Android开发手记(32) 使用摄像头拍照
在Android中,使用摄像头拍照一般有两种方法, 一种是调用系统自带的Camera,另一种是自己写一个摄像的界面。
我们要添加如下权限:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.CAMERA"/>
1、调用系统Camera
调用系统自带的Camera主要的步骤为:
(1)构造图片存储的路径名
(2)使用Intent启动Camera Activity
(3)将拍摄的图片写入到文件
(4)将图片显示在MainActivity中
首先,构造图片名:
File filePath = new File(Environment.getExternalStorageDirectory(), "myCamera"); if(!filePath.exists()){ filePath.mkdirs(); } fileName = new File(filePath, System.currentTimeMillis() + ".jpg"); try{ if(!fileName.exists()){ fileName.createNewFile(); } }catch (Exception e){ e.printStackTrace(); }
然后,启动Camera Activity:
// intent用来启动系统自带的Camera Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); // 将系统Camera的拍摄结果写入到文件 intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(fileName)); // 启动intent对应的Activity,返回默认消息 startActivityForResult(intent, Activity.DEFAULT_KEYS_DIALER);
最后,将图片显示在MainActivity内。这时,我们通过重载onActivityResult()方法来获取Camera返回的消息。
@Override protected void onActivityResult(int requestCode, int resultCode, Intent data){ if(requestCode == Activity.DEFAULT_KEYS_DIALER){ // MainActivity接收Camera返回的消息,然后将已经写入的图片显示在ImageView内 imageView.setImageURI(Uri.fromFile(fileName)); } }
完整代码为:
import android.app.Activity; import android.content.Intent; import android.net.Uri; import android.os.Bundle; import android.os.Environment; import android.provider.MediaStore; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.ImageView; import java.io.File; public class MainActivity extends Activity { private File fileName = null; private Button button; private ImageView imageView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = (Button)findViewById(R.id.button); imageView = (ImageView)findViewById(R.id.imageView); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { File filePath = new File(Environment.getExternalStorageDirectory(), "myCamera"); if(!filePath.exists()){ filePath.mkdirs(); } fileName = new File(filePath, System.currentTimeMillis() + ".jpg"); try{ if(!fileName.exists()){ fileName.createNewFile(); } }catch (Exception e){ e.printStackTrace(); } // intent用来启动系统自带的Camera Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); // 将系统Camera的拍摄结果写入到文件 intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(fileName)); // 启动intent对应的Activity,返回默认消息 startActivityForResult(intent, Activity.DEFAULT_KEYS_DIALER); } }); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data){ if(requestCode == Activity.DEFAULT_KEYS_DIALER){ // MainActivity接收Camera返回的消息,然后将已经写入的图片显示在ImageView内 imageView.setImageURI(Uri.fromFile(fileName)); } } }
2、自己写一个摄像界面
自己写摄像的界面,主要应用了SurfaceView来显示摄像机的画面。然后通过一个Button来保存当前的画面。
同样的,我们需要添加camera和SDCard权限:
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.CAMERA"/>
首先,我们初始化这个SurfaceView,为这个SurfaceView添加一个对应的Callback即可:
private SurfaceView surfaceView; private SurfaceHolder.Callback callback; surfaceView = (SurfaceView)findViewById(R.id.surfaceView); callback = new SurfaceHolder.Callback(){ @Override public void surfaceCreated(SurfaceHolder holder) { startCamera(); // 用于启动摄像头 } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } @Override public void surfaceDestroyed(SurfaceHolder holder) { stopCamera(); // 用于关闭摄像头 } }; surfaceView.getHolder().addCallback(callback); // 将Callback绑定到SurfaceView
在启动摄像头的时候,首先打开摄像头连接,然后将其图像输出到SurfaceView上,然后启动摄像头预览即可在SurfaceView上显示摄像头的画面,这里的画面和实际画面相差有90度,所以我们需要将图像旋转90度之后才可以和拍摄的物体方向一致。
在关闭摄像头时,只要停止预览,然后释放摄像头资源即可。
public void startCamera(){ camera = Camera.open(); try { camera.setPreviewDisplay(surfaceView.getHolder()); camera.setDisplayOrientation(90); camera.startPreview(); } catch (IOException e) { e.printStackTrace(); } } public void stopCamera(){ camera.stopPreview(); camera.release(); camera = null; }
最后,是将拍摄到的图片保存到SDCard,我们单击Button来拍摄图片,调用Camera.takePicture()方法,其原型为:
/** * Equivalent to takePicture(shutter, raw, null, jpeg). * * @see #takePicture(ShutterCallback, PictureCallback, PictureCallback, PictureCallback) */ public final void takePicture(ShutterCallback shutter, PictureCallback raw, PictureCallback jpeg) { takePicture(shutter, raw, null, jpeg); }
其中,shutter为按快门瞬间的回调,就是说按快门瞬间会调用ShutterCallback.onShutter()方法。raw是未压缩的图像的回调,即处理图像原始数据的时候会调用PictureCallback.onPictureTaken()方法。jpeg为处理JPEG图片时候的回调,即我们需要将图像数据按照jpg格式保存的时候会调用这个方法,PictureCallback.onPIctureTaken()。这里我们就调用了这个方法,从而将jpg图片存储到SDCard上。
button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { camera.takePicture(null, null, new Camera.PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { try { File filePath = new File(Environment.getExternalStorageDirectory(), "myCamera"); if(!filePath.exists()) { filePath.mkdirs(); } File fileName = new File(filePath, System.currentTimeMillis() + ".jpg"); fileName.createNewFile(); FileOutputStream fos = new FileOutputStream(fileName); fos.write(data); fos.flush(); fos.close(); } catch (IOException e) { e.printStackTrace(); } } }); } });
这样,我们便实现了用SurfaceView预览摄像头画面,点击Button将当前预览保存到SDCard中。
完整代码如下:
import android.app.Activity; import android.hardware.Camera; import android.os.Bundle; import android.os.Environment; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View; import android.widget.Button; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; public class MainActivity extends Activity { private Camera camera; private Button button; private SurfaceView surfaceView; private SurfaceHolder.Callback callback; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = (Button)findViewById(R.id.button); surfaceView = (SurfaceView)findViewById(R.id.surfaceView); callback = new SurfaceHolder.Callback(){ @Override public void surfaceCreated(SurfaceHolder holder) { startCamera(); } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } @Override public void surfaceDestroyed(SurfaceHolder holder) { stopCamera(); } }; surfaceView.getHolder().addCallback(callback); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { camera.takePicture(null, null, new Camera.PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { try { File filePath = new File(Environment.getExternalStorageDirectory(), "myCamera"); if(!filePath.exists()) { filePath.mkdirs(); } File fileName = new File(filePath, System.currentTimeMillis() + ".jpg"); fileName.createNewFile(); FileOutputStream fos = new FileOutputStream(fileName); fos.write(data); fos.flush(); fos.close(); } catch (IOException e) { e.printStackTrace(); } } }); } }); } public void startCamera(){ camera = Camera.open(); try { camera.setPreviewDisplay(surfaceView.getHolder()); camera.setDisplayOrientation(90); camera.startPreview(); } catch (IOException e) { e.printStackTrace(); } } public void stopCamera(){ camera.stopPreview(); camera.release(); camera = null; } }