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:
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<uses-permission android:name= "android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name= "android.permission.CAMERA" />
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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:
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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();
}
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然后,启动Camera Activity:
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// 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);
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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。
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@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));
}
}
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完整代码为:
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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));
}
}
}
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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:
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<uses-permission android:name= "android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name= "android.permission.CAMERA" />
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首先,我们初始化这个SurfaceView,为这个SurfaceView添加一个对应的Callback即可:
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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
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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。
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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 ;
}
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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:
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/**
* 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);
}
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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。
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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();
}
}
});
}
});
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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:
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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 ;
}
}
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