Question

我想使用一个整数来设置图像适配器添加到gridview的图像数量而不是数组的长度，但是当我在getCount（）中放入其他任何内容时，它总是会给出空指针异常。我需要设置它，因为我随机地将图像添加到网格中，我希望网格中显示一定数量的图像，具体取决于从上一个活动解析的整数。我也尝试制作一些if语句来检查diff是否为2或3，如果是这样，它将返回其他一个数组的长度，并设置一个else语句，所以如果diff是任何其他数字，它将使用当前数组长度，但这也给了一个空指针。

那么如何让它为我的gridview添加动态数量的图像而不是一个数组的长度呢？

Integer diff, gridSize, randomPosition, item;
GridView grid;
ImageView img;
Random rng;
ImageView imageView;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    grid = (GridView)findViewById(R.id.grid);
    grid.setAdapter(new ImageAdapter(this));
    rng = new Random();

    Bundle pack = this.getIntent().getExtras();
    diff = pack.getInt("dif");

    if (diff == 1){
        gridSize = 16;
        grid.setNumColumns(4);
    }

    if (diff == 2){
        gridSize = 25;
        grid.setNumColumns(5);
    }

    if (diff == 3){
        gridSize = 36;
        grid.setNumColumns(6);
    }


public class ImageAdapter extends BaseAdapter {
    private Context mContext;

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return gridSize; // this used to return mThumbIds.length by default and it worked then
    }

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

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

    public View getView(int position, View convertView, ViewGroup parent) {

            if (convertView == null) {
            randomPosition = rng.nextInt(gridSize);
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(3, 3, 3, 3); 
            } 
            else {
                imageView = (ImageView) convertView;
            }

            imgSet();
            return imageView;
    }

    public void imgSet(){
        if (diff == 1){
            imageView.setImageResource(mThumbIds[randomPosition]);
        }
        if (diff == 2){
            imageView.setImageResource(mThumbIds2[randomPosition]);
        }
        if (diff == 3){
            imageView.setImageResource(mThumbIds3[randomPosition]);
        }
    }

然后我有了我的图像阵列。

Answer 1

在设置图像适配器之前执行此操作

if (diff == 1){
    gridSize = 16;
    grid.setNumColumns(4);
}

if (diff == 2){
    gridSize = 25;
    grid.setNumColumns(5);
}

if (diff == 3){
    gridSize = 36;
    grid.setNumColumns(6);
}

让我知道它是否无效

Answer 2

在之后设置适配器 获取＆＃39; diff＆＃39;的值和＆＃39; rng＆＃39;，像这样：

grid = (GridView)findViewById(R.id.grid); rng = new Random(); Bundle pack = this.getIntent().getExtras(); diff = pack.getInt("dif"); if (diff == 1){ gridSize = 16; grid.setNumColumns(4); } if (diff == 2){ gridSize = 25; grid.setNumColumns(5); } if (diff == 3){ gridSize = 36; grid.setNumColumns(6); } grid.setAdapter(new ImageAdapter(this));

Android，图像适配器，getCount（）中的空指针异常

2 个答案: