![](/img/trans.png)
[英]Android Listview: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
[英]FacebookSdk Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
最近,我想使用Facebook api在我的应用程序中添加Facebook共享按钮,但是在尝试在设备上安装该应用程序时出现此错误:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.uz.zgora.tourdebar/com.uz.zgora.tourdebar.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:163)
at android.app.ActivityThread.main(ActivityThread.java:6238)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.uz.zgora.tourdebar.MainActivity.onCreate(MainActivity.java:95)
at android.app.Activity.performCreate(Activity.java:6857)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2676)
这是我的onCreate
方法:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FacebookSdk.sdkInitialize(this.getApplicationContext());
buttonShare = (Button) findViewById(R.id.nav_share);
callbackManager = CallbackManager.Factory.create();
shareDialog = new ShareDialog(this);
buttonShare.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ShareLinkContent linkContent = new ShareLinkContent.Builder().setQuote("This is useful link").setContentUrl(Uri.parse("https://google.de")).build();
if(ShareDialog.canShow(ShareLinkContent.class)){
shareDialog.show(linkContent);
}
}
});
}
这是我的布局(activity_main_drawer.xml):
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:showIn="navigation_view">
<group android:checkableBehavior="single">
<item
android:id="@+id/nav_map"
android:icon="@drawable/ic_menu_google_map"
android:title="Map" />
<item
android:id="@+id/nav_list"
android:icon="@drawable/ic_menu_bar_list"
android:title="List" />
</group>
<item android:title="Communicate">
<menu>
<item
android:id="@+id/nav_share"
android:icon="@drawable/ic_menu_share"
android:title="Share" />
<item
android:id="@+id/nav_send"
android:icon="@drawable/ic_menu_send"
android:title="Send" />
</menu>
</item>
我认为这个抽屉有问题。 也许当我创建按钮时, findviewbyid
存在问题,但是我想我已经尝试了所有findviewbyid
,但没有任何效果。
从activity_main_drawer.xml
,您正在使用菜单项。 您确定您的类文件中具有重写的onCreateOptionsMenu()
函数吗? 因为您需要给菜单充气。
从这里 ,您可以看到所需的方法。
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