Android开发: 调用Camera API 创建Camera

steps to follow to create your own camera using camera API,

1. add permission to AndroidManifest.xml to get the camera hardware resource and save picture into SD card,

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

[align=left]<uses-permission android:name= "android.permission.WRITE_EXTERNAL_STORAGE" />[/align]
[align=left] [/align]

AndroidManifest.xml[/b]

<? xml version= "1.0" encoding = "utf-8"?>
< manifest xmlns:android ="http://schemas.android.com/apk/res/android"
package= "android.study.sample"
android:versionCode= "1"
android:versionName= "1.0" >

<uses-sdk android:minSdkVersion= "15" />
<uses-permission android:name= "android.permission.CAMERA" />
<uses-permission android:name= "android.permission.WRITE_EXTERNAL_STORAGE" />

<application
android:icon ="@drawable/ic_launcher"
android:label ="@string/app_name" >

< activity android:name =".CameraActivity"
android:label ="@string/app_name"

android:screenOrientation ="landscape" >
<!-- configure this activity to use landscape orientation -->

< intent-filter>
< action android:name ="android.intent.action.MAIN" />
< category android:name ="android.intent.category.LAUNCHER" />
</ intent-filter>
</ activity>

</application >

</ manifest>

2. set a preview layout and button in your camera UI to control camera

res/layout/main.xml[/b]

<? xml version= "1.0" encoding = "utf-8"?>
< LinearLayout xmlns:android ="http://schemas.android.com/apk/res/android"
android:orientation= "horizontal"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
>
<FrameLayout
android:id= "@+id/camera_preview"
android:layout_width= "fill_parent"
android:layout_height= "fill_parent"
android:layout_weight= "1"
/>

<Button
android:id= "@+id/button_capture"
android:text= "Capture"
android:layout_width= "wrap_content"
android:layout_height= "wrap_content"
android:layout_gravity= "center"
/>
</ LinearLayout>

3.implement your a surfaceView for your own camera to preview the live image before taking a picture

android.study.sample.CameraPreview.java[/b]

package android.study.sample;

import java.io.IOException;

import android.content.Context;
import android.hardware.Camera;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;

String TAG= "CAMERAAPI";

public CameraPreview(Context context, Camera camera) {
super (context);
mCamera = camera;

// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback( this );
// deprecated setting, but required on Android versions prior to 3.0
mHolder. setType(SurfaceHolder. SURFACE_TYPE_PUSH_BUFFERS);
}

public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log. d( TAG, "Error setting camera preview: " + e.getMessage());
}
}

public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.

if (mHolder .getSurface() == null){
// preview surface does not exist
return ;
}

// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}

// set preview size and make any resize, rotate or
// reformatting changes here

// start preview with new settings
try {
mCamera.setPreviewDisplay( mHolder);
mCamera.startPreview();

} catch (Exception e){
Log. d( TAG, "Error starting camera preview: " + e.getMessage());
}
}
}

[align=left]4.build your CameraActivity to start the camera app [/align]

[align=left]get an camera available , add this camera to the surfaceview of the screen layout, listen for the User action, If user click to Copture button, call camera to take a picture, and save image into the SD card, this is implemented by the PictureCallback method set to Camera.takePicture() [/align]

android.study.sample.CameraActivity.java[/b]

package android.study.sample;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

import android.app.Activity;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.os.Bundle;
import android.os.Environment;
import android.study.sample.R.id;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;

public class CameraActivity extends Activity {

public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;

private Camera mCamera;
private CameraPreview mPreview;
String TAG= "CAMERAAPI";

@Override
public void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
setContentView(R.layout. main );

// Create an instance of Camera
mCamera = getCameraInstance();

// Create our Preview view and set it as the content of our activity.
mPreview = new CameraPreview( this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id. camera_preview );
preview.addView( mPreview);

Button captureButton = (Button) findViewById(id. button_capture );
captureButton.setOnClickListener( new CaptureButtonOnClickListener());
}

public class CaptureButtonOnClickListener implements View.OnClickListener{
public void onClick(View v) {

PictureCallback mPicture = new CameraPictureCallBack();
mCamera.takePicture( null , null , mPicture);
}
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null ;
try {
c = Camera. open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}

public class CameraPictureCallBack implements PictureCallback{

public void onPictureTaken( byte[] data, Camera camera) {

File pictureFile = getOutputMediaFile( MEDIA_TYPE_IMAGE);
if (pictureFile == null){
Log. d( TAG, "Error creating media file, check storage permissions!");
return ;
}

try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
Log. d( TAG, "File not found: " + e.getMessage());
} catch (IOException e) {
Log. d( TAG, "Error accessing file: " + e.getMessage());
}
}
}

/** Create a File for saving an image or video */
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
protected void onPause() {
super .onPause();
releaseCamera();              // release the camera immediately on pause event
}

private void releaseCamera(){
if (mCamera != null){
mCamera.release();        // release the camera for other applications
mCamera = null ;
}
}

}

5. when open the app, UI display like below ,





[align=left] [/align]

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