将下一个和上一个按钮添加到ViewPager

Question

我想用Android Studio制作一个图像滑块。我发现了一个新的滑块代码，它是用ViewPager构建的，我尝试了它并成功了。。但是我想为下一个和上一个添加2个按钮。。

单击按钮时，必须转到下一张图片或上一张图片。

这里是mainactivity，

package org.trial.slider;   
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
        ImageAdapter adapter = new ImageAdapter(this);
        viewPager.setAdapter(adapter);  
     }          
}

ImageAdapter.java文件，

    package org.trial.slider;
    import android.content.Context;
    import android.support.v4.view.PagerAdapter;
    import android.support.v4.view.ViewPager;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    import android.widget.ImageView;
    /**
     * Created by ismail on 30.03.16.
     */
    public class ImageAdapter extends PagerAdapter {
        Context context;

        private int[] GalImages = new int[] {
                R.drawable.one,
                R.drawable.two,
                R.drawable.three
        };
        ImageAdapter(Context context){
            this.context=context;
        }
        @Override
        public int getCount() {
            return GalImages.length;
        }
        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == ((ImageView) object);
        }
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            ImageView imageView = new ImageView(context);
            int padding = context.getResources().getDimensionPixelSize(R.dimen.padding_medium);
            imageView.setPadding(padding, padding, padding, padding);
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);
            imageView.setImageResource(GalImages[position]);
            ((ViewPager) container).addView(imageView, 0);
            return imageView;
        }
        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            ((ViewPager) container).removeView((ImageView) object);
        }
    }

我有两个XML文件；fragment_pager和swipe_fragment

Answer 1

1. 添加按钮您的MainActivity和activity_main.xml
2. 在OnCreate()中添加代码button.setonclicklister(this);

3. 此处的示例代码：

   @Override
   public void onClick(View v) {
       int id = v.getId();
       switch (id) {
           //prev button
           case R.id.btn_list_detail_img_prev:
               viewPager.setCurrentItem(mPager.getCurrentItem()-1,true);
               break;
           //nextbutton, 1st argument : pageindex, 2nd argument : Enable smooth 
           case R.id.btn_list_detail_img_next:
               viewPager.setCurrentItem(mPager.getCurrentItem()+1,true);
               break;
   }
   

Answer 2

有一个方法名称viewPager.setCurrentItem(position)
此方法将整数值作为索引，并在viewPager对象上设置。使用此方法，您可以更改寻呼机项的位置。

Answer 3

class MyClass extends Fragment implements ViewPager.OnPageChangeListener {
    private int selectedViewPager = 0;
    public void onViewClicked(View view) {
        switch (view.getId()) {
            case R.id.backward:
                if (selectedViewPager > 0) {
                    viewPager.setCurrentItem(selectedViewPager - 1, true);
                }
                break;
            case R.id.fwd:
                if (viewPager.getAdapter().getCount() > selectedViewPager) {
                    viewPager.setCurrentItem(selectedViewPager + 1, true);
                }
                break;
        }
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
    }
    @Override
    public void onPageSelected(int position) {
        selectedViewPager = position;
    }
    @Override
    public void onPageScrollStateChanged(int state) {
    }
}