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Android crash on resume

I have this user camera activity in my application that works fine, but when I press the home button during the camera’s action and then return to the application, it crashes and the log code says that there was a null pointer exception when creating kind of surface. This installation method is called onResume:

public void setup() { preview = new CameraPreview(this); ((FrameLayout) findViewById(R.id.camera_preview)).addView(preview); head=(ImageView)findViewById(R.id.head); head.setX((float)(Shared.screenWidth/5*1.8)); head.setY((float)(Shared.screenHeight*0.03)); LayoutParams params = (LayoutParams) head.getLayoutParams(); params.width = (int)((Shared.screenWidth/5*3.2)-(head.getX())); params.height=(int)((Shared.screenHeight/3.8)-(head.getY())); head.setLayoutParams(params); body=(ImageView)findViewById(R.id.body); body.setX((float)(Shared.screenWidth/7)); body.setY((float)(Shared.screenHeight/3.8)); LayoutParams params2 = (LayoutParams) body.getLayoutParams(); params2.width = (int)((Shared.screenWidth/7*6)-(body.getX())); params2.height=(int)((Shared.screenHeight)-(body.getY())); body.setLayoutParams(params2); go=(Button)findViewById(R.id.go); again=(Button)findViewById(R.id.again); stop=(ImageButton)findViewById(R.id.stop); stop.setOnClickListener( new OnClickListener() { public void onClick(View v) { Intent i =new Intent(CamActivity.this,Main.class); i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(i); } }); btn = (ImageButton) findViewById(R.id.takePic); btn.setOnClickListener( new OnClickListener() { public void onClick(View v) { preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback); btn.setVisibility(View.INVISIBLE); btn.setEnabled(false); go.setVisibility(View.VISIBLE); go.setEnabled(true); head.setVisibility(View.INVISIBLE); body.setVisibility(View.INVISIBLE); go.setOnClickListener( new OnClickListener() { public void onClick(View v) { Shared.bm=Bitmap.createScaledBitmap(bmp, Shared.screenWidth, Shared.screenHeight, true); Intent i=new Intent(CamActivity.this,IKill.class); i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(i); } }); again.setVisibility(View.VISIBLE); again.setEnabled(true); again.setOnClickListener( new OnClickListener() { public void onClick(View v) { if (Build.VERSION.SDK_INT >= 11) { recreate(); } else { Intent intent = getIntent(); overridePendingTransition(0, 0); intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION); finish(); overridePendingTransition(0, 0); startActivity(intent); } } }); } }); }

In addition, in my onCreate method, I also have the following:

 requestWindowFeature(Window.FEATURE_NO_TITLE); // hide status bar final Window win = getWindow(); win.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); setContentView(R.layout.activity_camera);

and logcat:

 08-23 08:56:20.174: E/AndroidRuntime(835): FATAL EXCEPTION: main 08-23 08:56:20.174: E/AndroidRuntime(835): java.lang.NullPointerException 08-23 08:56:20.174: E/AndroidRuntime(835): at com.example.i_kill.CameraPreview.surfaceCreated(CameraPreview.java:38) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.SurfaceView.updateWindow(SurfaceView.java:569) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.SurfaceView.access$000(SurfaceView.java:86) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:174) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:680) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1842) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.Choreographer.doCallbacks(Choreographer.java:562) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.Choreographer.doFrame(Choreographer.java:532) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.os.Handler.handleCallback(Handler.java:725) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.os.Handler.dispatchMessage(Handler.java:92) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.os.Looper.loop(Looper.java:137) 08-23 08:56:20.174: E/AndroidRuntime(835): at android.app.ActivityThread.main(ActivityThread.java:5041) 08-23 08:56:20.174: E/AndroidRuntime(835): at java.lang.reflect.Method.invokeNative(Native Method) 08-23 08:56:20.174: E/AndroidRuntime(835): at java.lang.reflect.Method.invoke(Method.java:511) 08-23 08:56:20.174: E/AndroidRuntime(835): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 08-23 08:56:20.174: E/AndroidRuntime(835): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 08-23 08:56:20.174: E/AndroidRuntime(835): at dalvik.system.NativeStart.main(Native Method) 08-23 08:56:26.065: E/Trace(909): error opening trace file: No such file or directory

and here is the whole class: com.example.i_kill package;

