Question

For my activity, I created a new view and saved it in a public static field. I then set the view with setContentView in the activity. However, whenever I try to change the color of the view from another class, I get a exception as follows:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.TwinBlade.PicturePassword/com.TwinBlade.PicturePassword.LockActivity}: java.lang.ClassNotFoundException: com.TwinBlade.PicturePassword.LockActivity
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
at android.app.ActivityThread.access$600(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:4945)
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:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassNotFoundException: com.TwinBlade.PicturePassword.LockActivity
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
    at android.app.Instrumentation.newActivity(Instrumentation.java:1039)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
    ... 11 more

java.lang.ClassNotFoundException: com.TwinBlade.PicturePassword.LockActivity
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:61)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:501)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:461)
    at android.app.Instrumentation.newActivity(Instrumentation.java:1039)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
    at android.app.ActivityThread.access$600(ActivityThread.java:139)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:4945)
    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:784)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    at dalvik.system.NativeStart.main(Native Method)

UPDATE:

Here is what i did in my activity

public static View mView;

public void onCreate(Bundle savedInstanceState) {
    mView = new LinearLayout(this);
    mView.setBackgroundColor(Color.argb(0, 0, 0, 0));
    setContentView(mView);
}

And to change the color of the view from another class:

LockActivity.mView.setBackgroundColor(Color.argb(255, 0, 0, 0));

The activity is added in the manifest and can be launched.

Any help would be appreciated

Answer 1

context.findViewById(); the context is your activity or you can try to

View view = (View) =LayoutInflater.from(activity.this).inflate(your layout,null)