如何在滚动时修复滚动依赖标题的闪烁？

Question

我需要实现带有标题的ListView，当用户向下滚动ListView时会隐藏它，并在用户向上滚动时再次显示。但是我遇到了一个问题：当我慢慢向下滚动ListView时，标题会闪烁。我知道这是因为ListView改变了大小。但是如何解决呢？

这是代码：

public class MainActivity extends ActionBarActivity implements AbsListView.OnScrollListener {

    private static final int LIST_DATA_COUNT = 100;
    private View mHeader;
    private int mLastFirstVisibleItem;

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

        mHeader = findViewById(R.id.textView);

        String[] listData = new String[LIST_DATA_COUNT];
        for (int i=0;i<LIST_DATA_COUNT;i++) {
            listData[i]= String.valueOf(i);
        }

        ListView listView = (ListView) findViewById(R.id.listView);
        listView.setAdapter(new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, android.R.id.text1, listData));
        listView.setOnScrollListener(this);
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {

    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        if (firstVisibleItem<mLastFirstVisibleItem) {
            Log.d("tag", "up");
            mHeader.setVisibility(View.VISIBLE);
        } else if (firstVisibleItem>mLastFirstVisibleItem) {
            Log.d("tag", "down");
            mHeader.setVisibility(View.GONE);
        }
        mLastFirstVisibleItem = firstVisibleItem;
    }
}

activity_main：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:tools="http://schemas.android.com/tools"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                tools:context=".MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Header"
        android:gravity="center"
        android:id="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"/>

    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/textView"/>
</RelativeLayout>

logcat的：

D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down
D/tag? up
D/tag? down

Answer 1

尝试将TouchListener用于ListView。这可能对你有用。

 listView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                int action = event.getAction();
                if (action == MotionEvent.ACTION_DOWN) {
                    startY = event.getY();//declare as global variable
                    return true;
                } else if (action == MotionEvent.ACTION_MOVE) {
                    float y = event.getY();
                    if(startY-y<-60){
                        Log.w(TAG, "scroll down");
                        mHeader.setVisibility(View.VISIBLE);
                    }else if(startY-y>60){
                        Log.w(TAG, "scroll up");
                        mHeader.setVisibility(View.GONE);
                    }
                }
                return false;
            }
        });

Answer 2

您可以将标题显示为叠加层。这将阻止ListView调整大小。对于第一个版本，只需尝试更改ListView和TextView顺序。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            tools:context=".MainActivity">
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/textView"/>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Header"
        android:gravity="center"
        android:id="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"/>

</RelativeLayout>