为什么在Android Studio中出现与主题相关的错误？

Question

I am following a tutorial on how to make a launcher but for some reason when I add this line of code to my main activity with in the manifest the app crashes saying that my app has stopped

 android:theme="@android:style/Theme.Holo.Wallpaper.NoTitleBar" 

 10-18 15:04:25.245 18122-18122/com.example.harrops.h20droidlauncher E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.harrops.h20droidlauncher, PID: 18122 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.harrops.h20droidlauncher/com.example.harrops.h20droidlauncher.HomeLayout}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity. at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2400) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2458) at android.app.ActivityThread.access$900(ActivityThread.java:172) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1305) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:146) at android.app.ActivityThread.main(ActivityThread.java:5598) 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:1283) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity. at android.support.v7.app.AppCompatDelegateImplV7.createSubDecor(AppCompatDelegateImplV7.java:309) at android.support.v7.app.AppCompatDelegateImplV7.ensureSubDecor(AppCompatDelegateImplV7.java:278) at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:252) at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109) at com.example.harrops.h20droidlauncher.HomeLayout.onCreate(HomeLayout.java:13) at android.app.Activity.performCreate(Activity.java:5459) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2458)            at android.app.ActivityThread.access$900(ActivityThread.java:172)            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1305)            at android.os.Handler.dispatchMessage(Handler.java:102)            at android.os.Looper.loop(Looper.java:146)            at android.app.ActivityThread.main(ActivityThread.java:5598)            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:1283)            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)            at dalvik.system.NativeStart.main(Native Method) 

if I remove the line of code the app runs just fine.

Any help would be great. Thanks as always in advance.

Answer 1

To change the Background use:

 android:background=" "

You selected a wallpaper.

Try this instead

android:background="#b6db49">

Below you have said that you want to use the theme. So you have to go in the manifest and edit the theme there which is

    <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.Holo.Wallpaper.NoTitleBar">

Answer 2

If You've begun Your project in Android Studio by default main activity extends ActionBarActivity which requires the AppCompat theme. Change the Java inheritance from ActionBarActivity to Activity and leave the theme in the manifest as it is. Or use AppCompat theme.