android訪問相冊、拍照

在訪問相冊的時候由於是跨進程訪問相冊資源，所以必須具備ContentProvider的基本知識，使用相機的時候需要指定照片存儲位置，需要具備FileProvider的原理和使用

由於訪問相冊和使用相機，所以我們需要動態申請權限。使用easypermissions

implementation 'pub.devrel:easypermissions:0.3.0'

所需權限

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

1. 動態申請權限

private String[] permissions = {Manifest.permission.CAMERA,
								Manifest.permission.READ_EXTERNAL_STORAGE,
								Manifest.permission.WRITE_EXTERNAL_STORAGE};
								
if(EasyPermissions.hasPermissions(this,permissions)){
}
else{
	EasyPermissions.requestPermissions(this,"訪問相冊權限",1,permissions);
}

使用easypermissions步驟
1.重寫onRequestPermissionsResult，在內部調用EasyPermissions.onRequestPermissionsResult

@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        EasyPermissions.onRequestPermissionsResult(requestCode,permissions,grantResults,this);
    }

2.使該類繼承implements EasyPermissions.PermissionCallbacks，然後重寫onPermissionsGranted和onPermissionsDenied進行授權判斷

	@Override
    public void onPermissionsGranted(int requestCode, List<String> perms) {
        Toast.makeText(this, "相關權限獲取成功", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onPermissionsDenied(int requestCode, List<String> perms) {
        Toast.makeText(this, "請同意相關權限，否則功能無法使用", Toast.LENGTH_SHORT).show();
    }

2. 打開相冊並且獲取選中的圖片
打開相冊:

Intent intent = new Intent();
intent.setAction(Intent.ACTION_PICK);
intent.setType("image/*");
startActivityForResult(intent,2);

獲取選中圖片

 @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == 2 &&resultCode == RESULT_OK){
            String imagePath = null;
            Uri uri = data.getData();

            if(DocumentsContract.isDocumentUri(MainActivity.this,uri)){
                String docId = DocumentsContract.getDocumentId(uri);
                if("com.android.providers.media.documents".equals(uri.getAuthority())) {
                    String id=docId.split(":")[1];
                    String selection= MediaStore.Images.Media._ID+"="+id;
                    imagePath = getImagePath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,selection);
                }else if("com.android.providers.downloads.documents".equals(uri.getAuthority())){
                    Uri contentUri= ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),Long.valueOf(docId));
                    imagePath = getImagePath(contentUri,null);
                }
            }
            else if("content".equalsIgnoreCase(uri.getScheme())){
                imagePath = getImagePath(uri,null);
            }
            else if("file".equalsIgnoreCase(uri.getScheme())){
                imagePath = uri.getPath();
            }
			
			//展示選中的圖片
            if(imagePath != null) {
                Intent intent = new Intent(MainActivity.this, PictureActivity.class);
                intent.putExtra("url", imagePath);
                startActivity(intent);
            }

        }
    }

private String getImagePath(Uri uri,String selection) {
        String path = null;
        Cursor cursor = getContentResolver().query(uri, null, selection, null, null);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
            }
            cursor.close();
        }
        return path;
    }

3.使用相機拍照並且存儲到指定文件
打開相機設定存儲位置

Intent takePhotoIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);//用來打開相機的Intent
	if(takePhotoIntent.resolveActivity(getPackageManager())!=null){//這句作用是如果沒有相機則該應用不會閃退，要是不加這句則當系統沒有相機應用的時候該應用會閃退
	File imageFile = createImageFile();//創建用來保存照片的文件
	Uri ImageUri = null;
	if(imageFile!=null){
		if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.N){
			/*7.0以上要通過FileProvider將File轉化爲Uri*/
	        ImageUri = FileProvider.getUriForFile(this,"com.example.qsbk.fileProvider",imageFile);
			}else {
				/*7.0以下則直接使用Uri的fromFile方法將File轉化爲Uri*/
            	ImageUri = Uri.fromFile(imageFile);
            	}
        }
                        //設置文件存儲位置
	takePhotoIntent.putExtra(MediaStore.EXTRA_OUTPUT,ImageUri);
    startActivityForResult(takePhotoIntent,3);//啓動相機
}

private File createImageFile() {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "JPEG_"+timeStamp+"_";
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File imageFile = null;
        try {
            imageFile = File.createTempFile(imageFileName,".jpg",storageDir);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return imageFile;
    }

FileProvider的源碼部分(這裏不做講解，具體請參考FileProvider的原理和使用：

<provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="com.example.qsbk.fileProvider"
            android:grantUriPermissions="true"
            android:exported="false">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>

file_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <!--代表的目錄即爲：Environment.getExternalStorageDirectory()/Android/data/包名/-->
    <external-path
        name="files_root"
        path="Android/data/com.example.qsbk/" />

    <!--代表的目錄即爲：Environment.getExternalStorageDirectory()-->
    <external-path
        name="external_storage_root"
        path="." />

    <!--代表的目錄即爲：Environment.getExternalStorageDirectory()/pics -->
    <external-path
        name="external"
        path="pics" />

</paths>

知識拓展Intent.ACTION_PICK

（一）、調用圖庫，獲取所有本地圖片：

Intent imageIntent = new Intent(Intent.ACTION_GET_CONTENT); 
imageIntent.setType("image/*"); 
startActivityForResult(imageIntent, PICK_CODE); //PICK_CODE是常量

（二）、調用本地聯繫人：

 Intent intent = new Intent(Intent.ACTION_PICK); 
 intent.setType(ContactsContract.Contacts.CONTENT_TYPE); 
 startActivityForResult(intent, PICK_CONTACT); 

（三）、調用音樂，獲取所有本地音樂文件：

Intent audioIntent = new Intent(Intent.ACTION_GET_CONTENT); 
audioIntent.setType("audio/*"); 
startActivityForResult(audioIntent, PICK_AUDIO); 

（四）、調用視頻，獲取所有本地視頻文件：

Intent videoIntent = new Intent(Intent.ACTION_GET_CONTENT); 
videoIntent.setType("video/*"); 
startActivityForResult(videoIntent, PICK_VIDEO); 

參考博客:https://www.cnblogs.com/wucaiyun1/p/4933049.html