Android 将图像保存到文件系统
Android save image to file system
我有一个 activity 在开始时调用启动相机应用程序的意图。相机应该拍摄一张照片，保存到本地系统，并将其呈现到图像视图中。然而，当拍照时我收到这条消息：
E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /external_storage_root/Pictures/HelloCamera/IMG_20170709_221239.jpg (No such file or directory)
此消息在
时抛出
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
options);
在 previewCapturedImage() 方法中
代码如下
我有以下activity
package it.cosmopolitans.around.boundary;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import it.cosmopolitans.around.R;
public class ImageTakenActivity extends AppCompatActivity {
// Activity request codes
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
public static final int PERMISSIONS_MULTIPLE_REQUEST = 123;
public static final int MEDIA_TYPE_IMAGE = 1;
private static final String IMAGE_DIRECTORY_NAME = "HelloCamera";
private Uri fileUri; // file url to store image/video
private ImageView imgPreview;
private boolean dir_perm;
private boolean cam_perm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_taken);
imgPreview = (ImageView) findViewById(R.id.imageTaken);
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA, Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSIONS_MULTIPLE_REQUEST);
//if( dir_perm == true )
captureImage();
// Checking camera availability
if (!isDeviceSupportCamera()) {
Toast.makeText(getApplicationContext(),
"Sorry! Your device doesn't support camera",
Toast.LENGTH_LONG).show();
// will close the app if the device does't have camera
finish();
}
}
/**
* Checking device has camera hardware or not
* */
private boolean isDeviceSupportCamera() {
if (getApplicationContext().getPackageManager().hasSystemFeature(
PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/**
* Capturing Camera Image will lauch camera app requrest image capture
*/
private void captureImage() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);
// start the image capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
}
/**
* Here we store the file url as it will be null after returning from camera
* app
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save file url in bundle as it will be null on scren orientation
// changes
outState.putParcelable("file_uri", fileUri);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
// get the file url
fileUri = savedInstanceState.getParcelable("file_uri");
}
/**
* Receiving activity result method will be called after closing the camera
* */
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// if the result is capturing Image
if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// successfully captured the image
// display it in image view
previewCapturedImage();
} else if (resultCode == RESULT_CANCELED) {
// user cancelled Image capture
Toast.makeText(getApplicationContext(),
"User cancelled image capture", Toast.LENGTH_SHORT)
.show();
} else {
// failed to capture image
Toast.makeText(getApplicationContext(),
"Sorry! Failed to capture image", Toast.LENGTH_SHORT)
.show();
}
}
}
/**
* Display image from a path to ImageView
*/
private void previewCapturedImage() {
try {
imgPreview.setVisibility(View.VISIBLE);
// bimatp factory
BitmapFactory.Options options = new BitmapFactory.Options();
// downsizing image as it throws OutOfMemory Exception for larger
// images
options.inSampleSize = 8;
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
options);
imgPreview.setImageBitmap(bitmap);
} catch (NullPointerException e) {
e.printStackTrace();
}
}
/**
* ------------ Helper Methods ----------------------
* */
public void requestStoragePermission() {
if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.READ_EXTERNAL_STORAGE)) {
//If the user has denied the permission previously your code will come to this block
//Here you can explain why you need this permission
//Explain here why you need this permission
}
}
/**
* Creating file uri to store image/video
*/
public Uri getOutputMediaFileUri(int type) {
//return Uri.fromFile(getOutputMediaFile(type));
return FileProvider.getUriForFile(this, "it.cosmopolitans.fileprovider", getOutputMediaFile(type));
}
/**
* returning image / video
*/
private static File getOutputMediaFile(int type) {
// External sdcard location
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
IMAGE_DIRECTORY_NAME);
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d(IMAGE_DIRECTORY_NAME, "Oops! Failed create "
+ IMAGE_DIRECTORY_NAME + " directory");
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
Locale.getDefault()).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "VID_" + timeStamp + ".mp4");
} else {
return null;
}
return mediaFile;
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case PERMISSIONS_MULTIPLE_REQUEST:
if (grantResults.length > 0) {
boolean cameraPermission = grantResults[1] == PackageManager.PERMISSION_GRANTED;
boolean readExternalFile = grantResults[0] == PackageManager.PERMISSION_GRANTED;
if(cameraPermission && readExternalFile)
{
cam_perm = true;
dir_perm = true;
} else {
Toast.makeText(this, "permission rejected", Toast.LENGTH_SHORT).show();
}
}
break;
}
}
}
我的清单中有以下供应商
<provider
android:name="android.support.v4.content.FileProvider"
android:authorities="it.cosmopolitans.fileprovider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/file_paths"/>
</provider>
及以下文件路径
<external-path name="external_storage_root" path="./" />
简单但缓慢的解决方案是替换：
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(), options);
与：
final Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(fileUri), options);
您可以进行的两项性能改进：
抓住 File 而不是 Uri，然后使用 File 和 decodeFile()
使用图像加载库（Glide、Picasso 等），它将在后台线程上进行图像解码和磁盘 I/O
