android - getActionBar()、getSupportActionBar() 返回 java.nullpointer.exception

Question

我已将 appcompat 文件设置为项目属性。错误日志中没有错误，问题中也没有。 logcat 在 getActionBar 中显示错误 java.nullpointer.exception。当我评论该行时，应用程序运行良好。需要有关如何解决此问题的建议

ActionBar actionBar= getActionBar();

View cview= getLayoutInflater().inflate(R.layout.actionbar_menu, null);
actionBar.setCustomView(cview);

构建 Gradle 文件包含以下内容

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.2"

    defaultConfig {
        applicationId "com.example.bumpintomums"
        minSdkVersion 15
        targetSdkVersion 19
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
    packagingOptions {
        exclude 'META-INF/LICENSE.txt'
        exclude 'META-INF/NOTICE.txt'
    }
}

错误日志

FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.bumpintomums/com.current.amnepal.bumpintomum.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
            at android.app.ActivityThread.access$600(ActivityThread.java:123)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4424)
            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:817)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.current.amnepal.bumpintomum.MainActivity.onCreate(MainActivity.java:83)
            at android.app.Activity.performCreate(Activity.java:4470)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
            at android.app.ActivityThread.access$600(ActivityThread.java:123)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4424)
            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:817)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

您可以检查“Theme”是否应用在Activity中

如果是没有ActionBar的主题，尝试获取action bar会返回null。