我是android的新手，现在我正在尝试制作自定义相机应用。我可以制作自定义相机并拍摄一些视频。但是未能更改相机原始数据。我想在相机上添加黑白等实时滤镜。我使用此方法更改了数据
final Camera.PreviewCallback callback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
//Do your processing here... Use the byte[] called "data"
int pixelCount = width * height;
int[] out = new int[pixelCount];
for (int i = 0; i < pixelCount; ++i) {
int luminance = data[i] & 0xFF;
out[i] = Color.argb(0xFF, luminance, luminance, luminance);
data[i] = (byte) out[i];
}
}
};
mCamera.setPreviewCallback(callback);
但是没有用。对于何时应调用mCamera.setPreviewCallback（callback）方法，我也感到困惑。
为了更好地理解，我在这里给出了完整的代码。
Mainactivity.java
package com.example.msi.magiccamera;
import android.content.Context;
import android.graphics.Color;
import android.hardware.Camera;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.Toast;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import static android.content.ContentValues.TAG;
public class MainActivity extends AppCompatActivity {
private Camera mCamera;
private CameraPreview mPreview;
private MediaRecorder mediaRecorder;
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
private boolean isRecording = false;
private SurfaceHolder mholder;
private Button captureButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_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);
DisplayMetrics displayMetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
final int height = displayMetrics.heightPixels;
final int width = displayMetrics.widthPixels;
preview.addView(mPreview);
mholder = mPreview.getHolder();
mPreview.surfaceCreated(mholder);
final Camera.PreviewCallback callback = new Camera.PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera camera) {
//Do your processing here... Use the byte[] called "data"
int pixelCount = width * height;
int[] out = new int[pixelCount];
for (int i = 0; i < pixelCount; ++i) {
int luminance = data[i] & 0xFF;
out[i] = Color.argb(0xFF, luminance, luminance, luminance);
data[i] = (byte) out[i];
}
}
};
//mCamera.setPreviewCallback(callback);
captureButton = findViewById(R.id.captureButton);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isRecording) {
// stop recording and release camera
mediaRecorder.stop(); // stop the recording
releaseMediaRecorder(); // release the MediaRecorder object
mCamera.lock(); // take camera access back from MediaRecorder
// inform the user that recording has stopped
//setCaptureButtonText("Capture");
captureButton.setText("Capture");
isRecording = false;
} else {
// initialize video camera
if (prepareVideoRecorder()) {
// Camera is available and unlocked, MediaRecorder is prepared,
// now you can start recording
mediaRecorder.start() ;
//mCamera.setPreviewCallback(callback);
// inform the user that recording has started
//setCaptureButtonText("Stop");
captureButton.setText("Stop");
isRecording = true;
} else {
// prepare didn't work, release the camera
releaseMediaRecorder();
// inform user
}
}
}
private void setCaptureButtonText(String capture) {
}
}
);
}
/** A safe way to get an instance of the Camera object. */
public static android.hardware.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
}
private boolean prepareVideoRecorder(){
mCamera = getCameraInstance();
mediaRecorder = new MediaRecorder();
// Step 1: Unlock and set camera to MediaRecorder
mCamera.unlock();
mediaRecorder.setCamera(mCamera);
// Step 2: Set sources
mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
// Step 3: Set a CamcorderProfile (requires API Level 8 or higher)
mediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));
// Step 4: Set output file
mediaRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString());
// Step 5: Set the preview output
mediaRecorder.setPreviewDisplay(mPreview.getHolder().getSurface());
// Step 6: Prepare configured MediaRecorder
try {
mediaRecorder.prepare();
} catch (IllegalStateException e) {
Log.d(TAG, "IllegalStateException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false;
} catch (IOException e) {
Log.d(TAG, "IOException preparing MediaRecorder: " + e.getMessage());
releaseMediaRecorder();
return false;
}
return true;
}
/** Create a file Uri for saving an image or video */
private static Uri getOutputMediaFileUri(int type){
return Uri.fromFile(getOutputMediaFile(type));
}
/** 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();
releaseMediaRecorder(); // if you are using MediaRecorder, release it first
releaseCamera(); // release the camera immediately on pause event
}
private void releaseMediaRecorder(){
if (mediaRecorder != null) {
mediaRecorder.reset(); // clear recorder configuration
mediaRecorder.release(); // release the recorder object
mediaRecorder = null;
mCamera.lock(); // lock camera for later use
}
}
private void releaseCamera(){
if (mCamera != null){
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
}
Camerapreview.java
package com.example.msi.magiccamera;
import android.content.Context;
import android.graphics.Color;
import android.hardware.Camera;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.WindowManager;
import java.io.IOException;
import static android.content.ContentValues.TAG;
/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
//New codes
@Override
public SurfaceHolder getHolder() {
return super.getHolder();
}
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());
} catch (Exception e) {
e.printStackTrace();
}
}
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());
}
}
}