【安卓】调用摄像头和相册

调用摄像头拍照

  新建一个CameraAlbumTest项目，然后修改activity_main.xml中的代码。在布局文件中添加两个控件：一个Button和一个ImageView。Button是用于打开摄像头进行拍照的，而ImageView则是用于将拍到的图片显示出来。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent" >
 <Button
 android:id="@+id/takePhotoBtn"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:text="Take Photo" />
 <ImageView
 android:id="@+id/imageView"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_gravity="center_horizontal" />
</LinearLayout>

  编写调用摄像头的具体逻辑，修改MainActivity中的代码。给Button注册点击事件，然后在点击事件里开始处理调用摄像头的逻辑。

public class MainActivity extends AppCompatActivity {

    public static final int TAKE_PHOTO = 1;
    private ImageView picture;
    private Uri imageUri;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button takePhoto = (Button) findViewById(R.id.takePhotoBtn);
        picture = (ImageView) findViewById(R.id.imageView);
        takePhoto.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                // 创建File对象，用于存储拍照后的图片
                File outputImage = new File(getExternalCacheDir(), "output_image.jpg");
                try {
                    if(outputImage.exists()){
                        outputImage.delete();
                    }
                    outputImage.createNewFile();
                } catch (IOException e){
                    e.printStackTrace();
                }
                if (Build.VERSION.SDK_INT >= 24) {
                    imageUri = FileProvider.getUriForFile(MainActivity.this,
                            "com.example.cameraalbumtest.fileprovider", outputImage);
                } else {
                    imageUri = Uri.fromFile(outputImage);
                }
                // 启动相机程序
                Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
                intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                startActivityForResult(intent, TAKE_PHOTO);
            }
        });
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case TAKE_PHOTO:
                if(resultCode == RESULT_OK) {
                    try {
                        // 将拍摄的照片显示出来
                        Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
                        picture.setImageBitmap(bitmap);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    }
                }
                break;
            default:
                break;
        }
    }
}

  getUriForFile()方法接收3个参数：第一个参数要求传入Context对象，第二个参数可以是任意唯一的字符串，第三个参数则是File对象。

  修改AndroidManifest.xml文件。

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.CameraAlbumTest"
        tools:targetApi="31">

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

        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

  添加资源文件file_paths.xml。在res文件下找到xml目录（如果没有在res目录下新建目录）新建file，取名file_paths.xml。然后修改file_paths.xml文件中的内容。

<?xml version="1.0" encoding="UTF-8" ?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="my_images" path="/" />
</paths>

  external-path就是用来指定Uri共享路径的，name属性的值可以随便填，path属性的值表示共享的具体路径。

从相册中选择照片

  修改activity_main.xml文件，在布局中加入一个新按钮。

	<Button
        android:id="@+id/fromAlbumBtn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="From Album" />

  然后修改MainActivity中的代码，加入从相册选择图片的逻辑。

public class MainActivity extends AppCompatActivity {

    public static final int TAKE_PHOTO = 1;
    private ImageView picture;
    private Uri imageUri;

    public static final int CHOOSE_PHOTO = 2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button takePhoto = (Button) findViewById(R.id.takePhotoBtn);
        Button chooseFromAlbum = (Button) findViewById(R.id.fromAlbumBtn);
        picture = (ImageView) findViewById(R.id.imageView);

        takePhoto.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                // 创建File对象，用于存储拍照后的图片
                File outputImage = new File(getExternalCacheDir(), "output_image.jpg");
                try {
                    if(outputImage.exists()){
                        outputImage.delete();
                    }
                    outputImage.createNewFile();
                } catch (IOException e){
                    e.printStackTrace();
                }
                if (Build.VERSION.SDK_INT >= 24) {
                    imageUri = FileProvider.getUriForFile(MainActivity.this,
                            "com.example.cameraalbumtest.fileprovider", outputImage);
                } else {
                    imageUri = Uri.fromFile(outputImage);
                }
                // 启动相机程序
                Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
                intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                startActivityForResult(intent, TAKE_PHOTO);
            }
        });

        chooseFromAlbum.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivity.this,
                        android.Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){
                    ActivityCompat.requestPermissions(MainActivity.this,
                            new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
                } else {
                    openAlbum();
                }
            }
        });
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case TAKE_PHOTO:
                if(resultCode == RESULT_OK) {
                    try {
                        // 将拍摄的照片显示出来
                        Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
                        picture.setImageBitmap(bitmap);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    }
                }
                break;
            case CHOOSE_PHOTO:
                if (resultCode == RESULT_OK) {
                    // 判断手机系统版本号
                    if (Build.VERSION.SDK_INT >= 19){
                        // 4.4及以上系统使用这个方法处理图片
                        handleImageOnKitKat(data);
                    } else {
                        // 4.4以下系统使用这个方法处理图片
                        handleImageBeforeKitKat(data);
                    }
                }
                break;
            default:
                break;
        }
    }
    // 打开相册
    private void openAlbum() {
        Intent intent = new Intent("android.intent.action.GET_CONTENT");
        intent.setType("image/*");
        startActivityForResult(intent, CHOOSE_PHOTO);   // 打开相册
    }

    public void onRequestPermissionResult(int requestCode, String[] permissions,
                                          int[] grantREsults){
        switch (requestCode) {
            case 1:
                if (grantREsults.length > 0 && grantREsults[0] == PackageManager.PERMISSION_GRANTED){
                    openAlbum();
                } else {
                    Toast.makeText(this, "You denied the permission",
                            Toast.LENGTH_SHORT).show();
                }
                break;
            default:
                break;
        }
    }

    @TargetApi(19)
    private void handleImageOnKitKat(Intent data) {
        String imagePath = null;
        Uri uri = data.getData();
        if (DocumentsContract.isDocumentUri(this, uri)) {
            // 如果是document类型的Uri，则通过document id处理
            String docId = DocumentsContract.getDocumentId(uri);
            if ("com.android.providers.media.documents".equals(uri.getAuthority())){
                String id = docId.split(":")[1]; // 解析出数字格式的id
                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())){
            // 如果是content类型的Uri，则使用普通方式处理
            imagePath = getImagePath(uri, null);
        } else if ("file".equalsIgnoreCase(uri.getScheme())){
            // 如果是file类型的Uri，直接获取图片路径即可
            imagePath = uri.getPath();
        }
        displayImage(imagePath); // 根据图片路径显示图片
    }
    private void handleImageBeforeKitKat(Intent data) {
        Uri uri = data.getData();
        String imagePath = getImagePath(uri, null);
        displayImage(imagePath);
    }
    private String getImagePath(Uri uri, String selection) {
        String path = null;
        // 通过Uri和selection来获取真实的图片路径
        Cursor cursor = getContentResolver().query(uri, null, selection, null, null);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                path = cursor.getString(cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA));
            }
            cursor.close();
        }
        return path;
    }
    private void displayImage(String imagePath) {
        if (imagePath != null) {
            Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
            picture.setImageBitmap(bitmap);
        } else {
            Toast.makeText(this, "failed to get iamge", Toast.LENGTH_SHORT).show();
        }
    }
}

  在AndroidManifest.xml中进行授权

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

  此时运行程序会报一个错：Unable to decode stream: java.io.FileNotFoundException，没查到错是什么原因导致的，但是有解决方法。在application中加一句：

android:requestLegacyExternalStorage=“true”