自定义listview适配器所选项目增量textview

Question

I used https://github.com/wdullaer/SwipeActionAdapter to swipe each items on listview

once i swipe one of the item, textview text will increment to one. The problem if i will scroll the list, the textview will return to each default value which is 0 and some hidden items also incrementing.

Code for onswipe event:

switch (direction) {
   case SwipeDirections.DIRECTION_FAR_LEFT:
        selectedText = (TextView) getViewByPosition(position, getListView()).findViewById(R.id.txtNumber);
        selectedText.setText(String.valueOf(Integer.parseInt(selectedText.getText().toString()) + 1));
        break;

and adapter code:

JSONArray jsonArray = null;
try {
    jsonArray = new JSONArray(data);

} catch (JSONException e) {
    e.printStackTrace();
}
String[] strArr = new String[jsonArray.length()];
ArrayList<String> arrayList = new ArrayList<String>();

for (int i = 0; i < jsonArray.length(); i++) {
    try {

        strArr[i] = jsonArray.getJSONObject(i).getString("name");
        arrayList.add(jsonArray.getString(i));

        stringAdapter = new ArrayAdapter<String>(
                this,
                R.layout.items,
                R.id.txtName,
                new ArrayList<String>(Arrays.asList(strArr))
        );

        setListAdapter(stringAdapter);
        stringAdapter.notifyDataSetChanged();


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

items.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="100sp"
    android:background="@drawable/listview_style"
    android:padding="8dp"
    android:descendantFocusability="blocksDescendants">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/imageView"
        android:src="@mipmap/ic_launcher"
        android:layout_centerVertical="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
        android:id="@+id/txtName"
        android:textSize="20sp"
        android:gravity="center"
        android:ellipsize="none"
        android:singleLine="false"
        android:scrollHorizontally="false"
        android:layout_centerVertical="true"
        android:layout_marginLeft="20sp"
        android:layout_marginRight="20sp"
        android:layout_toRightOf="@+id/imageView"
        android:layout_toLeftOf="@+id/txtNumber"
        android:layout_toStartOf="@+id/txtNumber"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="0"
        android:id="@+id/txtNumber"
        android:textSize="25sp"
        android:layout_centerVertical="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_marginRight="40dp"
        android:layout_marginEnd="40dp"
        />

</RelativeLayout>

i'm thinking of item position is not valid or view is not valid. anyidea how to solve this. thanks

UPDATE Incrementing now working properly, but item name is not populating. See attached

Answer 1

The problem is that listview cheats. It's a recycling view so what happens is that you actually just have the same like 10 views you are currently seeing. When you scroll far enough that the view goes away, it appears again as the view that just came into view. To do this, it got rid of the old view, asked the adapter to make this trashed view into something that will look like the new view (which is awesome for memory and quick view creation).

This is why your items go away, because the views are recycled by the listview using the adapter after you scroll away. If you really want to see this, try making swipe turn the visibility of your view to INVISIBLE, then you'll notice views all over the place just being missing. Because they are the same view.

In short, swipe must change the data used to build the view. Any changes to the view itself will either be wiped away, or mess up the other views (things like visibility and .transform() are not often reset by adapters), which are really just the same view again.

public class SwipeActivity extends AppCompatActivity {

SwipeActionAdapter mAdapter;

private class YourCustomRowEntry {
    String displayString;
    int swipes;

    public YourCustomRowEntry( String displayString, int swipes) {
        this.swipes = swipes;
        this.displayString = displayString;
    }
}

private class Holder {
    public TextView textName, textNumber;
    public ImageView imageView;
    public Holder(TextView textName, TextView textNumber, ImageView imageView) {
        this.textName = textName;
        this.textNumber = textNumber;
        this.imageView = imageView;
    }
}

ArrayList<YourCustomRowEntry> mDataYouEditThatBacksTheAdapter = new ArrayList<>();

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

    for (int i = 1; i <= 200; i++) {
        mDataYouEditThatBacksTheAdapter.add(new YourCustomRowEntry("Row " + i,0));
    }

    BaseAdapter customAdapter = new BaseAdapter() {
        @Override
        public int getCount() {
            return mDataYouEditThatBacksTheAdapter.size();
        }

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

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

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View itemView;
            Holder viewHolder;
            if (convertView != null) {
                itemView = convertView; //if you already made this view, and it's being recycled use that.
                viewHolder = (Holder)convertView.getTag(); //And fetch the already findByViews things.
            }
            else {
                //if this is the first time, inflate the view.
                itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.items, parent, false);
                TextView textName = (TextView)itemView.findViewById(R.id.txtName);
                TextView textNumber = (TextView)itemView.findViewById(R.id.txtNumber);
                ImageView imageView =  (ImageView)itemView.findViewById(R.id.imageView);
                viewHolder = new Holder(textName,textNumber,imageView);
                itemView.setTag(viewHolder); //store the data in the view's tag.
            }
            YourCustomRowEntry ycre = mDataYouEditThatBacksTheAdapter.get(position);
            viewHolder.textName.setText(ycre.displayString);
            viewHolder.textNumber.setText("" + ycre.swipes); // Gotta tell it that this is a string and not a resource.
            //You would also set the imageView from the saved set of data here too.
            return itemView;
        }
    };

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

    // Wrap your content in a SwipeActionAdapter
    mAdapter = new SwipeActionAdapter(customAdapter);

    // Pass a reference of your ListView to the SwipeActionAdapter
    mAdapter.setListView(listView);

    // Set the SwipeActionAdapter as the Adapter for your ListView
    listView.setAdapter(mAdapter);

    // Listen to swipes
    mAdapter.setSwipeActionListener(new SwipeActionAdapter.SwipeActionListener() {
        @Override
        public boolean hasActions(int position) {
            // All items can be swiped
            return true;
        }

        @Override
        public boolean shouldDismiss(int position, int direction) {
            // Only dismiss an item when swiping normal left
            return false;
            //return direction == SwipeDirections.DIRECTION_NORMAL_LEFT;
        }

        @Override
        public void onSwipe(int[] positionList, int[] directionList) {
            for (int i = 0; i < positionList.length; i++) {
                int direction = directionList[i];
                int position = positionList[i];
                switch (direction) {
                    case SwipeDirections.DIRECTION_FAR_LEFT:
                        mDataYouEditThatBacksTheAdapter.get(position).swipes++; //add 1 to swipes;
                        mAdapter.notifyDataSetChanged();
                        break;
                    case SwipeDirections.DIRECTION_FAR_RIGHT:
                        mDataYouEditThatBacksTheAdapter.get(position).swipes--; //subtract 1 to swipes;
                        mAdapter.notifyDataSetChanged();
                        break;
                }
            }
        }
    });


}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_swipe, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

}

Video of it working: https://youtu.be/6wPF2OOKu2U

Save the array you use to back your listview. You need to have that so you can change it and get the Adapter to build new views. notifyDataSetChanged() and it updates the and rebuilds the views, from the original data structure it saved. Meaning you need to modify that data, not the view. This properly writes a class and uses that to build the views.