Android 类似UC浏览器的效果：向上滑动地址栏隐藏功能

时间：2022-06-25 23:05:07 编辑：袖梨来源：一聚教程网

思路

要求

ScrollView 嵌套地址栏和 WebView

手指滑屏向下滚动（网页向上），如果网页有滚动条，首先把地址栏滚动到消失，然后 WebView 才开始滚动；

手指滑屏向上滚动（网页向下），如果地址栏隐藏，那么地址栏首先慢慢显示，然后 WebView 才开始滚动。

实现方案

1、根据 View 的 onInterceptTouchEvent 和 onTouchEvent 原理。把 ScrollView 设置为 WebView 的一个变量，在 WebView的 onInterceptTouchEvent 方法里检测到 MotionEvent.ACTION_DOWN 事件后中断事件，在 WebView 的 onTouchEvent 事件中根据具体情况决定是把 MotionEvent.ACTION_MOVE 事件传送给 ScrollView 还是留给自己

2、由于MotionEvent.ACTION_MOVE 事件传送给 ScrollView 后无法在一次 Touch 事件中再接收，所以会导致如果有地址栏，向下滑动第一次只能滑动到 ScrollView 消失

3、+

4、Hack网页，加入JS脚本，前行让网页顶部空出来一段空白，空白处覆盖地址栏

5、优点是WebView大小不变化，容易控制

6、缺点是比较复杂要处理各种网页元素,各种 position 情况，实现复杂，效率低

7、由手势接管所有触发操作，再由它分发给需要滚动的控件

本文方法

资源

SrollView下面包含节点地址栏,WebView控件

ScrollView继承自 ScrollView

onTouchEvent 中阻止 MotionEvent.ACTION_MOVE 事件
public class MyScrollView extends ScrollView {
 public MyScrollView(Context context) {
  super(context);
 }
 public MyScrollView(Context context, AttributeSet attrs) {
  super(context, attrs);
 }
 public MyScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
 }
 @TargetApi(Build.VERSION_CODES.LOLLIPOP)
 public MyScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
  super(context, attrs, defStyleAttr, defStyleRes);
 }
 @Override
 public boolean onTouchEvent(MotionEvent ev) {
  if(ev.getAction() == MotionEvent.ACTION_MOVE) {
   return true;
  }
  return super.onTouchEvent(ev);
 }
}

MyWebView继承自 WebView

onTouchEvent 中阻止 MotionEvent.ACTION_MOVE 事件

onDrawListner

计算竖直滚动范围

public class MyWebView extends WebView {
 public interface MyWebViewListener {
  void afterDraw(WebView webView);
 }
 private MyWebViewListener mListener;
 private int mMoveCheckedCnt;
 public MyWebView(Context context) {
  super(context);
 }
 public MyWebView(Context context, AttributeSet attrs) {
  super(context, attrs);
 }
 public MyWebView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
 }
 @TargetApi(Build.VERSION_CODES.LOLLIPOP)
 public MyWebView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
  super(context, attrs, defStyleAttr, defStyleRes);
 }
 public MyWebView(Context context, AttributeSet attrs, int defStyleAttr, boolean privateBrowsing) {
  super(context, attrs, defStyleAttr, privateBrowsing);
 }
 public void setListener(MyWebViewListener listener) {
  mListener = listener;
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
    mMoveCheckedCnt = 0;
    flingScroll(0, 0);
    break;
   case MotionEvent.ACTION_MOVE:
    mMoveCheckedCnt++;
    return false;
   case MotionEvent.ACTION_UP:
    if(mMoveCheckedCnt >= 2) {
     event.setAction(MotionEvent.ACTION_CANCEL);
     mMoveCheckedCnt = 0;
    }
    break;
  }
  return super.onTouchEvent(event);
 }
 @Override
 protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  MyWebViewListener listener = mListener;
  if(listener != null) {
   listener.afterDraw(this);
  }
 }
 public int getVScrollRange() {
  int v = computeVerticalScrollRange() - computeVerticalScrollExtent();
  if(v < 0) {
   v = 0;
  }
  return v;
 }
}

主窗口

GlobalLayoutListener 获取地址栏和滚动视图高度

GestureDetector 逻辑分发 - 决定是滑动webview还是改变webview高度从而改变ScrollView滚动范围（ScrollView总是滚动到最底）

