RecyclerView的功能扩展（Android图片选择器）

Android 应用程序开发中总会遇到从本地选择照片的操作，本文描述得是一个简单得图片选择器
支持设置图片张数、可以设置屏蔽得图片格式、图片预览。更多的功能正在开发中，项目已放到：码云git上我也在随时更新这个项目。下面就简单地介绍下这个内容。

效果图片

工程逻辑简述

实现原理则是，使用Android提供的媒体数据库，将图片资源的地址（存在本地的绝对地址（路径））提取出来，再使用Glide图片加载框架，将图片加载到RecyclerView列表中。
对于Glide框架和RecyclerView可以添加如下依赖（若遇到依赖版本问题就自行解决咯）

//Glidecompile 'com.github.bumptech.glide:glide:3.7.0'//RecyclerViewcompile 'com.android.support:recyclerview-v7:26.0.0-alpha1'

以上便是这个工程的基本思路

获取图片地址（路径）

package com.util.photopicker.util;import android.content.Context;import android.database.Cursor;import android.provider.MediaStore;import com.util.photopicker.bean.ImageBean;import java.util.ArrayList;import java.util.List;/** * Created by eric on 2017/12/3. */public class ImageFinder {    public static final String NONE = "none";    public static final String TYPE_GIF = "image/gif";    public static final String TYPE_JPEG = "image/jpeg";    public static final String TYPE_jpg = "image/jpg";    public static final String TYPE_PNG = "image/png";    //第二个参数是配置需要屏蔽的图片格式    public static List getImages(Context context, String typeShield){        String shield = typeShield;        List list = new ArrayList<>();        Cursor cursor = context.getContentResolver().query(                MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null, null, null, null);        while (cursor.moveToNext()){            String name = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME));            String path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));            String type = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE));            if (type.equals(shield)) continue;            list.add(0,new ImageBean(path,name));        }        return list;    }}

若是以上这个类看的头大，那我们只用知道一下这几行核心代码就OK了

 Cursor cursor = context.getContentResolver().query(                MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null, null, null, null);        while (cursor.moveToNext()){            String name = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DISPLAY_NAME));            String path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));            String type = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.MIME_TYPE));        }

以上便是通过Android为我们提供的媒体数据库来查询图片的name，path，type。当然还有更多的图片属性可以获取，例如文件大小等信息，但我们这儿暂时只需要这些就够了。除此之外，还得有个Bean类来存放我们得到的单个数据，然后放在一个List里，再返回这个list；Bean类如下

package com.util.photopicker.bean;/** * Created by eric on 2017/12/3. */public class ImageBean {    private String imagePath;    private String imageName;    private boolean isChoose = false;    public ImageBean(String path, String name){        this.imagePath = path;        this.imageName = name;    }    public String getImagePath() {        return imagePath;    }    public void setImagePath(String imagePath) {        this.imagePath = imagePath;    }    public String getImageName() {        return imageName;    }    public void setImageName(String imageName) {        this.imageName = imageName;    }    public boolean isChoose() {        return isChoose;    }    public void setChoose(boolean choose) {        isChoose = choose;    }}

当我们拿到了这个list之后就可以用列表的形式展示出来了，这里我采用的是RecyclerView，当然可以用其他的控件来代替，这里就自行考虑了。

RecyclerView
我都知道，RecyclerView简单易用，但是这个还是没法满足我们的需求，以下是对RecyclerView 的 adapter的一点小小的扩展。

