Android 清单中无法识别活动

Question

I'm trying to make a simple program where if I go and click a button in my app a new activity pops up that asks to input a browser. Here's the Exception I keep recieving:

02-26 04:38:11.900 1937-1937/? E/AndroidRuntime: FATAL EXCEPTION: main
    android.content.ActivityNotFoundException: Unable to find explicit activity class
        {com.course.example.widgets/com.course.example.widgets.WebLookup};
    have you declared this activity in your AndroidManifest.xml?
        at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1618)
        at android.app.Instrumentation.execStartActivity(Instrumentation.java:1417)
        at android.app.Activity.startActivityForResult(Activity.java:3370)
        at android.app.Activity.startActivityForResult(Activity.java:3331)
        at android.app.Activity.startActivity(Activity.java:3566)
        at android.app.Activity.startActivity(Activity.java:3534)
        at com.course.example.widgets.Widgets.onClick(Widgets.java:139)
        at android.view.View.performClick(View.java:4204)
        at android.view.View$PerformClick.run(View.java:17355)
        at android.os.Handler.handleCallback(Handler.java:725)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5041)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
        at dalvik.system.NativeStart.main(Native Method)

Here's my manifest xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.course.example.widgets"
      android:versionCode="1"
      android:versionName="1.0">

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Widgets"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="com.course.example.widgets.WebLookup"
                    android:label="@string/app_name"/>
    </application>
    <uses-sdk android:minSdkVersion="17" />
    <uses-permission android:name="android.permission.CALL_PHONE" />
</manifest> 

Here's the code that actually starts the activity:

case R.id.webButton:{
    Intent webLookup = new Intent(this, WebLookup.class);
    startActivity(webLookup);
    break;

It's in a switch block that is for determining 3 other button actions but I didn't think it was relevant.

Here's a picture of XML file and my two Java files in navigator on left.

Answer 1

Declare this Activity to AndroidMenifest , you error might be have not written package name before activity name

<activity
            android:name=".WebLookup" //write package name before activity name
            android:configChanges="orientation" //optional
            android:screenOrientation="portrait" //optional
            android:windowSoftInputMode="adjustResize" /> //optional

Answer 2

If you are adding this activity class manually, verify that the class is set to public. This way the AndroidManifest.xml should automatically show your activity class as a possible option.

public MyActivityClass extends AppCompatActivity{
...
}

Answer 3

If you have not included the package path at the top of the class you wont be able to reference it in the manifest, eg

Answer 4

use

<activity android:name="com.course.example.widgets.WebLookup"
                    android:label="@string/app_name"/>

the full name of the activity is much more comfortable in practice.

com.course.example.widgets.WebLookup mean the full path to your Activity class file.

Answer 5

You have to provide complete package name like this

<activity android:name="com.course.example.widgets.WebLookup"
                    android:label="@string/app_name"/>

Otherwise it will not detect your class whom to transfer the intent.