Question

我想访问另一个类的某个功能的特定数据。我可以访问另一个类的功能，我可以访问其公共数据吗？

  public class SessionManagement {

          public void createLoginSession(String accesstoken, String tokentype, String expiresin, String username, String masterId, String name, String access, String issued, String expires) {

        editor.putBoolean(IS_LOGIN, true);
        editor.putString(KEY_access_token, accesstoken);
        editor.putString(KEY_token_type, tokentype);
        editor.putString(Key_EXPIRES_IN, expiresin);
        editor.putString(KEY_USERNAME, username);
        editor.putString(KEY_MASTER_ID, masterId);
        editor.putString(KEY_Name, name);
        editor.putString(KEY_Access, access);
        editor.putString(KEY_Issued, issued);
        editor.putString(KEY_expires, expires);
        editor.apply();

        String user_new_access_token; = pref.getString(KEY_access_token, null);
        String user_new_access_tokentype = pref.getString(KEY_token_type, null);
        String user_name_expiresin = pref.getString(Key_EXPIRES_IN, null);
        String user_name_Username = pref.getString(KEY_USERNAME, null);
        String user_name_masterID = pref.getString(KEY_MASTER_ID, null);
        String user_name_name = pref.getString(KEY_Name, null);
        String user_name_access = pref.getString(KEY_Access, null);
        String user_name_issued = pref.getString(KEY_Issued, null);
        String user_name_expires = pref.getString(KEY_expires, null);


        Log.d("TAG", "Access Token :" + accesstoken + user_new_access_token);
        Log.d("TAG", "TokenType:" + user_new_access_tokentype);
        Log.d("TAG", "Expires in:" + user_name_expiresin);
        Log.d("TAG", "UserName:" + user_name_Username);
        Log.d("TAG", "MasterID:" + user_name_masterID);

        Log.d("TAG", "Name:" + user_name_name);
        Log.d("TAG", "Access:" + user_name_access);
        Log.d("TAG", "Issued:" + user_name_issued);
        Log.d("TAG", "Expires:" + user_name_expires);


        //  String user_name_new = pref.getString(KEY_access_token, null);

        //  Log.d("TAG", " :" + accesstoken + " user_name_new:" + user_name_new);


        //  Log.d(tokentype, "admin");
        //ad Log.d(expiresin, "expiresin");

        editor.commit();


    }
  public String getAccesstToken()
    {
        String user_new_access_token = pref.getString(KEY_access_token, null);
        return user_new_access_token;
    }
        }

家庭课程

public class Home extends AppCompatActivity{
     SessionManagement sessionManagement;
     protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        sessionManagement.createLoginSession();//i can access the function
    String user_new_access_token= sessionManagement.getAccesstToken();
     Log.d("",user_new_access_token);

    }
    }

这里我想访问函数String user_new_access_token的数据。我可以通过。（点）运算符访问函数，但不能访问函数的数据？为什么不能做到这一点？原因可能会有所帮助。

Answer 1

在SessionManagement类中添加此函数：

public String getAccesstToken()
{
     String user_new_access_token = pref.getString(KEY_access_token, null);
     return user_new_access_token;
}

使用以下方式获取

    SessionManagement sessionManagement=new SessionManagement();
    String user_new_access_token= sessionManagement.getAccesstToken();

Answer 2

方法createLoginSession可能会初始化您希望访问的某些变量，但这些变量仅存在于方法的范围内。一旦该方法完成，这些变量就被垃圾收集，从而无法访问。因此，您必须将要访问的变量放在方法的本地范围之外。我建议的是在SessionManagement类中创建要访问实例变量的变量。然后像任何实例变量一样检索（通过点运算符或getter方法）。

public class SessionManagement {
    String user_new_access_token = "";
    //Other instace variables
    public void createLoginSession(String accesstoken, String tokentype, String expiresin, String username, String masterId, String name, String access, String issued, String expires) {
        //code before assignment of user_new_access_token
        user_new_access_token = pref.getString(KEY_access_token, null);
        //rest of the method body
    }
}

然后您可以像user_new_access_token一样访问Home等public class Home extends AppCompatActivity{ SessionManagement sessionManagement; protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); sessionManagement.createLoginSession(); String temp = sessionManagement.user_new_access_token; } }之类的变量，

sessionManagement.createLoginSession().data(user_new_access_token)

至于为什么你不能写void，原因是createLoginSession（）是一个data方法，因此它不会返回任何内容。因此，没有生成对象来执行点运算符。此外，没有适合在此使用的public class TouchImageView extends ImageView { Matrix matrix; // We can be in one of these 3 states static final int NONE = 0; static final int DRAG = 1; static final int ZOOM = 2; int mode = NONE; // Remember some things for zooming PointF last = new PointF(); PointF start = new PointF(); float minScale = 1f; float maxScale = 3f; float[] m; int viewWidth, viewHeight; static final int CLICK = 3; float saveScale = 1f; protected float origWidth, origHeight; int oldMeasuredWidth, oldMeasuredHeight; ScaleGestureDetector mScaleDetector; Context context; public TouchImageView(Context context) { super(context); sharedConstructing(context); } public TouchImageView(Context context, AttributeSet attrs) { super(context, attrs); sharedConstructing(context); } private void sharedConstructing(Context context) { super.setClickable(true); this.context = context; mScaleDetector = new ScaleGestureDetector(context, new ScaleListener()); matrix = new Matrix(); m = new float[9]; setImageMatrix(matrix); setScaleType(ScaleType.MATRIX); setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { mScaleDetector.onTouchEvent(event); PointF curr = new PointF(event.getX(), event.getY()); switch (event.getAction()) { case MotionEvent.ACTION_DOWN: last.set(curr); start.set(last); mode = DRAG; break; case MotionEvent.ACTION_MOVE: if (mode == DRAG) { float deltaX = curr.x - last.x; float deltaY = curr.y - last.y; float fixTransX = getFixDragTrans(deltaX, viewWidth, origWidth * saveScale); float fixTransY = getFixDragTrans(deltaY, viewHeight, origHeight * saveScale); matrix.postTranslate(fixTransX, fixTransY); fixTrans(); last.set(curr.x, curr.y); } break; case MotionEvent.ACTION_UP: mode = NONE; int xDiff = (int) Math.abs(curr.x - start.x); int yDiff = (int) Math.abs(curr.y - start.y); if (xDiff < CLICK && yDiff < CLICK) performClick(); break; case MotionEvent.ACTION_POINTER_UP: mode = NONE; break; } setImageMatrix(matrix); invalidate(); return true; // indicate event was handled } }); } public void setMaxZoom(float x) { maxScale = x; } private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener { @Override public boolean onScaleBegin(ScaleGestureDetector detector) { mode = ZOOM; return true; } @Override public boolean onScale(ScaleGestureDetector detector) { float mScaleFactor = detector.getScaleFactor(); float origScale = saveScale; saveScale *= mScaleFactor; if (saveScale > maxScale) { saveScale = maxScale; mScaleFactor = maxScale / origScale; } else if (saveScale < minScale) { saveScale = minScale; mScaleFactor = minScale / origScale; } if (origWidth * saveScale <= viewWidth || origHeight * saveScale <= viewHeight) matrix.postScale(mScaleFactor, mScaleFactor, viewWidth / 2, viewHeight / 2); else matrix.postScale(mScaleFactor, mScaleFactor, detector.getFocusX(), detector.getFocusY()); fixTrans(); return true; } } void fixTrans() { matrix.getValues(m); float transX = m[Matrix.MTRANS_X]; float transY = m[Matrix.MTRANS_Y]; float fixTransX = getFixTrans(transX, viewWidth, origWidth * saveScale); float fixTransY = getFixTrans(transY, viewHeight, origHeight * saveScale); if (fixTransX != 0 || fixTransY != 0) matrix.postTranslate(fixTransX, fixTransY); } float getFixTrans(float trans, float viewSize, float contentSize) { float minTrans, maxTrans; if (contentSize <= viewSize) { minTrans = 0; maxTrans = viewSize - contentSize; } else { minTrans = viewSize - contentSize; maxTrans = 0; } if (trans < minTrans) return -trans + minTrans; if (trans > maxTrans) return -trans + maxTrans; return 0; } float getFixDragTrans(float delta, float viewSize, float contentSize) { if (contentSize <= viewSize) { return 0; } return delta; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); viewWidth = MeasureSpec.getSize(widthMeasureSpec); viewHeight = MeasureSpec.getSize(heightMeasureSpec); // // Rescales image on rotation // if (oldMeasuredHeight == viewWidth && oldMeasuredHeight == viewHeight || viewWidth == 0 || viewHeight == 0) return; oldMeasuredHeight = viewHeight; oldMeasuredWidth = viewWidth; if (saveScale == 1) { //Fit to screen. float scale; Drawable drawable = getDrawable(); if (drawable == null || drawable.getIntrinsicWidth() == 0 || drawable.getIntrinsicHeight() == 0) return; int bmWidth = drawable.getIntrinsicWidth(); int bmHeight = drawable.getIntrinsicHeight(); Log.e("bmSize", "bmWidth: " + bmWidth + " bmHeight : " + bmHeight); float scaleX = (float) viewWidth / (float) bmWidth; float scaleY = (float) viewHeight / (float) bmHeight; scale = Math.min(scaleX, scaleY); matrix.setScale(scale, scale); // Center the image float redundantYSpace = (float) viewHeight - (scale * (float) bmHeight); float redundantXSpace = (float) viewWidth - (scale * (float) bmWidth); redundantYSpace /= (float) 2; redundantXSpace /= (float) 2; matrix.postTranslate(redundantXSpace, redundantYSpace); origWidth = viewWidth - 2 * redundantXSpace; origHeight = viewHeight - 2 * redundantYSpace; setImageMatrix(matrix); } fixTrans(); } }方法。

我可以访问功能的特定数据吗？

2 个答案: