Question

我希望（继承自Activity）通过第二个类来访问ImageView并进行更改。不幸的是，当我尝试这个时，我得到一个NullPointerExeption。第二个类没有XML，也没有onCreate（）方法。它仅从Activity继承，因为我需要一些函数。

那么如何访问布局或其他组件？

这是我的第二堂课的代码。

public void changeLoerg() {
    int stufe;
    //layout = (RelativeLayout)findViewById(R.id.LayoutMain);
    imageViewLoerg = (ImageView)findViewById(R.id.imageViewLoerg);

    stufe = SettingsLoerg.getLevel(context);

    Object tag = imageViewLoerg.getTag();

    if (stufe == 1) {
        int loergId = R.drawable.animatedegg;

        if( tag != null && ((Integer)tag).intValue() == loergId) {
            loergId = R.drawable.animatedloerg;
            animatedLoerg.stop();
            //playAnimationNodelay();
            imageViewLoerg.setTag(loergId);
            imageViewLoerg.setBackgroundResource(loergId);
            playAnimationNodelay();
        }
    }
}

Und hier das LogCat：

01-05 21:34:39.685: W/dalvikvm(9905): threadid=1: thread exiting with uncaught exception (group=0x41b5b300)
01-05 21:34:39.693: E/AndroidRuntime(9905): FATAL EXCEPTION: main
01-05 21:34:39.693: E/AndroidRuntime(9905): java.lang.NullPointerException
01-05 21:34:39.693: E/AndroidRuntime(9905):     at android.app.Activity.findViewById(Activity.java:1825)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at at.android.dertestloerk.TimerLoerg.changeLoerg(TimerLoerg.java:42)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at at.android.dertestloerk.TimerLoerg$1.run(TimerLoerg.java:100)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at android.os.Handler.handleCallback(Handler.java:615)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at android.os.Looper.loop(Looper.java:137)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at android.app.ActivityThread.main(ActivityThread.java:4745)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at java.lang.reflect.Method.invokeNative(Native Method)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at java.lang.reflect.Method.invoke(Method.java:511)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-05 21:34:39.693: E/AndroidRuntime(9905):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

如果您要修改此View的类，则应在该类中创建一个方法来修改所述View。然后，您可以在Activity中调用该方法，并将您需要的任何内容作为参数传递。

public class BackGround { // please don't extend Activity unless it is one

    private ImageView img;

    ....

    public void changeLoerg(int resourceId) {
        img.setBackgroundResource(resourceId);      
    }
}

Android - 从其他类的Imageview更改背景资源

1 个答案: