[原创]Android Camera 开发之实现一附源码

2012-06-17 14:22 和尚释然阅读(4672) 评论(2) 编辑收藏举报

一、 Android Camera实现方式

Android提供两种实现方式给开发员来实现拍照功能:Camera API和Camera Intent.下面的章节主要是讲解如何使用Camera Intent进行Camera开发.

Camera Intent

通过”Camera Intent”方式可以快速,方便以及更少的代码来完成Camera功能.其通过Android的Intent调用系统现有的Camera应用程序来实现此功能.并实现”onActivityResult()”获取并处理拍照返回的结果.

调用Camera Intent流程主要分为如下几个步骤:

 构建一个Camera Intent来向Android系统请求图片和视频

 MediaStore.ACTION_IMAGE_CAPTURE 请求图像

 MediaStore.ACTION_VIDEO_CAPTURE 请求视频

 启动Camera Intent

 使用startActivityForResult()方法启动Camera Intent

 接收Camera Intent返回的结果

 创建onActivityResult()方法接收回调和返回图像数据

图像拍照意图(Image capture intent)

首先来看一下Demo的运行效果图,具体操作是点击”Take Photo!”按钮打开系统自带的Camera界面,拍摄完毕后将拍摄的照片显示ImageView中.

开发步骤:

A. 新建一个Android项目,取名为”CameraIntentDemo”.

B. 构建主界面元素.

main.xml文件内容如下:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="@string/hello" />

<Button

android:id="@+id/btnTakePhoto"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Take Photo!" />

<ImageView

android:id="@+id/imgvTakePhoto"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:background="#FFFFFF"/>

</LinearLayout>

C. 使用Intent来启动Camera功能.

首先声明一个Intent,并以MediaStore.ACTION_IMAGE_CAPTURE实例化该Intent.

Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

然后设置Intent的MediaStore.EXTRA_OUTPUT属性可以将拍摄的图像保存到指定路径.

// set the image file name

intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

最后调用startActivityForResult方法来启动系统的Camera功能.

D. 捕获系统Camera的回调

重写onActivityResult()方法,通过requestCode参数可以知道是否Camera Intent的Result,然后再根据Intent参数对接收到图像数据进行处理或者保存.如果通过

MediaStore.EXTRA_OUTPUT属性自动将图像数据保存到指定的位置,那么在

onActivityResult()得到的Intent的数据是为NULL的.这一点大家需要注意一下.

E. 在AndroidManifest.xml添加访问SD权限声明.

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

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

CameraIntentDemoActivity.java文件内容:

public class CameraIntentDemoActivity extends Activity {

private static final int MEDIA_TYPE_IMAGE = 1;

private static final int MEDIA_TYPE_VIDEO = 2;

private Uri fileUri;

private static Uri getOutputMediaFileUri(int type) {

return Uri.fromFile(getOutputMediaFile(type));

}

private static File getOutputMediaFile(int type){

// To be safe, you should check that the SDCard is mounted

// using Environment.getExternalStorageState() before doing this.

File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "MyCameraApp");

// This location works best if you want the created images to be shared

// between applications and persist after your app has been uninstalled.

// Create the storage directory if it does not exist

if (! mediaStorageDir.exists()){

if (! mediaStorageDir.mkdirs()){

Log.d("MyCameraApp", "failed to create directory");

return null;

}

// Create a media file name

String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());

File mediaFile;

if (type == MEDIA_TYPE_IMAGE){

mediaFile = new File(mediaStorageDir.getPath() + File.separator +

"IMG_"+ timeStamp + ".jpg");

} else if(type == MEDIA_TYPE_VIDEO) {

mediaFile = new File(mediaStorageDir.getPath() + File.separator +

"VID_"+ timeStamp + ".mp4");

} else {

return null;

}

return mediaFile;

}

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button btnTakePhoto = (Button)this.findViewById(R.id.btnTakePhoto);

btnTakePhoto.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

// create a file to save the image

fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);

// set the image file name

cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

// start the image capture Intent

startActivityForResult(cameraIntent, 0);

}

});

}

@Override

protected void onActivityResult(int requestCode, int resultCode, Intent data) {

try {

if (requestCode != 0) {

return;

}

Bitmap bmp = null;

super.onActivityResult(requestCode, resultCode, data);

if (data != null) {

Bundle extras = data.getExtras();

bmp = (Bitmap)extras.get("data");

}

else {

FileInputStream fis = new FileInputStream(fileUri.getPath());

bmp = BitmapFactory.decodeStream(fis);

}

ImageView imag = (ImageView)this.findViewById(R.id.imgvTakePhoto);

imag.setImageBitmap(bmp);

} catch (Exception e){

System.out.println(e.getMessage());

}

视频拍摄意图(Video capture intent)

使用Camera Intent同样可以快速,方便以及更少代码实现视频拍摄.它还支持多种扩展特性.

