Develop Reference

OnKeyDown inside WebView fragment

I made a Fragment, containing a WebView and I wanted to define an onKeyDown() to get back from one web page to the previous one. I did it, but the weirdest part for me was to share a WebView variable from my Fragment class to my Activity class because I can't define onKeyDown() in the Fragment. So I just defined a get method and made it static. But I wonder if it was a real mistake and my app can seriously crash in some circumstances.
My Fragment code:
public class BrowserFragment extends Fragment {
private static WebView webView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState){
View v = inflater.inflate(R.layout.fragment_activity, parent, false);
getActivity().setTitle(R.string.title_rus);
webView = (WebView) v.findViewById(R.id.webView);
webView.setWebViewClient(new SwingBrowserClient());
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
Uri data = Uri.parse("http://www.swinginmoscow.ru/m/");
webView.loadUrl(data.toString());
return v;
}
public static WebView getWebView() {
return webView;
}
}
And my Activity code:
public class MainBrowserActivity extends SingleFragmentActivity {
#Override
protected Fragment createFragment() {
return new BrowserFragment();
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && BrowserFragment.getWebView().canGoBack()) {
BrowserFragment.getWebView().goBack();
return true;
}
return super.onKeyDown(keyCode, event);
}
}

It might work, but it is not a good idea. It could very well cause a crash if you don't handle the Fragment correctly or are somewhere in your code a little careless regarding its lifecycle. But there is an easy way around this. Instead of using a static method, save the instance and call methods on the instance itself. This way you can check if the instance is null and if not the Fragment can handle calls to goBack() or canGoBack() itself:
public class MainBrowserActivity extends SingleFragmentActivity {
BrowserFragment browserFragment = null;
#Override
protected Fragment createFragment() {
this.browserFragment = BrowserFragment.newInstance();
return this.browserFragment;
}
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && this.browserFragment != null && this.browserFragment.canGoBack()) {
this.browserFragment.goBack();
return true;
}
return super.onKeyDown(keyCode, event);
}
}
As you can see the BrowserFragment instance is saved and then methods like goBack() or canGoBack() are called on the BrowserFragment itself. Of course you have to implement these methods in the BrowserFragment but that should not be a problem:
public class BrowserFragment extends Fragment {
public static BrowserFragment newInstance() {
BrowserFragment fragment = new BrowserFragment();
return fragment;
}
private WebView webView;
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState){
View v = inflater.inflate(R.layout.fragment_activity, parent, false);
getActivity().setTitle(R.string.title_rus);
webView = (WebView) v.findViewById(R.id.webView);
webView.setWebViewClient(new SwingBrowserClient());
WebSettings webSettings = webView.getSettings();
webSettings.setJavaScriptEnabled(true);
Uri data = Uri.parse("http://www.swinginmoscow.ru/m/");
webView.loadUrl(data.toString());
return v;
}
public boolean canGoBack() {
return this.webView != null && this.webView.canGoBack();
}
public void goBack() {
if(this.webView != null) {
this.webView.goBack();
}
}
}
I made a few extra improvements to your code. First of all I added null checks to prevent any possible NullPointerExceptions and secondly it is recommend to always use a static factory method to create new instances of Fragments. That is what the static newInstance() method is that I added to the BrowserFragment. The advantage of that is that you can implement a method which takes care of setting up the BrowserFragment for you regardless of where you use it. You can add parameters to newInstance() method to pass some value to the BrowserFragment or to add some required listener etc but since you don't pass any values to the BrowserFragment the newInstance() method remains pretty empty. Nevertheless it is best practice to always use such factory methods even if they only call new BrowserFragment().
Generally this approach is much better. Especially from a architecture perspective because you don't directly interact with the WebView in the Activity. The WebView doesn't have anything to do with the Activity, it is part of the implementation of the BrowserFragment and as such the Activity should not know that there even is a WebView. How calls to goBack() or canGoBack() are implemented or what they exactly do is of no interest to the Activity. The Activity just tells the BrowserFragment "I want to go back" and the BrowserFragment does the work. This separates the responsibilities better and makes the code more readable, more clear and more maintainable.
EDIT:
Also I don't know of a SingleFragmentActivity but generally any Activity implements onBackPressed() method. You don't have to override onKeyDown() to catch a back key event. You can just do something like this:
#Override
public void onBackPressed() {
if (this.browserFragment != null && this.browserFragment.canGoBack()) {
this.browserFragment.goBack();
} else {
// The back key event only counts if we execute super.onBackPressed();
super.onBackPressed();
}
}
If you have any other questions please feel free to ask!

