Question
So, as a bit of background, I am currently an iOS developer, and I wanted to branch out and develop for android as well, and I finally found time to do so.
I've been watching some video tutorials on developing for android, and in the lesson we made a simple app that when you click one button it adds 1 and when you click another it subtracts.
There's also a small textview which the number value of the total changes as well when the button is clicked, all of which can be easily identified in the code.
However, when I build and run the app, it displays an error on the screen saying "Unfortunately (Name of app) has stopped."
Add upon debugging the app only stops working and displays this message after I add my first On Click Listener method.
Here is the main XML:
https://stackoverflow.com/questions/22413329
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Russian <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Your total is 0"
android:textSize="45dp"
android:layout_gravity="center"
android:gravity="center"
android:id="@+id/tvDisplay"
/>
<Button
android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="Add One"
android:layout_gravity="center"
android:textSize="20dp"
android:id="@+id/bAdd"
/>
<Button
android:layout_width="250dp"
android:layout_height="wrap_content"
android:text="Subtract One"
android:layout_gravity="center"
android:textSize="20dp"
android:id="@+id/bSub"
/>
</LinearLayout>
Here is the Manifest XML:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.tutorial.thenewboston"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="13"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.tutorial.thenewboston.StartingPoint"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
Here is the Java:
public class StartingPoint extends ActionBarActivity {
int counter;
Button add, sub;
TextView display;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_starting_point);
counter = 0;
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter--;
display.setText("Your total is " + counter);
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
Here is the LogCat:
03-14 14:53:41.111: D/AndroidRuntime(17884): Shutting down VM
03-14 14:53:41.111: W/dalvikvm(17884): threadid=1: thread exiting with uncaught exception (group=0x41ce4ba8)
03-14 14:53:41.111: E/AndroidRuntime(17884): FATAL EXCEPTION: main
03-14 14:53:41.111: E/AndroidRuntime(17884): Process: com.tutorial.thenewboston, PID: 17884
03-14 14:53:41.111: E/AndroidRuntime(17884): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tutorial.thenewboston/com.tutorial.thenewboston.StartingPoint}: java.lang.NullPointerException
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.os.Handler.dispatchMessage(Handler.java:102)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.os.Looper.loop(Looper.java:136)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-14 14:53:41.111: E/AndroidRuntime(17884): at java.lang.reflect.Method.invokeNative(Native Method)
03-14 14:53:41.111: E/AndroidRuntime(17884): at java.lang.reflect.Method.invoke(Method.java:515)
03-14 14:53:41.111: E/AndroidRuntime(17884): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-14 14:53:41.111: E/AndroidRuntime(17884): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-14 14:53:41.111: E/AndroidRuntime(17884): at dalvik.system.NativeStart.main(Native Method)
03-14 14:53:41.111: E/AndroidRuntime(17884): Caused by: java.lang.NullPointerException
03-14 14:53:41.111: E/AndroidRuntime(17884): at com.tutorial.thenewboston.StartingPoint.onCreate(StartingPoint.java:31)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.Activity.performCreate(Activity.java:5231)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-14 14:53:41.111: E/AndroidRuntime(17884): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-14 14:53:41.111: E/AndroidRuntime(17884): ... 11 more
Console Log:
[2014-03-14 15:09:31 - TheNewBoston] ------------------------------
[2014-03-14 15:09:31 - TheNewBoston] Android Launch!
[2014-03-14 15:09:31 - TheNewBoston] adb is running normally.
[2014-03-14 15:09:31 - TheNewBoston] Performing com.tutorial.thenewboston.StartingPoint activity launch
[2014-03-14 15:09:31 - TheNewBoston] Automatic Target Mode: using device '015d483bce140216'
[2014-03-14 15:09:31 - TheNewBoston] Application already deployed. No need to reinstall.
