从相机和相册中捕获Android图片
在本教程中，我们将开发一个应用程序，在相机或图库中选择一张图片，并在ImageView中显示出来。注意：以下代码对于Android Nougat之前的版本可以正常工作。要查看最新的工作示例，请参阅更新的文章。（请注意：Google已经改变了Android版本的命名方式。Android Q已经改名为Android 10.由于本教程是在Google做出此决定之前编写的，因此在文章中会看到Android Q的一些地方。）
安卓照片捕获概述
随着Android Marshmallow的推出，运行时权限需要被置于前沿实施。将以下权限添加到Android Manifest.xml文件中，位于应用程序标签之上。
<uses-feature
android:name="android.hardware.camera"
android:required="false" />
<uses-feature
android:name="android.hardware.camera.autofocus"
android:required="false" />
<uses-feature
android:name="android.hardware.camera.flash"
android:required="false" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="ANDROID.PERMISSION.READ_EXTERNAL_STORAGE"/>
通过添加android.hardware.camera，Play商店可以检测并防止在没有相机的设备上安装该应用程序。Intent是将动作委托给其他应用程序的标准方式。要启动本机相机，Intent需要android.provider.MediaStore.ACTION_IMAGE_CAPTURE。要从图库选择图像，Intent需要以下参数：Intent.ACTION_GET_CONTENT。在本教程中，我们将调用一个图像选择器，它允许我们从相机或图库中选择图像，并在一个圆形图像视图和一个普通图像视图中显示图像。在build.gradle文件中添加以下依赖项：compile ‘de.hdodenhof:circleimageview:2.1.0’
安卓图像捕获项目结构
Android 拍照代码
activity_main.xml的布局保持不变，只需将FAB按钮的图标更改为@android：drawable/ic_menu_camera。下面给出了content_main.xml的内容。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
xmlns:app="https://schemas.android.com/apk/res-auto"
xmlns:tools="https://schemas.android.com/tools"
android:id="@+id/content_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:background="#000000"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.Olivia.imagepicker.MainActivity"
tools:showIn="@layout/activity_main">
<RelativeLayout
android:layout_width="250dp"
android:layout_height="250dp"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:background="@drawable/image_border"
android:clickable="true"
android:orientation="vertical">
<ImageView
android:id="@+id/imageView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:adjustViewBounds="true"
android:scaleType="centerCrop" />
</RelativeLayout>
<de.hdodenhof.circleimageview.CircleImageView
android:id="@+id/img_profile"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_gravity="center_horizontal"
android:src="@drawable/profile"
app:civ_border_width="5dp"
app:civ_border_color="#FFFFFF"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>
以下提供了 MainActivity.java 的代码。
public class MainActivity extends AppCompatActivity {
Bitmap myBitmap;
Uri picUri;
private ArrayList permissionsToRequest;
private ArrayList permissionsRejected = new ArrayList();
private ArrayList permissions = new ArrayList();
private final static int ALL_PERMISSIONS_RESULT = 107;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivityForResult(getPickImageChooserIntent(), 200);
}
});
permissions.add(CAMERA);
permissionsToRequest = findUnAskedPermissions(permissions);
//get the permissions we have asked for before but are not granted..
//we will store this in a global list to access later.
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (permissionsToRequest.size() > 0)
requestPermissions(permissionsToRequest.toArray(new String[permissionsToRequest.size()]), ALL_PERMISSIONS_RESULT);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* Create a chooser intent to select the source to get image from.<br />
* The source can be camera's (ACTION_IMAGE_CAPTURE) or gallery's (ACTION_GET_CONTENT).<br />
* All possible sources are added to the intent chooser.
*/
public Intent getPickImageChooserIntent() {
// Determine Uri of camera image to save.
Uri outputFileUri = getCaptureImageOutputUri();
List allIntents = new ArrayList();
PackageManager packageManager = getPackageManager();
// collect all camera intents
Intent captureIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
List listCam = packageManager.queryIntentActivities(captureIntent, 0);
for (ResolveInfo res : listCam) {
Intent intent = new Intent(captureIntent);
intent.setComponent(new ComponentName(res.activityInfo.packageName, res.activityInfo.name));
intent.setPackage(res.activityInfo.packageName);
if (outputFileUri != null) {
intent.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
}
allIntents.add(intent);
}
// collect all gallery intents
Intent galleryIntent = new Intent(Intent.ACTION_GET_CONTENT);
galleryIntent.setType("image/*");
List listGallery = packageManager.queryIntentActivities(galleryIntent, 0);
for (ResolveInfo res : listGallery) {
Intent intent = new Intent(galleryIntent);
intent.setComponent(new ComponentName(res.activityInfo.packageName, res.activityInfo.name));
intent.setPackage(res.activityInfo.packageName);
allIntents.add(intent);
}
// the main intent is the last in the list (fucking android) so pickup the useless one
Intent mainIntent = allIntents.get(allIntents.size() - 1);
for (Intent intent : allIntents) {
if (intent.getComponent().getClassName().equals("com.android.documentsui.DocumentsActivity")) {
mainIntent = intent;
break;
}
}
allIntents.remove(mainIntent);
// Create a chooser from the main intent
Intent chooserIntent = Intent.createChooser(mainIntent, "Select source");
// Add all other intents
chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, allIntents.toArray(new Parcelable[allIntents.size()]));
return chooserIntent;
}
/**
* Get URI to image received from capture by camera.
*/
private Uri getCaptureImageOutputUri() {
Uri outputFileUri = null;
File getImage = getExternalCacheDir();
if (getImage != null) {
outputFileUri = Uri.fromFile(new File(getImage.getPath(), "profile.png"));
}
return outputFileUri;
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
Bitmap bitmap;
if (resultCode == Activity.RESULT_OK) {
ImageView imageView = (ImageView) findViewById(R.id.imageView);
if (getPickImageResultUri(data) != null) {
picUri = getPickImageResultUri(data);
try {
myBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), picUri);
myBitmap = rotateImageIfRequired(myBitmap, picUri);
myBitmap = getResizedBitmap(myBitmap, 500);
CircleImageView croppedImageView = (CircleImageView) findViewById(R.id.img_profile);
croppedImageView.setImageBitmap(myBitmap);
imageView.setImageBitmap(myBitmap);
} catch (IOException e) {
e.printStackTrace();
}
} else {
bitmap = (Bitmap) data.getExtras().get("data");
myBitmap = bitmap;
CircleImageView croppedImageView = (CircleImageView) findViewById(R.id.img_profile);
if (croppedImageView != null) {
croppedImageView.setImageBitmap(myBitmap);
}
imageView.setImageBitmap(myBitmap);
}
}
}
private static Bitmap rotateImageIfRequired(Bitmap img, Uri selectedImage) throws IOException {
ExifInterface ei = new ExifInterface(selectedImage.getPath());
int orientation = ei.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
switch (orientation) {
case ExifInterface.ORIENTATION_ROTATE_90:
return rotateImage(img, 90);
case ExifInterface.ORIENTATION_ROTATE_180:
return rotateImage(img, 180);
case ExifInterface.ORIENTATION_ROTATE_270:
return rotateImage(img, 270);
default:
return img;
}
}
private static Bitmap rotateImage(Bitmap img, int degree) {
Matrix matrix = new Matrix();
matrix.postRotate(degree);
Bitmap rotatedImg = Bitmap.createBitmap(img, 0, 0, img.getWidth(), img.getHeight(), matrix, true);
img.recycle();
return rotatedImg;
}
public Bitmap getResizedBitmap(Bitmap image, int maxSize) {
int width = image.getWidth();
int height = image.getHeight();
float bitmapRatio = (float) width / (float) height;
if (bitmapRatio > 0) {
width = maxSize;
height = (int) (width / bitmapRatio);
} else {
height = maxSize;
width = (int) (height * bitmapRatio);
}
return Bitmap.createScaledBitmap(image, width, height, true);
}
/**
* Get the URI of the selected image from {@link #getPickImageChooserIntent()}.<br />
* Will return the correct URI for camera and gallery image.
