0

我在将 ImageView 放入 GridView 时遇到问题，我解析 JSON，我从 json 中获取 url 并将其放入我的 ImageView 到 GridView 中，我有一个错误，你能帮帮我吗？

日志猫

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.gazetaimage/com.gazetaimage.MainActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2309)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2359)
    at android.app.ActivityThread.access$600(ActivityThread.java:153)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5202)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:511)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:799)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
    at com.gazetaimage.ImageAdapter.<init>(ImageAdapter.java:37)
    at com.gazetaimage.MainActivity.onCreate(MainActivity.java:17)
    at android.app.Activity.performCreate(Activity.java:5106)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2263)
    ... 11 more

我的代码在我的 AsyncTask 中，我连接到我的 JSON 文件，并返回 JSONObject，在 ImageAdapter.class 中我得到这个对象，并放入 ImageView

public class ImageAdapter extends BaseAdapter {

    public Context mContext;

    public String[] mThumbs;

    final static String TAG_ITEM = "item";
    final static String TAG_BIG_IMAGE = "big_image";

    public ImageAdapter (Context c){
        mContext = c;
        BackTask task = new BackTask();
        task.execute();

            try {

                JSONObject result = task.get();
                JSONArray jarray = result.getJSONArray(TAG_ITEM);
                for(int i = 0; i < jarray.length(); i++){
                    JSONObject jrss = jarray.getJSONObject(i);

                    mThumbs[i] = jrss.getString(TAG_BIG_IMAGE);
                }

            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
    }


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

    @Override
    public Object getItem(int position) {
        return mThumbs[position];
    }

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

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

            ImageView imageView;
            if (convertView == null) { 
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(8, 8, 8, 8);
            } else {
                 imageView = (ImageView) convertView;
            }

            imageView.setImageURI(Uri.parse(mThumbs[position]));

            return imageView;
    }
4

2 回答 2

0

好像还没有初始化mThubs

在遍历 JSON 数组之前添加以下行：

mThumbs = new String[jarray.length()];
于 2012-12-09T17:26:46.423 回答
0

我相信你的空指针异常是由于 mThumbs 没有被初始化造成的。检查适配器中的第 37 行。

于 2012-12-09T17:28:40.787 回答