Android 相册选择图片

如何实现从相册中选取图片

• 1.运行时权限处理，申请WRITE_EXTERNAL_STORAGE这个危险权限，需要读写SD卡的能力

• 2.申请成功则继续构建Intent对象，指定action：android.intent.action.GET_CONTENT。用setType()设置返回类型为图片

• 3.调用startActivityForResult()隐式启动intent

• 4.回调onActivityResult()判断图片是否成功返回，如果成功，对4.4以上系统采用handleImageOnKitkat()，对4.4以下系统采用handleImageBeforeKitkat()

• 5.handleImageOnKitkat():

  • 返回的uri 如果是document类型，取出document id处理获取路径图片
    • 如果Uri的authority是media格式的话，document id 还要再一步处理才能获取路径图片
  • 不是的话则普通方式处理，直接获得路径图片

本项目在 26节调用摄像头项目的基础上修改

修改布局 增加选照片按钮

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/take_photo"
        android:text="拍照"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/choose_photo"
        android:text="选照片"/>

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/picture"
        android:layout_gravity="center_horizontal"/>

</LinearLayout>

活动

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private ImageView imageView;
    private Button takePhoto;
    private Button choosePhoto;
    private Uri imageUri;
    public static final int TAKE_PHOTO = 1;
    public static final int CHOOSE_PHOTO = 2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        imageView = findViewById(R.id.picture);
        takePhoto = findViewById(R.id.take_photo);
        choosePhoto = findViewById(R.id.choose_photo);
        takePhoto.setOnClickListener(this);
        choosePhoto.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.take_photo:
                File outputImage = new File(getExternalCacheDir(), "output_image.jpg");
                if (outputImage.exists()) {
                    outputImage.delete();
                }
                try {
                    outputImage.createNewFile();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (Build.VERSION.SDK_INT >= 24) {
                    imageUri = FileProvider.getUriForFile(MainActivity.this, getPackageName() + ".fileprovider", outputImage);
                } else {
                    imageUri = Uri.fromFile(outputImage);
                }
                Intent intent = new Intent("android.media.action.IMAGE_CAPTURE");
                intent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                startActivityForResult(intent, TAKE_PHOTO);
                break;
            case R.id.choose_photo:
                if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
                } else {
                    openAlbum(); //打开相册
                }
                break;
        }
    }

    private void openAlbum() {
        Intent intent = new Intent("android.intent.action.GET_CONTENT");
        intent.setType("image/*");
        Log.d("test", "选择照片");
        startActivityForResult(intent, CHOOSE_PHOTO);
    }

    //申请权限回调函数
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    openAlbum();
                } else {
                    Toast.makeText(MainActivity.this, "申请权限被拒绝", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }

  	//活动跳转回调函数
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
            case TAKE_PHOTO:   //拍照
                if (resultCode == RESULT_OK) {
                    try {
                        Bitmap bitmap = BitmapFactory.decodeStream(getContentResolver().openInputStream(imageUri));
                        imageView.setImageBitmap(bitmap);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    }
                } else {
                    Toast.makeText(MainActivity.this, "取消拍照", Toast.LENGTH_SHORT).show();
                }
                break;
            case CHOOSE_PHOTO:  //选照片
                if (resultCode == RESULT_OK) {
                    if (Build.VERSION.SDK_INT >= 19) {
                        handleImageOnKitkat(data);
                    } else {
                        handleImageBeforeKitkat(data);
                    }
                } else {
                    Toast.makeText(this, "未选择图片", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }
		//android4.4以下使用
    private void handleImageBeforeKitkat(Intent data) {
        Uri uri = data.getData();
        String imagePath = getImagePath(uri, null);
        Log.d("test", "before" + imagePath);
        displayImage(imagePath);
    }
		
    private String getImagePath(Uri externalContentUri, String selection) {
        String path = null;
        Cursor cursor = getContentResolver().query(externalContentUri, null, selection, null, null);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                path = cursor.getString(cursor.getColumnIndex(MediaStore.Images.Media.DATA));
            }
            cursor.close();
        }
        return path;
    }

  	//Android4.4以上使用
    @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    private void handleImageOnKitkat(Intent data) {
        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();
        }
        Log.d("test", imagePath);
        displayImage(imagePath);
    }

    private void displayImage(String imagePath) {
        if (imagePath != null) {
            Bitmap bitmap = BitmapFactory.decodeFile(imagePath);
            imageView.setImageBitmap(bitmap);
        } else {
            Toast.makeText(this, "图片加载错误！", Toast.LENGTH_SHORT).show();
        }
    }
}