タブ表示の学習の過程で、サンプルアプリを制作しました。
が、表題の通りエミュレータで起動するタイミングで強制終了されてしまいます。
原因の特定ができず困っています。。
完成時にエラーが出ていなかったので、構文以外の原因でしょうか?
ご教示のほどよろしくお願いします
■参考URL
http://qiita.com/mackiso/items/bb3cacac6c0bfb9eb3df
■エラーログ
04-06 04:12:34.168 1559-1559/? E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapp_fragment/com.example.myapp_fragment.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.myapp_fragment.MainActivity.onCreate(MainActivity.java:22)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
■MainActivity
java
1import android.app.ActionBar; 2import android.os.Bundle; 3import android.support.design.widget.FloatingActionButton; 4import android.support.design.widget.Snackbar; 5import android.support.v7.app.AppCompatActivity; 6import android.support.v7.widget.Toolbar; 7import android.view.View; 8import android.view.Menu; 9import android.view.MenuItem; 10 11public class MainActivity extends AppCompatActivity { 12 @Override 13 protected void onCreate(Bundle savedInstanceState) { 14 super.onCreate(savedInstanceState); 15 setContentView(R.layout.activity_main); 16 17 //ActionBarをGetしてTabModeをセット 18 final ActionBar actionBar = getActionBar(); 19 actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); 20 actionBar.addTab(actionBar.newTab() 21 .setText("First") 22 .setTabListener(new TabListener<FirstTabFragment>( 23 this, "tag1", FirstTabFragment.class))); 24 actionBar.addTab(actionBar.newTab() 25 .setText("Second") 26 .setTabListener(new TabListener<SecondTabFragment>( 27 this, "tag2", SecondTabFragment.class))); 28 } 29 30} 31
■TabListener
java
1import android.app.ActionBar; 2import android.app.Activity; 3import android.app.Fragment; 4import android.app.FragmentManager; 5import android.app.FragmentTransaction; 6 7public class TabListener<T extends Fragment> implements ActionBar.TabListener { 8 private Fragment mFragment; 9 private final Activity mActivity; 10 private final String mTag; 11 private final Class<T> mClass; 12 13 //コンストラクタ 14 public TabListener(Activity activity, String tag, Class<T> clz) { 15 mActivity = activity; 16 mTag = tag; 17 mClass = clz; 18 mFragment = mActivity.getFragmentManager().findFragmentByTag(mTag); 19 } 20 21 //タブが選択されたとき 22 public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) { 23 if (mFragment == null) { 24 mFragment = Fragment.instantiate(mActivity, mClass.getName()); 25 FragmentManager fm = mActivity.getFragmentManager(); 26 fm.beginTransaction().add(R.id.container, mFragment, mTag).commit(); 27 } else { 28 if (mFragment.isDetached()) { 29 FragmentManager fm = mActivity.getFragmentManager(); 30 fm.beginTransaction().attach(mFragment).commit() ; 31 } 32 } 33 } 34 35 //タブの選択が解除されたとき 36 public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) { 37 if (mFragment != null) { 38 FragmentManager fm = mActivity.getFragmentManager(); 39 fm.beginTransaction().detach(mFragment).commit(); 40 } 41 } 42 43 //選択されたタブが選択されたとき 44 public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) { 45 } 46}
■FirstTabFragment
java
1import android.os.Bundle; 2import android.app.Fragment; 3import android.view.LayoutInflater; 4import android.view.View; 5import android.view.ViewGroup; 6 7public class FirstTabFragment extends Fragment { 8 9 public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 10 return inflater.inflate(R.layout.fragment_first_tab, container, false); 11 } 12 13}
■SecondTabFragment
javs
1import android.os.Bundle; 2import android.app.Fragment; 3import android.view.LayoutInflater; 4import android.view.View; 5import android.view.ViewGroup; 6 7public class SecondTabFragment extends Fragment { 8 9 public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 10 return inflater.inflate(R.layout.fragment_first_tab, container, false); 11 } 12 13}
■AndroidManifest.xml
xml
1<?xml version="1.0" encoding="utf-8"?> 2<manifest xmlns:android="http://schemas.android.com/apk/res/android" 3 package="com.example.kmatsumaru.myapp_fragment"> 4 5 <application 6 android:allowBackup="true" 7 android:icon="@mipmap/ic_launcher" 8 android:label="@string/app_name" 9 android:supportsRtl="true" 10 android:theme="@style/AppTheme"> 11 <activity 12 android:name=".MainActivity" 13 android:label="@string/app_name" 14 android:theme="@style/AppTheme.NoActionBar"> 15 <intent-filter> 16 <action android:name="android.intent.action.MAIN" /> 17 18 <category android:name="android.intent.category.LAUNCHER" /> 19 </intent-filter> 20 </activity> 21 </application> 22 23</manifest> 24