卡片式佈局以及RecycleView的用法

配置build.gradle文件:

 compile 'com.android.support:recyclerview-v7:26.1.0'
 compile 'com.android.support:cardview-v7:26.1.0'

然後是兩個佈局文件:
顯示的界面:

<?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"
android:layout_width="match_parent"
android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

填充的頁面:

<?xml version="1.0" encoding="utf-8"?>

<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:orientation="vertical">
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <ImageView
            android:id="@+id/qr"
            android:layout_width="match_parent"
            android:layout_height="100dp"
            android:scaleType="centerCrop"
            app:srcCompat="@mipmap/ic_launcher" />
        <TextView
            android:id="@+id/add"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_margin="5dp"
            android:textSize="16sp"
            />
    </LinearLayout>
</android.support.v7.widget.CardView>

然後是類的定義以及適配器的書寫:
這裏是我的類:

package com.example.qr_code;

import org.litepal.crud.DataSupport;

/**
 * Created by 浩哥 on 2017/12/14.
 */

public class QR extends DataSupport{
    private String  ImageId;
    private String name;

    public String getImageId() {
        return ImageId;
    }

    public void setImageId(String imageId) {
        ImageId = imageId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

這裏是適配器，添加了一下圖片的長按監聽和普通監聽:

package com.example.qr_code;

import android.app.Activity;
import android.app.Service;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Vibrator;
import android.support.v7.app.AlertDialog;
import android.support.v7.widget.CardView;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;

import org.litepal.crud.DataSupport;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.List;

/**
 * Created by 浩哥 on 2017/12/14.
 */

public class QR_Adapter extends RecyclerView.Adapter<QR_Adapter.ViewHolder> {
    private List<QR> mQRlist;
    static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView imageView;
        TextView textView;
        public ViewHolder(View v)
        {
          super(v);
          imageView=(ImageView) ((CardView) v).findViewById(R.id.qr);
          textView=(TextView) ((CardView) v).findViewById(R.id.add);
        }
    }
    public QR_Adapter(List<QR> QRList)
    {
      mQRlist=QRList;
    }
    public ViewHolder onCreateViewHolder(final ViewGroup parent, int viewType)
    {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.qr_item,parent,false);
         final ViewHolder holder=new ViewHolder(view);
         holder.imageView.setOnLongClickListener(new View.OnLongClickListener() {
             @Override
             public boolean onLongClick(View v) {
                 final int position=holder.getAdapterPosition();
                 QR qr=mQRlist.get(position);
                 Vibrator vib = (Vibrator) parent.getContext().getSystemService(Service.VIBRATOR_SERVICE);
                 vib.vibrate(95);
                 AlertDialog.Builder dialog=new AlertDialog.Builder(parent.getContext());
                 dialog.setTitle("確定刪除該記錄嗎？");
                 dialog.setPositiveButton("確定", new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {
                         QR qr=mQRlist.get(position);
                         DataSupport.deleteAll(QR.class,"ImageId=?",qr.getImageId());
                         for(int i = 0; i < mQRlist.size(); i++)
                         {
                             if(mQRlist.get(i).getImageId().equals(qr.getImageId()))
                             {
                                 mQRlist.remove(i);
                                 i--;
                             }
                         }
                         notifyDataSetChanged();
                     }
                 });
                 dialog.setNegativeButton("取消", new DialogInterface.OnClickListener() {
                     @Override
                     public void onClick(DialogInterface dialog, int which) {
                     }
                 });
                 dialog.show();
                 return true;
             }
         });
         holder.imageView.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 final int position=holder.getAdapterPosition();
                 QR qr=mQRlist.get(position);
                 Intent intent=new Intent(parent.getContext(),testSaveActivity.class);
                 intent.putExtra("imageId",qr.getImageId());
                 intent.putExtra("name",qr.getName());
                 parent.getContext().startActivity(intent);
             }
         });
        return holder;
    }
    public void onBindViewHolder(ViewHolder viewHolder,int position)
    {
        QR qr=mQRlist.get(position);
        Bitmap bitmap= BitmapFactory.decodeFile(qr.getImageId());
        viewHolder.textView.setText(qr.getName());
        viewHolder.imageView.setImageBitmap(bitmap);
    }
    public int getItemCount()
    {
        return mQRlist.size();
    }
}

最後就是顯示了 :

package com.example.qr_code;

import android.os.Environment;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.util.Log;
import android.widget.Toast;

import org.litepal.crud.DataSupport;

import java.util.ArrayList;
import java.util.List;

public class Saved_QR_Activity extends AppCompatActivity {

    private DrawerLayout mDrawerLayout;
    private List<QR> qrList;
    private QR_Adapter adapter;
    private final static String ALBUM_PATH
            = Environment.getExternalStorageDirectory() + "/qr_image/";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_saved__qr_);
        init();
        int count=qrList.size();
        String c=Integer.toString(count);
        Toast.makeText(this, c, Toast.LENGTH_SHORT).show();
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycler_view);
        StaggeredGridLayoutManager layoutManager=new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(layoutManager);
        adapter=new QR_Adapter(qrList);
        recyclerView.setAdapter(adapter);
    }
    private void init()
    {
        qrList=DataSupport.findAll(QR.class);
    }
}

這裏我設置的是顯示兩列。