我无法理解破坏应用程序的logcat。 （我是一个初学者，我的应用程序只拍了一张照片，然后将其保存在一个特定的文件夹中，但当我按下应该允许我拍照的按钮时，它崩溃了，我得到了着名的消息（MY_APP_Name没有响应）
这是MySurfaceView.java中的代码
package android.cam_bouton_save;
private SurfaceHolder holder;
private Camera camera;
public MySurfaceView(Context context, Camera camera)
{
super(context);
this.camera = camera;
holder = getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceChanged(SurfaceHolder holder,
int format, int weight, int height)
{
if (holder.getSurface() == null)
return;
try
{
camera.stopPreview();
camera.setPreviewDisplay(holder);
camera.startPreview();
}
catch (Exception e){}
}
public void surfaceCreated(SurfaceHolder holder)
{
try
{
camera.setPreviewDisplay(holder);
camera.startPreview();
}
catch (IOException e){}
}
public void surfaceDestroyed(SurfaceHolder holder){}
}
这是日志猫：
05-14 17:15:04.216: E/AndroidRuntime(1123): FATAL EXCEPTION: main
05-14 17:15:04.216: E/AndroidRuntime(1123): java.lang.NullPointerException
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.cam_bouton_save.MySurfaceView.surfaceCreated(MySurfaceView.java:42)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.SurfaceView.updateWindow(SurfaceView.java:532)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.SurfaceView.dispatchDraw(SurfaceView.java:339)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.View.draw(View.java:6743)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.widget.FrameLayout.draw(FrameLayout.java:352)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.drawChild(ViewGroup.java:1640)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.drawChild(ViewGroup.java:1638)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewGroup.dispatchDraw(ViewGroup.java:1367)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.View.draw(View.java:6743)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.widget.FrameLayout.draw(FrameLayout.java:352)
05-14 17:15:04.216: E/AndroidRuntime(1123): at com.android.internal.policy.impl.PhoneWindow$DecorView.draw(PhoneWindow.java:1842)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewRoot.draw(ViewRoot.java:1407)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewRoot.performTraversals(ViewRoot.java:1163)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.os.Handler.dispatchMessage(Handler.java:99)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.os.Looper.loop(Looper.java:123)
05-14 17:15:04.216: E/AndroidRuntime(1123): at android.app.ActivityThread.main(ActivityThread.java:4627)
05-14 17:15:04.216: E/AndroidRuntime(1123): at java.lang.reflect.Method.invokeNative(Native Method)
05-14 17:15:04.216: E/AndroidRuntime(1123): at java.lang.reflect.Method.invoke(Method.java:521)
05-14 17:15:04.216: E/AndroidRuntime(1123): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-14 17:15:04.216: E/AndroidRuntime(1123): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-14 17:15:04.216: E/AndroidRuntime(1123): at dalvik.system.NativeStart.main(Native Method)
package android.cam_bouton_save;
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.main);
Button bouton = (Button) findViewById(R.id.btn_photo);
// camera = Camera.open();
mySurfaceView = new MySurfaceView(this, camera);
final FrameLayout myPreview = (FrameLayout) findViewById(R.id.preview);
myPreview.addView(mySurfaceView);
bouton.setOnClickListener(new View.OnClickListener() {
// @Override
public void onClick(View actuelView) {
/* //camera.open();
// camera.getParameters();*/
camera = Camera.open();
/* camera = Camera.open();
Parameters parameters = camera.getParameters();
parameters.setPictureFormat(PixelFormat.JPEG);
camera.setParameters(parameters);
// camera.setPreviewDisplay(surfaceHolder);
camera.startPreview();*/
camera.takePicture(shutterCallback, rawCallback, myPictureCallback_JPG);
}
});
}
// Called when shutter is opened
ShutterCallback shutterCallback = new ShutterCallback() {
public void onShutter() {
//Log.d(TAG, "onShutter'd");
}
};
PictureCallback rawCallback = new PictureCallback() {
public void onPictureTaken(byte[] data, Camera camera) {
}
};
PictureCallback myPictureCallback_JPG = new PictureCallback(){
public void onPictureTaken(byte[] arg0, Camera arg1) {
int imageNum = 0;
Intent imageIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
//Gets the Android external storage directory
File imagesFolder = new File(Environment.getExternalStorageDirectory(), "Punch");
imagesFolder.mkdirs(); // <----
