我正在尝试制作自定义相机应用，但每当我运行我的程序时，
获取 -
不幸的是，App已停止
logcat的：
05-30 14:47:09.844: D/CameraCaptureActivity(797): getCameraInstance()Camera:: null
05-30 14:47:09.855: D/CameraCaptureActivity(797): getCameraInstance()open:: null
05-30 14:47:09.855: D/CameraCaptureActivity(797): mCamera:: null
05-30 14:47:09.895: D/CameraCaptureActivity(797): mCamera :: null
05-30 14:47:09.895: D/CameraCaptureActivity(797): mSurfaceHolder :: android.view.SurfaceView$4@40d06ef8
05-30 14:47:09.924: D/CameraCaptureActivity(797): mCameraPreview :: com.example.demo.CameraPreview{40d06860 V.E..... ......I. 0,0-0,0}
05-30 14:47:09.924: D/CameraCaptureActivity(797): FrameLayout :: android.widget.FrameLayout{40cfa7d8 V.E..... ......I. 0,0-0,0 #7f080000 app:id/camera_preview}
05-30 14:47:09.954: D/CameraCaptureActivity(797): captureButton :: android.widget.Button{40cfad50 VFED..C. ......I. 0,0-0,0 #7f080001 app:id/button_capture}
05-30 14:47:04.327: D/AndroidRuntime(797): Shutting down VM
05-30 14:47:04.327: W/dalvikvm(797): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
05-30 14:47:04.458: E/AndroidRuntime(797): FATAL EXCEPTION: main
05-30 14:47:04.458: E/AndroidRuntime(797): java.lang.NullPointerException
05-30 14:47:04.458: E/AndroidRuntime(797): at com.example.demo.CameraPreview.surfaceCreated(CameraPreview.java:33)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.SurfaceView.updateWindow(SurfaceView.java:569)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.SurfaceView.access$000(SurfaceView.java:86)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:174)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:680)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1842)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.Choreographer.doFrame(Choreographer.java:532)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.os.Handler.handleCallback(Handler.java:725)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.os.Handler.dispatchMessage(Handler.java:92)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.os.Looper.loop(Looper.java:137)
05-30 14:47:04.458: E/AndroidRuntime(797): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-30 14:47:04.458: E/AndroidRuntime(797): at java.lang.reflect.Method.invokeNative(Native Method)
05-30 14:47:04.458: E/AndroidRuntime(797): at java.lang.reflect.Method.invoke(Method.java:511)
05-30 14:47:04.458: E/AndroidRuntime(797): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-30 14:47:04.458: E/AndroidRuntime(797): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-30 14:47:04.458: E/AndroidRuntime(797): at dalvik.system.NativeStart.main(Native Method)
错误：
java.lang.NullPointerException
行：
mCamera.setPreviewDisplay(surfaceHolder);
CameraPreview.java：
public class CameraPreview extends SurfaceView implements
SurfaceHolder.Callback {
public static final String LOG_TAG = "CameraPreview";
private SurfaceHolder mSurfaceHolder;
private Camera mCamera;
// Constructor that obtains context and camera
@SuppressWarnings("deprecation")
public CameraPreview(Context context, Camera camera) {
super(context);
this.mCamera = camera;
Log.d(CameraCaptureActivity.LOG_TAG, "mCamera :: " +mCamera);
this.mSurfaceHolder = this.getHolder();
this.mSurfaceHolder.addCallback(this);
this.mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
Log.d(CameraCaptureActivity.LOG_TAG, "mSurfaceHolder :: " +mSurfaceHolder);
}
@Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
try {
mCamera.setPreviewDisplay(surfaceHolder);
Log.d(CameraCaptureActivity.LOG_TAG, "surfaceCreated (setPreview) :: " +mCamera);
mCamera.startPreview();
Log.d(CameraCaptureActivity.LOG_TAG, "surfaceCreated (startPreview) :: " +mCamera);
} catch (IOException e) {
// left blank for now
}
}
@Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
mCamera.stopPreview();
Log.d(CameraCaptureActivity.LOG_TAG, "surfaceDestroyed (stopPreview) :: " +mCamera);
mCamera.release();
}
@Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int format,
int width, int height) {
// start preview with new settings
try {
mCamera.setPreviewDisplay(surfaceHolder);
mCamera.startPreview();
} catch (Exception e) {
// intentionally left blank for a test
}
}
}
CameraCaptureActivity.java：
public static final String LOG_TAG = "CameraCaptureActivity";
private Camera mCamera;
private CameraPreview mCameraPreview;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mCamera = getCameraInstance();
Log.d(CameraCaptureActivity.LOG_TAG, "mCamera:: " + mCamera);
mCameraPreview = new CameraPreview(this, mCamera);