 import android.app.Activity; import android.content.Intent; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.hardware.Camera; import android.hardware.Camera.PictureCallback; import android.hardware.Camera.ShutterCallback; import android.os.Build; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup.LayoutParams; import android.view.Window; import android.view.WindowManager; import android.widget.Button; import android.widget.FrameLayout; import android.widget.ImageButton; import android.widget.ImageView; public class CamActivity extends Activity { public static final int MEDIA_TYPE_IMAGE = 1; public static String TAG="MainActivity"; private static Camera camera; private CameraPreview preview; private ImageView head,body; private ImageButton btn, stop; private Button again,go; private Bitmap bmp; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); // hide status bar final Window win = getWindow(); win.setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); setContentView(R.layout.activity_camera); } public void setup() { preview = new CameraPreview(this); ((FrameLayout) findViewById(R.id.camera_preview)).addView(preview); head=(ImageView)findViewById(R.id.head); head.setX((float)(Shared.screenWidth/5*1.8)); head.setY((float)(Shared.screenHeight*0.03)); LayoutParams params = (LayoutParams) head.getLayoutParams(); params.width = (int)((Shared.screenWidth/5*3.2)-(head.getX())); params.height=(int)((Shared.screenHeight/3.8)-(head.getY())); head.setLayoutParams(params); body=(ImageView)findViewById(R.id.body); body.setX((float)(Shared.screenWidth/7)); body.setY((float)(Shared.screenHeight/3.8)); LayoutParams params2 = (LayoutParams) body.getLayoutParams(); params2.width = (int)((Shared.screenWidth/7*6)-(body.getX())); params2.height=(int)((Shared.screenHeight)-(body.getY())); body.setLayoutParams(params2); go=(Button)findViewById(R.id.go); again=(Button)findViewById(R.id.again); stop=(ImageButton)findViewById(R.id.stop); stop.setOnClickListener( new OnClickListener() { public void onClick(View v) { Intent i =new Intent(CamActivity.this,Main.class); i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(i); } }); btn = (ImageButton) findViewById(R.id.takePic); btn.setOnClickListener( new OnClickListener() { public void onClick(View v) { preview.camera.takePicture(shutterCallback, rawCallback, jpegCallback); btn.setVisibility(View.INVISIBLE); btn.setEnabled(false); go.setVisibility(View.VISIBLE); go.setEnabled(true); head.setVisibility(View.INVISIBLE); body.setVisibility(View.INVISIBLE); go.setOnClickListener( new OnClickListener() { public void onClick(View v) { Shared.bm=Bitmap.createScaledBitmap(bmp, Shared.screenWidth, Shared.screenHeight, true); Intent i=new Intent(CamActivity.this,IKill.class); i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(i); } }); again.setVisibility(View.VISIBLE); again.setEnabled(true); again.setOnClickListener( new OnClickListener() { public void onClick(View v) { if (Build.VERSION.SDK_INT >= 11) { recreate(); } else { Intent intent = getIntent(); overridePendingTransition(0, 0); intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION); finish(); overridePendingTransition(0, 0); startActivity(intent); } } }); } }); } ShutterCallback shutterCallback = new ShutterCallback() { public void onShutter() { Log.d(TAG, "onShutter'd"); } }; PictureCallback rawCallback = new PictureCallback() { public void onPictureTaken(byte[] data, Camera camera) { Log.d(TAG, "onPictureTaken - raw"); } }; /** Handles data for jpeg picture */ PictureCallback jpegCallback = new PictureCallback() { public void onPictureTaken(byte[] data, Camera camera) { bmp=BitmapFactory.decodeByteArray(data, 0, data.length ); System.out.println(bmp.getHeight()); System.out.println(bmp.getWidth()); }; }; public void onPause(){ super.onPause(); if(camera!=null){ camera.stopPreview(); camera.setPreviewCallback(null); camera.release(); camera = null; } } public void onResume() { super.onResume(); setup(); } }

and camera preview class:

 package com.example.i_kill; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.util.List; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.hardware.Camera; import android.hardware.Camera.PreviewCallback; import android.hardware.Camera.Size; import android.util.Log; import android.view.SurfaceHolder; import android.view.SurfaceView; public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { private SurfaceHolder holder; public Camera camera; public static String TAG="CameraPreview"; public CameraPreview(Context context) { super(context); holder=getHolder(); holder.addCallback(this); holder.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. camera = getCameraInstance(); try { camera.setPreviewDisplay(holder); camera.setPreviewCallback(new PreviewCallback() { public void onPreviewFrame(byte[] data, Camera arg1) { FileOutputStream outStream = null; try { outStream = new FileOutputStream(String.format("/sdcard/%d.jpg", System.currentTimeMillis())); outStream.write(data); outStream.close(); Log.d(TAG, "onPreviewFrame - wrote bytes: " + data.length); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { } CameraPreview.this.invalidate(); } }); } catch (IOException e) { e.printStackTrace(); } } public void surfaceDestroyed(SurfaceHolder holder) { if(camera!=null){ camera.stopPreview(); camera.setPreviewCallback(null); camera.release(); camera = null; } } public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { Camera.Parameters parameters = camera.getParameters(); List<Size> previewSizes = parameters.getSupportedPreviewSizes(); Size bestSize = null; int bestDiff = 0; int diff = 0; for (Size size : previewSizes) { diff = Math.abs(h - size.height) + Math.abs(w - size.width); if (bestSize == null || diff < bestDiff) { bestSize = size; bestDiff = diff; } parameters.setPreviewSize(bestSize.width, bestSize.height); camera.setParameters(parameters); } //start preview of camera camera.startPreview(); } @Override public void draw(Canvas canvas) { super.draw(canvas); Paint p= new Paint(Color.RED); Log.d(TAG,"draw"); canvas.drawText("PREVIEW", canvas.getWidth()/2, canvas.getHeight()/2, p ); } private 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 } }

Thanks for your help:)

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3 answers

I solved this by calling setContentView in the summary. Thanks everyone!

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This is my decision.

 public void onResume(){ super.onResume(); if(mCamera ==null){ setContentView(R.layout.activity_capture_local_plates); autoFocusHandler = new Handler(); mCamera = getCameraInstance(); mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB); FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview); preview.addView(mPreview); } }
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Should I call getHolder () on the surfaceCreated method? Found below in the documentation :

Access to the underlying surface is via the SurfaceHolder interface, which can be obtained by calling getHolder ().

A surface will be created for you, while a SurfaceView window is visible; you must implement surfaceCreated (SurfaceHolder) and surfaceDestroyed (SurfaceHolder) to detect when a surface is created and destroyed when a window is displayed and hidden.

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Source: https://habr.com/ru/post/1498558/

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