Change background color of an item in Android List

问题:

I know it sounds very simple, and there are questions about this. But none of it could solve my problem. So here we go:

I want to change background color of a list item in a ListActivity when user clicks on it, and change it back to original color when user clicks again (i.e. Select/Unselect item sort of look)

I tried using getChildAt, it works perfectly if I have all the items visible in one screen without having to scroll.

Code:

getListView().getChildAt(position).setBackgroundColor(Color.CYAN);

The problem begins when I have more items in the list and user has to scroll through them. Once background for an item is changed, The background color shows up on the newly visible items as I scroll. Also, the getChildAt(position) returns null (and hence a NullPointerException) when clicking again on the item.

Can anyone please help me with a simple code that helps me change background color of a list item?

Thanks in advance!

回答1:

Sure thing. I would do this in the getView() method of a custom ListAdapter.

MyAdapter extends SimpleAdapter {
    private ArrayList<Integer> coloredItems = new ArrayList<Integer>();

    public MyAdapter(...) {
        super(...);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = super.getView(position, convertView, parent);

        if (coloredItems.contains(position)) {
            v.setBackgroundColor(Color.CYAN);
        } else {
            v.setBackgroundColor(Color.BLACK); //or whatever was original
        }

        return v;
    }
}

Update coloredItems when a list item is clicked.

@Override
public void onListItemClick(ListView l, View v, int position, long id) {
    if (coloredItems.contains(position)) {
        //remove position from coloredItems
        v.setBackgroundColor(Color.BLACK); //or whatever was original
    } else {
        //add position to coloredItems
        v.setBackgroundColor(Color.CYAN);
    }
}

回答2:

If you are dealing with ListFragment then this code will be helpful,

  @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        if (view != null) {
            getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
            getListView().setDescendantFocusability(ListView.FOCUS_AFTER_DESCENDANTS);
            catagoryValueListView=getListView();
            catagoryValueListView.setOnItemClickListener(new OnItemClickListener() {

             @Override
             public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                 if (ColoredView != null)
                     ColoredView.setBackgroundColor(Color.WHITE); //original color

                 view.setBackgroundColor(Color.BLUE); //selected color
                 ColoredView = view;
                                  }
        });
    }

}

回答3:

What I do is I create an xml file called i.e. list_background and put it in the drawable folder.

The xml looks like this:

<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:drawable="@color/list_selected" android:state_pressed="true" />
   <item android:drawable="@android:color/white" />
</selector>

And in the xml code for the ListView's item I put this xml as the items background i.e.

item.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
          style="@style/Fill"
          android:background="@drawable/list_background">

     <!-- Your layout here -->
</RelativeLayout>

style=@style/Fill is only a short cut i made for android:layout_height="match_parent" and android:layout_width="match_parent

Then in onListItemCLick:

public void onListItemClick(ListView l, View v, int position, long id) {
    v.setPressed( !v.isPressed ) //Toggle between colors of the view
}

回答4:

Simply you can do it like this in onListItemClick method

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    super.onListItemClick(l, v, position, id);

    for (int a = 0; a < l.getChildCount(); a++) {
        l.getChildAt(a).setBackgroundColor(Color.TRANSPARENT);
    }

    ColorDrawable colorDrawable1 = new ColorDrawable(
            Color.parseColor("#A0A3A0"));
    v.setBackgroundDrawable(colorDrawable1);   

    if (position == 0) {
        Intent i = new Intent(MainActivity.this, NewActivity.class);

        startActivity(i);
    }

}

回答5:

this is how I did it:

create a global variable View ColoredView; then when you setOnItemClickListener for your ListView, do this:

MenuList.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                if (ColoredView != null)
                    ColoredView.setBackgroundColor(Color.WHITE); //original color

                view.setBackgroundColor(Color.BLUE); //selected color
                ColoredView = view;
            }
        });

it's the simplest way in my opinion.

回答6:

Thanks heycosmo. your solution solved my problem.

Have no clue why we should set background in 2 places.

1. Adapter's getView()

@Override
public View getView(int position, View convertView, ViewGroup parent) {
     ....
     ....
     ....
        if(arrayBools[position]) {
            view.setBackgroundColor(Common.colorBkgroundSelected);
        }
        else{
            view.setBackgroundColor(Common.colorBkgroundNormal);            
        } 
     ....
     ....
     ....
}

2. ListActivity's onListItemClick().

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
      super.onListItemClick(l, v, position, id);       
      arrayBools[position] = ( arrayBools[position] ? false : true );

     if(arrayBools[position]) {
         v.setBackgroundColor(colorBkgroundSelected);
     }
     else{
        v.setBackgroundColor(colorBkgroundNormal);          
     }    
}