我正在开发一个定制的相机应用程序。当应用程序启动相机打开时，底部有三个按钮。
- 捕获（拍照）。
- 拍摄新照片（从预览返回相机以再次拍照。）
- 不用于任何事情。
一切正常。按抓图拍照并准确预览所拍照片。但是当我按下新按钮从预览模式进入相机模式时，应用程序崩溃不知道我做错了什么。以下是我正在使用的代码。
public class MainActivity extends Activity {
protected static final String TAG = null;
private Camera mCamera;
private CameraPreview mPreview;
public static final int MEDIA_TYPE_IMAGE = 1;
static int result;
static int degrees = 90;
private Button captureButton, btn_new;
public FrameLayout preview;
private static File mediaFile;
@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);
preview.addView(mPreview);
captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
// get an image from the camera
mCamera.takePicture(null, null, mPicture);
}
}
);
btn_new = (Button) findViewById(R.id.button_new);
btn_new.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mCamera = getCameraInstance();
//preview = (FrameLayout) findViewById(R.id.camera_preview);
//preview.addView(mPreview);
}
});
}
private PictureCallback mPicture = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
if (pictureFile == null){
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_DCIM), "Camera");
// 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());
if (type == MEDIA_TYPE_IMAGE){
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"IMG_"+ timeStamp + ".jpg");
}
else {
return null;
}
return mediaFile;
}
@SuppressWarnings("null")
public static Camera getCameraInstance(){
Camera c = null;
Context context = null;
try{
c = Camera.open();
//setCameraDisplayOrientation(MainActivity, 0, c);
c.setDisplayOrientation(degrees);
}
catch (Exception e) {
Toast.makeText(context.getApplicationContext(),"Camera is not available" , Toast.LENGTH_LONG).show();
}
return c;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
提前致谢。最后这是我的错误日志：
02-21 18:24:01.868: E/AndroidRuntime(937): 致命异常: main 02-21 18:24:01.868: E/AndroidRuntime(937): java.lang.NullPointerException 02-21 18:24:01.868: E/AndroidRuntime(937): 在 com.example.facebooktag.MainActivity.getCameraInstance(MainActivity.java:136) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 com.example.facebooktag.MainActivity$3。 onClick(MainActivity.java:66) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 android.view.View.performClick(View.java:4202) 02-21 18:24:01.868: E/ AndroidRuntime(937): 在 android.view.View$PerformClick.run(View.java:17340) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 android.os.Handler.handleCallback(Handler.java :725) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 android.os.Handler.dispatchMessage(Handler.java:92) 02-21 18:24:01.868: E/AndroidRuntime(937):在 android.os.Looper.loop(Looper.java:137) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 android.app.ActivityThread.main(ActivityThread.java:5039) 02-21 18:24:01.868: E/AndroidRuntime(937): 在java.lang.reflect.Method.invokeNative(Native Method) 02-21 18:24:01.868: E/AndroidRuntime(937): at java.lang.reflect.Method.invoke(Method.java:511) 02-21 18 :24:01.868: E/AndroidRuntime(937): 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 02-21 18:24:01.868: E/AndroidRuntime(937): 在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 02-21 18:24:01.868: E/AndroidRuntime(937): at dalvik.system.NativeStart.main(Native Method)E/AndroidRuntime(937): 在 java.lang.reflect.Method.invoke(Method.java:511) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 com.android.internal.os.ZygoteInit $MethodAndArgsCaller.run(ZygoteInit.java:793) 02-21 18:24:01.868: E/AndroidRuntime(937): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 02-21 18 ：24：01.868：E / AndroidRuntime（937）：在dalvik.system.NativeStart.main（本机方法）E/AndroidRuntime(937): 在 java.lang.reflect.Method.invoke(Method.java:511) 02-21 18:24:01.868: E/AndroidRuntime(937): 在 com.android.internal.os.ZygoteInit $MethodAndArgsCaller.run(ZygoteInit.java:793) 02-21 18:24:01.868: E/AndroidRuntime(937): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 02-21 18 ：24：01.868：E / AndroidRuntime（937）：在dalvik.system.NativeStart.main（本机方法）