package com.util.photopicker.component;import android.support.v7.widget.RecyclerView;import android.view.View;/** * Created by eric on 2017/12/4. */public abstract class BaseViewHolder extends RecyclerView.ViewHolder {    public BaseViewHolder(View itemView) {        super(itemView);        findViewById(itemView);    }    /**     * 转发传入的OnItemChooseCallback与位置     * @param chooseCallback 点击回调     * @param position 位置     */    public void setChooseCallback(OnItemChooseCallback chooseCallback,int position) {        if (chooseCallback != null){            intOnItemChooseCallback(chooseCallback,position);        }    }    /**     * 传入Item的点击事件的监听器     * @param listener     */    public void setOnItemClickListener(OnRecyclerViewItemClickListener listener, int position){        if (listener != null){            initOnItemClickListener(listener, position);        }    }    /**     * 传入Item的长按事件的监听器     * @param longClickListener     */    public void setOnItemLongClickListener(OnRecyclerViewItemLongClickListener longClickListener, int position){        if (longClickListener != null){            iniOnItemLongClickListener(longClickListener,position);        }    }    /**     * 初始化点击事件（开发者自行实现）     * @param chooseCallback 单项选择回调     * @param position 当前点击的位置     */    abstract public void intOnItemChooseCallback(OnItemChooseCallback chooseCallback, int position);    /**     * 初始化Item的点击事件（开发者自行实现）     * @param listener 监听器     */    abstract public void initOnItemClickListener(OnRecyclerViewItemClickListener listener, int position);    /**     * 初始化Item的长按事件（开发者自行实现）     * @param longClickListener 监听器     */    abstract public void iniOnItemLongClickListener(OnRecyclerViewItemLongClickListener longClickListener, int position);    /**     * 通过id匹配控件（开发者自行实现）     * @param itemView 父布局     */    abstract protected void findViewById(View itemView);    /**     * 用于装载数据（开发者自行实现）     * @param position 当前位置     */    abstract public void onBind(int position);}

对于一个列表来说，我们必定会用到adapter，RecyclerView也不列外，会用到 adapter 和 ViewHolder。
看上面这个类的名字变知道BaseViewHolder ，是自己写的一个ViewHolder的基类，然后我们的ViewHolder继承这个类便可以得到它的属性和功能。当然只有这个类是不够的，我们都知道 RecyclerView 显示列表，是adapter 和 ViewHolder的结合。可能你已经猜到了，还有一个BaseRecyclerAdapter的基类。

package com.util.photopicker.component;import android.support.v7.widget.RecyclerView;/** * Created by eric on 2017/12/4. */public abstract class BaseRecyclerAdapter extends RecyclerView.Adapter {    private OnItemChooseCallback chooseCallback;    private OnRecyclerViewItemClickListener onRecyclerViewItemClickListener;    private OnRecyclerViewItemLongClickListener onRecyclerViewItemLongClickListener;    @Override    public void onBindViewHolder(BaseViewHolder holder, int position) {        holder.setChooseCallback(chooseCallback,position);        holder.setOnItemClickListener(onRecyclerViewItemClickListener,position);        holder.setOnItemLongClickListener(onRecyclerViewItemLongClickListener,position);        holder.onBind(position);    }    public void setChooseCallback(OnItemChooseCallback chooseCallback) {        this.chooseCallback = chooseCallback;    }    public void setOnRecyclerViewItemClickListener(OnRecyclerViewItemClickListener onRecyclerViewItemClickListener) {        this.onRecyclerViewItemClickListener = onRecyclerViewItemClickListener;    }    public void setOnRecyclerViewItemLongClickListener(OnRecyclerViewItemLongClickListener onRecyclerViewItemLongClickListener) {        this.onRecyclerViewItemLongClickListener = onRecyclerViewItemLongClickListener;    }}

以上便是BaseRecyclerAdapter，其中很有灵性的是这几个方法

public void setChooseCallback(OnItemChooseCallback chooseCallback) {        this.chooseCallback = chooseCallback;    }    public void setOnRecyclerViewItemClickListener(OnRecyclerViewItemClickListener onRecyclerViewItemClickListener) {        this.onRecyclerViewItemClickListener = onRecyclerViewItemClickListener;    }    public void setOnRecyclerViewItemLongClickListener(OnRecyclerViewItemLongClickListener onRecyclerViewItemLongClickListener) {        this.onRecyclerViewItemLongClickListener = onRecyclerViewItemLongClickListener;    }

可以看出，这个便是设置事件的监听，OnItemChooseCallback，OnRecyclerViewItemClickListener ，OnRecyclerViewItemLongClickListener 相信看名字就知道是什么意思了

1、 OnItemChooseCallback

package com.util.photopicker.component;/** * Created by eric  on 2017/12/4. */public interface OnItemChooseCallback {    /**     * 点击单项时     * @param position 位置     * @param isChosen 是否选中     */    void chooseState(int position, boolean isChosen);    /**     * 现在的值     * @param countNow     */    void countNow(int countNow);    /**     * 警告不能再选了     * @param count     */    void countWarning(int count);}

2、 OnRecyclerViewItemClickListener

package com.util.photopicker.component;/** * Created by eric  on 2017/12/5. */public interface OnRecyclerViewItemClickListener {    void onItemClick(int position);}

