Android 多媒体应用：开启摄像头、查看相册中的照片

开启摄像头

开启摄像头是在ACtivity中打开系统自带的摄像头应用。

主函数代码

private Button mButtonStartCamera;    private ImageView mImageView;    private File file;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mButtonStartCamera = (Button) findViewById(R.id.button_start_camera);        mImageView = (ImageView) findViewById(R.id.imageview);        mButtonStartCamera.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent();                intent.setAction(MediaStore.ACTION_IMAGE_CAPTURE);//隐式启动系统相机                file = new File(Environment.getExternalStorageDirectory(), System.currentTimeMillis() + ".jpg");                try {                    file.createNewFile();                } catch (IOException e) {                    e.printStackTrace();                }                intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(file));//告诉系统相机将照片保存的位置                startActivityForResult(intent, 0x23);//开始启动            }        });    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        if (requestCode ==0x23) {            if (resultCode==RESULT_OK){            //有些手机不能显示出拍出来的图片是因为图片过大，所以在显示之前需要把图片压缩一下——————ImageZip.zipImage(file.getAbsolutePath());//压缩图片                mImageView.setImageURI(Uri.fromFile(file));//得到图片            }        }    }

布局

<Button        android:id="@+id/button_start_camera"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="调用系统相机"/>    <ImageView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/imageview"/>

注意：在manifests中加权限

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

压缩图片的方法

public class ImageZip {    public static void zipImage(String savePath) {        BitmapFactory.Options options = new BitmapFactory.Options();        options.inJustDecodeBounds = true;        BitmapFactory.decodeFile(savePath, options);        options.inSampleSize = computeInitialSampleSize(options, 480, 480 * 960);        options.inJustDecodeBounds = false;        Bitmap bitmap = BitmapFactory.decodeFile(savePath, options);        try {            FileOutputStream fos = new FileOutputStream(savePath);            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, fos);            fos.flush();            fos.close();        } catch (IOException e) {            e.printStackTrace();        }        bitmap.recycle();        bitmap = null;        System.gc();    }    public static int computeSampleSize(BitmapFactory.Options options,                                 int minSideLength, int maxNumOfPixels) {        int initialSize = computeInitialSampleSize(options, minSideLength,                maxNumOfPixels);        int roundedSize;        if (initialSize <= 8) {            roundedSize = 1;            while (roundedSize < initialSize) {                roundedSize <<= 1;            }        } else {            roundedSize = (initialSize + 7) / 8 * 8;        }        return roundedSize;    }    private static int computeInitialSampleSize(BitmapFactory.Options options,                                         int minSideLength, int maxNumOfPixels) {        double w = options.outWidth;        double h = options.outHeight;        int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math                .sqrt(w * h / maxNumOfPixels));        int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(                Math.floor(w / minSideLength), Math.floor(h / minSideLength));        if (upperBound < lowerBound) {            // return the larger one when there is no overlapping zone.            return lowerBound;        }        if ((maxNumOfPixels == -1) && (minSideLength == -1)) {            return 1;        } else if (minSideLength == -1) {            return lowerBound;        } else {            return upperBound;        }    }}

压缩图片中后面两个方法是Google的压缩图片，第一个是老师写的

查看相册中照片的代码

mButtonOpenGallery= (Button) findViewById(R.id.button_open_gallery);        mButtonOpenGallery.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent=new Intent(Intent.ACTION_GET_CONTENT);//启动存有相册的活动                intent.setType("image/*");                startActivityForResult(intent,GET_PIC_FORM_GALLERY);            }        });  //      *********************************          protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        if (resultCode==RESULT_OK) {            switch(requestCode){                case 0x23:                ImageZip.zipImage(file.getAbsolutePath());//压缩图片                mImageView.setImageURI(Uri.fromFile(file));//得到图片                break;                case GET_PIC_FORM_GALLERY:                    Uri uri=data.getData();                    mImageView.setImageURI(uri);                    break;            }        }    }

压缩相册里的原有图片的方法

public String getFilePathFromUri(Uri uri) {        String[] proj = {MediaStore.Images.Media.DATA};        Cursor cursor = managedQuery(uri, proj, null, null, null);        int index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);        cursor.moveToFirst();        String path = cursor.getString(index);        cursor.close();        cursor = null;        return path;    }

然后只需要在主函数里调用这个方法就行了

case GET_PIC_FORM_GALLERY:                    Uri uri = data.getData();                    //根据Uri在数据库中查询出文件详细信息，从数据库中查出详细路径，然后在压缩                    String s = getFilePathFromUri(uri);                    ImageZip.zipImage(s);//压缩图片-----ImageZip这个类已经在上面写了。                    mImageView.setImageURI(uri);                    break;