Android imitation Weibo loading long pictures scrolling to view the effect

package org.wandcf_ces.; 
 
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/**
  * Created by sunrui on 2017/3/8.
  * Loading long pictures
  * Solution steps
  * 1. Scale the image to the same width as the control
  * 2. Determine the height of the zoomed image. If the height is greater than the height of the control (the setting here is 1.5 times), it is considered a long image and can be viewed by sliding the image.
  * |-If the height is less than 1.5 times the height of the control, rescaling the image based on the height of the control
  *
  */ 
public class LongImageView extends View { 
 
  private int width, height; 
 
  //Bitmap that needs to be drawn  private Bitmap bitmap; 
 
  /**
    * Area of ​​the picture to be drawn
    */ 
  private Rect srcRect; 
 
  /**
    * The drawn area
    */ 
  private RectF dstRectF; 
 
  /**
    * Paintbrush
    */ 
  private Paint paint; 
 
 
  /**
    * Is it necessary to slide
    */ 
  private boolean isNeedSlide; 
 
  /**
    * Distance that has been sliding
    */ 
  private float slideLength; 
 
 
  /**
    * Drawn Bitmap
    */ 
  private Bitmap drawBitmap; 
 
  { 
    srcRect = new Rect(); 
    dstRectF = new RectF(); 
    paint = new Paint(); 
    (true); 
    (); 
    (1.0f); 
  } 
 
  public LongImageView(Context context) { 
    super(context); 
  } 
 
  public LongImageView(Context context, @Nullable AttributeSet attrs) { 
    super(context, attrs); 
  } 
 
  public LongImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { 
    super(context, attrs, defStyleAttr); 
  } 
 
  @TargetApi(Build.VERSION_CODES.LOLLIPOP) 
  public LongImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) { 
    super(context, attrs, defStyleAttr, defStyleRes); 
  } 
 
  /**
    * Setting up Bitmap
    *
    * @param bitmap
    * Bitmap to be drawn
    */ 
  public void setBitmap(Bitmap bitmap) { 
     = bitmap; 
  } 
 
  @Override 
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
    int specSize = (widthMeasureSpec); 
    width = getPaddingLeft() + getPaddingRight() + specSize; 
    specSize = (heightMeasureSpec); 
    height = getPaddingTop() + getPaddingBottom() + specSize; 
    if (drawBitmap == null) { 
      drawBitmap = resizeImage(bitmap, width); 
      if (() > 1.5 * height) { 
        //Swipe required        setNeedSlide(true); 
      } else { 
        //No need to slide        setNeedSlide(false); 
         = 0; 
         = 0; 
         = (); 
         = (); 
        if (() > height) { 
          drawBitmap = resizeImageH(drawBitmap, height - 20); 
        } else { 
          float space = (height - ()); 
           = 0; 
           = space; 
           = width; 
           = height - space; 
        } 
      } 
    } 
    setMeasuredDimension(width, height); 
  } 
 
  @Override 
  protected void onDraw(Canvas canvas) { 
    (drawBitmap, (width - ()) / 2, slideLength, paint); 
  } 
 
  /**
    * Set whether sliding is required
    *
    * @param needSlide
    * true or false
    */ 
  public void setNeedSlide(boolean needSlide) { 
    isNeedSlide = needSlide; 
  } 
 
  /**
    * Coordinates for touch operation
    */ 
  private float lastX; 
  private float lastY; 
 
  @Override 
  public boolean onTouchEvent(MotionEvent event) { 
    if (!isNeedSlide) { 
      return (event); 
    } 
    int action = (); 
    switch (action) { 
      case MotionEvent.ACTION_DOWN: 
        //Press        lastX = (); 
        lastY = (); 
        break; 
      case MotionEvent.ACTION_MOVE: 
        float moveX = (); 
        if (moveX - lastX > 50) { 
          //It is determined to be sliding left and right          return (event); 
        } 
        float moveY = (); 
        float distance = moveY - lastY; 
        lastY = moveY; 
        slideLength += distance; 
        if (slideLength >= 0) { 
          slideLength = 0; 
        } 
        if (slideLength <= (-1) * (() - height)) { 
          slideLength = (-1) * (() - height); 
        } 
        postInvalidate(); 
        break; 
      default: 
        break; 
    } 
    return true; 
  } 
 
  public Bitmap resizeImage(Bitmap bitmap, int w) { 
    int width = (); 
    int height = (); 
    float scaleWidth = ((float) w) / width; 
    Matrix matrix = new Matrix(); 
    (scaleWidth, scaleWidth); 
    return (bitmap, 0, 0, width, 
        height, matrix, true); 
  } 
 
  public Bitmap resizeImageH(Bitmap bitmap, int h) { 
    int width = (); 
    int height = (); 
    float scaleWidth = ((float) h) / height; 
    Matrix matrix = new Matrix(); 
    (scaleWidth, scaleWidth); 
    return (bitmap, 0, 0, width, 
        height, matrix, true); 
  } 
 
}