Android开发-Android常用组件-ScrollView滚动条

@Override

public void fling(int velocityY) { super.fling(velocityY / 2);   //速度变为原来的一半

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <Button
        android:id="@+id/btn_down"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="滚动到底部"/>
    <Button
        android:id="@+id/btn_up"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="滚动到顶部"/>
    <ScrollView
        android:id="@+id/scroll_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:scrollbars="vertical"
        android:layout_weight="1">
        <TextView
            android:id="@+id/txt_show"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text=""/>
    </ScrollView>

</LinearLayout>

package com.example.myapplication;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ScrollView;
import android.widget.TextView;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

public class ScrollViewActivity extends AppCompatActivity implements View.OnClickListener {
    private Button btn_down;
    private Button btn_up;
    private ScrollView scrollView;
    private TextView txt_show;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.scrollview_layout);
        bindViews();
    }
    private void bindViews(){
        btn_down = (Button) findViewById(R.id.btn_down);
        btn_up = (Button) findViewById(R.id.btn_up);
        scrollView = (ScrollView) findViewById(R.id.scroll_view);
        txt_show = (TextView) findViewById(R.id.txt_show);

        btn_down.setOnClickListener(this);
        btn_up.setOnClickListener(this);

        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 100 ; i++) {
            sb.append("我是一条文本内容 * " + i + "\n");
        }
        txt_show.setText(sb.toString());
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_down:
                scrollView.fullScroll(ScrollView.FOCUS_DOWN);
                break;
            case R.id.btn_up:
                scrollView.fullScroll(ScrollView.FOCUS_UP);
                break;
        }
    }
}