列表适配器仅将1个项添加到列表视图

Question

我正在为应用程序创建一个评论部分，每次单击“评论”按钮，我都想将评论添加到我的ListView。

不幸的是，我的代码只允许我在ListView中添加1条评论。每次我键入并单击添加注释按钮时，ListView在1项保持静态。

我相信我必须修改我的客户适配器中的getCount（）方法，但我想寻求帮助

以下是我的代码：

public class Discussion_Activity extends AppCompatActivity {

private EditText mUserComment;
private String mUserID;
private ImageView mUserAvatar;
private ListView mPollComments;
private ArrayAdapter<Comments> mCommentAdapter;
private Firebase mBaseRef;
private int mCommentCounter;

private static final String FIREBASE_URL = "https://fan-polls.firebaseio.com/";


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_discussion);
    Toolbar toolbar = (Toolbar) findViewById(R.id.tool_bar);
    setSupportActionBar(toolbar);

    mBaseRef = new Firebase(FIREBASE_URL);

    mUserComment = (EditText) findViewById(R.id.user_comment);
    mUserAvatar = (ImageView) findViewById(R.id.profile_image_avatar);
    mPollComments = (ListView) findViewById(R.id.poll_comments_list);
    final ArrayList<Comments> pollComments = new ArrayList<Comments>();
    mCommentAdapter = new ListAdapter(getApplicationContext(),R.layout.individual_comment, pollComments);
    mPollComments.setAdapter(mCommentAdapter);
    mCommentCounter = 0;
    getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_HIDDEN);


    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.add_comment_button);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            pollComments.add(mCommentCounter, new Comments(mUserAvatar, mBaseRef.getAuth().getUid(), mUserComment.getText().toString() ));
            mCommentAdapter.notifyDataSetChanged();
            mCommentCounter++;
            hideKeyboard(view);
            mUserComment.setText("");
        }
    });
}

public void hideKeyboard(View view) {
    InputMethodManager inputMethodManager =(InputMethodManager)getSystemService(Activity.INPUT_METHOD_SERVICE);
    inputMethodManager.hideSoftInputFromWindow(view.getWindowToken(), 0);
}

public class ListAdapter extends ArrayAdapter<Comments> {

    public ListAdapter(Context context, int textViewResourceId) {
        super(context, textViewResourceId);
    }

    public ListAdapter(Context context, int resource, List<Comments> items) {
        super(context, resource, items);
    }

    @Override
    public int getCount() {
        return mCommentCounter;
    }

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

        View v = convertView;

        if (v == null) {
            LayoutInflater vi;
            vi = LayoutInflater.from(getContext());
            v = vi.inflate(R.layout.individual_comment, null);
        }

        Comments p = getItem(position);

        if (p != null) {
            TextView userID = (TextView) v.findViewById(R.id.user_ID);
            TextView userComment = (TextView) v.findViewById(R.id.user_comment);

            if (userID != null) {
                userID.setText(p.getUserID());
            }

            if (userComment != null) {
                userComment.setText(p.getUserComment());
            }
        }


        return v;
    }

  }

}

XML

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <include
        android:id="@+id/tool_bar"
        layout="@layout/toolbar" />

    <ImageView
        android:id="@+id/poll_image"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight=".475"
        android:background="@drawable/heyward"
        android:scaleType="fitXY" />

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight=".2"
        android:orientation="horizontal">

        <FrameLayout
            android:layout_width="match_parent"
            android:layout_height="70dp"
            android:layout_margin="10dp"
            android:background="@drawable/textlines">

            <de.hdodenhof.circleimageview.CircleImageView
                android:id="@+id/profile_image_avatar"
                android:layout_width="50dp"
                android:layout_height="50dp"
                android:layout_gravity="center_vertical"
                android:layout_marginLeft="8dp"
                android:src="@drawable/empty_avatar_256x256"
                app:civ_border_color="#FF000000"
                app:civ_border_width="2dp" />

            <EditText
                android:id="@+id/user_comment"
                android:layout_width="match_parent"
                android:layout_height="60dp"
                android:layout_gravity="bottom"
                android:layout_marginEnd="60dp"
                android:layout_marginLeft="65dp"
                android:layout_marginRight="60dp"
                android:layout_marginStart="65dp"
                android:hint="Enter a comment....."
                android:inputType="textCapSentences|textMultiLine"
                android:scrollHorizontally="false"
                android:textSize="16sp" />