Log.d(CameraCaptureActivity.LOG_TAG, "mCameraPreview :: " + mCameraPreview);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mCameraPreview);
Log.d(CameraCaptureActivity.LOG_TAG, "FrameLayout :: " + preview);
Button captureButton = (Button) findViewById(R.id.button_capture);
Log.d(CameraCaptureActivity.LOG_TAG, "captureButton :: " + captureButton);
captureButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCamera.takePicture(null, null, mPicture);
Log.d(CameraCaptureActivity.LOG_TAG, "mCamera.takePicture :: " + mCamera);
}
});
}
/**
* Helper method to access the camera returns null if it cannot get the
* camera or does not exist
*
* @return
*/
private Camera getCameraInstance() {
Camera camera = null;
Log.d(CameraCaptureActivity.LOG_TAG, "getCameraInstance()Camera:: " + camera);
try {
camera = Camera.open();
Log.d(CameraCaptureActivity.LOG_TAG, "getCameraInstance()open:: " + camera);
} catch (Exception e) {
// cannot get camera or does not exist
}
return camera;
}
PictureCallback mPicture = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
File pictureFile = getOutputMediaFile();
if (pictureFile == null) {
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
} catch (IOException e) {
}
}
};
private static File getOutputMediaFile() {
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
"MyCameraApp");
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;
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
return mediaFile;
}
}
答案 0 :(得分：14)
此处mCamera返回null。这是由于相机初始化不当造成的。
使用Camera.open();对其进行初始化。还要检查初始化过程中抛出的任何异常。还要确保您在清单文件中具有所有必要的权限
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-feature android:name="android.hardware.camera" />
try {
camera = Camera.open();
Log.d(CameraCaptureActivity.LOG_TAG, "getCameraInstance()open:: " + camera);
} catch (Exception e) {
// Check here for any exceptions
}
答案 1 :(得分：0)
请看下面的答案。
Custom_CameraActivity.java
public class Custom_CameraActivity extends Activity { private Camera mCamera; private CameraPreview mCameraPreview; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mCamera = getCameraInstance(); mCameraPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mCameraPreview); Button captureButton = (Button) findViewById(R.id.button_capture); captureButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { mCamera.takePicture(null, null, mPicture); } }); } /** * Helper method to access the camera returns null if it cannot get the * camera or does not exist * * @return */ private Camera getCameraInstance() { Camera camera = null; try { camera = Camera.open(); } catch (Exception e) { // cannot get camera or does not exist } return camera; } PictureCallback mPicture = new PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { File pictureFile = getOutputMediaFile(); if (pictureFile == null) { return; } try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (FileNotFoundException e) { } catch (IOException e) { } } }; private static File getOutputMediaFile() { File mediaStorageDir = new File( Environment .getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "MyCameraApp"); 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; mediaFile = new File(mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp + ".jpg"); return mediaFile; } }
CameraPreview.java
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { private SurfaceHolder mSurfaceHolder; private Camera mCamera; // Constructor that obtains context and camera @SuppressWarnings("deprecation") public CameraPreview(Context context, Camera camera) { super(context); this.mCamera = camera; this.mSurfaceHolder = this.getHolder(); this.mSurfaceHolder.addCallback(this); this.mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } @Override public void surfaceCreated(SurfaceHolder surfaceHolder) { try { mCamera.setPreviewDisplay(surfaceHolder); mCamera.startPreview(); } catch (IOException e) { // left blank for now } } @Override public void surfaceDestroyed(SurfaceHolder surfaceHolder) { mCamera.stopPreview(); mCamera.release(); } @Override public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) { // start preview with new settings try { mCamera.setPreviewDisplay(surfaceHolder); mCamera.startPreview(); } catch (Exception e) { // intentionally left blank for a test } } }
main.xml中
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal" > <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:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:text="Capture" /> </LinearLayout>
将以下行添加到androidmanifest.xml文件
<uses-feature android:name="android.hardware.camera" /> <uses-permission android:name="android.permission.CAMERA" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />