内容提供者——获取媒体库里面的图片

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我是靠谱客的博主瘦瘦龙猫，最近开发中收集的这篇文章主要介绍内容提供者——获取媒体库里面的图片，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

内容提供者——获取媒体库里面的图片

——写在前面

对于媒体内容提供者的应用场景有哪些呢？

比如说你的上传头像，比如说你做行车记录的，抓拍图片功能用户查看预览，比如说你的微信,QQ发动态，比如说你淘宝购物，要从图片中扫描二维码。这些都从图库里拿这个图片。

一、获取到图片内容

1.URI

URI的常量

图片URI

MediaStore.Images.Media.EXTERNAL_CONTENT_URI

视频的Url

MediaStore.Video.Media.EXTERNAL_CONTENT_URI

音频的

MediaStore.Audio.Media.EXTERNAL_CONTENT_URI

2.权限

 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

检查权限


private void checkPermission() {
int readExternalStoragePermissionResult = checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE);
if(readExternalStoragePermissionResult != PackageManager.PERMISSION_GRANTED) {
requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE},PERMISSION_REQUEST_CODE);
}
}

3.获取数据表字段

 ContentResolver contentResolver = getContentResolver();
Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
Cursor query = contentResolver.query(uri,null,null,null,null,null);
String[] columnNames = query.getColumnNames();
while(query.moveToNext()) {
Log.d(TAG,"----------------------------");
for(String columnName : columnNames) {
Log.d(TAG,columnName + " ==== " + query.getString(query.getColumnIndex(columnName)));
}
Log.d(TAG,"----------------------------");
}
query.close();

4准备一个封装数据bean类

public class PhotoItem {
private String path;
private String name;
private long createDate;
private boolean isSelected = false;
public boolean isSelected() {
return isSelected;
}
public void setSelected(boolean selected) {
isSelected = selected;
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public long getCreateDate() {
return createDate;
}
public void setCreateDate(long createDate) {
this.createDate = createDate;
}
}

5.将获取到的图片数据封装起来并且显示

public class ImagePickerActivity extends AppCompatActivity {
private static final String TAG = "ImagePickerActivity";
private RecyclerView mPicListView;
private List<PhotoItem> mPics = new ArrayList<>();
private PicListAdapter mPicListAdapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_picker);
initView();
initData();
}
private void initData() {
//这些事情其实不能在主线程做，我们稍后修改
ContentResolver contentResolver = getContentResolver();
Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
Cursor query = contentResolver.query(uri,new String[]{
MediaStore.Images.Media.DATA,
MediaStore.Images.Media.DISPLAY_NAME,
MediaStore.Images.Media.DATE_ADDED,
MediaStore.Images.Media._ID},null,null,null,null);
while(query.moveToNext()) {
PhotoItem photoItem = new PhotoItem();
photoItem.setPath(query.getString(0));
//这里的下标跟上面的query第一个参数对应，时间是第2个，所以下标为1
photoItem.setCreateDate(query.getLong(1));
photoItem.setName(query.getString(2));
mPics.add(photoItem);
}
query.close();
mPicListAdapter.setData(mPics);
}
private void initView() {
mPicListView = this.findViewById(R.id.pic_list);
mPicListView.setLayoutManager(new GridLayoutManager(this,3));
mPicListAdapter = new PicListAdapter();
mPicListView.setAdapter(mPicListAdapter);
}
}

6.为RecycleView准备适配器

public class PicListAdapter extends RecyclerView.Adapter<PicListAdapter.InnerHolder> {
private List<PhotoItem> mData = new ArrayList<>();
@NonNull
@Override
public InnerHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType) {
ImageView iv = new ImageView(parent.getContext());
iv.setScaleType(ImageView.ScaleType.CENTER_CROP);
Point point = new Point();
((WindowManager) parent.getContext().getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay().getSize(point);
RecyclerView.LayoutParams layoutParams = new RecyclerView.LayoutParams(point.x / 3,point.x / 3);
iv.setLayoutParams(layoutParams);
return new InnerHolder(iv);
}
@Override
public void onBindViewHolder(@NonNull InnerHolder holder,int position) {
if(holder.itemView instanceof ImageView) {
Glide.with(holder.itemView.getContext()).load(mData.get(position).getPath()).into((ImageView) holder.itemView);
}
}
@Override
public int getItemCount() {
return mData.size();
}
public void setData(List<PhotoItem> pics) {
mData.clear();
mData.addAll(pics);
notifyDataSetChanged();
}
public class InnerHolder extends RecyclerView.ViewHolder {
public InnerHolder(@NonNull View itemView) {
super(itemView);
}
}
}

二、使用LoaderManager来加载

前面我们直接在onCreate的地方加载数据，如果数据量大的话，会导致主线程阻塞出现ANR异常。如果数据量小，会影响页面的打开速度。

所以我们要么自己创建子线程去获取，或者可以通过LoaderManager去获取。

public class MediaContentPickerActivity extends AppCompatActivity {
private static final int LOADER_ALL = 0;
// 获取所有图片
private static final String TAG = "ContentPickerActivity";
private List<PhotoItem> photoInfoList = new ArrayList<>();
// 本地图片信息List
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_media_picker);
initLoader();
}
private void initLoader() {
LoaderManager loaderManager = LoaderManager.getInstance(this);
loaderManager.initLoader(LOADER_ALL,null,new LoaderManager.LoaderCallbacks<Cursor>() {
private final String[] IMAGE_PROJECTION = {
MediaStore.Images.Media.DATA,
MediaStore.Images.Media.DISPLAY_NAME,
MediaStore.Images.Media.DATE_ADDED,
MediaStore.Images.Media._ID,
};
@NonNull
@Override
public Loader<Cursor> onCreateLoader(int id,@Nullable Bundle args) {
if(id == LOADER_ALL) {
return new CursorLoader(MediaContentPickerActivity.this,
MediaStore.Images.Media.EXTERNAL_CONTENT_URI,IMAGE_PROJECTION,
null,null,IMAGE_PROJECTION[2] + " DESC");
}
return null;
}
@Override
public void onLoadFinished(@NonNull Loader<Cursor> loader,Cursor data) {
if(data != null) {
int count = data.getCount();
if(count > 0) {
List<PhotoItem> tempPhotoList = new ArrayList<>();
data.moveToFirst();
do {
String path = data.getString(data.getColumnIndexOrThrow(IMAGE_PROJECTION[0]));
String name = data.getString(data.getColumnIndexOrThrow(IMAGE_PROJECTION[1]));
long dateTime = data.getLong(data.getColumnIndexOrThrow(IMAGE_PROJECTION[2]));
PhotoItem photoItem = new PhotoItem();
photoItem.setName(name);
photoItem.setPath(path);
photoItem.setCreateDate(dateTime);
tempPhotoList.add(photoItem);
} while(data.moveToNext());
photoInfoList.clear();
photoInfoList.addAll(tempPhotoList);
}
//输出结果
for(PhotoItem photoItem : photoInfoList) {
Log.d(TAG,"photoItem -- > " + photoItem);
}
}
}
@Override
public void onLoaderReset(@NonNull Loader<Cursor> loader) {
}
});
}
}