The advice rotation charges again my webviews class

When I rotate my devices, this charge again his class. For example, if I have a google search when I change the orientation charges again to google.
I've try it with:
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setContentView(R.layout.principal);
}
and onRestoreInstanceState and onSaveInstanceState. But my problem persist. I would appreciate if somebody can help me with a example or explication of how can to do it.
Thank's!
I've solved the problem, I needed to do the if (savedInstanceState == null) :
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.principal);
webview.setWebViewClient(new WebViewClient());
if (savedInstanceState == null)
{
webview.loadUrl("http://www.apple.es");
}
}
#Override
protected void onSaveInstanceState(Bundle outState)
{
super.onSaveInstanceState(outState);
// Save the state of the WebView
webview.saveState(outState);
}
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState)
{
super.onRestoreInstanceState(savedInstanceState);
// Restore the state of the WebView
webview.restoreState(savedInstanceState);
}
I hope than my problem and my solution can help to somebody!

Christian you have to see this doc on android developer web site and learn how romain guy stores his last loaded image and call them when the configuration screen changes!! the solution is to use
onRetainNonConfigurationInstance()
getLastNonConfigurationInstance()
I also refer to this tutorial always to get rid of the screen change behavour of android
hope this will help you

Add configChanges in your AndroidManifest file.
For example:
<activity android:name="YourActivityName"
android:configChanges="orientation">
</activity>
and save your current url in local variable and load it in onConfigChanges
#Override
public void onConfigurationChanged(Configuration newConfig) {
yourWebView.loadUrl(yourUrl);
}

use following piece of code
public void onConfigurationChanged(Configuration newConfig) {
yourWebView.loadUrl(yourUrl);
}
Refer this link
Activity restart on rotation Android

Fragments, DialogFragment, and Screen Rotation

I have an Activity that calls setContentView with this XML:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal"
>
<fragment android:name="org.vt.indiatab.GroupFragment"
android:id="#+id/home_groups"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1" />
<..some other fragments ...>
</LinearLayout>
The GroupFragment extends Fragment, and all is well there. However, I show a DialogFragment from within GroupFragment. This shows correctly, HOWEVER when the screen rotates, I get a Force Close.
What's the proper way to display a DialogFragment from within another Fragment other than DialogFragment.show(FragmentManager, String)?

There's a bug in the compatibility library that can cause this. Try putting this in you dialogfragment:
#Override
public void onDestroyView() {
if (getDialog() != null && getRetainInstance())
getDialog().setOnDismissListener(null);
super.onDestroyView();
}
I also suggest setting your dialogfragment as retained, so it won't get dismissed after the rotation. Put "setRetainInstance(true);" e.g. in the onCreate() method.

OK, while Zsombor's method works, this is due to me being inexperienced with Fragments and his solution causes issues with the saveInstanceState Bundle.
Apparently (at least for a DialogFragment), it should be a public static class. You also MUST write your own static DialogFragment newInstance() method. This is because the Fragment class calls the newInstance method in its instantiate() method.
So in conclusion, you MUST write your DialogFragments like so:
public static class MyDialogFragment extends DialogFragment {
static MyDialogFragment newInstance() {
MyDialogFragment d = new MyDialogFragment();
return d;
}
#Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
...
}
}
And show them with:
private void showMyDialog() {
MyDialogFragment d = MyDialogFragment.newInstance();
d.show(getFragmentManager(), "dialog");
}
This may be unique to the ActionBarSherlock Library, but the official samples in the SDK documentation use this paradigm also.