String fileName = "image_" + String.valueOf(imageNum) + ".jpg";
File output = new File(imagesFolder, fileName);
while (output.exists()){
imageNum++;
fileName = "image_" + String.valueOf(imageNum) + ".jpg";
output = new File(imagesFolder, fileName);
}
Uri uriSavedImage = Uri.fromFile(output);
imageIntent.putExtra(MediaStore.EXTRA_OUTPUT, uriSavedImage);
OutputStream imageFileOS;
try {
imageFileOS = getContentResolver().openOutputStream(uriSavedImage);
imageFileOS.write(arg0);
imageFileOS.flush();
imageFileOS.close();
Toast.makeText(Cam_bouton_save_picActivity.this,
"Image saved: ",
Toast.LENGTH_LONG).show();
camera.release() ;
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// camera.startPreview();
}};
}
答案 0 :(得分：1)
您的LogCat表示您在NullPointerException方法内的活动类第36行获得onClick：m Cam_bouton_save_picActivity.java:36。
只是一个猜测，但也许您的Camera实例为空。这种情况最常发生的原因是androidManifest.xml中缺少权限，因此请确保您已将其包含在内：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
另请注意，如果您要将拍摄的照片保存到SD卡，您还需要获得其他许可：
<uses-permission android:name="android.permission.CAMERA" />
编辑1 ：尝试代码！
现在很明显，您需要初始化camera成员！在没有初始化的情况下，这是以NullPointerException结束的弱点。
在onCreate方法中，你应该有这一行：
camera = Camera.open();
如果操作正确，您将无法再获得NPE。
编辑2 ：对于相机预览： - 已删除 -
编辑3 ： 请 - 以后 - 如果您遇到新问题并需要帮助，请提出新问题，而不是修改现有问题。这个答案已经与你原来的问题无关。
请记住，StackOverflow是针对特定问题的答案，而不是解决特定人员的所有问题。
这是一个小型且非常集中的示例应用程序，它展示了如何连续拍摄相机并将其保存在SD卡上：
public class AndroidCamera extends Activity implements
SurfaceHolder.Callback, View.OnClickListener
{
private static final String TAG = "CS";
private Camera camera;
private SurfaceView surface;
private SurfaceHolder holder;
private boolean isPreview = false;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
surface = (SurfaceView) findViewById(R.id.preview);
holder = surface.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
final Button shotButton = (Button) findViewById(R.id.btn_shot);
shotButton.setOnClickListener(this);
}
@Override
public void onClick(View v)
{
camera.takePicture(shutterCallback, rawCallback, jpgCallback);
}
ShutterCallback shutterCallback = new ShutterCallback()
{
@Override
public void onShutter()
{}
};
PictureCallback rawCallback = new PictureCallback()
{
@Override
public void onPictureTaken(byte[] arg0, Camera arg1)
{}
};
PictureCallback jpgCallback = new PictureCallback()
{
@Override
public void onPictureTaken(byte[] arg0, Camera arg1)
{
if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState()))
{
final String imageDir =
Environment.getExternalStorageDirectory() +
File.separator + "Punch" + File.separator;
int counter = 0;
String imageName = "image_" + counter + ".jpg";
File outputFile = new File(imageDir, imageName);
if (!outputFile.getParentFile().exists())
outputFile.getParentFile().mkdirs();
while (outputFile.exists())
{
counter++;
imageName = "image_" + counter + ".jpg";
outputFile = new File(imageDir, imageName);
}
Uri uriSavedImage = Uri.fromFile(outputFile);
OutputStream imageFileOS;
try
{
imageFileOS = getContentResolver().openOutputStream(uriSavedImage);
imageFileOS.write(arg0);
imageFileOS.flush();
imageFileOS.close();
Log.w(TAG, "Image saved: " + uriSavedImage.toString());
camera.startPreview();
}
catch (FileNotFoundException e)
{
Log.e(TAG, "onPictureTaken", e);
}
catch (IOException e)
{
Log.e(TAG, "onPictureTaken", e);
}
}
}
};
@Override
public void surfaceChanged(SurfaceHolder sHolder, int format, int width, int height)
{
if (isPreview)
{
try
{
camera.stopPreview();
isPreview = false;
}
catch (Exception e)
{
Log.e(TAG, "surfaceChanged", e);
}
}
if (camera != null)
{
try
{
camera.setPreviewDisplay(holder);
camera.startPreview();
isPreview = true;
}
catch (IOException e)
{
Log.e(TAG, "surfaceChanged", e);
releaseCamera();
}
}
}
@Override
public void surfaceCreated(SurfaceHolder holder)
{
try
{
camera = Camera.open();
}
catch (Exception e)
{
Log.e(TAG, "surfaceCreated Camera.open()", e);
releaseCamera();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder)
{
releaseCamera();
}
private void releaseCamera()
{
try
{
camera.stopPreview();
camera.release();
camera = null;
isPreview = false;
}
catch (Exception e)
{
Log.e(TAG, "releaseCamera", e);
}
}
}
为此，您只需要一个非常简单的布局（ main.xml ）：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<SurfaceView android:id="@+id/preview"
android:layout_width="fill_parent" android:layout_height="wrap_content"/>
<Button android:id="@+id/btn_shot" android:text="Shot!"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentBottom="true" />
</RelativeLayout>
我希望它足够清楚：）