[2014-03-14 15:09:31 - TheNewBoston] Starting activity com.tutorial.thenewboston.StartingPoint on device 015d483bce140216
[2014-03-14 15:09:32 - TheNewBoston] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.tutorial.thenewboston/.StartingPoint }
And here is some more hopefully relevant information: I'm testing my apps on my personal Android Tablet not the Simulator, because the sim is dirt slow. My tablet is an Asus Nexus 7, with NVIDIA Tegra 3 1.20GHz 1GB RAM, 32GB Flash Storage and is running Kit Kat, 4.4.2
EDIT:
My previous java contained an error which was linking it to my main XML view. it was calling activity_starting_point when it should have been calling fragment_starting_point.
This is the new code
public class StartingPoint extends ActionBarActivity {
int counter;
Button add, sub;
TextView display;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.fragment_starting_point);
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter--;
display.setText("Your total is " + counter);
}
});
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
However my problem is the exact same, the app crashes with the same message as before, but it does contain new logcat info:
03-14 15:25:44.621: E/FragmentManager(20269): No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: E/FragmentManager(20269): Activity state:
03-14 15:25:44.621: D/FragmentManager(20269): Local FragmentActivity 4245cf60 State:
03-14 15:25:44.621: D/FragmentManager(20269): mCreated=truemResumed=false mStopped=false mReallyStopped=false
03-14 15:25:44.621: D/FragmentManager(20269): mLoadersStarted=false
03-14 15:25:44.621: D/FragmentManager(20269): Active Fragments in 4245e0b8:
03-14 15:25:44.621: D/FragmentManager(20269): #0: PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: D/FragmentManager(20269): mFragmentId=#7f05003c mContainerId=#7f05003c mTag=null
03-14 15:25:44.621: D/FragmentManager(20269): mState=0 mIndex=0 mWho=android:fragment:0 mBackStackNesting=0
03-14 15:25:44.621: D/FragmentManager(20269): mAdded=true mRemoving=false mResumed=false mFromLayout=false mInLayout=false
03-14 15:25:44.621: D/FragmentManager(20269): mHidden=false mDetached=false mMenuVisible=true mHasMenu=false
03-14 15:25:44.621: D/FragmentManager(20269): mRetainInstance=false mRetaining=false mUserVisibleHint=true
03-14 15:25:44.621: D/FragmentManager(20269): mFragmentManager=FragmentManager{4245e0b8 in StartingPoint{4245cf60}}
03-14 15:25:44.621: D/FragmentManager(20269): mActivity=com.tutorial.thenewboston.StartingPoint@4245cf60
03-14 15:25:44.621: D/FragmentManager(20269): Added Fragments:
03-14 15:25:44.621: D/FragmentManager(20269): #0: PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.621: D/FragmentManager(20269): FragmentManager misc state:
03-14 15:25:44.621: D/FragmentManager(20269): mActivity=com.tutorial.thenewboston.StartingPoint@4245cf60
03-14 15:25:44.621: D/FragmentManager(20269): mContainer=android.support.v4.app.FragmentActivity$2@4245ea30
03-14 15:25:44.621: D/FragmentManager(20269): mCurState=2 mStateSaved=false mDestroyed=false
03-14 15:25:44.621: D/FragmentManager(20269): View Hierarchy:
03-14 15:25:44.621: D/FragmentManager(20269): com.android.internal.policy.impl.PhoneWindow$DecorView{424636b0 V.E..... ... 0,0-0,0}
03-14 15:25:44.621: D/FragmentManager(20269): com.android.internal.widget.ActionBarOverlayLayout{424646a0 V.ED.... ... 0,0-0,0 #1020313 android:id/action_bar_overlay_layout}
03-14 15:25:44.621: D/FragmentManager(20269): android.widget.FrameLayout{42465448 V.E..... ... 0,0-0,0 #1020002 android:id/content}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.LinearLayout{42472528 V.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.TextView{42472840 V.ED.... ... 0,0-0,0 #7f05003d app:id/tvDisplay}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.Button{42472e30 VFED..C. ... 0,0-0,0 #7f05003e app:id/bAdd}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.Button{42473838 VFED..C. ... 0,0-0,0 #7f05003f app:id/bSub}
