ScrollView滚动

package com.imooc.android_scrollview;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ScrollView;
import android.widget.TextView;
import android.os.Build;

public class MainActivity extends Activity implements OnClickListener{

    private TextView tv;
    private ScrollView scroll;
    private Button up_btn;
    private Button down_btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);
        tv = (TextView) findViewById(R.id.content);
        up_btn=(Button) findViewById(R.id.up);
        down_btn=(Button) findViewById(R.id.down);
        up_btn.setOnClickListener(this);
        down_btn.setOnClickListener(this);
        tv.setText(getResources().getString(R.string.content));
        scroll = (ScrollView) findViewById(R.id.scroll);
        scroll.setOnTouchListener(new OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                // TODO Auto-generated method stub
                switch (event.getAction()) {
                case MotionEvent.ACTION_MOVE: {
                    /**
                     * (1)getScrollY()————滚动条滑动的距离 (2)getMeasuredHeight()
                     * (3)getHeight()
                     */

                    // 顶部状态
                    if (scroll.getScrollY() <= 0) {
                        Log.i("Main", "滑动到顶部");
                    }

                    // 底部状态
                    // TextView的总高度<=一屏幕的高度+滚动条的滚动距离
                    if (scroll.getChildAt(0).getMeasuredHeight() <= scroll
                            .getHeight() + scroll.getScrollY()) {

                        Log.i("Main", "滑动到底部");
                        Log.i("Main",
                                "scroll.getChildAt(0).getMeasuredHeight()="
                                        + scroll.getChildAt(0)
                                                .getMeasuredHeight()
                                        + "scroll,getHeight()="
                                        + scroll.getHeight()
                                        + "scroll.getScrollY()="
                                        + scroll.getScrollY());
                        tv.append(getResources().getString(R.string.content));

                    }
                    break;
                }
                }

                return false;
            }
        });
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId())
        {
        //scrollTo：以滚动视图起始位置开始计算的
        //scrollBy：相对前一次的位置，去滚动对应的距离

        case R.id.up:
        {
            scroll.scrollBy(0, -30);
            break;
        }

        case R.id.down:
        {

            scroll.scrollBy(0, 30);
            break;
        }
        }
    }
}