WebView 重画之后检测当前地址栏偏移

public class MainActivity extends AppCompatActivity implements MyWebView.MyWebViewListener {
 MyWebView mWebView;
 GestureDetector mGesture = null;
 View mToolBar;
 int mToolBarHeight;
 MyScrollView mScrollView;
 int mScrollViewHeight;
 int mScrollOffset;
 EditText mUrlEdit;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  mWebView = (MyWebView) findViewById(R.id.webView);
  mWebView.setWebViewClient(new WebViewClient() {
   @Override
   public boolean shouldOverrideUrlLoading(WebView view, String url) {
    return false;
   }
  });
  mWebView.setListener(this);
  mWebView.loadUrl("http://www.sohu.com");
  mUrlEdit = (EditText) findViewById(R.id.urlEdit);
  findViewById(R.id.goButton).setOnClickListener(new View.OnClickListener() {
   @Override
   public void onClick(View v) {
    String url = mUrlEdit.getText().toString();
    if (!url.startsWith("http://") && !url.startsWith("https://")) {
     url = "http://" + url;
    }
    mWebView.loadUrl(url);
   }
  });
  mToolBar = findViewById(R.id.toolBar);
  mScrollView = (MyScrollView)findViewById(R.id.scrollView);
  ScrollView scrollView = (ScrollView) mScrollView;
  findViewById(R.id.root).getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
   @Override
   public void onGlobalLayout() {
    mToolBarHeight = mToolBar.getHeight();
    mScrollViewHeight = mScrollView.getHeight();
    adjustScrollView();
   }
  });
  mGesture = new GestureDetector(this, new GestureListener());
 }
 @Override
 public boolean dispatchTouchEvent(MotionEvent ev) {
  mGesture.onTouchEvent(ev);
  return super.dispatchTouchEvent(ev);
 }
 @Override
 public void afterDraw(WebView webView) {
  if (mWebView.getVScrollRange() < mScrollOffset) {
   mScrollOffset = mWebView.getVScrollRange();
   adjustScrollView();
  }
 }
 class GestureListener extends GestureDetector.SimpleOnGestureListener {
  @Override
  public boolean onDoubleTap(MotionEvent e) {
   Log.e("Temp", "onDoubleTap");
   return super.onDoubleTap(e);
  }
  @Override
  public boolean onDown(MotionEvent e) {
   Log.e("Temp", "onDown");
   return super.onDown(e);
  }
  @Override
  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
        float velocityY) {
   Log.e("Temp", "onFling:velocityX = " + velocityX + " velocityY" + velocityY);
   int effectX = (int) velocityX;
   int effectY = (int) velocityY;
   if (effectOnScrollViewByScroll((velocityY < 0 ? 1 : -1) * 8000)) {
    effectY = 0;
   }
   mWebView.flingScroll(-effectX, -effectY);
   return super.onFling(e1, e2, velocityX, velocityY);
  }
  @Override
  public void onLongPress(MotionEvent e) {
   Log.e("Temp", "onLongPress");
   super.onLongPress(e);
  }
  @Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2,
        float distanceX, float distanceY) {
   Log.e("Temp", "onScroll:distanceX = " + distanceX + " distanceY = " + distanceY);
   int effectX = (int) distanceX;
   int effectY = (int) distanceY;
   if (effectOnScrollViewByScroll((int) distanceY)) {
    effectY = 0;
   }
   mWebView.scrollBy(effectX, effectY);
   return super.onScroll(e1, e2, distanceX, distanceY);
  }
  @Override
  public boolean onSingleTapUp(MotionEvent e) {
   Log.e("Temp", "onSingleTapUp");
   return super.onSingleTapUp(e);
  }
 }
 private boolean effectOnScrollViewByScroll(int distanceY) {
  if (distanceY > 0) {
   // scroll up, the web will scroll down
   if (mScrollOffset >= mToolBarHeight || mScrollOffset >= mWebView.getVScrollRange()) {
    return false;
   }
   mScrollOffset += distanceY;
   if (mScrollOffset > mToolBarHeight) {
    mScrollOffset = mToolBarHeight;
   }
   if (mScrollOffset > mWebView.getVScrollRange()) {
    mScrollOffset = mWebView.getVScrollRange();
   }
  } else {
   if (mScrollOffset <= 0) {
    return false;
   }
   mScrollOffset += distanceY;
   if (mScrollOffset <= 0) {
    mScrollOffset = 0;
   }
  }
  adjustScrollView();
  return true;
 }
 private void adjustScrollView() {
  Log.e("Temp", "offset is " + mScrollOffset);
  ViewGroup.LayoutParams layoutParams = mWebView.getLayoutParams();
  int newHeight = (mScrollViewHeight - mToolBarHeight) + mScrollOffset;
  Log.e("Temp", "newHeight is " + newHeight + ", layoutParams.height" + layoutParams.height);
  if (newHeight != layoutParams.height) {
   layoutParams.height = newHeight;
   mWebView.setLayoutParams(layoutParams);
   new Handler(Looper.getMainLooper()).post(new Runnable() {
    @Override
    public void run() {
     mScrollView.fullScroll(ScrollView.FOCUS_DOWN);
    }
   });
  }
 }
}

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