3、OnRecyclerViewItemLongClickListener

package com.util.photopicker.component;/** * Created by 肖庆鸿 on 2017/12/5. */public interface OnRecyclerViewItemLongClickListener {    void onItemLongClick(int position);}

以上这样写的好处再哪儿呢，下面就可以看出来

ImagesListAdapter

package com.util.photopicker.adapter;import android.content.Context;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import com.bumptech.glide.Glide;import com.util.photopicker.R;import com.util.photopicker.bean.ImageBean;import com.util.photopicker.component.BaseRecyclerAdapter;import com.util.photopicker.component.BaseViewHolder;import com.util.photopicker.component.OnItemChooseCallback;import com.util.photopicker.component.OnRecyclerViewItemClickListener;import com.util.photopicker.component.OnRecyclerViewItemLongClickListener;import java.util.List;/** * Created by eric on 2017/12/3. */public class ImagesListAdapter extends BaseRecyclerAdapter {    private int count = 0;    private int maxNum = 1;    private Context context;    private List list;    public ImagesListAdapter(Context context, List list){        this.context = context;        this.list = list;    }    @Override    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_picker,null);        return new MyViewHolder(view);    }    @Override    public int getItemCount() {        return list.size();    }    public void setMaxNum(int maxNum) {        if (maxNum < 1) return;        this.maxNum = maxNum;    }    private class MyViewHolder extends BaseViewHolder {        private ImageView mImageSrc;        private ImageView mImageChoose;        private MyViewHolder(View itemView) {            super(itemView);        }        @Override        public void intOnItemChooseCallback(final OnItemChooseCallback chooseCallback, final int position) {           mImageChoose.setOnClickListener(new View.OnClickListener() {               @Override               public void onClick(View view) {                   if (count < maxNum){                       if (!list.get(position).isChoose()){                           mImageChoose.setImageResource(R.drawable.checked_yes);                           list.get(position).setChoose(true);                           chooseCallback.chooseState(position,true);                           count ++;                       } else {                           mImageChoose.setImageResource(R.drawable.checked_null);                           list.get(position).setChoose(false);                           chooseCallback.chooseState(position,false);                           count--;                       }                   } else { //count >= maxNum                       if (!list.get(position).isChoose()){                           chooseCallback.countWarning(count);                       } else {                           mImageChoose.setImageResource(R.drawable.checked_null);                           list.get(position).setChoose(false);                           chooseCallback.chooseState(position,false);                           count--;                       }                   }                   chooseCallback.countNow(count);               }           });        }        @Override        public void initOnItemClickListener(final OnRecyclerViewItemClickListener listener, final int position) {            itemView.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                    listener.onItemClick(position);                }            });        }        @Override        public void iniOnItemLongClickListener(OnRecyclerViewItemLongClickListener longClickListener, int position) {        }        @Override        protected void findViewById(View itemView) {            mImageSrc = itemView.findViewById(R.id.image_src);            mImageChoose = itemView.findViewById(R.id.image_choose);        }        @Override        public void onBind(int position) {            if (list.get(position).isChoose()){                mImageChoose.setImageResource(R.drawable.checked_yes);            } else {                mImageChoose.setImageResource(R.drawable.checked_null);            }            Glide.with(context)                    .load(list.get(position).getImagePath())                    .into(mImageSrc);        }    }}

adapter里面我们只需要重写两个方法就OK了

 @Override    public BaseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_picker,null);        return new MyViewHolder(view);    }    @Override    public int getItemCount() {        return list.size();    }

这个相信已经不用解释了，然后再viewholder中处理逻辑就很清晰了

private MyViewHolder(View itemView) {            //这里super不可省略            super(itemView);        }        @Override        public void intOnItemChooseCallback(final OnItemChooseCallback chooseCallback, final int position) {              //初始化选择事件的callback        }        @Override        public void initOnItemClickListener(final OnRecyclerViewItemClickListener listener, final int position) {            //初始化单击事件        }        @Override        public void iniOnItemLongClickListener(OnRecyclerViewItemLongClickListener longClickListener, int position) {            //初始化长按事件        }        @Override        protected void findViewById(View itemView) {            //通过id来初始化itemView内的控件        }        @Override        public void onBind(int position) {            //装配数据        }    }

