Android: ListView - multicolored items?

Question

Android

Hello, is it possible to implement the following, and if possible, I will be grateful for a piece of code, if not, then at least some advice.
I want to make sure that when loading my ListView, each item is painted over in a certain color (for example, some kind of my gradient) and also change when clicked.
Well, there is a way to change the color of examples when you click, but how to make all items be created in different colors ..?
So far this is the status

import java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

public class RowAdapter extends BaseAdapter
{
    private List<Row> elements;
    private Context context;

    public RowAdapter(Context c, List<Row> rows) {
        this.elements = rows;
        this.context = c;
    }

    @Override
    public int getCount() {
        return elements.size();
    }

    @Override
    public Object getItem(int position) {
        return elements.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        return elements.get(position);
    }
}

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.util.DisplayMetrics;
import android.view.View;

public class Row extends View {

  private DisplayMetrics displayMetrics;

  public Row(Context context, DisplayMetrics displayMetrics) {
    super(context);
    this.displayMetrics = displayMetrics;
  }

  @Override
  public void onDraw(Canvas canvas) {
    Paint paint = new Paint();

    int xPos = (canvas.getWidth() / 2);
    int yPos = (int) ((canvas.getHeight() / 2) - ((paint.descent() + paint.ascent()) / 2));

    paint.setColor(Color.GREEN);
    paint.setTextSize(30);
    canvas.drawText("Some Text", xPos, yPos, paint);
  }

  @Override
  public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    setMeasuredDimension(displayMetrics.widthPixels, 300);
  }
}

Thanks for the hint tips.

Answer 1

PVOID asked a fair question - why store views in the adapter? This is absolutely not a rational use of resources. Basically, all you need to know is the type of the current sheet element. By this type, you can set the background of the desired color.
Example:
1) We create a static class (optionally static, you can stuff it into the load somewhere) with all the colors - let's say ListColors.

public class ListColors {
    public static final Integer RED      = 0;
    public static final Integer GREEN    = 1;
    public static final Integer BLUE     = 2;
    public static final Integer YELLOW   = 3;
    public static final Integer PURPLE   = 4;
}

2) We create a class that describes the list item - ListItem. The type property is important here, which will store the type of the element. And the element type will be any of the constants of the ListColors class.

class ListItem {
    private Long id;
    private Integer type;

    public ListItem(Long id, Integer type){
        this.id     = id;
        this.type   = type;
    }

    public Long getId(){
        return id;
    }

    public Integer getType(){
        return type;
    }
}

3) Next, we write the adapter itself, to the constructor of which Context will be passed (it never hurts) and a list of elements in the List<ListItem>.

class TestAdapter extends BaseAdapter implements ListAdapter {

    private Context context;
    private List<ListItem> items;

    public TestAdapter(Context context, List<ListItem> items){
        this.context    = context;
        this.items      = items;
    }

    @Override
    public int getCount() {
        return items.size();
    }

    @Override
    public ListItem getItem(int position) {
        return items.get(position);
    }

    @Override
    public long getItemId(int position) {
        return items.get(position).getId();
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ListItem item = getItem(position);
        convertView = LayoutInflater.from(context).inflate(R.layout.list_row_item, null);

        LinearLayout layout = (LinearLayout) convertView.findViewById(R.id.view_background);

        Integer colorRes;
        switch (item.getType())
        {
            default:
            case ListColors.RED:
                colorRes = context.getResources().getColor(R.id.red);
                break;
            case ListColors.GREEN:
                colorRes = context.getResources().getColor(R.id.green);
                break;
            case ListColors.BLUE:
                colorRes = context.getResources().getColor(R.id.blue);
                break;
            case ListColors.YELLOW:
                colorRes = context.getResources().getColor(R.id.yellow);
                break;
            case ListColors.PURPLE:
                colorRes = context.getResources().getColor(R.id.purple);
                break;
        }
        layout.setBackgroundColor(colorRes);
        return convertView;
    }
}

In the getView() method, we get the list item, get the list item's base layot ​​(in this case, of type LinearLayout), then check the item's type, and set the layout'y to the desired color. You can also store the view of the list element in holder'e, so as not to create it every time, but this is particular.

Answer 2

Hint: BaseAdapter.getItemViewType(int position)
BTW, why are you storing views in the adapter?

Answer 3

And why not save information about the state of the line through settag / gettag?

Answer 4

@Override
 public View getView(int position, View convertView, ViewGroup parent) 
{
if (convertView == null)
{
convertView = LayoutInflater.from(context).inflate(R.layout.list_row_item, null);
//первое место где каждой вьюшке можно задать свой цвет, но она будет 
//переиспользоваться и появляться в разных местах при листаниии
}

int color = 0;
switch(position)
{
case 0:
color = 0xFFff0000;

case 1:
color = 0xFF00ff00;

case 2:
color = 0xFF0000ff;
}
//можно напридумывать миллион правил по которым будет генерить цвет так-то )
converView.setBackgroundColor(color);
return converView;
}