Android Development

The second part of this series will show you how you can scroll smoothly over the simple 2D Map which was created in the first part.

Note: I changed my coding style to fit the Java/Android coding style. Please be aware that variables like _mapSize are now mMapSize.

The performance issue we discovered in the first part was awful and no one will play a game which needs seconds to draw another frame. But why do we have this performance issue?
Do you remember how we draw the Map? We go trough the map in a loop and draw each cell. If our map has only a size of 10, everything is fine, but if we go to 100 and more, we draw a lot of cells and most of them are not on our display. And thats the mistake: We use resources and time to draw cells we don’t see.
continue reading…

This how to will show you how you can create a simple 2D Map with Cells to place stuff on it. Just like the old school SimCity.

The first thing you need is an Activity with a SurfaceView and a Thread to trigger the drawing. Who doesn’t know these fundamentals, please read my series on 2d graphics first.

Lets start with the smallest unit for our map: the Cell.
Each Cell will have a background color and a unique ID.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37

package com.droidnova.android.games;
 
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
 
/**
 * A part of the map.
 */
public class Cell {
    public int _id = 0;
    public int _backgroundColor = Color.GREEN;
 
    /**
     * Konstruktor.
     * @param id
     */
    public Cell(int id) {
        _id = id;
    }
 
    /**
     * Draw the cell
     *  
     * @param canvas Canvas to draw on.
     * @param paint Color of the "pencil".
     * @param x X coordinate.
     * @param y Y coordinate.
     */
    public void draw(Canvas canvas, Paint paint, int x, int y) {
        paint.setColor(_backgroundColor);
        canvas.drawRect(x, y, x + CellMap._cellSize, y + CellMap._cellSize, paint);
 
        paint.setColor(Color.BLACK);
        canvas.drawText("" + _id, x + 1, y + 10, paint);
    }
}

On line 32 you see, how we draw the cell. The variable _cellSize is a static variable from CellMap, which will be introduced later. Everything else should be already known.
continue reading…

Sometimes I am a bit over motivated. Thats the reason I upgraded my Ubuntu to 9.10 RC1 yesterday.
Nearly everything worked fine and after 90 minutes downloading and installing Ubuntu 9.10 booted the first time.
The disillusion followed today: What happened with my Eclipse installation?
The LogCat view has no logging type buttons, the Devices view has lost its button for stopping processes and some windows don’t accept a mouse click on their buttons (mostly the OK button). I have to press Enter to get them work.

After a short search I found this bug report for ubuntu: https://bugs.launchpad.net/ubuntu/+source/gtk+2.0/+bug/442078

A workaround is also mentioned there:

Create a launch script for eclipse with the following code:

#!/bin/sh
GDK_NATIVE_WINDOWS=1 /path/to/eclipse

I am not sure if Ubuntu is responsible or Eclipse, but after using this launch script, everything worked fine.