Démarrage d'une 3ème activité Configuration d'interfaces et d'écouteurs

Question

Mon MainActivity a donc pu démarrer ma deuxième activité à partir d'un clic btn. maintenant sur ma deuxième activité, j'ai un glisser-déposer jeu de type où ce que je veux est l'un a été abandonné l'image correcte, je veux commencer une 3ème activité mais je reçois un java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference

Ceci est mon code de mon principal qui commence la 2ème activité. Cela fonctionne bien.

public void onClickadjectives(View v4) { 

MainActivitytest.this.startActivity(new Intent(MainActivitytest.this, DragActivityV2.class)); 
} 

maintenant sur la deuxième classe, j'ai une classe helper qui détermine le point de chute correct

public class DropSpot extends MyAbsoluteLayout 
implements DropTarget, DragController.DragListener 
{ // codes... 
if (controller != null) { 
    controller.setDragListener (this); 
    controller.addDropTarget (this); 
    System.out.println("Correct Spot"); 

    DragActivityV2 ca = new DragActivityV2(); 
    ca.correctAns(); 

} 

Et maintenant c'est ma deuxième activité

public class DragActivityV2 extends Activity 
      implements View.OnLongClickListener, View.OnClickListener, View.OnTouchListener 
    {  //more codes... 
    public void correctAns() 

     { 
      Context context; 
      Intent intent = new Intent(this, FallAnimationActivity.class); 
      DragActivityV2.this.startActivity(intent); 
      finish(); 
     } 

quand je le lance, il se bloque quand je clique sur le btn pour aller à ma deuxième activité. Ceci est l'erreur

E/AndroidRuntime: FATAL EXCEPTION: main 
        Process: info.androidhive.tabsswipe, PID: 4141 
        java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.tabsswipe/info.androidhive.tabsswipe.dragview.DragActivityV2}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 
         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) 
         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
         at android.app.ActivityThread.-wrap12(ActivityThread.java) 
         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
         at android.os.Handler.dispatchMessage(Handler.java:102) 
         at android.os.Looper.loop(Looper.java:154) 
         at android.app.ActivityThread.main(ActivityThread.java:6119) 
         at java.lang.reflect.Method.invoke(Native Method) 
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
        Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 
         at android.content.ContextWrapper.getPackageName(ContextWrapper.java:132) 
         at android.content.ComponentName.<init>(ComponentName.java:128) 
         at android.content.Intent.<init>(Intent.java:4900) 
         at info.androidhive.tabsswipe.dragview.DragActivityV2.correctAns(DragActivityV2.java:548) 
         at info.androidhive.tabsswipe.dragview.DropSpot.setup(DropSpot.java:346) 
         at info.androidhive.tabsswipe.dragview.DragActivityV2.setupViews(DragActivityV2.java:456) 
         at info.androidhive.tabsswipe.dragview.DragActivityV2.onCreate(DragActivityV2.java:104) 
         at android.app.Activity.performCreate(Activity.java:6679) 
         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) 
         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
         at android.app.ActivityThread.-wrap12(ActivityThread.java)  
         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
         at android.os.Handler.dispatchMessage(Handler.java:102)  
         at android.os.Looper.loop(Looper.java:154)  
         at android.app.ActivityThread.main(ActivityThread.java:6119)  
         at java.lang.reflect.Method.invoke(Native Method)  
         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)  
Application terminated. 

Maintenant, si je retire l'appel de la méthode et de mettre simplement sur un bouton, il fonctionne très bien. Mais je veux vraiment que ça passe à la 3ème activité SEULEMENT si le bon img a été abandonné.

Quelqu'un peut-il s'il vous plaît m'aider à vous remercier tellement à l'avance.

EDIT j'ai ajouté la plupart de mes 2e codes d'activité ...

public class DragActivityV2 extends Activity 
     implements View.OnLongClickListener, View.OnClickListener, View.OnTouchListener 

// Constants 

    private static final int ENABLE_S2_MENU_ID = Menu.FIRST; 
    private static final int DISABLE_S2_MENU_ID = Menu.FIRST + 1; 
    private static final int ADD_OBJECT_MENU_ID = Menu.FIRST + 2; 
    private static final int CHANGE_TOUCH_MODE_MENU_ID = Menu.FIRST + 3; 

    public int ind = 0; 
    public String[] myShuffledArray; 
    public String[] quesDescription; 
    public Context context; 
    public MyDBEmbrASD db; 
    public String selectedImg; 
    public int dmw; 
    public int dmh; 

    /** 
    */ 
// Variables 

    private DragController mDragController; // Object that sends out drag-drop events while a view is being moved. 
    private DragLayer mDragLayer;    // The ViewGroup that supports drag-drop. 
    private DropSpot mSpot2;     // The DropSpot that can be turned on and off via the menu. 

    private boolean mLongClickStartsDrag = false; // If true, it takes a long click to start the drag operation. 
    public boolean showbutton = false; 
    // Otherwise, any touch event starts a drag. 


    public static final boolean Debugging = false; 
    private DragController controller; 

    @Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) 
    { 
     super.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 
     super.onCreate(savedInstanceState); 
     mDragController = new DragController(this); 

     setContentView(R.layout.main); 
     setupViews(); 
    } 

public boolean onTouch (View v, MotionEvent ev) 
{ 
    // If we are configured to start only on a long click, we are not going to handle any events here. 
    if (mLongClickStartsDrag) return false; 

    boolean handledHere = false; 

    final int action = ev.getAction(); 

    // In the situation where a long click is not needed to initiate a drag, simply start on the down event. 
    if (action == MotionEvent.ACTION_DOWN) { 
     handledHere = startDrag (v); 


     System.out.println("value of selectedTag ID " + v.getTag()); 
     System.out.println("value of corrAns " + selectedImg); 
     if (v.getTag() != selectedImg) 
     { 
      mSpot2.setDragLayer(null); 
     } 
     else 
     { 
      mSpot2.setDragLayer(mDragLayer); 
      System.out.println("Correct Answer!"); 

     } 

    } 
    return handledHere; 
} 

/** 
* Start dragging a view. 
* 
*/ 

public boolean startDrag (View v) 
{ 
    // Let the DragController initiate a drag-drop sequence. 
    // I use the dragInfo to pass along the object being dragged. 
    // I'm not sure how the Launcher designers do this. 
    Object dragInfo = v; 
    mDragController.startDrag (v, mDragLayer, dragInfo, DragController.DRAG_ACTION_MOVE); 
    return true; 
} 


public boolean onTouch (View v, MotionEvent ev) 
{ 
    // If we are configured to start only on a long click, we are not going to handle any events here. 
    if (mLongClickStartsDrag) return false; 

    boolean handledHere = false; 

    final int action = ev.getAction(); 

    // In the situation where a long click is not needed to initiate a drag, simply start on the down event. 
    if (action == MotionEvent.ACTION_DOWN) { 
     handledHere = startDrag (v); 


     System.out.println("value of selectedTag ID " + v.getTag()); 
     System.out.println("value of corrAns " + selectedImg); 
     if (v.getTag() != selectedImg) 
     { 
      mSpot2.setDragLayer(null); 
     } 
     else 
     { 
      mSpot2.setDragLayer(mDragLayer); 
      System.out.println("Correct Answer!"); 

     } 

    } 
    return handledHere; 
} 


public boolean startDrag (View v) 
{ 
    // Let the DragController initiate a drag-drop sequence. 
    // I use the dragInfo to pass along the object being dragged. 
    // I'm not sure how the Launcher designers do this. 
    Object dragInfo = v; 
    mDragController.startDrag (v, mDragLayer, dragInfo, 

    DragController.DRAG_ACTION_MOVE); 
     return true; 
    } 

private void setupViews() 
{ 
    DragController dragController = mDragController; 

    mDragLayer = (DragLayer) findViewById(R.id.drag_layer); 
    mDragLayer.setDragController(dragController); 
    dragController.addDropTarget (mDragLayer); 

    context = this; 
    db = new MyDBEmbrASD(this); 


    String[] myShuffledArray = new Extract().invoke(); 

    List<QuestionGetterSetter> resources3 = db.QuestionGetterSetter(); 
    int numQues = resources3.size(); 
    String[] quesNum = new String[resources3.size()]; 
    String[] quesDesc = new String[resources3.size()]; 
    String[] corrAnsr = new String[resources3.size()]; 
    String[] corrAnsIMPID = new String[resources3.size()]; 
    String[] lessnModule = new String[resources3.size()]; 

    System.out.println("TESTESTESTESTESTEST"); 
    for (int i = 0; i < resources3.size(); i++) { 
     quesNum[i] = resources3.get(i).getQuesNum(); 
     quesDesc[i] = resources3.get(i).getquesDesc(); 
     corrAnsr[i] = resources3.get(i).getcorrAns(); 
     corrAnsIMPID[i] = resources3.get(i).getcorrAnsIMPID(); 
     lessnModule[i] = resources3.get(i).getlessnModule(); 
     System.out.println("test + " + quesNum[i]); 
     System.out.println("test + " + quesDesc[i]); 
     System.out.println("test + " + corrAnsr[i]); 
     System.out.println("test + " + corrAnsIMPID[i]); 
     System.out.println("test + " + lessnModule[i]); 
    } 


    Random rQuestion = new Random(); 
    int iQues = rQuestion.nextInt(numQues - 1)+1; 
    System.out.println("testCorrAnsr " + corrAnsIMPID[iQues]); 
    System.out.println("testCorrAnsr " + corrAnsr[0]); 
    selectedImg = corrAnsIMPID[iQues]; 
    System.out.println("corrAnsIMPID" + selectedImg); 
    int id5 = getResources().getIdentifier(corrAnsIMPID[iQues], "drawable", getPackageName()); 
    System.out.println ("img1id" + id5); 



    ArrayList<String> quesList = new ArrayList<>(); 

    quesList.add(corrAnsIMPID[iQues]); 
    quesList.add(myShuffledArray[rQuestion.nextInt(numQues - 1) + 1]); 
    quesList.add(myShuffledArray[rQuestion.nextInt(numQues - 1) + 1]); 
    quesList.add(myShuffledArray[rQuestion.nextInt(numQues - 1) + 1]); 
    Collections.shuffle(quesList); 

    String[] ranQues = new String[quesList.size()]; 
    ranQues = quesList.toArray(ranQues); 
    for(String s : ranQues); 
    System.out.println("test ranques" + ranQues[0]); 
    System.out.println("test ranques" + ranQues[1]); 
    System.out.println("test ranques" + ranQues[2]); 
    System.out.println("test ranques" + ranQues[3]); 

    DisplayMetrics size = new DisplayMetrics(); 
    getWindowManager().getDefaultDisplay().getMetrics(size); 
    dmw = size .widthPixels; 
    dmh = size .heightPixels; 

    System.out.println("displaymetrics w" + dmw); 
    System.out.println("displaymetrics h" + dmh); 

    ///// 
    ImageView newView1 = new ImageView(this); 
    int id1 = getResources().getIdentifier(ranQues[0], "drawable", getPackageName()); 
    newView1.setImageResource(id1); 
    //newView1.setImageResource (android.R.drawable.alert_dark_frame); 
    Random r = new Random(); 
    int w1 = (int) (dmw*.2)+50; 
    int h1 = (int) (dmh*.2)+50; 
    int left1 =r.nextInt((int) (dmw - ((dmw*.3)+50))) + 0; 
    int top1 = r.nextInt((int) (dmh - ((dmh*.4)+50))) + 0; 
    DragLayer.LayoutParams lp1 = new DragLayer.LayoutParams (w1, h1, left1, top1); 

    mDragLayer.addView (newView1, lp1); 
    newView1.setOnClickListener(this); 
    newView1.setOnLongClickListener(this); 
    newView1.setOnTouchListener(this); 
    newView1.setTag(ranQues[0]); 
    String imgTag1 = (String) newView1.getTag(); 
    System.out.println("imgTag 1" + imgTag1); 

    System.out.println ("img1id" + newView1.getId()); 
    ///// 

    ///// 
    ImageView newView2 = new ImageView(this); 
    int id2 = getResources().getIdentifier(ranQues[1], "drawable", getPackageName()); 
    newView2.setImageResource(id2); 
    //newView2.setImageResource (android.R.drawable.alert_dark_frame); 
    int w2 = (int) (dmw*.2)+50; 
    int h2 = (int) (dmh*.2)+50; 
    int left2 =r.nextInt((int) (dmw - ((dmw*.3)+50))) + 0; 
    int top2 = r.nextInt((int) (dmh - ((dmh*.4)+50))) + 0; 
    DragLayer.LayoutParams lp2 = new DragLayer.LayoutParams (w2, h2, left2, top2); 
    mDragLayer.addView (newView2, lp2); 
    newView2.setOnClickListener(this); 
    newView2.setOnLongClickListener(this); 
    newView2.setOnTouchListener(this); 
    newView2.setTag(ranQues[1]); 
    String imgTag2 = (String) newView2.getTag(); 
    System.out.println("imgTag 1" + imgTag2); 

    System.out.println ("img1id" + newView2.getId()); 
    ///// 

    ///// 
    ImageView newView3 = new ImageView(this); 
    int id3 = getResources().getIdentifier(ranQues[2], "drawable", getPackageName()); 
    newView3.setImageResource(id3); 
    //newView3.setImageResource (android.R.drawable.alert_dark_frame); 
    int w3 = (int) (dmw*.2)+50; 
    int h3 = (int) (dmh*.2)+50; 
    int left3 =r.nextInt((int) (dmw - ((dmw*.3)+50))) + 0; 
    int top3 = r.nextInt((int) (dmh - ((dmh*.4)+50))) + 0; 
    DragLayer.LayoutParams lp3 = new DragLayer.LayoutParams (w3, h3, left3, top3); 
    mDragLayer.addView (newView3, lp3); 
    newView3.setOnClickListener(this); 
    newView3.setOnLongClickListener(this); 
    newView3.setOnTouchListener(this); 
    newView3.setTag(ranQues[2]); 
    String imgTag3= (String) newView3.getTag(); 
    System.out.println("imgTag 1" + imgTag3); 

    System.out.println ("img1id" + newView3.getId()); 
    ///// 

    ///// 
    ImageView newView4 = new ImageView(this); 
    int id4 = getResources().getIdentifier(ranQues[3], "drawable", getPackageName()); 
    newView4.setImageResource(id4); 

    //newView4.setImageResource (android.R.drawable.alert_dark_frame); 
    int w4 = (int) (dmw*.2)+50; 
    int h4 = (int) (dmh*.2)+50; 
    int left4 =r.nextInt((int) (dmw - ((dmw*.3)+50))) + 0; 
    int top4 = r.nextInt((int) (dmh - ((dmh*.4)+50))) + 0; 

    DragLayer.LayoutParams lp4 = new DragLayer.LayoutParams (w4, h4, left4, top4); 
    mDragLayer.addView (newView4, lp4); 
    newView4.setOnClickListener(this); 
    newView4.setOnLongClickListener(this); 
    newView4.setOnTouchListener(this); 
    newView4.setTag(ranQues[3]); 
    String imgTag4 = (String) newView2.getTag(); 

    System.out.println("imgTag 4" + imgTag4); 

    System.out.println ("img1id" + newView4.getId()); 
    ///// 


    TextView textView = new TextView(this); 
    textView.setText(quesDesc[iQues]); 
    textView.setTextSize(25); 

    int w = 100; 
    int h = 100; 
    int left = 0; 
    int top = (int) (dmh - ((dmh*.2)+50)); 
    DragLayer.LayoutParams lp = new DragLayer.LayoutParams (MyAbsoluteLayout.LayoutParams.WRAP_CONTENT, MyAbsoluteLayout.LayoutParams.WRAP_CONTENT, MyAbsoluteLayout.LayoutParams.WRAP_CONTENT, top); 
    mDragLayer.addView (textView, lp); 


    DropSpot drop2 = (DropSpot) mDragLayer.findViewById (R.id.drop_spot2); 
    drop2.setup (null, dragController, R.color.drop_target_color2); 
    mSpot2 = drop2; 

    mSpot2.mListener = DragActivityV2.this; //I put this but it said incompatible types 




    // Note: It might be interesting to allow the drop spots to be movable too. 
    // Unfortunately, in the current implementation, that does not work 
    // because the parent view of the DropTarget objects is not the drag layer. 
    // The current DragLayer.onDrop method makes assumptions about how to reposition a dropped view. 

    // Give the user a little guidance. 
    //String message = mLongClickStartsDrag ? "Press and hold to start dragging." 
    //          : "Touch a view to start dragging."; 
    //Toast.makeText (getApplicationContext(), message, Toast.LENGTH_LONG).show(); 

} 

    public void onRightAnswerSelected() { 
     Intent intent = new Intent(this, FallAnimationActivity.class); 
       startActivity(intent); 
     finish(); 
    } 

} 

public interface CorrectAnswerListener { 

    void onRightAnswerSelected(); 

} 

Answer 1

@ Mark, Il n'est pas influençable à mettre en œuvre l'architecture de la manière ci-dessus. Il est préférable d'utiliser une interface pour y parvenir.

Étape 1: créer une interface.

public interface CorrectAnswerListener { 

void onRightAnswerSelected(); 

} 

Étape 2:

public class DropSpot extends MyAbsoluteLayout 
implements DropTarget, DragController.DragListener 
{ // codes... 

public CorrectAnswerListener mListener; // Set This attribute from //DragActivityV2 

if (controller != null) { 
    controller.setDragListener (this); 
    controller.addDropTarget (this); 
    System.out.println("Correct Spot"); 

    //DragActivityV2 ca = new DragActivityV2(); 
    //ca.correctAns(); 

if(mListener != null) { 
mListener.onRightAnswerSelected(); 
} 
} 

Étape 3:

public class DragActivityV2 extends Activity 
      implements View.OnLongClickListener, View.OnClickListener, View.OnTouchListener, CorrectAnswerListener; 
    { 

@override 
public void onCreate() { 

setContentView(); 

//Where ever you create an object to helper class, initiate the value as 
helperClassObject.mListener = DragActivityV2.this; 
}  
//more codes... 
    //public void correctAns() 

     // { 
     // Context context; 
      // Intent intent = new Intent(this, FallAnimatio//nActivity.class); 
      //DragActivityV2.this.startActivity(intent); 
      //finish(); 


@override 
public void onRightAnswerSelected() { 
Intent intent = new Intent(this, FallAnimatio//nActivity.class); 
startActivity(intent); 
finish(); 
} 

Answer 2

Ne pas instancier Activité avec une nouvelle activty()

Sur la classe DropSpot obtenir le context de FirstActivity,

public class DropSpot extends MyAbsoluteLayout 
implements DropTarget, DragController.DragListener 
{ // codes... 
if (controller != null) { 
    controller.setDragListener (this); 
    controller.addDropTarget (this); 
    System.out.println("Correct Spot"); 

    context.startActivtiy(context,DragActivityV2.class); 

} 

Sur le DragActivityV2onCreate appellent le correctAns()

public class DragActivityV2 extends Activity 
      implements View.OnLongClickListener, View.OnClickListener, View.OnTouchListener 
    {  //more codes... 

@Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

////code 
correctAns(); 
    } 


public void correctAns() 

     { 
      Context context; 
      Intent intent = new Intent(this, FallAnimationActivity.class); 
      DragActivityV2.this.startActivity(intent); 
      finish(); 
     }