Android以编程方式更改imageview

Question

I am making an android app where the same imageview is displayed every time the user enters a value. but I want the imageview to be changed every time the user enters a value. I wrote a code to do this but the problem is after the first image is displayed I face black screen and it takes me to the first page in the app, it doesn't crash just shows black screen.

here is the imageview code in xml file:

    <ImageView
        android:id="@+id/ImageSuccess"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_gravity="center"
        android:layout_marginBottom="20dip"
        android:layout_marginTop="20dip"
        android:scaleType="centerInside"
        android:src="@drawable/image1" />

and here where I changed the imageview in java file:

  ImageView myImage= (ImageView) findViewById(R.id.ImageSuccess);    

   if(userVlue.equals("SCHOOL")){

        myImage.setImageResource(R.drawable.image1);    
    }
    else if(userVlue.equals("CAR")){
        myImage.setImageResource(R.drawable.image2);    
    }
   else if(userVlue.equals("TOY")){
       myImage.setImageResource(R.drawable.image3); 
    }

Answer 1

One of myImage or userVlue is not set properly and probably is null. Debug and share logs. Your partcular activity is getting distroyed probably because of nullpointexception hence returning to main activity in backtrack.

I tried with a sample app and your logic is working perfectly.

You are handling user action on some UI element, when you do findViewById, cotext is that UI element, so this method searches ImageSuccess in children of it. Try giving page layout as rootlayout and do rootlayout.findViewById("ImageSuccess");

Answer 2

我终于找到了解决方案，因为图像仅在可绘制文件中而出现了黑屏，所以我需要在所有可绘制桥文件夹中添加图像，例如drawable-ldp，drawable-ldpi等。可以在不同尺寸的手机上使用。