03-14 15:25:44.631: D/FragmentManager(20269): com.android.internal.widget.ActionBarContainer{42465960 V.ED.... ... 0,0-0,0 #1020314 android:id/action_bar_container}
03-14 15:25:44.631: D/FragmentManager(20269): com.android.internal.widget.ActionBarView{42465fb8 V.E..... ... 0,0-0,0 #1020315 android:id/action_bar}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.LinearLayout{42466718 V.....C. ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269): com.android.internal.widget.ActionBarView$HomeView{42467a90 V.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.ImageView{42467f58 G.ED.... ... 0,0-0,0 #102025a android:id/up}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.ImageView{42469038 V.ED.... ... 0,0-0,0 #102002c android:id/home}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.LinearLayout{4246a3f0 G.E..... ... 0,0-0,0}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.TextView{4246a890 V.ED.... ... 0,0-0,0 #1020265 android:id/action_bar_title}
03-14 15:25:44.631: D/FragmentManager(20269): android.widget.TextView{4246b578 G.ED.... ... 0,0-0,0 #1020266 android:id/action_bar_subtitle}
03-14 15:25:44.631: D/FragmentManager(20269): com.android.internal.widget.ActionBarContextView{4246bc60 G.E..... ... 0,0-0,0 #1020316 android:id/action_context_bar}
03-14 15:25:44.631: D/FragmentManager(20269): com.android.internal.widget.ActionBarContainer{4246c248 G.ED.... ... 0,0-0,0 #1020317 android:id/split_action_bar}
03-14 15:25:44.631: D/AndroidRuntime(20269): Shutting down VM
03-14 15:25:44.631: W/dalvikvm(20269): threadid=1: thread exiting with uncaught exception (group=0x41ce4ba8)
03-14 15:25:44.631: E/AndroidRuntime(20269): FATAL EXCEPTION: main
03-14 15:25:44.631: E/AndroidRuntime(20269): Process: com.tutorial.thenewboston, PID: 20269
03-14 15:25:44.631: E/AndroidRuntime(20269): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tutorial.thenewboston/com.tutorial.thenewboston.StartingPoint}: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread.access$800(ActivityThread.java:135)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.os.Handler.dispatchMessage(Handler.java:102)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.os.Looper.loop(Looper.java:136)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread.main(ActivityThread.java:5017)
03-14 15:25:44.631: E/AndroidRuntime(20269): at java.lang.reflect.Method.invokeNative(Native Method)
03-14 15:25:44.631: E/AndroidRuntime(20269): at java.lang.reflect.Method.invoke(Method.java:515)
03-14 15:25:44.631: E/AndroidRuntime(20269): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-14 15:25:44.631: E/AndroidRuntime(20269): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-14 15:25:44.631: E/AndroidRuntime(20269): at dalvik.system.NativeStart.main(Native Method)
03-14 15:25:44.631: E/AndroidRuntime(20269): Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f05003c (com.tutorial.thenewboston:id/container) for fragment PlaceholderFragment{4247a988 #0 id=0x7f05003c}
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:919)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.Activity.performStart(Activity.java:5241)
03-14 15:25:44.631: E/AndroidRuntime(20269): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
03-14 15:25:44.631: E/AndroidRuntime(20269): ... 11 more
Solution
EDIT:
I just watched the tutoiral:
You are setting the wrong layout file:
setContentView(R.layout.activity_starting_point);
You are supposed to set:
setContentView(R.layout.main);
Assuming what you are saying in your question is correct and the XML code you posted really belongs to "main.xml". This is why you are getting a NullPointerException. The Views (TextView, Button, ...) you are trying to reference are not in the layout file you set as the content view.
OTHER TIPS
Try this:
add = (Button) findViewById(R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter++;
display.setText("Your total is " + counter);
}
});
sub.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter--;
display.setText("Your total is " + counter);
}
});
Regards. Jose
