如何使用ContentProvider打造自己的本地图片库

效果如图

图库xml界面代码

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/re_photo_wall"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingTop="6dp"
        android:paddingLeft="6dp"/>


LinearLayout>

其中用recyclerView 来加载图片设置与上方间隔6dp
paddingLeft的功能下面会讲到

PhotoWallActivity代码

public class PhotoWallActivity extends AppCompatActivity {
    private HashMap> mGruopMap = new HashMap>();
    private List imgs = new ArrayList<>();
    private final static int SCAN_OK = 1;
    private ProgressDialog mProgressDialog;
    private RecyclerView rePhotoWall;
    private PhotoWallAdapter adapter;

    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
                case SCAN_OK:
                    //扫描完毕,关闭进度dialog
                    mProgressDialog.dismiss();
                    adapter.notifyDataSetChanged();
                    break;
            }
        }

    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_photo_wall);
        initView();
    }

    private void initView() {
        rePhotoWall = (RecyclerView) findViewById(R.id.re_photo_wall);
        //设置recyclerView 为网格布局，3列
        rePhotoWall.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL));
        adapter = new PhotoWallAdapter(PhotoWallActivity.this, imgs);
        rePhotoWall.setAdapter(adapter);
        if (imgs.size() == 0) {
            getImages();
        }
    }


    /**
     * 利用ContentProvider扫描手机中的图片，此方法在运行在子线程中
     */
    private void getImages() {
        //显示进度dialog
        mProgressDialog = ProgressDialog.show(this, null, "正在加载...");
        //开启线程扫描
        new Thread(new Runnable() {
            @Override
            public void run() {
                Uri mImageUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                ContentResolver mContentResolver = PhotoWallActivity.this.getContentResolver();
                //只查询jpeg和png的图片
                Cursor mCursor = mContentResolver.query(mImageUri, null,
                        MediaStore.Images.Media.MIME_TYPE + "=? or "
                                + MediaStore.Images.Media.MIME_TYPE + "=?",
                        new String[]{"image/jpeg", "image/png"}, MediaStore.Images.Media.DATE_MODIFIED);
                if (mCursor == null) {
                    return;
                }
                while (mCursor.moveToNext()) {
                    //获取图片的路径
                    String path = mCursor.getString(mCursor
                            .getColumnIndex(MediaStore.Images.Media.DATA));
                    ImageBean bean = new ImageBean(path, false);
                    imgs.add(bean);
                    //获取该图片的父路径名
                    String parentName = new File(path).getParentFile().getName();
                    //根据父路径名将图片放入到mGruopMap中
                    if (!mGruopMap.containsKey(parentName)) {
                        List childList = new ArrayList();
                        ImageBean imageBean = new ImageBean(path, false);
                        childList.add(imageBean);
                        mGruopMap.put(parentName, childList);
                    } else {
                        mGruopMap.get(parentName).add(new ImageBean(path, false));
                    }
                }
                //添加全部图片的集合
                mGruopMap.put("全部图片", imgs);

                //通知Handler扫描图片完成
                mHandler.sendEmptyMessage(SCAN_OK);
                mCursor.close();
            }
        }).start();

    }


    /**
     * 组装分组界面的数据源，因为我们扫描手机的时候将图片信息放在HashMap中
     * 所以需要遍历HashMap将数据组装成List
     * 用于展示图库分组列表
     * @param mGruopMap
     * @return
     */
    private List subGroupOfImage(HashMap> mGruopMap) {
        if (mGruopMap.size() == 0) {
            return null;
        }
        //遍历
        List list = new ArrayList();
        Iterator>> it = mGruopMap.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry> entry = it.next();
            ImageGroupBean mImageBean = new ImageGroupBean();

            //根据key获取其中图片list
            String key = entry.getKey();
            List value = entry.getValue();

            mImageBean.setFolderName(key);//获取该组文件夹名称
            mImageBean.setImageCounts(value.size());//获取该组图片数量
            mImageBean.setTopImagePath(value.get(0).getImgPath());//获取该组的第一张图片
            //将全部图片放在第一位置
            if (mImageBean.getFolderName().equals("全部图片")){
                list.add(0,mImageBean);
            }else {
                list.add(mImageBean);
            }
        }
        return list;
    }
}

在PhotoWallActivity我获取了本地所有图片，并对图片按存储路径进行了分组存放到HashMap中。
其中subGroupOfImage方法，将HashMap中每组的第一张图片、图片数量、以及父文件名存放到list中，提供后面选择分组展示使用（目前没做，但数据都有了）。

ImageBean与ImageGroupBean 代码

public class ImageBean {
    private String imgPath;
    private boolean isChoosed;

    public ImageBean(String imgPath, boolean isChoosed) {
        this.imgPath = imgPath;
        this.isChoosed = isChoosed;
    }

    public String getImgPath() {
        return imgPath;
    }

    public void setImgPath(String imgPath) {
        this.imgPath = imgPath;
    }

    public boolean isChoosed() {
        return isChoosed;
    }

    public void setChoosed(boolean choosed) {
        isChoosed = choosed;
    }
}


public class ImageGroupBean {
    /**
     * 文件夹的第一张图片路径
     */
    private String topImagePath;
    /**
     * 文件夹名
     */
    private String folderName;
    /**
     * 文件夹中的图片数
     */
    private int imageCounts;

    public String getTopImagePath() {
        return topImagePath;
    }

    public void setTopImagePath(String topImagePath) {
        this.topImagePath = topImagePath;
    }

    public String getFolderName() {
        return folderName;
    }

    public void setFolderName(String folderName) {
        this.folderName = folderName;
    }

    public int getImageCounts() {
        return imageCounts;
    }

    public void setImageCounts(int imageCounts) {
        this.imageCounts = imageCounts;
    }
}

PhotoWallAdapter的代码：

public class PhotoWallAdapter extends RecyclerView.Adapter<PhotoWallAdapter.PhotoWallViewHolder> {
    private Context context;
    private List imgs;

    public PhotoWallAdapter(Context context, List imgs) {
        this.context = context;
        this.imgs = imgs;
    }

    @Override
    public PhotoWallViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.view_photo_item, parent, false);
        return new PhotoWallViewHolder(view);
    }

    @Override
    public void onBindViewHolder(PhotoWallViewHolder holder, int position) {
        //图片每行3个，则有4个间隔，每个6dp，就为24dp（前面的paddingLeft 6dp为第一个左边的间距）,这样得出每个图片的宽度
        holder.ivPhoto.setLayoutParams(new FrameLayout.LayoutParams((ScreenUtils.getScreenWidth(context) - SizeUtils.dp2px(context, 24)) / 3,
                (ScreenUtils.getScreenWidth(context) - SizeUtils.dp2px(context, 24)) / 3));
        //glide加载
        Glide.with(context)
                .load(imgs.get(position).getImgPath())
                .centerCrop()
                .crossFade()
                .diskCacheStrategy(DiskCacheStrategy.RESULT)
                .placeholder(R.drawable.default_img)
                .into(holder.ivPhoto);
    }

    @Override
    public int getItemCount() {
        return imgs.size();
    }

    static class PhotoWallViewHolder extends RecyclerView.ViewHolder {
        ImageView ivPhoto;
        ImageView ivChoose;

        public PhotoWallViewHolder(View itemView) {
            super(itemView);
            ivChoose = (ImageView) itemView.findViewById(R.id.iv_choose);
            ivPhoto = (ImageView) itemView.findViewById(R.id.iv_photo);
        }
    }
}

规定每张图片的宽高，然后用glide加载。

view_photo_item.xml界面：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="6dp"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/iv_photo"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitXY" />

    <ImageView
        android:id="@+id/iv_choose"
        android:layout_width="16dp"
        android:layout_height="16dp"
        android:layout_gravity="right|top"
        android:layout_margin="2dp"
        android:src="@mipmap/un_choose" />
FrameLayout>

在父布局中设置android:layout_marginBottom=”6dp”，实现上下的间隔。
到这里，基本的图库功能就可以实现了，但是还有一些功能没做，例如上面提到的分组展示、图片多选，以后有时间的话就把他补上。