Asked  7 Months ago    Answers:  5   Viewed   25 times

I have 2 ScrollViews in my android layout. How can I synchronise their scroll positions?

 Answers

65

There is a method in ScrollView...

protected void onScrollChanged(int x, int y, int oldx, int oldy)

Unfortunately Google never thought that we would need to access it, which is why they made it protected and didn't add a "setOnScrollChangedListener" hook. So we will have to do that for ourselves.

First we need an interface.

package com.test;

public interface ScrollViewListener {

    void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);

}

Then we need to override the ScrollView class, to provide the ScrollViewListener hook.

package com.test;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ScrollView;

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);
        }
    }

}

And we should specify this new ObservableScrollView class in the layout, instead of the existing ScrollView tags.

<com.test.ObservableScrollView
    android:id="@+id/scrollview1"
    ... >

    ...

</com.test.ObservableScrollView>

Finally, we put it all together in the Layout class.

package com.test;

import android.app.Activity;
import android.os.Bundle;

public class Q3948934 extends Activity implements ScrollViewListener {

    private ObservableScrollView scrollView1 = null;
    private ObservableScrollView scrollView2 = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.q3948934);

        scrollView1 = (ObservableScrollView) findViewById(R.id.scrollview1);
        scrollView1.setScrollViewListener(this);
        scrollView2 = (ObservableScrollView) findViewById(R.id.scrollview2);
        scrollView2.setScrollViewListener(this);
    }

    public void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy) {
        if(scrollView == scrollView1) {
            scrollView2.scrollTo(x, y);
        } else if(scrollView == scrollView2) {
            scrollView1.scrollTo(x, y);
        }
    }

}

The scrollTo() code takes care of any loop conditions for us, so we don't need to worry about that. The only caveat is that this solution is not guaranteed to work in future versions of Android, because we are overriding a protected method.

Tuesday, June 1, 2021
 
Uours
answered 7 Months ago
12

Here is the solution. Found online. I have subclassed WebView and i'm using the requestDisallowInterceptTouchEvent(true); method to allow my webview to handle the scroll event.

TouchyWebView.java

package com.mypackage.common.custom.android.widgets

public class TouchyWebView extends WebView {

    public TouchyWebView(Context context) {
        super(context);
    }

    public TouchyWebView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public TouchyWebView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event){
        requestDisallowInterceptTouchEvent(true);
        return super.onTouchEvent(event);
    }          
}

And in layout.xml

<com.mypackage.common.custom.android.widgets.TouchyWebView 
                android:id="@+id/description_web"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                 />
Wednesday, June 9, 2021
 
JohnnyW
answered 6 Months ago
59

It would be much easier if you paste your piece of code with your question, allowing to see why it goes wrong. My best guess without this information is to check you usage of fill_parent vs wrap_content.

Monday, August 9, 2021
 
Pascal
answered 4 Months ago
37

Try this code. It is working for me`

 parentScrollView.setOnTouchListener(new View.OnTouchListener() {

public boolean onTouch(View v, MotionEvent event)
{
    findViewById(R.id.childScrollView).getParent().requestDisallowInterceptTouchEvent(false);
return false;
}
});
childScrollView.setOnTouchListener(new View.OnTouchListener() {

public boolean onTouch(View v, MotionEvent event)
{

// Disallow the touch request for parent scroll on touch of
// child view
v.getParent().requestDisallowInterceptTouchEvent(true);
return false;
}
});`
Saturday, August 14, 2021
 
pwaring
answered 4 Months ago
92

You Should not have a listview within a ScrollView.

But you can have a custom class and use that to accomplish A Listview with in a ScrollView.

Try the following code

first make a custom ScrollView Class.

public class VerticalScrollview extends ScrollView{

public VerticalScrollview(Context context) {
    super(context);
}

 public VerticalScrollview(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public VerticalScrollview(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
    final int action = ev.getAction();
    switch (action)
    {
        case MotionEvent.ACTION_DOWN:
                super.onTouchEvent(ev);
                break;

        case MotionEvent.ACTION_MOVE:
                return false; // redirect MotionEvents to ourself

        case MotionEvent.ACTION_CANCEL:
                super.onTouchEvent(ev);
                break;

        case MotionEvent.ACTION_UP:
                return false;

        default: break;
    }

    return false;
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    super.onTouchEvent(ev);
     return true;
}
}

Then use this class for you layout

<LinearLayout 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"
android:background="@android:color/white"
android:orientation="vertical" >

<com.gui.today.VerticalScrollview
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000000"
    tools:context=".MainActivity" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >
     <FrameLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content" >

            <ProgressBar
                android:id="@+id/progressBar3"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical|center_horizontal" />

            <TextView
                android:id="@+id/empty_calender"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical|center_horizontal"
                android:text="@string/empty_calender"
                android:textColor="#ffffff"
                android:visibility="gone" />

            <ListView
                android:id="@+id/listView2"
                android:layout_width="fill_parent"
                android:layout_height="150dp" >
            </ListView>
        </FrameLayout>
    </LinearLayout>
  </com.gui.today.VerticalScrollview>
Saturday, August 21, 2021
 
iteong
answered 4 Months ago
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