尝试使用自定义预览布局开发用于录制视频的Android相机应用。
给出这个来源：
http://developer.android.com/guide/topics/media/camera.html
相机的预览效果很好，
但是当我尝试录制视频时问题就出现了
按下捕获按钮后，应用程序崩溃。
在调试过程中，我发现在创建Camera实例期间出现了问题。 Camera.open（）不起作用（表示相机不可用），我收到Camera object = null（getCameraInstance（）方法返回null）。
我尝试在此处指定要打开的相机 Camera.open() returns null 但它没有任何帮助。
此应用程序在暂停和恢复后崩溃（我认为问题也出现在onPause（）/ onResume（）上。
非常感谢任何建议
我的代码在这里：
的活动：
package com.leo.leoscamera;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
public class CameraActivity extends Activity {
private Camera mCamera;
private CameraPreview mPreview;
private MediaRecorder mMediaRecorder;
private static final int MEDIA_TYPE_VIDEO = 2;
private static final String TAG = "L-Camera";
private boolean isRecording = false;
Button captureButton;
@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);
// Add a listener to the Capture button
captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isRecording) {
// stop recording and release camera
mMediaRecorder.stop(); // stop the recording
releaseMediaRecorder(); // release the MediaRecorder object
mCamera.lock(); // take camera access back from MediaRecorder
// inform the user that recording has stopped
captureButton.setText("Capture");
isRecording = false;
} else {
// initialize video camera
if (prepareVideoRecorder()) {
// Camera is available and unlocked, MediaRecorder is prepared,
// now you can start recording
mMediaRecorder.start();
// inform the user that recording has started
captureButton.setText("Stop");
isRecording = true;
} else {
// prepare didn't work, release the camera
releaseMediaRecorder();
// inform user
}
}
}
}
);
}
/**
* Configuring the MediaRecorder
* @return
*/
private boolean prepareVideoRecorder(){
mCamera = getCameraInstance();
mMediaRecorder = new MediaRecorder();
// Step 1: Unlock and set camera to MediaRecorder
mCamera.unlock();
mMediaRecorder.setCamera(mCamera);
// Step 2: Set sources
mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
// Step 3: Set a CamcorderProfile (requires API Level 8 or higher)
mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));
// Step 4: Set output file
mMediaRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString());
// Step 5: Set the preview output
mMediaRecorder.setPreviewDisplay(mPreview.getHolder().getSurface());
// Step 6: Prepare configured MediaRecorder
try {
mMediaRecorder.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;
}
/** 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)
Log.d(TAG, "Camera is not available");
}
return c; // returns null if camera is unavailable
}
/** Check if this device has a camera */
private boolean checkCameraHardware(Context context) {
if (context.getPackageManager().hasSystemFeature(
PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/** 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 (only video files)
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
File mediaFile;
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
}
@Override
protected void onResume() {
super.onResume();
if(mCamera == null){
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
}
private void releaseMediaRecorder(){
if (mMediaRecorder != null) {
mMediaRecorder.reset(); // clear recorder configuration
mMediaRecorder.release(); // release the recorder object
mMediaRecorder = null;
mCamera.lock(); // lock camera for later use
}
}
private void releaseCamera(){
if (mCamera != null){
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
}
预览：
package com.leo.leoscamera;
import java.io.IOException;
import java.util.List;
import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.Size;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
private static final String TAG = "Preview";
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());
}
}
}
清单：
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<uses-feature android:name="android:hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen" >
<activity
android:name=".CameraActivity"
android:label="@string/app_name"
android:screenOrientation="landscape" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
logcat的：
07-23 22:22:51.715: W/ActivityThread(17225): Application com.leo.leoscamera is waiting for the debugger on port 8100...
07-23 22:22:51.717: I/System.out(17225): Sending WAIT chunk
07-23 22:22:51.735: I/dalvikvm(17225): Debugger is active
07-23 22:22:51.918: I/System.out(17225): Debugger has connected
07-23 22:22:51.919: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:52.119: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:52.320: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:52.520: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:52.721: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:52.921: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:53.122: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:53.323: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:53.523: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:53.724: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:53.924: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:54.125: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:54.326: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:54.526: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:54.727: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:54.928: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:55.129: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:55.330: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:55.530: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:55.731: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:55.932: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:56.133: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:56.334: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:56.535: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:56.735: I/System.out(17225): waiting for debugger to settle...
