Android开发指南：从相机和相册获取图片的完整教程
这是文章《从相机和相册中捕获Android图片》的第1部分（共2部分）。
在本教程中，我们将开发一个应用程序，该程序可以从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（牛轧糖）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（棉花糖）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（意图）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
这是文章《从相机和相册中捕获Android图片》的第2部分（共2部分）。
内容片段: 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。
- 我们需要在用户启动活动时请求相机运行时权限。
- 由于我们启动意图是为了获取一些返回结果，因此需要使用相关参数调用startActivityForResult。
- 我们没有使用对话框分别调用相机和相册的意图，而是使用了getPickImageChooserIntent()方法，该方法为所有相机和相册意图创建一个单独的选择器意图（注意文档意图）。Intent.EXTRA_INITIAL_INTENTS用于在一个地方添加多个应用程序意图。
- 对于相机意图，MediaStore.EXTRA_OUTPUT作为额外参数传递，以指定图像存储路径。没有这个参数，您将只能获得一个小分辨率的图像。
- 相机返回的图像的URI路径是在getCaptureImageOutputUri()方法中获取的。
- onActivityResult本质上返回一个图像的URI。有些设备确实会以data.getExtras().get(“data”)的形式返回位图。
- 当点击图像时，相机屏幕在返回时会重新启动活动，从而导致从getCaptureImageOutputUri()方法存储的URI变为null。因此，我们必须使用onSaveInstanceState()和onRestoreInstanceState()来存储和恢复该URI。
- 位图是通过以下代码行从URI中检索的：myBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), picUri);
- 像三星Galaxy这样的设备以横向模式捕获图像。按原样检索和显示图像可能会导致其以错误的方向显示。因此我们调用了rotateImageIfRequired(myBitmap, picUri)方法。
- ExifInterface是一个用于读取和写入JPEG文件或RAW图像文件中的Exif标签的类。
- 最后，我们调用getResizedBitmap()方法按宽度或高度（以较大者为准）缩放位图，并使用setImageBitmap将图像设置到图像视图中。
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。
