在活动启动时更改线性布局背景图像

Question

I change Linear Layout background image via this code:

mainlayout.setBackgroundResource(R.drawable.back);

But i want do this on every time that activity starts, In first start and switching between activities. I put this code inside an IF statement in onCreate() but background not change! Of course when i set this code to a button works fine! How and where i have to put my code?

my complete code is:

            //check theme id
    if(myDbHelper.gettheme()==1)
    {
        mainlayout.setBackgroundResource(R.drawable.back);
    }else if(myDbHelper.gettheme()==2)
    {
        mainlayout.setBackgroundResource(R.drawable.blueback);
    }

Answer 1

You need to put your code into the onResume() method.

Here are details that will explain why http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle

Answer 2

您可能要参考Android活动生命周期 ，但我建议使用onResume()方法。

Answer 3

EDIT: Are you sure theme is either 1 or 2?

If you want to do it everytime, why don't you just define it as mainLayout's background in your layout.xml? Otherwise, use onResume() rather than onCreate().

Answer 4

I'm assuming based off your code snippet you have the image you want as a background as a drawable resource already in project. If so you could just go into the XML and add into the linerayout:

android:background="@drawable/back"

This should just set the background within the XML layout avoiding having to have code set it within one of the activity life-cycle functions.

Though in the case you wanted different themes as I just saw in the original post (seemed to be edited since I was typing this up), you could try storing the constant int of the R.drawable that the user wants as the background or theme, and have your DB Helper's getTheme() return that reference to set the background without the if statements.

Such saying the user changes their preference to R.drawable.black or .blueback store the int within the DB so it get return by gettheme rather than a 1 or 2 enumeration. Not sure if this would be a best practice though.