Develop Reference

Firebae with mediaplayer.setDataSource() gives an err

I'm trying to get url from firebase and give it to mediaplayer.setDataSource but I get an err says :- `
java.lang.IllegalStateException
at android.media.MediaPlayer._setDataSource(Native Method)
at android.media.MediaPlayer.setDataSource(MediaPlayer.java:991)
at android.media.MediaPlayer.setDataSource(MediaPlayer.java:944)
at mks.master.musest.home$onCreateView$16$1$1.onDataChange(home.kt:425)
at com.firebase.client.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:45)
at com.firebase.client.core.view.DataEvent.fire(DataEvent.java:45)
at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:38)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5019)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
`
here is my code :-
`var mediaplayer:MediaPlayeria
mediaplayer=MediaPlayer()
firebase= Firebase(link+"song2song")
firebase.addValueEventListener(object:ValueEventListener{
override fun onCancelled(p0: FirebaseError?) {
}
override fun onDataChange(p0: DataSnapshot) {
mediaplayer.setDataSource(p0.getValue(String()::class.java))
mediaplayer.prepareAsync()
}
})`
and the main err is in this part mediaplayer.setDataSource(p0.getValue(String()::class.java))

You should call reset() before calling setDataSource().
Look at the following state diagram in Android reference, it gives you a clear vision of the different states of MediaPlayer
Also This table shows that setDataSource() can be executed from Idle state only.

android page transition laybrary integration null pointer exception

Hello everyone i've got this error a nullPointerException error after i tried to integrate the android-page-transition and i couldn't find it's cause
this is the code where the error is shown PS: it's the same exact caude in the library i just integrated the code into mywork
/**
* Réglage Menu immersive title
*/
private void dealStatusBar() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
int statusBarHeight = getStatusBarHeight();
ViewGroup.LayoutParams lp = positionView.getLayoutParams();
lp.height = statusBarHeight;
positionView.setLayoutParams(lp);
}
}
this is the error i get when i run
11-19 12:11:30.781 16089-16089/mobile.esprit.tn.mobileteam E/AndroidRuntime: FATAL EXCEPTION: main
Process: mobile.esprit.tn.mobileteam, PID: 16089
java.lang.RuntimeException: Unable to start activity ComponentInfo{mobile.esprit.tn.mobileteam/mobile.esprit.tn.mobileteam.Activities.Project.PrjectsCardViews}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5942)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewGroup$LayoutParams android.view.View.getLayoutParams()' on a null object reference
at mobile.esprit.tn.mobileteam.Activities.Project.PrjectsCardViews.dealStatusBar(PrjectsCardViews.java:129)
at mobile.esprit.tn.mobileteam.Activities.Project.PrjectsCardViews.onCreate(PrjectsCardViews.java:54)
at android.app.Activity.performCreate(Activity.java:6289)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758) 
at android.app.ActivityThread.access$900(ActivityThread.java:177) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:145) 
at android.app.ActivityThread.main(ActivityThread.java:5942) 
at java.lang.reflect.Method.invoke(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:372) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195) 
the PrjectsCardViews.java:129 is the code i posted above

ok i found the problem it was a dump fault caused by the copy and paste , i dident refere the oncreate to the necessary activity layout

You might have copied the projet but you may forgotten to change
<com.stone.transition.DragLayout
android:id="#+id/drag_layout" when you merged the code in your project check this out it will work