07-23 22:22:56.940: I/System.out(17225): debugger has settled (1448)
07-23 22:23:02.545: I/SurfaceView(17225): updateWindow -- onWindowVisibilityChanged, visibility = 0
07-23 22:23:02.615: E/(17225): appName=com.leo.leoscamera, acAppName=/system/bin/surfaceflinger
07-23 22:23:02.615: E/(17225): 0
07-23 22:23:02.621: I/MaliEGL(17225): [Mali]window_type=1, is_framebuffer=0, errnum = 0
07-23 22:23:02.622: I/MaliEGL(17225): [Mali]surface->num_buffers=4, surface->num_frames=3, win_min_undequeued=1
07-23 22:23:02.622: I/MaliEGL(17225): [Mali]max_allowed_dequeued_buffers=3
07-23 22:23:02.674: I/[MALI][Gralloc](17225): dlopen libsec_mem.so fail
07-23 22:23:02.683: I/SurfaceView(17225): updateWindow -- setFrame
07-23 22:23:02.689: I/SurfaceView(17225): updateWindow -- OnPreDrawListener, mHaveFrame = true
07-23 22:23:02.692: I/SurfaceView(17225): Changes: creating=true format=true size=true visible=true left=true top=true mUpdateWindowNeeded=false mReportDrawNeeded=false redrawNeeded=false forceSizeChanged=true mVisible=false mRequestedVisible=true
07-23 22:23:02.699: I/SurfaceView(17225): Cur surface: Surface(name=null)/@0x424b3588
07-23 22:23:02.727: I/SurfaceView(17225): New surface: Surface(name=null)/@0x424b3658, vis=true, frame=Rect(0, 0 - 866, 540)
07-23 22:23:02.728: I/SurfaceView(17225): Callback --> surfaceCreated
07-23 22:23:02.729: I/SurfaceView(17225): surfaceCreated callback +
07-23 22:23:03.318: I/SurfaceView(17225): surfaceCreated callback -
07-23 22:23:03.320: I/SurfaceView(17225): surfaceChanged -- format=4 w=866 h=540
07-23 22:23:03.320: I/SurfaceView(17225): surfaceChanged callback +
07-23 22:23:04.670: I/SurfaceView(17225): surfaceChanged callback -
07-23 22:23:04.670: I/SurfaceView(17225): surfaceRedrawNeeded
07-23 22:23:04.670: I/SurfaceView(17225): finishedDrawing
07-23 22:23:04.683: I/Choreographer(17225): Skipped 136 frames! The application may be doing too much work on its main thread.
07-23 22:23:04.700: I/SurfaceView(17225): updateWindow -- OnPreDrawListener, mHaveFrame = true
07-23 22:23:04.706: I/SurfaceView(17225): Changes: creating=false format=false size=false visible=false left=false top=false mUpdateWindowNeeded=true mReportDrawNeeded=true redrawNeeded=false forceSizeChanged=false mVisible=true mRequestedVisible=true
07-23 22:23:04.709: I/SurfaceView(17225): Cur surface: Surface(name=null)/@0x424b3588
07-23 22:23:04.729: I/SurfaceView(17225): New surface: Surface(name=null)/@0x424b3658, vis=true, frame=Rect(0, 0 - 866, 540)
07-23 22:23:04.730: I/SurfaceView(17225): surfaceRedrawNeeded
07-23 22:23:04.731: I/SurfaceView(17225): finishedDrawing
07-23 22:23:04.871: I/SurfaceView(17225): updateWindow -- UPDATE_WINDOW_MSG
07-23 22:23:04.915: I/SurfaceView(17225): updateWindow -- setFrame
07-23 22:23:04.919: I/SurfaceView(17225): updateWindow -- OnPreDrawListener, mHaveFrame = true
07-23 22:23:07.744: I/View(17225): Touch down dispatch to android.widget.Button{424a2650 VFED..C. ........ 866,234-960,306 #7f090040 app:id/button_capture}, event = MotionEvent { action=ACTION_DOWN, id[0]=0, x[0]=20.077026, y[0]=9.548996, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=191289023, downTime=191289023, deviceId=3, source=0x1002 }
07-23 22:23:07.776: I/View(17225): Touch up dispatch to android.widget.Button{424a2650 VFED..C. ...P..ID 866,234-960,306 #7f090040 app:id/button_capture}, event = MotionEvent { action=ACTION_UP, id[0]=0, x[0]=21.075989, y[0]=9.548996, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=191289100, downTime=191289023, deviceId=3, source=0x1002 }
07-23 22:23:07.800: I/SurfaceView(17225): updateWindow -- OnPreDrawListener, mHaveFrame = true
07-23 22:23:09.951: W/CameraBase(17225): An error occurred while connecting to camera: 0
07-23 22:23:13.078: W/dalvikvm(17225): threadid=1: thread exiting with uncaught exception (group=0x41e25cf8)
07-23 22:23:13.078: W/dalvikvm(17225): threadid=1: uncaught exception occurred
07-23 22:23:13.088: W/System.err(17225): java.lang.NullPointerException
07-23 22:23:13.092: W/System.err(17225): at com.leo.leoscamera.CameraActivity.prepareVideoRecorder(CameraActivity.java:95)
07-23 22:23:13.095: W/System.err(17225): at com.leo.leoscamera.CameraActivity.access$5(CameraActivity.java:89)
07-23 22:23:13.097: W/System.err(17225): at com.leo.leoscamera.CameraActivity$1.onClick(CameraActivity.java:64)
07-23 22:23:13.100: W/System.err(17225): at android.view.View.performClick(View.java:4463)
07-23 22:23:13.102: W/System.err(17225): at android.view.View$PerformClick.run(View.java:18770)
07-23 22:23:13.105: W/System.err(17225): at android.os.Handler.handleCallback(Handler.java:808)
07-23 22:23:13.118: W/System.err(17225): at android.os.Handler.dispatchMessage(Handler.java:103)
07-23 22:23:13.120: W/System.err(17225): at android.os.Looper.loop(Looper.java:193)
07-23 22:23:13.123: W/System.err(17225): at android.app.ActivityThread.main(ActivityThread.java:5333)
07-23 22:23:13.125: W/System.err(17225): at java.lang.reflect.Method.invokeNative(Native Method)
07-23 22:23:13.128: W/System.err(17225): at java.lang.reflect.Method.invoke(Method.java:515)
07-23 22:23:13.130: W/System.err(17225): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
07-23 22:23:13.132: W/System.err(17225): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
07-23 22:23:13.134: W/System.err(17225): at dalvik.system.NativeStart.main(Native Method)
07-23 22:23:13.135: W/dalvikvm(17225): threadid=1: calling UncaughtExceptionHandler
07-23 22:23:13.183: E/AndroidRuntime(17225): FATAL EXCEPTION: main
07-23 22:23:13.183: E/AndroidRuntime(17225): Process: com.leo.leoscamera, PID: 17225
07-23 22:23:13.183: E/AndroidRuntime(17225): java.lang.NullPointerException
07-23 22:23:13.183: E/AndroidRuntime(17225): at com.leo.leoscamera.CameraActivity.prepareVideoRecorder(CameraActivity.java:95)
07-23 22:23:13.183: E/AndroidRuntime(17225): at com.leo.leoscamera.CameraActivity.access$5(CameraActivity.java:89)
07-23 22:23:13.183: E/AndroidRuntime(17225): at com.leo.leoscamera.CameraActivity$1.onClick(CameraActivity.java:64)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.view.View.performClick(View.java:4463)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.view.View$PerformClick.run(View.java:18770)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.os.Handler.handleCallback(Handler.java:808)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.os.Handler.dispatchMessage(Handler.java:103)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.os.Looper.loop(Looper.java:193)
07-23 22:23:13.183: E/AndroidRuntime(17225): at android.app.ActivityThread.main(ActivityThread.java:5333)
07-23 22:23:13.183: E/AndroidRuntime(17225): at java.lang.reflect.Method.invokeNative(Native Method)
07-23 22:23:13.183: E/AndroidRuntime(17225): at java.lang.reflect.Method.invoke(Method.java:515)
07-23 22:23:13.183: E/AndroidRuntime(17225): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
07-23 22:23:13.183: E/AndroidRuntime(17225): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
07-23 22:23:13.183: E/AndroidRuntime(17225): at dalvik.system.NativeStart.main(Native Method)
07-23 22:23:17.512: I/Process(17225): Sending signal. PID: 17225 SIG: 9