Question

我下载了一个名为SimpleGestureListener的Java类，该类是由名为CoXier的用户创建的。

  import android.util.Log;
  import android.view.GestureDetector;
  import android.view.MotionEvent;
  public class SimpleGestureListener extends GestureDetector.SimpleOnGestureListener {
      private static final String TAG = "SimpleGestureListener";
      private Listener mListener;

  @Override
  public boolean onDown(MotionEvent e) {
      return true;
  }

  @Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
      Log.i(TAG,e1.toString()+"\n"+e2.toString());
      Log.d(TAG,"distanceX = "+distanceX+",distanceY = "+distanceY);
      if (mListener == null)
          return true;

      if (distanceX == 0 && Math.abs(distanceY) > 1){
          mListener.onScrollVertical(distanceY);
      }

      if (distanceY == 0 && Math.abs(distanceX) > 1){
          mListener.onScrollHorizontal(distanceX);
      }
      return true;
  }


  public void setListener(Listener mListener) {
      this.mListener = mListener;
  }

  interface Listener{
      /**
       * left scroll dx >0
       * right scroll dx <0
       * @param dx
       */
      void onScrollHorizontal(float dx);

      /**
       * upward scroll dy > 0
       * downward scroll dy < 0
       * @param dy
       */
      void onScrollVertical(float dy);
  }

}

在仅包含1个活动的应用程序中使用它时，它可以完美运行。例如，在这里我可以使用水平或垂直滑动来更改布局的背景颜色：（此后，我禁用了水平滑动功能）

  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;

  public class MainActivity extends AppCompatActivity
  {
      private static final String TAG = "MainActivity";
      private GestureDetector mDetector;
      @Override
      protected void onCreate(Bundle savedInstanceState)
      {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          SimpleGestureListener simpleGestureListener = new SimpleGestureListener();
          simpleGestureListener.setListener(new SimpleGestureListener.Listener()
          {
              @Override
              public void onScrollHorizontal(float dx)
              {

          }
          @Override
          public void onScrollVertical(float dy)
          {

              ConstraintLayout constraintLayout = findViewById(R.id.constraint_layout);
              if (dy > 0)
              {
                  constraintLayout.setBackgroundColor(getResources().getColor(R.color.blue));
              }
              if (dy < 0)
              {
                  constraintLayout.setBackgroundColor(getResources().getColor(R.color.yellow));
              }
          }
      });
      mDetector = new GestureDetector(this, simpleGestureListener);
  }

  @Override
  public boolean onTouchEvent(MotionEvent event)
  {
      mDetector.onTouchEvent(event);
      return super.onTouchEvent(event);
  }

}

现在我的问题是我想在我的原始应用程序中使用它，该应用程序由片段和ViewPager组成。我想在1个片段中添加此SwipeUp / Down功能。（其他片段我不需要。）

我必须在片段类中包含什么？

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class Page_2 extends Fragment
{
    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View PageTwo = inflater.inflate(R.layout.page2, container, false);
        return PageTwo;
    }
}

我是否必须使MainActivity.java与代码块2相同？（示例应用）目前，我的MainActivity.java如下所示：

import android.os.Bundle;
    import android.support.annotation.Nullable;
    import android.support.v4.app.Fragment;
    import android.support.v4.app.FragmentManager;
    import android.support.v4.app.FragmentPagerAdapter;
    import android.support.v4.view.ViewPager;
    import android.support.v7.app.AppCompatActivity;
    import android.util.Log;
    import android.view.GestureDetector;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.MotionEvent;
    import java.util.ArrayList;
    import java.util.List;

    public class MainActivity extends AppCompatActivity
    {
        ViewPager vp;
        private static final String TAG = "MainActivity";
        private static GestureDetector mDetector;
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            SimpleGestureListener simpleGestureListener = new SimpleGestureListener();
            simpleGestureListener.setListener(new SimpleGestureListener.Listener()
            {
                @Override
                public void onScrollHorizontal(float dx)
                {
                    Log.wtf("swipe", "horizontal = " + dx);
                }
                @Override
                public void onScrollVertical(float dy)
                {
                    Log.wtf("swipe", "vertical = " + dy);
                }
            });
            mDetector = new GestureDetector(this, simpleGestureListener);

            ViewPager vp = findViewById(R.id.vp);
            SetUpViewPager(vp);
        }
        @Override
        public boolean onTouchEvent(MotionEvent event)
        {
            mDetector.onTouchEvent(event);
            return super.onTouchEvent(event);
        }
        public void SetUpViewPager(ViewPager viewpage)
        {
            MyViewPagerAdapter Adapter = new MyViewPagerAdapter(getSupportFragmentManager());
            Adapter.AddPageFragment(new Page_1(), "Page 1"); // Load pages inside of ViewPager
            Adapter.AddPageFragment(new Page_2(), "Page 2");
            Adapter.AddPageFragment(new Page_3(), "Page 3");
            Adapter.AddPageFragment(new Page_5(), "Page 5");
            viewpage.setAdapter(Adapter);
        }
        public class MyViewPagerAdapter extends FragmentPagerAdapter
        {
            private List<Fragment> MyFragment = new ArrayList<>();
            private List<String> MyPageTitle = new ArrayList<>();

            public MyViewPagerAdapter(FragmentManager manager)
            {
                super(manager);
            }
            public void AddPageFragment(Fragment Frag, String Title)
            {
                MyFragment.add(Frag);
                MyPageTitle.add(Title);
            }
            @Override
            public Fragment getItem(int i)
            {
                return MyFragment.get(i);
            }
            @Nullable
            @Override
            public CharSequence getPageTitle(int position)
            {
                return MyPageTitle.get(position);
            }
            @Override
            public int getCount()
            {
                return 4; // 4 pages total
            }
        }
        @Override
        public boolean onCreateOptionsMenu(Menu menu)
        {
            getMenuInflater().inflate(R.menu.menu_main, menu);
            return true;
        }
        @Override
        public boolean onOptionsItemSelected(MenuItem item)
        {
            int id = item.getItemId();

            if (id == R.id.action_settings)
            {
                return true;
            }
            return super.onOptionsItemSelected(item);
        }
    }

我认为大多数代码（与GestureDetector相关）都必须在Page_2中？也许我也必须使用

mDetector = new GestureDetector(getActivity(), simpleGestureListener);

在Page_2中，因为否则它将找不到它。

无论如何，无论我如何尝试，它都无法像单项活动测试应用程序那样发挥作用。

有什么主意吗？

Answer 1

也许您只是在做一些测试，而不是仅仅通过左右滚动来更改背景颜色。我不知道。我只是对您提供的代码提出建议。

有一个ViewPager.OnPageChangeListener。就像Adapter或ClickListener是ListView一样，告诉您哪个页面/项目正在调用该方法。

您只需跟踪页面更改索引即可知道寻呼机向左或向右摆动。

int lastPosition = 0;
void onPageSelected(int position) {
   if(position < lastPosition);
   else if(position > lastPosition);

   lastPosition = position;
}

顺便说一句，我没有测试我的代码。但是我今天才使用ViewPager.OnPageChangedListener。

将ViewPager与GestureListener一起使用？

1 个答案: