Android开发实现标题随scrollview滑动变色的方法详解

2019-10-22 18:22:54

字体：大中小

来源：转载

供稿：网友

本文实例讲述了Android开发实现标题随scrollview滑动变色的方法。分享给大家供大家参考，具体如下：

要实现某个view的背景透明度跟随scrollview滑动而改变需要重新scrollview的onOverScrolled方法，该方法随着滑动变化（包括手指滑动、手指移开惯性滑动）而响应，所以最适合做变色处理。

step1:设定布局

由于我们要实现的是滑动时标题的背景透明度改变，固定顶部的标题view不能在srcollview里面跟随滑动，所以需要这样布局:

<FrameLayout    android:layout_width="match_parent"    android:layout_height="match_parent">    <com.****.ScrollChangeScrollView      android:id="@+id/scrollView"      android:layout_width="match_parent"      android:layout_height="match_parent"      android:fillViewport="true">      <LinearLayout        android:layout_width="match_parent"        android:layout_height="match_parent"        android:orientation="vertical">          <TextView            android:layout_width="0dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:drawablePadding="5dp"            android:drawableTop="@drawable/dicovery_vintner_icon_wine"            android:gravity="center"            android:text="葡萄酒"            android:textColor="@color/hometitlebg" />      </LinearLayout>    </com.***.ScrollChangeScrollView>    <Button      android:id="@+id/btn_back"      android:layout_width="match_parent"      android:layout_height="35dp"      android:layout_centerVertical="true"      android:background="@null"      android:drawableLeft="@drawable/icon_back"      android:padding="10dp" /></FrameLayout>

step2:添加需要用到的方法

滑动时，某个view要变色，重新scrollview后，添加方法让其知道该view需要变色

private View mTitleView;/*** 变色标题view* @param view*/public void setupTitleView (View view) {    this.mTitleView = view;}

滑动时变色需要参考scrollview里面的某个子view的滑动高度，如果该子view上划完全划出屏幕，则标题view背景透明为0：

private View mByWhichView;/*** 跟随的view* @param view*/public void setupByWhichView(View view) {    mByWhichView = view;}

再添加一个设置，如果不要背景透明度渐变：

private boolean shouldSlowlyChange;public void setShouldSlowlyChange(boolean slowlyChange) {    this.shouldSlowlyChange = slowlyChange;}

step3:代码实现

** * 滑动时标题变色view * Created by george.yang on 16/2/21. */public class ScrollChangeScrollView extends ScrollView {  private View mByWhichView;  private View mTitleView;  private boolean shouldSlowlyChange = true;  public ScrollChangeScrollView(Context context) {    super(context);  }  public ScrollChangeScrollView(Context context, AttributeSet attrs) {    super(context, attrs);  }  public ScrollChangeScrollView(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);  }  @TargetApi(Build.VERSION_CODES.LOLLIPOP)  public ScrollChangeScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {    super(context, attrs, defStyleAttr, defStyleRes);  }  @Override  public void scrollTo(int x, int y) {    //这是为了修复noScrllListView嵌套在srcollview时就自动滑动到noscrolllistview的顶部的bug，不影响使用    if (x == 0 && y == 0 || y <= 0) {      super.scrollTo(x, y);    }  }  public void setListener(OnScrollListener listener){    this.mListener = listener;  }  public void setShouldSlowlyChange(boolean slowlyChange) {    this.shouldSlowlyChange = slowlyChange;  }  /**   * 设置透明度渐变的标题view   * @param view   */  public void setupTitleView (View view) {    this.mTitleView = view;  }  /**   * 跟随的view   * @param view   */  public void setupByWhichView(View view) {    mByWhichView = view;  }  @Override  protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX,                 boolean clampedY) {    super.onOverScrolled(scrollX, scrollY, clampedX, clampedY);    if (scrollY >= mByWhichView.getTop() + mByWhichView.getMeasuredHeight()) {      mTitleView.setBackgroundColor(Color.BLACK);    } else if (scrollY>=0) {      if (!shouldSlowlyChange) {        mTitleView.setBackgroundColor(Color.TRANSPARENT);      } else {        float persent = scrollY * 1f / (mByWhichView.getTop() + mByWhichView.getMeasuredHeight());        int alpha = (int) (255 * persent);        int color = Color.argb(alpha,0,0,0);        mTitleView.setBackgroundColor(color);      }    }    if (mListener!=null) {      mListener.onScroll(scrollX, scrollY);    }  }}

效果如下:

滑动前

Android,标题,scrollview,滑动变色