java - 适配器内 Intent 的 Android 错误消息

Question

我正在尝试让 map Intent 在我的 Json 适配器中工作。但不知怎的，我总是收到错误消息:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.content.Context.startActivity(android.content.Intent)' on a null object reference

这是我的第二个 Android 项目，我找不到我的错误。 我希望你们中的一些人可以帮助我。

class  JSONAdapter extends BaseAdapter implements ListAdapter{

private final Activity activity;
private Context context;
private final JSONArray jsonArray;

JSONAdapter(Activity activity, JSONArray jsonArray) {
    assert activity != null;
    assert jsonArray != null;

    this.jsonArray = jsonArray;
    this.activity = activity;
}


@Override public int getCount() {
    if(null==jsonArray)
        return 0;
    else
        return jsonArray.length();
}

@Override public JSONObject getItem(int position) {
    if(null==jsonArray) return null;
    else
        return jsonArray.optJSONObject(position);
}

@Override public long getItemId(int position) {
    JSONObject jsonObject = getItem(position);

    return jsonObject.optLong("id");
}

@Override public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null)
        convertView = activity.getLayoutInflater().inflate(R.layout.row, null);



    TextView tBrand =(TextView)convertView.findViewById(R.id.tvbrand);
    TextView tStreet =(TextView)convertView.findViewById(R.id.tvstreet);
    final TextView tPrice = (TextView)convertView.findViewById(R.id.tvprice);
    final TextView tPlace = (TextView)convertView.findViewById(R.id.tvplace);
    TextView tOpen = (TextView)convertView.findViewById(R.id.tvopen);



    JSONObject json_data = getItem(position);
    if(null!=json_data ) {
        String brand = null;
        String street = null;
        String price = null;
        String houseNumber = null;
        String place = null;
        String postCode = null;
        boolean open = false;
        Double statLng = null;
        Double statLat = null;

        try {
            brand = json_data.getString("brand");
            street = json_data.getString("street");
            price = Double.toString(json_data.getDouble("price"));
            houseNumber = json_data.getString("houseNumber");
            place = json_data.getString("place");
            postCode = json_data.getString("postCode");
            open = json_data.getBoolean("isOpen");
            statLng = json_data.getDouble("lng");
            statLat = json_data.getDouble("lat");

        } catch (JSONException e) {
            e.printStackTrace();
        }
        if (houseNumber.equals("null")) {
            houseNumber = "";
        }
        tBrand.setText(brand);
        tPrice.setText(price + "€");
        tStreet.setText(street + " " + houseNumber);
        tPlace.setText(postCode + " " + place);
        if (open == true) {
            tOpen.setText("geöffnet");
            tOpen.setTextColor(Color.GREEN);
        } else {
            tOpen.setText("geschlossen");
            tOpen.setTextColor(Color.RED);
        }


        final Double finalStatLng = statLng;
        final Double finalStatLat = statLat;
        tPrice.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Uri gmmIntentUri = Uri.parse("google.navigation:q=" + finalStatLat + "," + finalStatLng);
                Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
                mapIntent.setPackage("com.google.android.apps.maps");
                context.startActivity(mapIntent);

            }
        });

    }

    return convertView;
}

Answer 1

您错过了为上下文赋值

context = Activity; 或使用 activity.startActivity(mapIntent);