CODEWITHSUNDEEP
javaandroidarraysobjectgrid
Marcel Ochs
Marcel Ochs

Reputation: 17

Android game - Trying to create an array fails?

I am currently starting understanging Java. So while I've been trying to develop some minesweeper application I noticed, that when trying to add coordinates to a "Mines[]" array, the debugging window opens and my application doesn't continue displaying the purposed Minefield.

So that's my code:

package com.ochs.minesweeper;

public class MineField {

public Mine[] mines;

public MineField(int xMines, int yMines) {
    mines = new Mine[xMines*yMines];
    int xCounter = 0;
    int yCounter = 0;
    for(int i = 0; i < yMines; i++) {
        for(int j = 0; j < xMines; j++) {
            mines[i*j].setX(xCounter);
            mines[i*j].setY(yCounter);
            xCounter += 100;
        }yCounter += 100;
    }
}   
}

Even when I just try something like:

for(int i = 0; i < xMines*yMines; i++) {
    mines[i].setX(2);
}

or something like that it seems like I can't use the variable of the for-loop in my array to process...

Does anyone has an idea what I am doing wrong? I just want my MineField to have it's Mine[] array. This Mines are all created in the for loop with different coordinates so that they can be displayed in a grid on my surfaceview. Does anyone has an idea? Or maybe another solution how I can create a simple grid of objects, in my example mines?

Thanks in advance!

Upvotes: 0

Views: 78

Answers (2)

user0
user0

Reputation: 163

There is a problem with where you are setting the coordinates in this bit of code:

mines[i*j].setX(xCounter);
mines[i*j].setY(yCounter);

For example, the coordinates (x=2, y=3) and (x=3, y=2) refer to different locations on the grid, however 2*3=6 and 3*2=6. You need slightly more complicated logic to get a unique index for every coordinate (semihyagcioglu's approach is much better):

public MineField(int xMines, int yMines) {
mines = new Mine[xMines*yMines];
int xCounter = 0;
int yCounter = 0;
for(int i = 0; i < yMines; i++) {
    for(int j = 0; j < xMines; j++) {
        mines[i+(j*yMines)].setX(xCounter);
        mines[i+(j*yMines)].setY(yCounter);
        xCounter += 100;
    }yCounter += 100;
}
}

The reason the application crashes is that you need to instantiate each mine object in your Mine[] array before trying to call setX() and setY() on them.

for (int i=0; i< (xMines*yMines); i++)
  Mine[i] = new Mine();

Upvotes: 1

Semih Yagcioglu
Semih Yagcioglu

Reputation: 4101

Why not use 2 dimensional arrays? You can define Mine[][] mines and then in the loop:

 for(int i = 0; i < yMines; i++) {
        for(int j = 0; j < xMines; j++) {
            mines[i][j].setX(xCounter);
            mines[i][j].setY(yCounter);
            xCounter += 100;
        }yCounter += 100;
    }

Upvotes: 1

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