To overcome the Bundle always being null, I save it to a static field in onSaveInstanceState. It's a code smell, but the only solution I found for both restoring the dialog and saving the state.
The Bundle reference should be nulled in onDestroy.
#Override
public void onCreate(Bundle savedInstanceState)
{
if (savedInstanceState == null)
savedInstanceState = HackishSavedState.savedInstanceState;
setRetainInstance(true);
}
#Override
public Dialog onCreateDialog(Bundle savedInstanceState)
{
if (savedInstanceState == null)
savedInstanceState = HackishSavedState.savedInstanceState;
...
}
#Override
public void onDestroyView() // necessary for restoring the dialog
{
if (getDialog() != null && getRetainInstance())
getDialog().setOnDismissListener(null);
super.onDestroyView();
}
#Override
public void onSaveInstanceState(Bundle outState)
{
...
HackishSavedState.savedInstanceState = outState;
super.onSaveInstanceState(outState);
}
#Override
public void onDestroy()
{
HackishSavedState.savedInstanceState = null;
super.onDestroy();
}
private static class HackishSavedState
{
static Bundle savedInstanceState;
}

I used a mix of the presented solutions and added one more thing.
This is my final solution:
I used setRetainInstance(true) in the onCreateDialog;
I used this:
public void onDestroyView() {
if (getDialog() != null && getRetainInstance())
getDialog().setDismissMessage(null);
super.onDestroyView();
}
And as a workaround of the savedInstanceState not working, I created a private class called StateHolder (the same way a holder is create for a listView):
private class StateHolder {
String name;
String quantity;
}
I save the state this way:
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
stateHolder = new StateHolder();
stateHolder.name = actvProductName.getText().toString();
stateHolder.quantity = etProductQuantity.getText().toString();
}
In the onDismiss method I set the stateHolder back to null. When the dialog is created, it verifies if the stateHolder isn't null to recover the state or just initialize everything normally.

I solved this issue with answers of #ZsomborErdődy-Nagy and #AndyDennie . You must subclass this class and in you parent fragment call setRetainInstance(true), and dialogFragment.show(getFragmentManager(), "Dialog");
public class AbstractDialogFragment extends DialogFragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
#Override
public void onDestroyView() {
if (getDialog() != null && getRetainInstance())
getDialog().setDismissMessage(null);
super.onDestroyView();
}
}

I had a similar issue, however none of the above worked for me. In the end I needed to create the fragment in code instead of in the XML layout.
See: Replacing fragments and orientation change

I ran into this on my project and none of the above solutions helped.
If the exception looks something like
java.lang.RuntimeException: Unable to start activity ComponentInfo{
...
Caused by: java.lang.IllegalStateException: Fragment....
did not create a view.
It's caused by an issue with a fallback container Id that gets used after rotation. See this ticket for more details:
https://code.google.com/p/android/issues/detail?id=18529
Basically you can prevent the crash by making sure all of your xml fragments have a tag defined in the layout. This prevents the fallback condition from occurring if you rotate when a fragment is visible.
In my case I was able to apply this fix without having to override onDestroyView() or setRetainInstance(true), which is the common recommendation for this situation.

I encountered this problem and the onDestroyView() trick wasn't working. It turned out that it was because I was doing some rather intensive dialog creation in onCreate(). This included saving a reference to the AlertDialog, which I would then return in onCreateDialog().
When I moved all of this code to onCreateDialog() and stopped retaining a reference to the dialog, it started working again. I expect I was violating one of the invariants DialogFragment has about managing its dialog.

In onCreate() call setRetainInstance(true) and then include this:
#Override
public void onDestroyView() {
if (getDialog() != null && getRetainInstance()) {
getDialog().setOnDismissMessage(null);
}
super.onDestroyView();
}
When you call setRetainInstance(true) in onCreate(), onCreate() will no longer be called across orientation changes, but onCreateView() will still be called.
So you can still save the state to your bundle in onSaveInstanceState() and then retrieve it in onCreateView():
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("myInt", myInt);
}
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.my_layout, container);
if (savedInstanceState != null) {
myInt = savedInstanceState.getInt("myInt");
}
...
return view;
}

View was clear data when screen rotation in Android

I have a View that was created on runtime then I draw some canvas on that View(runtime) after that I rotated my screen.All data was gone(reset).So I put the some code in AndroidManifest.xml like this
android:configChanges="keyboardHidden|orientation"
in my <activity> then I put a #Override function
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
setContentView(R.layout.main);
LinearLayout layout = (LinearLayout) findViewById(R.id.myPaint);
layout.addView(mView);
}
but everything couldn't solved my problem.I want to keep my data from View(runtime) on every single rotation.
That's my onCreate function.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mView = new MyView(this);
setContentView(mView);
mView.requestFocus();
setContentView(R.layout.main);
LinearLayout layout = (LinearLayout) findViewById(R.id.myPaint);
layout.addView(mView);
}

