Android通过PagerSnapHelper改造RecyclerView成“ViewPager”

清疚 2023-10-18 09:12 64阅读 0赞

## Android通过PagerSnapHelper改造RecyclerView成“ViewPager” ##

最新Android平台针对RecyclerView引入一个辅助类PagerSnapHelper，PagerSnapHelper可以把一个普通的RecyclerView改造成ViewPager，每一个RecyclerView的子item在翻动时候，像ViewPager一样。  
如代码：

package zhangphil.test;
    
    import android.content.Context;
    import android.content.res.Resources;
    import android.graphics.Color;
    import android.os.Bundle;
    import android.support.v7.app.AppCompatActivity;
    import android.support.v7.widget.LinearLayoutManager;
    import android.support.v7.widget.PagerSnapHelper;
    import android.support.v7.widget.RecyclerView;
    import android.util.DisplayMetrics;
    import android.util.TypedValue;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.LinearLayout;
    import android.widget.TextView;
    
    public class RVActivity extends AppCompatActivity {
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            RecyclerView mRecyclerView = findViewById(R.id.recycler_view);
    
            LinearLayoutManager mLayoutManager = new LinearLayoutManager(this);
            mLayoutManager.setOrientation(LinearLayout.HORIZONTAL);
            mRecyclerView.setLayoutManager(mLayoutManager);
    
            PagerSnapHelper mPagerSnapHelper = new PagerSnapHelper();
            mPagerSnapHelper.attachToRecyclerView(mRecyclerView);
    
            RecyclerView.Adapter mAdapter = new MyAdapter();
            mRecyclerView.setAdapter(mAdapter);
        }
    
        private class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
            public MyAdapter() {
                super();
            }
    
            @Override
            public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
                View view = LayoutInflater.from(getApplicationContext()).inflate(android.R.layout.simple_list_item_2, null);
                ViewHolder holder = new ViewHolder(view);
                return holder;
            }
    
            @Override
            public void onBindViewHolder(ViewHolder viewHolder, int i) {
                viewHolder.text1.setText(String.valueOf(i));
                viewHolder.text2.setText("pos:" + i);
    
                int n = i % 2;
                int color = n == 0 ? Color.DKGRAY : Color.LTGRAY;
    
                viewHolder.itemView.setBackgroundColor(color);
            }
    
            @Override
            public int getItemCount() {
                return 20;
            }
    
            public class ViewHolder extends RecyclerView.ViewHolder {
                public TextView text1;
                public TextView text2;
    
                public ViewHolder(View itemView) {
                    super(itemView);
    
                    float[] size = getDeviceDisplaySize(getApplicationContext());
                    itemView.setMinimumWidth((int) size[0]);
    
                    text1 = itemView.findViewById(android.R.id.text1);
                    text1.setTextColor(Color.RED);
                    text1.setTextSize(TypedValue.COMPLEX_UNIT_DIP, 160);
    
                    text2 = itemView.findViewById(android.R.id.text2);
                    text2.setTextColor(Color.BLUE);
                }
            }
        }
    
        public static float[] getDeviceDisplaySize(Context context) {
            Resources resources = context.getResources();
            DisplayMetrics dm = resources.getDisplayMetrics();
            int width = dm.widthPixels;
            int height = dm.heightPixels;
    
            float[] size = new float[2];
            size[0] = width;
            size[1] = height;
    
            return size;
        }
    }

本例特意把RecyclerView设置成水平方向，并且把每一个子元素的宽度设置成和手机设备屏幕宽度一样的值，以达到和ViewPager相同的效果。  
运行如图：

![70][]

![70 1][]

[70]: https://img-blog.csdn.net/20180925112931275?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5ncGhpbA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 1]: https://img-blog.csdn.net/20180925112949308?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5ncGhpbA==/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70