显示从服务器检索的图像

Question

我正在开发一个 Android 应用程序，用户在其中上传照片。现在，我正在从服务器调用一个方法，它将返回一个用户列表。我想将此列表与照片一起显示。 存储在服务器中的图像是字节数组。所以我将它们转换为字符串，然后转换为位图进行显示。不幸的是，它不起作用，因为我也在使用适配器做事。在适配器类中检索到的图像为空。我做错了什么？

其他用户.java：

public class OtherUsers extends Activity {

    private PersonServiceImpl personService = new PersonServiceImpl();

    private static volatile List<RestPerson> restPersonList = new ArrayList<>();

    public static final String firstName = "firstname";
    public static final String userImage = "userimage";

    static final Long userId = (long)0;
    ListView listView;
    UserAdapter userAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.displayuserlist);

        restPersonList = this.personService.getOtherUsers();
       // Base64 base64Encoder = new Base64();

        ArrayList<HashMap<String, String>> usersArrayHashList = new ArrayList<>();
        for(RestPerson restPerson : restPersonList){
            HashMap<String, String> restDisplay = new HashMap<>();
            restDisplay.put("userId",String.valueOf(restPerson.getUserId()));
            restDisplay.put("firstName",restPerson.getFirstName());

           restDisplay.put("userImage","data:image/png;base64," + Base64.encode(restPerson.getProfilePhoto()));
            usersArrayHashList.add(restDisplay);
        }

        listView = (ListView) findViewById(R.id.usersdisplaylist);

        userAdapter = new UserAdapter(this,usersArrayHashList);

        listView.setAdapter(userAdapter);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                Long userid = restPersonList.get(position).getUserId();
                Log.d("Userid is ", String.valueOf(userid));
            }

        });

UserAdapter 类：

public class UserAdapter extends BaseAdapter {

    private Activity activity;
    private ArrayList<HashMap<String, String>> data;
    private static LayoutInflater inflater = null;

    public UserAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
        activity = a;
        data = d;
        inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }


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

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

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view = convertView;
        if (convertView == null)
            view = inflater.inflate(R.layout.userprofiles, null);

        TextView username = (TextView) view.findViewById(R.id.userName);
        ImageView userImage = (ImageView) view.findViewById(R.id.userImage);
        HashMap<String, String> usersList = new HashMap<>();
        usersList = data.get(position);
       username.setText(usersList.get(OtherUsers.firstName));
        String image = usersList.get(OtherUsers.userImage);
        Log.d("Image is ",image);
        byte[] newImageBytes = image.getBytes();
        Bitmap bitmap = BitmapFactory.decodeByteArray(newImageBytes,0,newImageBytes.length);
        userImage.setImageBitmap(bitmap);
        userImage.setImageBitmap(null);
        return view;
    }
}

如果需要任何其他信息，请告诉我。谢谢。

更新 抱歉，忘记放LogCat了

08-24 13:43:16.618  29948-29948/internetlegion.com.gradlecheck E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: internetlegion.com.gradlecheck, PID: 29948
    java.lang.NullPointerException: println needs a message
            at android.util.Log.println_native(Native Method)
            at android.util.Log.d(Log.java:139)
            at internetlegion.com.gradlecheck.Adapters.UserAdapter.getView(UserAdapter.java:62)
            at android.widget.AbsListView.obtainView(AbsListView.java:2347)
            at android.widget.ListView.measureHeightOfChildren(ListView.java:1270)
            at android.widget.ListView.onMeasure(ListView.java:1182)
            at android.view.View.measure(View.java:17547)

Answer 1

您在适配器中使用的数据结构很奇怪。最好创建一个具有三个属性的类并将其中的一个列表发送到适配器类。 无论如何，你的问题是：

public static final String userImage = "userimage";

你用值userimage定义userImage，然后你用不等于userImage的值的“userImage”插入hashmap（值有小写i）然后你尝试从hashmap 不存在，所以 value 为 null。

答案：

您可以更改以下行：

restDisplay.put("userImage","data:image/png;base64," + Base64.encode(restPerson.getProfilePhoto()));

到

restDisplay.put(userImage,"data:image/png;base64," + Base64.encode(restPerson.getProfilePhoto()));

但更好的方法是创建自定义对象。