这个类里是重写继承自抽象类BaseViewHolder的一些方法，看名字就知道这个方法里该写什么。这里放心，若是没有调用adapter对象的set方法这些初始化方法是不会调用的。以上便是图片选择器中对RecyclerView 的 adapter的扩展。

ImagesPickActivity
再下来就是展示图片的ImagesPickActivity了，这里的一系列操作都是些固定的方式，没什么可说的

package com.util.photopicker.activities;import android.app.Activity;import android.content.Intent;import android.content.pm.PackageManager;import android.net.Uri;import android.os.Build;import android.provider.MediaStore;import android.support.annotation.NonNull;import android.support.v4.app.ActivityCompat;import android.support.v4.content.FileProvider;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.support.v7.widget.GridLayoutManager;import android.support.v7.widget.RecyclerView;import android.support.v7.widget.Toolbar;import android.view.View;import android.widget.Button;import android.widget.ImageButton;import android.widget.TextView;import android.widget.Toast;import com.util.photopicker.R;import com.util.photopicker.bean.ImageBean;import com.util.photopicker.adapter.ImagesListAdapter;import com.util.photopicker.component.OnItemChooseCallback;import com.util.photopicker.component.OnRecyclerViewItemClickListener;import com.util.photopicker.util.ImageFinder;import java.io.File;import java.io.IOException;import java.util.ArrayList;import java.util.List;public class ImagesPickActivity extends AppCompatActivity implements View.OnClickListener{    public final static String RESULT_IMAGES_LIST = "imagesPath";    private final static int REQUEST_CAMERA = 200;    private final static String EXTRA_COUNT = "max";    private static final int REQUEST_EXTERNAL_STORAGE = 1;    private static String[] PERMISSIONS_STORAGE = {            "android.permission.READ_EXTERNAL_STORAGE",            "android.permission.WRITE_EXTERNAL_STORAGE" };    private Toolbar mTbPickActivity;    private TextView mTvCount;    private ImageButton mImageBtnPickerBack;    private Button mBtnSure;    private RecyclerView mRecyclerViewPickActivity;    private List list;    private Uri cameraImageUri;    private int maxCount;    private ArrayList chosenList = new ArrayList<>();    /**     * 提供启动活动的方法     * @param activity 起点活动     * @param max 最大图片数     * @param requestCode 请求值     */    public static void startPicker(Activity activity, int max, int requestCode){        Intent intent = new Intent(activity,ImagesPickActivity.class);        intent.putExtra(EXTRA_COUNT,max);        activity.startActivityForResult(intent,requestCode);    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_pick);        Intent intent = getIntent();        maxCount = intent.getIntExtra(EXTRA_COUNT,9);        initView();        requestStoragePermission();    }    /**     * 初始化控件资源     */    private void initView() {        mTbPickActivity = (Toolbar) findViewById(R.id.tb_pick_activity);        mTvCount = (TextView) findViewById(R.id.tv_count);        mImageBtnPickerBack = (ImageButton) findViewById(R.id.imageBtn_picker_back);        mBtnSure = (Button) findViewById(R.id.btn_sure);        mRecyclerViewPickActivity = (RecyclerView) findViewById(R.id.recyclerView_pick_activity);        mTvCount.setText(0+"/"+maxCount);        mImageBtnPickerBack.setOnClickListener(this);        mBtnSure.setOnClickListener(this);    }    /**     * 初始化图片列表     */    private void initRecyclerView(){        list = ImageFinder.getImages(this,ImageFinder.TYPE_GIF);        MyChooseCallback callback = new MyChooseCallback();        MyOnItemClickListener listener = new MyOnItemClickListener();        ImagesListAdapter adapter = new ImagesListAdapter(this,list);        RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this,3);        adapter.setMaxNum(maxCount);        adapter.setChooseCallback(callback);        adapter.setOnRecyclerViewItemClickListener(listener);        mRecyclerViewPickActivity.setLayoutManager(layoutManager);        mRecyclerViewPickActivity.setAdapter(adapter);    }    /**     * 照相机     */    private void takePhoto(){        //文件io流存储图片        File outputImage = new File(getExternalCacheDir(),"outputImage.jpg");        try {            if (outputImage.exists()){                outputImage.delete();            }            outputImage.createNewFile(); //创建新的对象        } catch (IOException e) {            e.printStackTrace();        }        if (Build.VERSION.SDK_INT >= 24){            cameraImageUri = FileProvider.getUriForFile(this,"com.eric.photopicker.camera",outputImage);        } else {            cameraImageUri = Uri.fromFile(outputImage);        }        //启动相机        Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");        intent.putExtra(MediaStore.EXTRA_OUTPUT,cameraImageUri);        startActivityForResult(intent,REQUEST_CAMERA);    }    /**     * 请求读写权限     */    private void