一個拍照和相簿選擇圖片的demo
注意：在有些機型上，這種寫法獲取到的相簿圖片的路徑為空，先看demo，解決方法在後面

public class MainActivity extends Activity{

    private static final int TAKE_PICTURE = 0;
    private static final int CHOOSE_PICTURE = 1;

    private static final int SCALE = 5;//照片縮小比例
    private ImageView iv_image = null;

    @Override
 

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

        iv_image = (ImageView) this.findViewById(R.id.img);
        this.findViewById(R.id.btn).setOnClickListener(new OnClickListener() {

            @Override
 

            public void onClick(View v) {
                showPicturePicker(MainActivity.this);
            }
        });

        this.findViewById(R.id.btn2).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
            }
        });
    }

    @Override
 

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_OK) {
            switch (requestCode) {
            case TAKE_PICTURE:
                //將儲存在本地的圖片取出並縮小後顯示在介面上
                Bitmap bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory()+"/image.jpg");
                Bitmap newBitmap = ImageTools.zoomBitmap(bitmap, bitmap.getWidth() / SCALE, bitmap.getHeight() / SCALE);
                //由於Bitmap記憶體佔用較大，這裡需要回收記憶體，否則會報out of memory異常
                bitmap.recycle();

                //將處理過的圖片顯示在介面上，並儲存到本地
                iv_image.setImageBitmap(newBitmap);
                ImageTools.savePhotoToSDCard(newBitmap, Environment.getExternalStorageDirectory().getAbsolutePath(), String.valueOf(System.currentTimeMillis()));
                break;

            case CHOOSE_PICTURE:
                ContentResolver resolver = getContentResolver();
                //照片的原始資源地址
                Uri originalUri = data.getData(); 
                // 獲取照片路徑
                String[] proj = {MediaStore.Images.Media.DATA};
                // 好像是Android多媒體資料庫的封裝介面，具體的看Android文件
                Cursor cursor = managedQuery(originalUri, proj, null, null, null); 
                // 按我個人理解 這個是獲得使用者選擇的圖片的索引值
                int column_index = cursor
                        .getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                // 將游標移至開頭 ，這個很重要，不小心很容易引起越界
                cursor.moveToFirst();
                // 最後根據索引值獲取圖片路徑
                String path = cursor.getString(column_index);
                try {
                    //使用ContentProvider通過URI獲取原始圖片
                    Bitmap photo = MediaStore.Images.Media.getBitmap(resolver, originalUri);
                    if (photo != null) {
                        //為防止原始圖片過大導致記憶體溢位，這裡先縮小原圖顯示，然後釋放原始Bitmap佔用的記憶體
                        Bitmap smallBitmap = ImageTools.zoomBitmap(photo, photo.getWidth() / SCALE, photo.getHeight() / SCALE);
                        //釋放原始圖片佔用的記憶體，防止out of memory異常發生
                        photo.recycle();

//                      iv_image.setImageBitmap(smallBitmap);
                    }
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }  
                break;

            default:
                break;
            }
        }
    }

    public void showPicturePicker(Context context){
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        builder.setTitle("圖片來源");
        builder.setNegativeButton("取消", null);
        builder.setItems(new String[]{"拍照","相簿"}, new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {
                switch (which) {
                case TAKE_PICTURE:
                    Intent openCameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                    Uri imageUri = Uri.fromFile(new File(Environment.getExternalStorageDirectory(),"image.jpg"));
                    //指定照片儲存路徑（SD卡），image.jpg為一個臨時檔案，每次拍照後這個圖片都會被替換
                    openCameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
                    startActivityForResult(openCameraIntent, TAKE_PICTURE);
                    break;

                case CHOOSE_PICTURE:
                    Intent openAlbumIntent = new Intent(Intent.ACTION_GET_CONTENT);
                    openAlbumIntent.setType("image/*");
                    startActivityForResult(openAlbumIntent, CHOOSE_PICTURE);
                    break;

                default:
                    break;
                }
            }
        });
        builder.create().show();
    }


}

解決獲取相簿圖片路徑為空的方法：
如果intent.setAction(Intent.ACTION_GET_CONTENT);話可能在4.4以後的版本機型會獲取不到真實的路徑，所以改成

Intent intent = new Intent(Intent.ACTION_PICK,android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                            intent.setDataAndType(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,"image/*");
                            startActivityForResult(intent, CHOOSE_PICTURE);