TransactionTooLargeException when appying wallpaper

I know that TransactionTooLargeException occurs when there is a large amount of data being transferred between services in the system. Usually, I would have some kind of control if I were to transfer large amount of data, but in this case, when I'm appying a wallpaper, I don't have that amount of control.
I'm applying a wallpaper by first cropping it with android-image-cropper, and then applying it by
WallpaperManager.setBitmap(bitmap);
...in a separate thread, to avoid overloading the UI thread. Now, when I press "apply wallpaper", and wait for some time, and then return to the homescreen, it works flawlessly, but when I apply the wallpaper and then immediately return to the homescreen, I get the alert that the app has crashed, along with this log:
07-31 18:50:41.611 32720-32720/elementary.elementarywallpapers E/JavaBinder: !!! FAILED BINDER TRANSACTION !!! (parcel size = 16385936)
07-31 18:50:41.614 32720-32720/elementary.elementarywallpapers D/AndroidRuntime: Shutting down VM
07-31 18:50:41.621 32720-32720/elementary.elementarywallpapers E/AndroidRuntime: FATAL EXCEPTION: main
Process: elementary.elementarywallpapers, PID: 32720
java.lang.RuntimeException: android.os.TransactionTooLargeException: data parcel size 16385936 bytes
at android.app.ActivityThread$StopInfo.run(ActivityThread.java:3752)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
Caused by: android.os.TransactionTooLargeException: data parcel size 16385936 bytes
at android.os.BinderProxy.transactNative(Native Method)
at android.os.BinderProxy.transact(Binder.java:615)
at android.app.ActivityManagerProxy.activityStopped(ActivityManagerNative.java:3606)
at android.app.ActivityThread$StopInfo.run(ActivityThread.java:3744)
at android.os.Handler.handleCallback(Handler.java:751) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
How can I fix this?

Android app crashing when i hit a button [duplicate]

This question already has answers here:
What is a NullPointerException, and how do I fix it?
(12 answers)
Closed 6 years ago.
Hey guys so when I hit this particular button it is supposed to take me to the another layout. However everytime i hit it, the entire app crashes. Here is the onCreate method for that page im trying to get to:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bench_data_entry);
//opens the database
openDB();
//Initializes and declares the sensors, and accelerometer
mInitialized = false;
mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
// tv.setText("Aasfdaf");
}
Here is the onClick for the button I am pressing:
public void onClick_Bench(View v){
//Intent to create a new activity
Intent intent = new Intent(MainMenuActivity.this, BenchDataEntry.class);
//Goes to the Data Entry Screen
startActivity(intent);
}
and here is the error log I am getting when I press the button:
08-08 17:30:30.785 31113-31113/com.example.jacob.repcapture E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.jacob.repcapture, PID: 31113
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jacob.repcapture/com.example.jacob.repcapture.BenchDataEntry}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5422)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2096)
at com.example.jacob.repcapture.BenchDataEntry.<init>(BenchDataEntry.java:49)
at java.lang.Class.newInstance(Native Method)
at android.app.Instrumentation.newActivity(Instrumentation.java:1067)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
            at android.app.ActivityThread.-wrap11(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:148)
            at android.app.ActivityThread.main(ActivityThread.java:5422)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

I think error not in these code blocks logcat about android.view.View android.view.Window.findViewById(int)' on a null object reference
First - do clean project under build-menu, and restart the emulator. After that the exception went away in my situation.
Second - check FindviewById items You need to initialize them in the onCreate too. 

WiFi Scan No Such Instance field 'ChannelWidth'

Using
wifiManager.startScan();
ScanResultsList scanresultsList = wifiManager.getScanResults();
I obtain a list of scan results defined by ScanResult objects.
Problem:
Refering to scanResult.channelWidth I am presented with an error:
scanResult.channelWidth = No such instance field: 'channelWidth'
and
Exception
java.lang.NoSuchFieldError: No instance field channelWidth of type I
in class Landroid/net/wifi/ScanResult; or its superclasses
(declaration of 'android.net.wifi.ScanResult' appears in
/system/framework/framework.jar)
Stacktrace:
06-14 02:57:19.732 27116-27116/com.cynetstudios.frequencyselector E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.cynetstudios.frequencyselector, PID: 27116
java.lang.NoSuchFieldError: No instance field channelWidth of type I in class Landroid/net/wifi/ScanResult; or its superclasses (declaration of 'android.net.wifi.ScanResult' appears in /system/framework/framework.jar)
at com.cynetstudios.frequencyselector.main.initWiFiArrays(main.java:161)
at com.cynetstudios.frequencyselector.main.access$000(main.java:35)
at com.cynetstudios.frequencyselector.main$1$1.run(main.java:115)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5291)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
I require this int value for further processing,
what is causing this no instance field?

This may be useful,check this link
https://developer.android.com/reference/android/net/wifi/ScanResult.html>