requestStoragePermission(){        int permission = ActivityCompat.checkSelfPermission(this, "android.permission.WRITE_EXTERNAL_STORAGE");        if (permission != PackageManager.PERMISSION_GRANTED) {            ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE,REQUEST_EXTERNAL_STORAGE);        } else {            initRecyclerView();        }    }    /**     * 启动活动返回值处     * @param requestCode 请求码     * @param resultCode 结果码     * @param data 数据     */    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        switch (requestCode){            case REQUEST_CAMERA:                if (resultCode == RESULT_OK){                    Toast.makeText(this,"图片获取成功",Toast.LENGTH_SHORT).show();                }                break;            default:                break;        }    }    /**     * 权限请求结果处理     * @param requestCode 请求码     * @param permissions 权限数组     * @param grantResults 结果     */    @Override    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {        switch (requestCode){            case REQUEST_EXTERNAL_STORAGE:                if (grantResults.length > 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED){                    initRecyclerView();                } else {                    Toast.makeText(this,"您未开启读取储存权限", Toast.LENGTH_SHORT).show();                }                break;            default:                break;        }    }    /**     * 系统view点击回调     * @param v view     */    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.imageBtn_picker_back:                finish();                break;            case R.id.btn_sure:                onPickedDone();                break;            default:                break;        }    }    /**     * 返回一组图片path     */    private void onPickedDone(){        ArrayList images = new ArrayList<>();        for (int i : chosenList){            images.add(list.get(i).getImagePath());        }        onResult(images);    }    /**     * 返回结果     * @param images     */    private void onResult(ArrayList images){        Intent intent = new Intent();        intent.putStringArrayListExtra(RESULT_IMAGES_LIST,images);        setResult(RESULT_OK,intent);        finish();    }    /**     * Item点击事件的监听类     */    private class MyOnItemClickListener implements OnRecyclerViewItemClickListener{        @Override        public void onItemClick(int position) {            ImagesPreviewActivity.startPreView(ImagesPickActivity.this,list.get(position).getImagePath());        }    }    /**     * Item选则事件的监听类     */    private class MyChooseCallback implements OnItemChooseCallback {        @Override        public void chooseState(int position, boolean isChosen) {            if (isChosen){                chosenList.add(position);            } else {                int index = 0;                for (int i : chosenList){                    if (i == position){                        chosenList.remove(index);                    }                    index ++;                }            }        }        @Override        public void countNow(int countNow) {            mTvCount.setText(countNow +"/"+ maxCount);        }        @Override        public void countWarning(int count) {            Toast.makeText(ImagesPickActivity.this,"最多选择"+count+"张图片",Toast.LENGTH_SHORT).show();        }    }}

当我们单击图片时，想要查看图片

ImagesPreviewActivity

package com.util.photopicker.activities;import android.app.Activity;import android.content.Intent;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.ImageButton;import android.widget.ImageView;import com.bumptech.glide.Glide;import com.util.photopicker.R;public class ImagesPreviewActivity extends AppCompatActivity {    private final static String EXTRA_PREVIEW = "imagePath";    private ImageView mImagePreviewShow;    private String imagePath;    private ImageButton mImgBtnPreviewBack;    public static void startPreView(Activity activity, String imagePath){        Intent intent = new Intent(activity,ImagesPreviewActivity.class);        intent.putExtra(EXTRA_PREVIEW,imagePath);        activity.startActivity(intent);    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_images_preview);        Intent intent = getIntent();        imagePath = intent.getStringExtra(EXTRA_PREVIEW);        mImagePreviewShow = (ImageView) findViewById(R.id.image_preview_show);        mImgBtnPreviewBack = (ImageButton) findViewById(R.id.imgBtn_preview_back);        mImgBtnPreviewBack.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                finish();            }        });        Glide.with(this)                .load(imagePath)                .into(mImagePreviewShow);    }}

以上便是一个简单的图片选择器工程，工程源码地址点击：码云（git）

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