添加导航栏活动片段时遇到问题。我使用Android Studio中提供的默认导航栏使用片段。最初，$conn = new PDO("mysql:host=$host;dbname=$db_name",$username,$password);
$conn->query('SET NAMES UTF8');
$sql = "SELECT * FROM $tbl_name";
$q = $conn->prepare($sql);
$q->execute(array($title));
$q->setFetchMode(PDO::FETCH_BOTH);
$phpvar = '';
while($data = $q->fetchAll()){
$phpvar .= $data->names;
$phpvar .= ',';
}
echo rtrim($phpvar, ",");
中的代码是（工作正常）：
MainActivity.java但是在修改它以在选择的导航抽屉项目上显示特定片段之后，我添加了以下代码而不是上面的代码＆amp;该应用崩溃。 ：
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.container, PlaceholderFragment.newInstance(position + 1))
.commit();
}
其他信息： 我通过File-＆gt; New-＆gt; Fragment-＆gt; Fragment（Blank）创建了2个片段（MyFragment1＆amp; MyFragment2）。
没有语法错误
根据需要记录：
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
Fragment fragment;
FragmentManager fragmentManager = getFragmentManager();
switch(position){
default:
case 0:
fragment=new MyFragment1();
break;
case 1:
fragment=new MyFragment2();
break;
}
fragmentManager.beginTransaction()
.replace(R.id.container, fragment)
.commit();
}
11-28 15:12:17.137 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ Late-enabling CheckJNI
11-28 15:12:17.177 26622-26622/com.example.harni_000.navigationdrawer D/ActivityThread﹕ handleBindApplication:com.example.harni_000.navigationdrawer
11-28 15:12:17.177 26622-26622/com.example.harni_000.navigationdrawer D/ActivityThread﹕ setTargetHeapUtilization:0.75
11-28 15:12:17.177 26622-26622/com.example.harni_000.navigationdrawer D/ActivityThread﹕ setTargetHeapMinFree:2097152
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ VFY: unable to find class referenced in signature (Landroid/view/SearchEvent;)
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer I/dalvikvm﹕ Could not find method android.view.Window$Callback.onSearchRequested, referenced from method android.support.v7.view.WindowCallbackWrapper.onSearchRequested
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ VFY: unable to resolve interface method 14530: Landroid/view/Window$Callback;.onSearchRequested (Landroid/view/SearchEvent;)Z
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ VFY: replacing opcode 0x72 at 0x0002
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer I/dalvikvm﹕ Could not find method android.view.Window$Callback.onWindowStartingActionMode, referenced from method android.support.v7.view.WindowCallbackWrapper.onWindowStartingActionMode
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ VFY: unable to resolve interface method 14534: Landroid/view/Window$Callback;.onWindowStartingActionMode (Landroid/view/ActionMode$Callback;I)Landroid/view/ActionMode;
11-28 15:12:17.197 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ VFY: replacing opcode 0x72 at 0x0002
11-28 15:12:17.207 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ GetMethodID: not returning static method Landroid/os/Process;.getTotalMemory ()J
11-28 15:12:17.207 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ GetMethodID: not returning static method Landroid/os/Process;.getFreeMemory ()J
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.widget.TintTypedArray.getChangingConfigurations
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ VFY: unable to resolve virtual method 416: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer I/dalvikvm﹕ Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.widget.TintTypedArray.getType
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ VFY: unable to resolve virtual method 438: Landroid/content/res/TypedArray;.getType (I)I
11-28 15:12:17.237 26622-26622/com.example.harni_000.navigationdrawer D/dalvikvm﹕ VFY: replacing opcode 0x6e at 0x0002
11-28 15:12:17.297 26622-26622/com.example.harni_000.navigationdrawer D/AndroidRuntime﹕ Shutting down VM
11-28 15:12:17.297 26622-26622/com.example.harni_000.navigationdrawer W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x415f5d58)
11-28 15:12:17.297 26622-26622/com.example.harni_000.navigationdrawer E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.harni_000.navigationdrawer, PID: 26622
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.harni_000.navigationdrawer/com.example.harni_000.navigationdrawer.MainActivity}: java.lang.ClassCastException: com.example.harni_000.navigationdrawer.MainActivity@424062c8 must implement OnFragmentInteractionListener
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2200)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2249)
at android.app.ActivityThread.access$800(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1212)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5113)
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:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassCastException: com.example.harni_000.navigationdrawer.MainActivity@424062c8 must implement OnFragmentInteractionListener
at com.example.harni_000.navigationdrawer.MyFragment1.onAttach(MyFragment1.java:83)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:849)
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
at android.app.BackStackRecord.run(BackStackRecord.java:690)
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1449)
at android.app.Activity.performStart(Activity.java:5257)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2249)
at android.app.ActivityThread.access$800(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1212)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5113)
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:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)
的代码
MyFragment1.java