目前我正在使用Google Mobile Vision API進行人臉檢測。假設在屏幕旋轉後，活動將重新啓動，所有變量將重新初始化。但是，我知道爲什麼該應用程序停止工作並顯示NullPointerException。這是我的代碼。Android應用在屏幕旋轉後停止工作
public class MainActivity extends AppCompatActivity {
private ImageView mIvDetected;
private Bitmap mImage;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mIvDetected = (ImageView) findViewById(R.id.iv_detected);
//Load an image
BitmapFactory.Options opts = new BitmapFactory.Options();
opts.inMutable = true;
mImage = BitmapFactory.decodeResource(getResources(), R.drawable.face2);
//Configure FaceDetector
FaceDetector detector = new FaceDetector.Builder(this)
.setMode(FaceDetector.ACCURATE_MODE)
.setLandmarkType(FaceDetector.ALL_LANDMARKS)
.setClassificationType(FaceDetector.ALL_CLASSIFICATIONS)
.setTrackingEnabled(false)
.build();
if(false == detector.isOperational()){
Toast.makeText(this, "Face detection service is not ready", Toast.LENGTH_SHORT).show();
return;
}
//Add the image on a Frame object
Frame frame = new Frame.Builder().setBitmap(mImage).build();
//Detect all faces from Frame object
SparseArray<Face> faceArray = detector.detect(frame);
//Do some drawing on faces
**Bitmap outBitmap = drawOnFace(faceArray);**
mIvDetected.setImageBitmap(outBitmap);
//Releasing the detector object
detector.release();
}
/** Method to do some drawing on faces */
private Bitmap drawOnFace(SparseArray<Face> faceArray){
Paint mIdPaint = new Paint();
mIdPaint.setColor(Color.RED);
mIdPaint.setTextSize(40.f);
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(5);
paint.setStyle(Paint.Style.STROKE);
Paint mTextPaint = new Paint();
mTextPaint.setAntiAlias(true);
mTextPaint.setDither(true);
mTextPaint.setTextSize(20);
mTextPaint.setColor(Color.GREEN);
mTextPaint.setStyle(Paint.Style.FILL);
// Create a blank bitmap same size with the source image
Bitmap outBitmap = Bitmap.createBitmap(mImage.getWidth(), mImage.getHeight(), Bitmap.Config.RGB_565);
// Put the bitmap on canvas for drawing
Canvas canvas = new Canvas(outBitmap);
canvas.drawBitmap(mImage, 0, 0, null);
for(int i=0; i < faceArray.size(); i++){
Face face = faceArray.get(i);
//Drawing rectangle on each face
**drawRectangle(canvas, face.getPosition(), face.getWidth(), face.getHeight());**
//Drawing a point on each face features
for(Landmark landmark : face.getLandmarks()) {
switch (landmark.getType()){
case Landmark.LEFT_EYE:
drawPoint(canvas, landmark.getPosition());
canvas.drawText("Left eye: " + face.getIsLeftEyeOpenProbability(), landmark.getPosition().x, landmark.getPosition().y - 30, mTextPaint);
break;
case Landmark.RIGHT_EYE:
drawPoint(canvas, landmark.getPosition());
canvas.drawText("Right eye: " + face.getIsRightEyeOpenProbability(), landmark.getPosition().x, landmark.getPosition().y - 30, mTextPaint);
break;
case Landmark.BOTTOM_MOUTH:
drawPoint(canvas, landmark.getPosition());
canvas.drawText("Smile: " + face.getIsSmilingProbability(), landmark.getPosition().x, landmark.getPosition().y + 40, mTextPaint);
break;
case Landmark.LEFT_MOUTH:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.RIGHT_MOUTH:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.NOSE_BASE:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.LEFT_CHEEK:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.RIGHT_CHEEK:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.LEFT_EAR:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.LEFT_EAR_TIP:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.RIGHT_EAR:
drawPoint(canvas, landmark.getPosition());
break;
case Landmark.RIGHT_EAR_TIP:
