关于scrollview监听的一些方法

一 

package cn.testscrollview;

import android.os.Bundle;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ScrollView;

import android.app.Activity;

/**

 * Demo描述:

 * 监听ScrollView滑动到顶端和底部

 *

 * 注意事项:

 * 1 mScrollView.getChildAt(0).getMeasuredHeight()表示:

 *   ScrollView所占的高度.即ScrollView内容的高度.常常有一

 *   部分内容要滑动后才可见,这部分的高度也包含在了

 *   mScrollView.getChildAt(0).getMeasuredHeight()中

 *  

 * 2 view.getScrollY表示:

 *   ScrollView顶端已经滑出去的高度

 *  

 * 3 view.getHeight()表示:

 *   ScrollView的可见高度

 *  

 */

public class MainActivity extends Activity {

    private ScrollView mScrollView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        init();

    }

    private void init(){

        mScrollView=(ScrollView) findViewById(R.id.scrollView);

        mScrollView.setOnTouchListener(new TouchListenerImpl());

    }

    private class TouchListenerImpl implements OnTouchListener{

        @Override

        public boolean onTouch(View view, MotionEvent motionEvent) {

            switch (motionEvent.getAction()) {

            case MotionEvent.ACTION_DOWN:

 

                break;

            case MotionEvent.ACTION_MOVE:

                 int scrollY=view.getScrollY();

                 int height=view.getHeight();

                 int scrollViewMeasuredHeight=mScrollView.getChildAt(0).getMeasuredHeight();

                 if(scrollY==0){

                        System.out.println("滑动到了顶端 view.getScrollY()="+scrollY);

                    }

                 if((scrollY+height)==scrollViewMeasuredHeight){

                        System.out.println("滑动到了底部 scrollY="+scrollY);

                        System.out.println("滑动到了底部 height="+height);

                        System.out.println("滑动到了底部 scrollViewMeasuredHeight="+scrollViewMeasuredHeight);

                    }

                break;

 

            default:

                break;

            }

            return false;

        }

         

    };

}

 

二 。

有时候我们需要监听ScroView的滑动情况，比如滑动了多少距离，是否滑到布局的顶部或者底部。可惜的是SDK并没有相应的方法，不过倒是提供了一个 

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

   方法，显然这个方法是不能被外界调用的，因此就需要把它暴露出去，方便使用。解决方式就是写一个接口， 

package com.example.demo1;

public interface ScrollViewListener {

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

}

 

 

  然后重写ScrollView类，给它提供上面写的回调接口。 

package com.example.demo1;

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);
        }
    }

}

 

  注意在xml布局的时候，不要写错了包。 

<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:orientation="horizontal"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <com.example.demo1.ObservableScrollView
        android:id="@+id/view1"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" >

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

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试1" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试2" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试3" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试4" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试5" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试6" />
        </LinearLayout>
    </com.example.demo1.ObservableScrollView>

    <com.example.demo1.ObservableScrollView
        android:id="@+id/view2"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" >

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

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试1" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试2" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试3" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试4" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试5" />

            <TextView
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:text="试试6" />
        </LinearLayout>
    </com.example.demo1.ObservableScrollView>

</LinearLayout>

 

  最后activity代码如下， 

package com.example.demo1;

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

public class MainActivity extends Activity implements ScrollViewListener {

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

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

        scrollView1 = (ObservableScrollView) findViewById(R.id.view1);
        scrollView1.setScrollViewListener(this);
        scrollView2 = (ObservableScrollView) findViewById(R.id.view2);
        scrollView2.setScrollViewListener(this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    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);
        }
    }

}