在 Activity 判斷滑動手勢主要是透過 View.OnTouchListener 和 GestureDetector.OnGestureListener
透過讓 Activity 繼承 GestureDetector.OnGestureListener 並實作其中的 onFling 方法，在 onFling 方法中判斷第 1 個按下點的 X 座標和第 2 個按下點的 X 座標是否超過標準值來決定是否為滑動手勢。

import android.support.constraint.ConstraintLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
public class FlingGestureExampleMainActivity extends AppCompatActivity implements View.OnTouchListener,
    GestureDetector.OnGestureListener{
  private static final String TAG = FlingGestureExampleMainActivity.class.getSimpleName();
  //main ui
  private LinearLayout mBasicLayout;
  private GestureDetector mGesetureDetector;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.fling_gesture_example_main_activity);
    mBasicLayout = findViewById(R.id.basic_layout_activity);
    mBasicLayout.setOnTouchListener(this);
    mBasicLayout.setLongClickable(true);
    mGesetureDetector = new GestureDetector((GestureDetector.OnGestureListener) this);
  }
  @Override
  public boolean onDown(MotionEvent e) {
    return false;
  }
  @Override
  public void onShowPress(MotionEvent e) {
  }
  @Override
  public boolean onSingleTapUp(MotionEvent e) {
    return false;
  }
  @Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
    return false;
  }
  @Override
  public void onLongPress(MotionEvent e) {
  }
  @Override
  public boolean onFling(MotionEvent firstMotion, MotionEvent secondMotion, float velocityX, float velocityY) {
    final int FLING_MIN_DISTANCE = 100;
    final int FLING_MIN_VELOCITY = 200;
    boolean isFlingToLeft = firstMotion.getX() - secondMotion.getX() > FLING_MIN_DISTANCE && Math.abs(velocityX) > FLING_MIN_VELOCITY;
    if (isFlingToLeft) {
      Log.d(TAG, "to left");
    }
    boolean isFlingToRight = firstMotion.getX() - secondMotion.getX() < FLING_MIN_DISTANCE && Math.abs(velocityX) < FLING_MIN_VELOCITY;
    if (isFlingToRight) {
      Log.d(TAG, "to right");
    }
    return false;
  }
  @Override
  public boolean onTouch(View view, MotionEvent motionEvent) {
    return mGesetureDetector.onTouchEvent(motionEvent);
  }
}

主要的重點為讓 Activity實作 onDown, onShowPress, on SingleTapUp, onScroll, onLongPress, onFling, onTouch 方法，
並在 onFling 方法判斷滑動的邏輯。
以及第23~26行的手勢和 layout 物件的連結
layout檔(fling_gesture_example_main_activity.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:id="@+id/basic_layout_activity"
  tools:context=".FlingGestureExampleMainActivity">
  <ListView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    .../>
</LinearLayout>

重點為 LinearLayout 建立 id，以便在程式碼中參考。
以上便是讓 Activity 加入滑動手勢的判斷，若是想讓該 Activity中
的 ListView 也可偵測滑動，作法相當簡單，直接讓該 ListView 呼叫 setOnTouchListener 和 setLongClickable 即可。

        mListView = getListView();
        mListViewAdapter = new ListViewAdapter();
        setListAdapter(mListViewAdapter);
        ...
        mPatrolPointListView.setOnTouchListener(this);
        mPatrolPointListView.setLongClickable(true);