我有一个 activity 在开始时调用启动相机应用程序的意图。相机应该拍摄一张照片，保存到本地系统，并将其呈现到图像视图中。然而，当拍照时我收到这条消息：
E/BitmapFactory: Unable to decode stream: java.io.FileNotFoundException: /external_storage_root/Pictures/HelloCamera/IMG_20170709_221239.jpg (No such file or directory)
此消息在
时抛出 final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
options);
在 previewCapturedImage() 方法中
代码如下
我有以下activity
package it.cosmopolitans.around.boundary;
import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;
import it.cosmopolitans.around.R;
public class ImageTakenActivity extends AppCompatActivity {
// Activity request codes
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
public static final int PERMISSIONS_MULTIPLE_REQUEST = 123;
public static final int MEDIA_TYPE_IMAGE = 1;
private static final String IMAGE_DIRECTORY_NAME = "HelloCamera";
private Uri fileUri; // file url to store image/video
private ImageView imgPreview;
private boolean dir_perm;
private boolean cam_perm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_image_taken);
imgPreview = (ImageView) findViewById(R.id.imageTaken);
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA, Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSIONS_MULTIPLE_REQUEST);
//if( dir_perm == true )
captureImage();
// Checking camera availability
if (!isDeviceSupportCamera()) {
Toast.makeText(getApplicationContext(),
"Sorry! Your device doesn't support camera",
Toast.LENGTH_LONG).show();
// will close the app if the device does't have camera
finish();
}
}
/**
* Checking device has camera hardware or not
* */
private boolean isDeviceSupportCamera() {
if (getApplicationContext().getPackageManager().hasSystemFeature(
PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/**
* Capturing Camera Image will lauch camera app requrest image capture
*/
private void captureImage() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);
// start the image capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
}
/**
* Here we store the file url as it will be null after returning from camera
* app
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save file url in bundle as it will be null on scren orientation
// changes
outState.putParcelable("file_uri", fileUri);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
// get the file url
fileUri = savedInstanceState.getParcelable("file_uri");
}
/**
* Receiving activity result method will be called after closing the camera
* */
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// if the result is capturing Image
if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// successfully captured the image
// display it in image view
previewCapturedImage();
} else if (resultCode == RESULT_CANCELED) {
// user cancelled Image capture
Toast.makeText(getApplicationContext(),
"User cancelled image capture", Toast.LENGTH_SHORT)
.show();
} else {
// failed to capture image
Toast.makeText(getApplicationContext(),
"Sorry! Failed to capture image", Toast.LENGTH_SHORT)
.show();
}
}
}
/**
* Display image from a path to ImageView
*/
private void previewCapturedImage() {
try {
imgPreview.setVisibility(View.VISIBLE);
// bimatp factory
BitmapFactory.Options options = new BitmapFactory.Options();
// downsizing image as it throws OutOfMemory Exception for larger
// images
options.inSampleSize = 8;
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(),
options);
imgPreview.setImageBitmap(bitmap);
} catch (NullPointerException e) {
e.printStackTrace();
}
}
/**
* ------------ Helper Methods ----------------------
* */
public void requestStoragePermission() {
if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.READ_EXTERNAL_STORAGE)) {
//If the user has denied the permission previously your code will come to this block
//Here you can explain why you need this permission
//Explain here why you need this permission
}
}
/**
* Creating file uri to store image/video
*/
public Uri getOutputMediaFileUri(int type) {
//return Uri.fromFile(getOutputMediaFile(type));
return FileProvider.getUriForFile(this, "it.cosmopolitans.fileprovider", getOutputMediaFile(type));
}
/**
* returning image / video
*/
private static File getOutputMediaFile(int type) {
// External sdcard location
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
IMAGE_DIRECTORY_NAME);
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d(IMAGE_DIRECTORY_NAME, "Oops! Failed create "
+ IMAGE_DIRECTORY_NAME + " directory");
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
Locale.getDefault()).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "VID_" + timeStamp + ".mp4");
} else {
return null;
}
return mediaFile;
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case PERMISSIONS_MULTIPLE_REQUEST:
if (grantResults.length > 0) {
boolean cameraPermission = grantResults[1] == PackageManager.PERMISSION_GRANTED;
boolean readExternalFile = grantResults[0] == PackageManager.PERMISSION_GRANTED;
if(cameraPermission && readExternalFile)
{
cam_perm = true;
dir_perm = true;
} else {
Toast.makeText(this, "permission rejected", Toast.LENGTH_SHORT).show();
}
}
break;
}
}
}
我的清单中有以下供应商
<provider
android:name="android.support.v4.content.FileProvider"
android:authorities="it.cosmopolitans.fileprovider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/file_paths"/>
</provider>
及以下文件路径
<external-path name="external_storage_root" path="./" />
简单但缓慢的解决方案是替换：
final Bitmap bitmap = BitmapFactory.decodeFile(fileUri.getPath(), options);
与：
final Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(fileUri), options);
您可以进行的两项性能改进：
抓住
File而不是Uri，然后使用File和decodeFile()使用图像加载库（Glide、Picasso 等），它将在后台线程上进行图像解码和磁盘 I/O