            <android.support.design.widget.FloatingActionButton
                android:id="@+id/add_comment_button"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_gravity="end|center_vertical"
                android:layout_marginEnd="4dp"
                android:layout_marginRight="4dp"
                android:clickable="true" />


        </FrameLayout>

    </LinearLayout>

    <ScrollView
        android:layout_marginStart="30dp"
        android:layout_marginLeft="30dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0.40">

        <ListView
            android:id="@+id/poll_comments_list"
            android:divider="@drawable/list_divide"
            android:dividerHeight="1px"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">


        </ListView>


    </ScrollView>

</LinearLayout>

Answer 1

在增加计数之前，请致电notifyDataSetChanged()。在notifyDataSetChanged()之前增加计数器，它应该起作用

mCommentCounter++;
mCommentAdapter.notifyDataSetChanged();

您也可以使用适配器add方法，因此您不需要覆盖getCount并拥有计数器，也不需要添加索引。适配器添加方法已添加该项并调用notifyDataSetChanged

adapter.add(new Comments(....));

还有如下所述的scrollview / listview问题回答

Answer 2

将一个可滚动元素添加到另一个可执行元素是一种不好的做法。如果没有肮脏的黑客攻击，你就无法行动。

因此，请删除您的ScrollView，您的ListView将按预期工作

Answer 3

问题是您要将项目直接添加到ListView。您应该管理Comments的全局列表，并与ListAdapter共享。

请注意，通过这种方式，您根本不需要mCommentCounter变量。

然后，在此列表中添加新注释并通知您的适配器。下面我提供了更新的代码。让我知道它是否适合你。

public class Discussion_Activity extends AppCompatActivity {

    private EditText mUserComment;
    private String mUserID;
    private ImageView mUserAvatar;
    private ListView mPollComments;
    private List<Comments> mComments;
    private ArrayAdapter<Comments> mCommentAdapter;
    private Firebase mBaseRef;

    private static final String FIREBASE_URL = "https://fan-polls.firebaseio.com/";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_discussion);
        Toolbar toolbar = (Toolbar) findViewById(R.id.tool_bar);
        setSupportActionBar(toolbar);

        private List<Comments> mComments = new ArrayList<Comments>;
        mBaseRef = new Firebase(FIREBASE_URL);

        mUserComment = (EditText) findViewById(R.id.user_comment);
        mUserAvatar = (ImageView) findViewById(R.id.profile_image_avatar);
        mPollComments = (ListView) findViewById(R.id.poll_comments_list);
        mCommentAdapter = new ListAdapter(getApplicationContext(),R.layout.individual_comment, mComments);
        mPollComments.setAdapter(mCommentAdapter);
        mCommentCounter = 0;
        getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_HIDDEN);


        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.add_comment_button);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mComments.add(new Comments(mUserAvatar, mBaseRef.getAuth().getUid(), mUserComment.getText().toString()));
                mCommentAdapter.notifyDataSetChanged();
                hideKeyboard(view);
                mUserComment.setText("");
            }
        });
    }

    public void hideKeyboard(View view) {
        InputMethodManager inputMethodManager =(InputMethodManager)getSystemService(Activity.INPUT_METHOD_SERVICE);
        inputMethodManager.hideSoftInputFromWindow(view.getWindowToken(), 0);
    }

    public class ListAdapter extends ArrayAdapter<Comments> {

        public ListAdapter(Context context, int textViewResourceId) {
            super(context, textViewResourceId);
        }

        public ListAdapter(Context context, int resource, List<Comments> items) {
            super(context, resource, items);
        }

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

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

            View v = convertView;

            if (v == null) {
                LayoutInflater vi;
                vi = LayoutInflater.from(getContext());
                v = vi.inflate(R.layout.individual_comment, null);
            }

            Comments p = getItem(position);

            if (p != null) {
                TextView userID = (TextView) v.findViewById(R.id.user_ID);
                TextView userComment = (TextView) v.findViewById(R.id.user_comment);

                if (userID != null) {
                    userID.setText(p.getUserID());
                }

                if (userComment != null) {
                    userComment.setText(p.getUserComment());
                }
            }

            return v;
        }

    }

}

我现在注意到关于ScrollView / ListView的评论。这也是一个问题。您只能保留ListView。