Question

我的应用程序运行完美然后突然出现错误，我不知道该怎么做..我应用不同的解决方案，但没有任何帮助..我正在使用片段查看寻呼机，当我在我的片段中添加按钮然后此错误后来这个我删除按钮但错误不会..

slider_activity类

public class Slider_activity extends FragmentActivity {

    ViewPager viewPager = null;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.slider_activity);
         setPager(); /// line 26
    }

    private void setPager(){
        viewPager = (ViewPager) findViewById(R.id.pager);
        FragmentManager fragmentManager = getSupportFragmentManager();
        viewPager.setAdapter(new MyAdapter(fragmentManager));

    }
}

slider_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</android.support.v4.view.ViewPager>

错误

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.amir.namaztimer/com.example.amir.namaztimer.Slider_activity}: java.lang.NullPointerException
                                                                               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
                                                                               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
                                                                               at android.app.ActivityThread.access$600(ActivityThread.java:141)
                                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
                                                                               at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                               at android.os.Looper.loop(Looper.java:137)
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5041)
                                                                               at java.lang.reflect.Method.invokeNative(Native Method)
                                                                               at java.lang.reflect.Method.invoke(Method.java:511)
                                                                               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
                                                                               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
                                                                               at dalvik.system.NativeStart.main(Native Method)
                                                                            Caused by: java.lang.NullPointerException
                                                                               at com.example.amir.namaztimer.Slider_activity.onCreate(Slider_activity.java:26)
                                                                               at android.app.Activity.performCreate(Activity.java:5104)
                                                                               at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
                                                                               at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
                                                                               at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
                                                                               at android.app.ActivityThread.access$600(ActivityThread.java:141) 
                                                                               at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
                                                                               at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                                               at android.os.Looper.loop(Looper.java:137) 
                                                                               at android.app.ActivityThread.main(ActivityThread.java:5041) 
                                                                               at java.lang.reflect.Method.invokeNative(Native Method)

Answer 1

如果您的xml名称为silder.xml，那么您将错误的xml放在contentview中。

写：

setContentView(R.layout.silder);

无法启动活动ComponentInfo ... java.lang.NullPointerException

1 个答案: