Matthew Deyell Matthew Deyell - 3 months ago 18
Android Question

Change Color of gridview cell on click

I have a gridview that contains text and images. When a user touches a cell in the grid, it changes color to show that it is selected and when selected again it returns to the default color to show that it is no longer selected. Any number of cells can be selected. The problem is when a user has to scroll through the grid to see all of the icons the selected icons sometimes become unselected and select "random" other cells.
I suspect this is related to the gridview being recycled but am unsure how to address this.

public class Onboarding extends Activity {
GridView grid;
ArrayList selectedCategories = new ArrayList<>();
CustomGrid adapter;
String[] dummyString = {
"item 1",
"item 2",
"item 3",
"item 4",
"item 5",
"item 6",
"item 7",
"item 8",
"item 9",
"item 10",
"item 11",
"item 12",
"item 13",
"item 14",
"item 15",
"item 16",
"item 17",
"item 18",
"item 19"
};
int[] imageId = {
R.drawable.1,
R.drawable.2,
R.drawable.3,
R.drawable.4,
R.drawable.5,
R.drawable.6,
R.drawable.7,
R.drawable.8,
R.drawable.9,
R.drawable.10,
R.drawable.11,
R.drawable.12,
R.drawable.13,
R.drawable.14,
R.drawable.15,
R.drawable.16,
R.drawable.17,
R.drawable.18,
R.drawable.19
};


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_onboarding);
getWindow().setSoftInputMode(
WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN
); //makes sure keyboard is hidden on this view as it is not needed
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_PORTRAIT);

grid = (GridView) findViewById(R.id.grid);

//deals with settings the number of Columns
DisplayMetrics displayMetrics = this.getResources().getDisplayMetrics();
double dpWidth = displayMetrics.widthPixels / displayMetrics.density;
if (dpWidth <= 400) {
grid.setNumColumns(2);
} else if (dpWidth > 400 && dpWidth < 500) {
grid.setNumColumns(3);
} else if (dpWidth >= 500 && dpWidth < 550) {
grid.setNumColumns(4);
} else {
grid.setNumColumns(5);
}

adapter = new CustomGrid(Onboarding.this, dummyString, imageId);
grid.setAdapter(adapter);
grid.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
//the position is the actual position that is pressed. but the getChildAt returns gets the relative position, ie what's being drawn
//on the grid.
//to fix this, the first visible position is obtained and the difference is subtracted
int firstPos = grid.getFirstVisiblePosition();
View tv = grid.getChildAt(position - firstPos);
Toast.makeText(Onboarding.this, "You Clicked at position" + position + " " + dummyString[+position] + "firstPos " + firstPos, Toast.LENGTH_SHORT).show(); //debug

if (tv == null) { //this shouldn't/doesn't happen
Log.e("OnBoarding.java", "Issue with null view at line " + Thread.currentThread().getStackTrace()[2].getLineNumber() +
"grid is having a problem");
return;
}

if (selectedCategories.contains(dummyString[+position]) == false) {//add the item if it doesn't exist
selectedCategories.add(dummyString[+position]);
tv.setBackgroundColor(Color.parseColor("#FFE5CD"));
} else { //remove the item if it already exists, as the user is removing it by touching it again
selectedCategories.remove(dummyString[+position]);
tv.setBackgroundColor(Color.parseColor("#EEEEEE"));
}
}
});

}


}

public class CustomGrid extends BaseAdapter {
private Context mContext;
private final String[] genreString;
private final int[] Imageid;

public CustomGrid(Context c, String[] genreString, int[] Imageid) {
mContext = c;
this.Imageid = Imageid;
this.genreString = genreString;
}

@Override
public int getCount() {
return genreString.length;
}

@Override
public Object getItem(int position) {
return null;
}

@Override
public long getItemId(int position) {
return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
View grid;
LayoutInflater inflater = (LayoutInflater) mContext
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
TextView textView;
ImageView imageView;
if (convertView == null) {
grid = inflater.inflate(R.layout.grid_single, null);
} else {
grid = convertView;
}
textView = (TextView) grid.findViewById(R.id.grid_text);
imageView = (ImageView) grid.findViewById(R.id.grid_image);
textView.setText(genreString[position]);
imageView.setImageResource(Imageid[position]);

return grid;
}


}

Answer

What I ended up doing to fix this was using a scroll listener on the gridview.

        grid.setOnScrollListener(new AbsListView.OnScrollListener() {
        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            //Log.d("Onboarding 7331", "onScroll: onScroll " + firstVisibleItem + " " + selectedPositions.toString());
            for (int i = 0; i < totalItemCount; i++) {
                View tv = grid.getChildAt(i - firstVisibleItem);
                if (tv == null) {
                    continue;
                }
                if (selectedPositions.contains(Integer.toString(i))) {
                    tv.setBackgroundColor(Color.parseColor("#FFE5CD"));
                } else {
                    tv.setBackgroundColor(Color.parseColor("#EEEEEE"));
                }
            }
        }

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            //     Log.d("Onboarding 7331", "onScroll: state changed "+selectedPositions.toString());
        }
    });