하나의 RelativeLayout에 중첩 된 3 개의 RelativeLayouts가 포함 된 앱을 만들려고합니다. RelativeLayouts의 가시성을 프로그래밍 방식으로 변경하고 싶습니다. 내 스마트 폰 (Android 4.4.2)에서는 정상적으로 작동하지만 태블릿에서는 안됩니다 (Android 5.1.1)Android : Findviewbyid()가 null을 반환합니다.
findViewById()
이 태블릿에서 호출되면 null을 반환합니다.
내가 뭘 잘못하고 있니?
MainActivity.java :
RelativeLayout mainactivity, multiplewifi, nowifi;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState != null) //if switched from landscape to portrait mode or vice versa
((WebView) findViewById(R.id.webvieew)).restoreState(savedInstanceState); //restore webview
else {
Initialize();
wifiManager.startScan(); //start a scan for available wifi networks
}
}
public void Initialize() {
mainactivity = (RelativeLayout) findViewById(R.id.MainActivity);
multiplewifi = (RelativeLayout) findViewById(R.id.MultipleWifi);
nowifi = (RelativeLayout) findViewById(R.id.NoWifi);
}
activity_main.xml :
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<RelativeLayout
android:id="@+id/MultipleWifi">
<Button/>
<TextView/>
<Spinner/>
</RelativeLayout>
<RelativeLayout
android:id="@+id/MainActivity">
<WebView
android:id="@+id/webvieew"/>
<ImageButton/>
</RelativeLayout>
<RelativeLayout
android:id="@+id/NoWifi">
<TextView/>
</RelativeLayout>
로그 :
응용 프로그램이 휴대 전화에 있지만 태블릿에 노력하고 있습니다E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.wdt, PID: 5243
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.wdt/com.example.wdt.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.setVisibility(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2335)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1310)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5268)
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:902)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.setVisibility(int)' on a null object reference
at com.example.wdt.MainActivity.Initialize(MainActivity.java:95)
at com.example.wdt.MainActivity.onCreate(MainActivity.java:75)
at android.app.Activity.performCreate(Activity.java:6033)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2288)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2397)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1310)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5268)
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:902)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:697)
stacktrace도 게시하십시오. – user2582318
여러분의 acitivty에서 어디서든 호출 할 수 있습니다 ... 문제가 아닙니다 ... –
이 줄에 id를 입력하지 않았습니다. ((WebView) findViewById (R.id .webvieew)). restoreState (savedInstanceState); // 웹 뷰 복원 XML에 안드로이드 : id = "@ + id/webvieew"가 없습니다. 문제가 있다고 생각합니다. –