can find are questions about how to
Implement onclick listeners for buttons or other elements in a fragment but that is not what I want. I want the onclick listener for the fragment itself.
Can anyone please tell me how to do that!?
You can do this by set ClickListener on the view inflating in a onCreateView of fragment like this :
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v=inflater.inflate(R.layout.layout_your, container, false);
v.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//do your operation here
// this will be called whenever user click anywhere in Fragment
}
});
return v;
}
It goes like below
public class fragmentOne extends Fragment implements OnClickListener {
Button myButton;
#Override
public View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedinstanceState) {
View myView = inflater.inflate(R.layout.fragment_1, container, false);
myButton = (Button) myView.findViewById(R.id.myButton);
myButton.setOnClickListener(this);
return myView;
}
#Override
public void onClick(View v) {
// implements your things
}
}
Why do I get NullPointerException when I don't access the Button view in my fragment through rootView view?
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Button buttonClick =(Button)rootView.findViewById(R.id.button);
buttonClick.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view)
{
//Do something when button is clicked
}
});
findViewById() looks for the requested view on the content of the calling view.
So if you call it from the activity it will look for the view on the contentView you set with setContentView(), thats why its returning null.
You need to call findViewById() on the view that holds the view you want.
Hope this helps.
You are inflating to the variable rootView, so the only way to get ahold of your button is through your variable.
Declare Button in Fragment
Button buttonClick;
And then Write below code in Fragment.
buttonClick = (Button) rootView.findViewById(R.id.button);
buttonClick.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
}
});
you can initialize button onClick() inside the fragment
initialize like this
public class Yourclassname extends Fragment implements View.OnClickListener
{
Button button1
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View rootview=inflater.inflate(R.layout.postpaid, container, false);
button1 = (Button) rootview.findViewById(R.id.button);
button1.setOnClickListener(this);
return rootview;
}
public void onClick(View view)
{
//Do something when button is clicked
}
}
I'm trying to convert a layout so that it will include fragments.
One of the views is an ImageButton that has a listener.
The code worked fine as an Activity but makes trouble as a Fragment...
First problem was that I couldn't use findViewById,
but I was able to find the answer for that here and fixed it with getView().
I can't find an answer to the second problem...
after I declared:
ImageButton camBt = (ImageButton)getView().findViewById(R.id.button1);
I want to set an on click listener:
camBt.setOnClickListener(listener);
But it keeps acting like the ImageButton (camBt) doesn't exist...
I don't even know what's the problem... it worked fine in the Activity...
Here's the full code.
Many thanks!
public class CameraFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View V = inflater.inflate(R.layout.camera_fragment, container, false);
return V;
}
ImageButton camBt = (ImageButton)getView().findViewById(R.id.button1);
camBt.setOnClickListener(listener);
ImageButton.OnClickListener listener = new ImageButton.OnClickListener()
{
#Override
public void onClick(View arg0)
{
Camera.open().getParameters();
}
};
}
Move
ImageButton camBt = (ImageButton)getView().findViewById(R.id.button1);
camBt.setOnClickListener(listener);
inside onCreateView().
Like
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.camera_fragment, container, false);
// Here it is
ImageButton camBt = (ImageButton)v.findViewById(R.id.button1);
camBt.setOnClickListener(listener);
return v;
}
And one more thing you need to understand that variable name should starts with small letter. So you should use View v instead of View V.
You should add
ImageButton camBt = (ImageButton)getView().findViewById(R.id.button1);
camBt.setOnClickListener(listener);
inside onCreateView() like:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View V = inflater.inflate(R.layout.camera_fragment, container, false);
ImageButton camBt = (ImageButton)v.findViewById(R.id.button1);
camBt.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
}
});
return V;
}
public class CameraFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View V = inflater.inflate(R.layout.camera_fragment, container, false);
ImageButton camBt = (ImageButton)V.findViewById(R.id.button1);
ImageButton.OnClickListener listener = new ImageButton.OnClickListener()
{
#Override
public void onClick(View arg0)
{
Camera.open().getParameters();
}
};
camBt.setOnClickListener(listener);
return V;
}
}