*
* @param data the returned data of the activity result
*/
public Uri getPickImageResultUri(Intent data) {
boolean isCamera = true;
if (data != null) {
String action = data.getAction();
isCamera = action != null && action.equals(MediaStore.ACTION_IMAGE_CAPTURE);
}
return isCamera ? getCaptureImageOutputUri() : data.getData();
}
@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("pic_uri", picUri);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
// get the file url
picUri = savedInstanceState.getParcelable("pic_uri");
}
private ArrayList findUnAskedPermissions(ArrayList wanted) {
ArrayList result = new ArrayList();
for (String perm : wanted) {
if (!hasPermission(perm)) {
result.add(perm);
}
}
return result;
}
private boolean hasPermission(String permission) {
if (canMakeSmores()) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
return (checkSelfPermission(permission) == PackageManager.PERMISSION_GRANTED);
}
}
return true;
}
private void showMessageOKCancel(String message, DialogInterface.OnClickListener okListener) {
new AlertDialog.Builder(this)
.setMessage(message)
.setPositiveButton("OK", okListener)
.setNegativeButton("Cancel", null)
.create()
.show();
}
private boolean canMakeSmores() {
return (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP_MR1);
}
@TargetApi(Build.VERSION_CODES.M)
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case ALL_PERMISSIONS_RESULT:
for (String perms : permissionsToRequest) {
if (hasPermission(perms)) {
} else {
permissionsRejected.add(perms);
}
}
if (permissionsRejected.size() > 0) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (shouldShowRequestPermissionRationale(permissionsRejected.get(0))) {
showMessageOKCancel("These permissions are mandatory for the application. Please allow access.",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
//Log.d("API123", "permisionrejected " + permissionsRejected.size());
requestPermissions(permissionsRejected.toArray(new String[permissionsRejected.size()]), ALL_PERMISSIONS_RESULT);
}
}
});
return;
}
}
}
break;
}
}
}
从上面的代码中可以得出许多推断。
- We need to ask for the Camera runtime permissions when the user starts the activity.
- As we are starting the intent to get some result back, we need to call startActivityForResult with the relevant arguments
- Instead of using a dialog to separately call the Intents for Camera and Gallery, we’ve used a method getPickImageChooserIntent() that creates a single chooser intent for all the camera and gallery intents(note the documents intent). Intent.EXTRA_INITIAL_INTENTS is used to add the multiple application intents at one place
- For the camera intent, MediaStore.EXTRA_OUTPUT is passed as an extra to specify the image storage path. Without this you’ll be returned only a small resolution image.
- The URI path for the image returned by camera is fetched inside the method getCaptureImageOutputUri().
- The onActivityResult essentially returns a URI to the image. Some devices do return the bitmap as data.getExtras().get(“data”);.
- When an image is clicked, the camera screen while returning restarts the activity thereby causing the URI stored from the method getCaptureImageOutputUri() to become null. Hence it’s essential that we store and restore that URI using onSaveInstanceState() and onRestoreInstanceState().
- The bitmap is retrieved from the URI in the following line of code. myBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), picUri);
- Devices like Samsung galaxy are known to capture the image in landscape orientation. Retrieving the image and displaying as it is can cause it to be displayed in the wrong orientation. Hence we’ve called the method rotateImageIfRequired(myBitmap, picUri);
- ExifInterface is a class for reading and writing Exif tags in a JPEG file or a RAW image file.
- In the end we call the method getResizedBitmap() to scale the bitmap by width or height(whichever is larger) and set the image to the image view using setImageBitmap.
以下是应用程序在运行时的输出结果。注意：为了捕捉并显示相机图像，您需要在智能手机上运行该应用程序，这是显而易见的。这结束了本教程。您可以通过下面的链接下载Image Capture的Android项目。
下载 Android 相机拍照项目的图片捕捉功能。