drawPoint(canvas, landmark.getPosition());
break;
}
}
/** Other useful details that may be of your interest */
Log.d("", "FaceDetection- FaceId:" + face.getId()
+ " Smiling:" + face.getIsSmilingProbability()
+ " LeftEyeOpen:" + face.getIsLeftEyeOpenProbability()
+ " RightEyeOpen:" + face.getIsRightEyeOpenProbability());
}
return outBitmap;
}
/** This method draws a rectangle */
private void drawRectangle(Canvas canvas, PointF point, float width, float height){
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(5);
paint.setStyle(Paint.Style.STROKE);
float x1 = point.x;
float y1 = point.y;
float x2 = x1 + width;
float y2 = y1 + height;
RectF rect = new RectF(x1, y1, x2, y2);
canvas.drawRect(rect, paint);
}
/** This method draws a point with hole */
private void drawPoint(Canvas canvas, PointF point){
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(48);
paint.setStyle(Paint.Style.STROKE);
float x = point.x;
float y = point.y;
canvas.drawCircle(x, y, 1, paint);
}
}
這是我的錯誤。
12月4日至24日：59：50.231 2865年至2865年/ com.example.andy318.cameraone E/AndroidRuntime：致命異常：主 工藝：com.example.andy318.cameraone，PID：2865 的java。 lang.RuntimeException：無法恢復活動{com.example.andy318.cameraone/com.example.andy318.cameraone.MainActivity}：java.lang.NullPointerException：嘗試調用虛擬方法'android.graphics.PointF com.google.android （ActivityThread.java:3134）上的空對象引用 上的.gms.vision.face.Face.getPosition（）'在android.app.ActivityThread.performResumeActivity（ActivityThread.java:3103） 上的空對象引用 （android.app.ActivityThread.handleResumeActivity）在android.app.ActivityThread.-wrap15（ActivityThread.java）上的android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2481） .app.ActivityThread $ H.handleMessage（ActivityThread.java:1350） at android.os.Handler.dispatchMessage（Handler.java:102） at android.os.Looper.loop（Looper.java:148） at android .app.ActivityThread.main（ActivityThread.java:5417） at java.lang.reflect.Method.invoke（Native Method） at com.android.internal.os.ZygoteInit $ Method AndArgsCaller.run（ZygoteInit.java:726） at com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616） 引起：java.lang.NullPointerException：嘗試調用虛擬方法'android.graphics。 PointF com.google.android.gms.vision.face.Face.getPosition（）'位於空對象引用 處com.example.andy318.cameraone.MainActivity.drawOnFace（MainActivity.java:106） at com.example。 andy318.cameraone.MainActivity.onResume（MainActivity.java:69） 在android.app.Instrumentation.callActivityOnResume（Instrumentation.java:1258） 在android.app.Activity.performResume（Activity.java:6312） 在機器人。 app.ActivityThread.performResumeActivity（ACTI （ActivityThread.java:9280） at android.app.ActivityThread.handleResumeActivity（ActivityThread.java:3134） java：4077） at android.app.ActivityThread.-wrap15（ActivityThread.java） at android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1350） at android.os.Handler.dispatchMessage（Handler.java ：102） at android.os.Looper.loop（Looper.java:148） at android.app.ActivityThread.main（ActivityThread.java:5417） at java.lang.reflect.Method.invoke（Native Method） at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726） at com.android.internal.os.ZygoteInit.main （ZygoteInit。的java：616）
錯誤發生在
位圖outBitmap = drawOnFace（faceArray）;
和
的DrawRectangle（帆布，face.getPosition（），face.getWidth（），face.getHeight（））;
我把**放在編碼中。
我知道我的錯誤在哪裏，但我知道如何解決它。屏幕旋轉後，SparseArray faceArray具有空值。我試圖使用如果檢查空條件，但它不會顯示檢測。 （只顯示原圖）
的可能的複製[什麼是空指針異常，並且我怎麼修復它？]（http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it） –
你只得到的關鍵，而不是對象：http://stackoverflow.com/a/8006994/6247492 – user6247492