You need to save and load the data you want to retain. Even though you're handling the screen rotation yourself when you modified the Manifest the way you did, you're still reloading the view yourself. Reread the reference document on Handling Runtime Changes. You need to store your data and reload it accordingly. Otherwise it will be lost when the application restarts or when you reload your ContentView.
http://developer.android.com/guide/topics/resources/runtime-changes.html

You could approach this a few ways.
I assume MyView is your own class which extends View. If so there are two methods which you may care to know, onSaveInstanceState() and onRestoreInstanceState(). When saving you create a parcelable that will contain enough data for you to re-render your view if it were to be destroyed and recreated.
class MyView extends View {
private String mString;
onDraw(Canvas v) { ... }
Parcelable onSaveInstanceState() {
Bundle b = new Bundle();
bundle.putString("STRING", mString);
return b;
void onRestoreInstanceState(Parcelable c) {
Bundle b = (Bundle) c;
mString = bundle.getString("STRING", null);
}
}
Activity has similar state saving mechanics allowed in onCreate and onSaveInstanceState() (inside Activity, not View in this case) which will allow the activity to reset the state of it's view to the state it desires.
This should solve most of your worries. If you are wanting to use the onConfigurationChanged method, then you should reclarify your question as it is not clear what the current behavior is that you aren't expecting in each situation (only using onConfigurationChanged, or only using onCreate, or using both, etc).

I've just used my data-class as singleton (java-pattern).
And it works fine.
--> Application is a Stop-Timer for Racing, where i can stop time from different opponents on the track, so i need the data for longer time, also if the view is repainted.
regz
public class Drivers {
// this is my singleton data-class for timing
private static Drivers instance = null;
public static Drivers getInstance() {
if (instance == null) {
instance = new Drivers();
}
return instance;
}
// some Timer-Definitions.......
}
Then in MainActivity:
// now the class is static, and will alive during application is running
private Drivers drivers = Drivers.getInstance();
#Override
public void onClick(View v) {
if (v == runButton1) {
drivers.startTimer1();
// do some other crazy stuff ...
}
}
// here i put out the current timing every second
private myUpdateFunction(){
time01.setText(drivers.getTimer1());
// update other timers etc ...
}

Close the current activity when you only have a reference to Context

If I have a reference to Context, is it possible to finish the current activity?
I don't have the reference to current activity.

yes, with a cast:
((Activity) ctx).finish();

In my Case following worked,
I need to finish my activity in a AsyncTask onPostExcute().
Where my AsyncTask class is separate public class , which has a constructor with param of Context.
((Activity)(mContext)).finish();
Only the above worked for me... Anyway I got this idea from #2red13 and #lucy answers... Thanks to all...

I know it's an old post but, perhaps it could be a good idea to call it this way:
if(context instanceof Activity){
((Activity)context).finish(); }
This way we make sure we don't get any unnecesary ClassCastExceptions

If you have access to the running view of the Activity you want to finish (for example, you are in a click listener), you could do:
((Activity)getContext()).finish();
(With thanks to 2red13 to get me here).

If you start the activity using:
startActivityForResult(i, 1);
you can call finishActivity(1) to finish any activities started with that request code, like this:
((Activity)getContext()).finishActivity(1);
In my case I need to use one in a handler postDelayed. Using this you can be sure of which activity you are finishing. Hope it helps!

I had the same problem when closing a preference activity. Here is what I did:
public class T2DPreferenceActivity extends PreferenceActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getFragmentManager().beginTransaction().replace(android.R.id.content,
new T2DPreferenceFragment()).commit();
}
public static class T2DPreferenceFragment extends PreferenceFragment {
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.server_screen_preference);
Preference testServicePreference = getPreferenceScreen().findPreference("PREFERRED SERVER");
testServicePreference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
#Override
public boolean onPreferenceChange(Preference preference, Object newValue) {
T2DPreferenceActivity.closeActivity(getActivity());
return true; //returning true still makes the activity handle the change to preferences
}
});
}
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ListView lv = (ListView)view.findViewById(android.R.id.list);
ViewGroup parent = (ViewGroup)lv.getParent();
parent.setPadding(0, 100, 0, 0);
}
}
protected static void closeActivity(Activity activity) {
activity.finish();
}
}

Try:
((Activity) context.getApplicationContext()).finish();