Question

我创建了一个自定义列表视图来解析JSON对象并在List中处理它！一切正常，但当我尝试通过单击ListView项目打开一个新的Intent时，应用程序崩溃了！我还使用内存缓存来存储从JSON对象url解析的图像，以便在ListView中显示它！

public class ListViewAdapter extends BaseAdapter {

    // Declare Variables
    Context context;
    LayoutInflater inflater;
    ArrayList<HashMap<String, String>> data;
    ImageLoader imageLoader;
    HashMap<String, String> resultp = new HashMap<String, String>();

    public ListViewAdapter(Context context,
            ArrayList<HashMap<String, String>> arraylist) {
        this.context = context;
        data = arraylist;
        imageLoader = new ImageLoader(context);
    }

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

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

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

    public View getView(final int position, View convertView, ViewGroup parent) {
        TextView rank;
        TextView country;
        TextView population;
        ImageView flag;

        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        View itemView = inflater.inflate(R.layout.listview_item, parent, false);
        // Get the position
        resultp = data.get(position);

        rank = (TextView) itemView.findViewById(R.id.rank);
        country = (TextView) itemView.findViewById(R.id.country);
        population = (TextView) itemView.findViewById(R.id.population);

        flag = (ImageView) itemView.findViewById(R.id.flag);

        rank.setText(resultp.get(MainActivity.RANK));
        country.setText(resultp.get(MainActivity.COUNTRY));
        population.setText(resultp.get(MainActivity.POPULATION));
        imageLoader.DisplayImage(resultp.get(MainActivity.FLAG), flag);
        itemView.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                resultp = data.get(position);
                Intent intent = new Intent(context, SingleItemView.class);
                intent.putExtra("rank", resultp.get(MainActivity.RANK));
                intent.putExtra("country", resultp.get(MainActivity.COUNTRY));
                intent.putExtra("population",resultp.get(MainActivity.POPULATION));
                intent.putExtra("flag", resultp.get(MainActivity.FLAG));
                context.startActivity(intent);

            }
        });
        return itemView;
    }
}

Logcat输出：

12-25 14:50:50.929: E/AndroidRuntime(1501): FATAL EXCEPTION: main
12-25 14:50:50.929: E/AndroidRuntime(1501): Process: com.android.jsonparse, PID: 1501
12-25 14:50:50.929: E/AndroidRuntime(1501): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.android.jsonparse/com.android.jsonparse.SingleItemView}: java.lang.NullPointerException
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2102)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.os.Handler.dispatchMessage(Handler.java:102)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.os.Looper.loop(Looper.java:137)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread.main(ActivityThread.java:4998)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at java.lang.reflect.Method.invokeNative(Native Method)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at java.lang.reflect.Method.invoke(Method.java:515)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at dalvik.system.NativeStart.main(Native Method)
12-25 14:50:50.929: E/AndroidRuntime(1501): Caused by: java.lang.NullPointerException
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.content.ContextWrapper.getCacheDir(ContextWrapper.java:230)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at com.androidbegin.jsonparsetutorial.FileCache.<init>(FileCache.java:18)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at com.androidbegin.jsonparsetutorial.ImageLoader.<init>(ImageLoader.java:34)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at com.androidbegin.jsonparsetutorial.SingleItemView.<init>(SingleItemView.java:16)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at java.lang.Class.newInstanceImpl(Native Method)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at java.lang.Class.newInstance(Class.java:1208)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
12-25 14:50:50.929: E/AndroidRuntime(1501):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2093)

从Context启动新的Activity不在Custom ListView Adapter中工作

0 个答案: