Android滑动组件悬浮固定在顶部效果

2019-12-12 03:54:22

字体：大中小

来源：转载

供稿：网友

要想实现的效果是如下：

场景：有些时候是内容中间的组件当滑动至顶部的时候固定显示在顶部。

实现的思路：

1.目标组件（button）有两套，放在顶部和内容中间；

2.当内容中间的组件滑动至顶部栏位置时控制显示/隐藏顶部和中间的组件（涉及到组件获取在屏幕的位置知识点）；

activity代码：

public class MainActivity extends AppCompatActivity implements ObservableScrollView.ScrollViewListener {   private ObservableScrollView scrollView;   private Button topBtn1, topBtn2, middleBtn1, middleBtn2;   private View topPanel, middlePanel;   private int topHeight;    @Override   protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     initViews();     initListeners();    }    @Override   public void onWindowFocusChanged(boolean hasFocus) {     super.onWindowFocusChanged(hasFocus);      Rect frame = new Rect();     getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);     int statusBarHeight = frame.top;//状态栏高度      int titleBarHeight = getWindow().findViewById(Window.ID_ANDROID_CONTENT).getTop();//标题栏高度     topHeight = titleBarHeight + statusBarHeight;   }     private void initViews() {     scrollView = (ObservableScrollView) findViewById(R.id.scrollView);     topPanel = findViewById(R.id.topPanel);     topBtn1 = (Button) topPanel.findViewById(R.id.button1);     topBtn2 = (Button) topPanel.findViewById(R.id.button2);      middlePanel = findViewById(R.id.middlePanel);     middleBtn1 = (Button) middlePanel.findViewById(R.id.button1);     middleBtn2 = (Button) middlePanel.findViewById(R.id.button2);    }    private void initListeners() {     topBtn1.setOnClickListener(new View.OnClickListener() {       @Override       public void onClick(View view) {         middleBtn1.setBackgroundColor(Color.WHITE);         topBtn1.setBackgroundColor(Color.WHITE);       }     });      middleBtn1.setOnClickListener(new View.OnClickListener() {       @Override       public void onClick(View view) {         middleBtn1.setBackgroundColor(Color.BLUE);         topBtn1.setBackgroundColor(Color.BLUE);       }     });      scrollView.setScrollViewListener(this);     }     @Override   public void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy) {     int[] location = new int[2];     middleBtn1.getLocationOnScreen(location);     int locationY = location[1];     Log.e("locationY", locationY + "  " + "topHeight的值是：" + topHeight);      if (locationY <= topHeight && (topPanel.getVisibility() == View.GONE || topPanel.getVisibility() == View.INVISIBLE)) {       topPanel.setVisibility(View.VISIBLE);     }      if (locationY > topHeight && topPanel.getVisibility() == View.VISIBLE) {       topPanel.setVisibility(View.GONE);     }    } }

要点解析：

1.在onWindowFocusChanged()方法中获取屏幕状态栏和标题栏的高度（在onCreate()方法中是获取是0）；

2.因为布局中的ScrollView的onScrollChangeListener()方法低版本API不支持――>所以activity实现了自定义ScrollView中的onScrollChanged()接口方法――>在此方法中实现组件的显示/隐藏；

自定义ScrollView的代码：

public class ObservableScrollView extends ScrollView {    private ScrollViewListener scrollViewListener = null;    public ObservableScrollView(Context context) {     super(context);   }    public ObservableScrollView(Context context, AttributeSet attrs,                 int defStyle) {     super(context, attrs, defStyle);   }    public ObservableScrollView(Context context, AttributeSet attrs) {     super(context, attrs);   }    public void setScrollViewListener(ScrollViewListener scrollViewListener) {     this.scrollViewListener = scrollViewListener;   }    @Override   protected void onScrollChanged(int x, int y, int oldx, int oldy) {     super.onScrollChanged(x, y, oldx, oldy);     if (scrollViewListener != null) {       scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);     }   }    public interface ScrollViewListener {      void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);    } }

然后是布局文件：

<?xml version="1.0" encoding="utf-8"?> <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"   xmlns:tools="http://schemas.android.com/tools"   android:id="@+id/activity_main"   android:layout_width="match_parent"   android:layout_height="match_parent"   tools:context="com.example.administrator.slideholdapp.MainActivity">    <com.example.administrator.slideholdapp.ObservableScrollView     android:layout_width="match_parent"     android:layout_height="match_parent"     android:id="@+id/scrollView">      <LinearLayout       android:layout_width="match_parent"       android:layout_height="wrap_content"       android:orientation="vertical">        <TextView         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_marginBottom="30dp"         android:text="@string/content" />        <include android:id="@+id/middlePanel" layout="@layout/middle_item_layout"></include>        <TextView         android:layout_width="match_parent"         android:layout_height="wrap_content"         android:layout_marginTop="30dp"         android:text="@string/content" />       </LinearLayout>    </com.example.administrator.slideholdapp.ObservableScrollView>    <include android:id="@+id/topPanel" layout="@layout/middle_item_layout" android:visibility="gone"/> </FrameLayout>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。

上一篇：Android自定义view绘制圆环占比动画

下一篇：简单实现Android滚动公告栏