Android通过代码控制ListView上下滚动的方法

本文将介绍一种通过代码控制ListView上下滚动的方法。

先上图：

按下按钮会触发ListView滚动或停止。

实现该功能并不难，下面给出主要代码MainActivity.java

package cn.guet.levide;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ListView;
public class MainActivity extends Activity implements OnClickListener {
 private Button btn_up, btn_down, btn_stop; // 三个按钮
 private ListView listview;
 private Adapter adapter;
 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 findBy();
 init();
 }
 private void init() {
 btn_up.setOnClickListener(this);
 btn_down.setOnClickListener(this);
 btn_stop.setOnClickListener(this);
 adapter = new Adapter(this);
 listview.setAdapter(adapter);
 }
 private void findBy() {
 btn_up = (Button) findViewById(R.id.btn_scroll_up);
 btn_down = (Button) findViewById(R.id.btn_scroll_down);
 btn_stop = (Button) findViewById(R.id.btn_scroll_stop);
 listview = (ListView) findViewById(R.id.listview);
 }
 @Override
 public void onClick(View v) {
 switch (v.getId()) {
 case R.id.btn_scroll_down:
  listScrollDown();
  break;
 case R.id.btn_scroll_up:
  listScrollUp();
  break;
 case R.id.btn_scroll_stop:
  listScrollOff();
  break;
 }
 }
 Handler handler = new Handler() {
 @Override
 public void handleMessage(Message msg) {
  handler.removeCallbacks(run_scroll_down);
  handler.removeCallbacks(run_scroll_up);
 }
 };
 /**
 * 向上滚动
 */
 public void listScrollUp() {
 listScrollOff();
 handler.postDelayed(run_scroll_up, 0);
 }
 /**
 * 向下滚动
 */
 public void listScrollDown() {
 listScrollOff();
 handler.postDelayed(run_scroll_down, 0);
 }
 /**
 * 停止滚动
 */
 public void listScrollOff() {
 handler.removeCallbacks(run_scroll_down);
 handler.removeCallbacks(run_scroll_up);
 }
 Runnable run_scroll_up = new Runnable() {
 @Override
 public void run() {
  /**
  * public void smoothScrollBy (int distance, int duration) 
  * 
  * Added in API level 8 Smoothly scroll by distance pixels over duration milliseconds.
  * 
  * Parameters 
  *   distance Distance to scroll in pixels.
  *   duration Duration of the scroll animation in milliseconds.
  */
  listview.smoothScrollBy(1, 10);
  handler.postDelayed(run_scroll_up, 10);
 }
 };
 Runnable run_scroll_down = new Runnable() {
 @Override
 public void run() {
  listview.smoothScrollBy(-1, 10);
  handler.postDelayed(run_scroll_down, 10);
 }
 };
}

实现ListView位置变动的是smoothScrollBy方法。

public void smoothScrollBy (int distance, int duration)
  Smoothly scroll by distance pixels over duration milliseconds.

Parameters
  distance Distance to scroll in pixels.
  duration Duration of the scroll animation in milliseconds. 

总结

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