• MediaStore.EXTRA_OUTPUT – 设置视频输出位置.

• MediaStore.EXTRA_VIDEO_QUALITY – 设置视频质量,0为最差,1为最清晰.

• MediaStore.EXTRA_DURATION_LIMIT – 设置视频的限制长度.

• MediaStore.EXTRA_SIZE_LIMIT – 设置视频的限制大小.

开发步骤:

A. 新建一个Android Project命名为VideoIntentDemo,指定最低版本号.

B. 构建界面元素

同样是放置一个Button来触发视频拍摄,下面放置一个TextView用来存放返回信息.

界面布局:

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="@string/hello" />

<Button

android:id="@+id/btTakeVideo"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Take Video" />

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:background="#FFFFFF"

android:id="@+id/tvActivityResult"

android:minLines="5"

</LinearLayout>

C. 代码实现

首先声明一个Uri对象用来保存视频文件保存的路径.

private Uri fileUri;

然后实现Video功能代码.

// create new Intent

Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);

// create a file to save the video

fileUri = getOutputMediaFileUri(MEDIA_TYPE_VIDEO);

// set the video file name

intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

// set the video image quality to high

intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);

// start the Video Capture Intent

startActivityForResult(intent, 1);

VideoIntentDemoActivity.java文件内容:

public class VideoIntentDemoActivity extends Activity {

private Uri fileUri;

private static final int MEDIA_TYPE_IMAGE = 1;

private static final int MEDIA_TYPE_VIDEO = 2;

private static Uri getOutputMediaFileUri(int type) {

return Uri.fromFile(getOutputMediaFile(type));

}

private static File getOutputMediaFile(int type){

// To be safe, you should check that the SDCard is mounted

// using Environment.getExternalStorageState() before doing this.

File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "MyCameraApp");

// This location works best if you want the created images to be shared

// between applications and persist after your app has been uninstalled.

// Create the storage directory if it does not exist

if (! mediaStorageDir.exists()){

if (! mediaStorageDir.mkdirs()){

Log.d("MyCameraApp", "failed to create directory");

return null;

}

// Create a media file name

String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());

File mediaFile;

if (type == MEDIA_TYPE_IMAGE){

mediaFile = new File(mediaStorageDir.getPath() + File.separator +

"IMG_"+ timeStamp + ".jpg");

} else if(type == MEDIA_TYPE_VIDEO) {

mediaFile = new File(mediaStorageDir.getPath() + File.separator +

"VID_"+ timeStamp + ".mp4");

} else {

return null;

}

return mediaFile;

}

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button btnTakeVideo = (Button)this.findViewById(R.id.btTakeVideo);

btnTakeVideo.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

// create new Intent

Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);

// create a file to save the video

fileUri = getOutputMediaFileUri(MEDIA_TYPE_VIDEO);

// set the video file name

intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);

// set the video image quality to high

intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);

// start the Video Capture Intent

startActivityForResult(intent, 1);

}

});

}

@Override

protected void onActivityResult(int requestCode, int resultCode, Intent data) {

TextView tvVideo = (TextView)this.findViewById(R.id.tvActivityResult);

try {

if (requestCode == 1) {

tvVideo.setText("视频保存成功,路径为:" + fileUri.getPath());

}

super.onActivityResult(requestCode, resultCode, data);

} catch (Exception e) {

tvVideo.setText(e.getLocalizedMessage());

}

D. 在AndroidManifest.xml添加访问SD权限声明.

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

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

最后附上源码下载:

http://download.csdn.net/detail/guenli/4373794

http://download.csdn.net/detail/guenli/4373786

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和尚释然和尚不看佛经,改看编程宝典.