Android可以动态控制图片显示区域的自定义ImageView

r囧r小猫 2022-08-18 13:27 205阅读 0赞

一个imageView经常需要动态的控制里面图片的显示区域，比如根据触摸去改变里面图片的显示位置，或者放大镜效果等，于是做了这么个自定义控件，亲测好用，而且已经做了参数容错，只要传入上下左右的偏移量即可，不用担心传入的数过大。而且还可以设置默认的偏移量

package com.npi.blureffect;
    
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.util.AttributeSet;
    import android.util.Log;
    import android.view.View;
    
    /**
     * Custom view used to render an horizontal part (slice) of an image.
     * 
     * @author Nicolas POMEPUY
     * 
     */
    class ScrollableImageView extends View {
    
    	// A bitmap adapted to the View size
    	private Bitmap adaptedImage;
    	// A Paint object used to render the image
    	private Paint paint = new Paint();
    	// The original Bitmap
    	private Bitmap originalImage;
    	// The screen width used to render the image
    	private int scrollY = 0;//初始纵轴偏移，应该为正
    	private int scrollX = 0;//初始横轴偏移，应该为正
    
    	public ScrollableImageView(Context context, AttributeSet attrs, int defStyle) {
    		super(context, attrs, defStyle);
    	}
    
    	public ScrollableImageView(Context context, AttributeSet attrs) {
    		this(context, attrs, 0);
    	}
    
    	public ScrollableImageView(Context context) {
    		this(context, null);
    	}
    
    	/**
    	 * Draws the view if the adapted image is not null
    	 */
    	@Override
    	protected void onDraw(Canvas canvas) {
    
    		if (adaptedImage != null)
    			canvas.drawBitmap(adaptedImage, 0, 0, paint);
    
    	}
    
    	/**
    	 * Handle an external scroll and render the image by switching it by a
    	 * distance
    	 * 最核心的方法
    	 * 传入的应为正值,为向下和向右的偏移量
    	 * @param distY
    	 *            the distance from the top
    	 */
    	public void handleScroll(float distY,float distX) {
    		if (getHeight() > 0 && getWidth()>0 && originalImage != null) {
    			Log.i("Alex", "scrolly是"+scrollY+"  distY是"+distY+"  origi高是"+originalImage.getHeight()+"  自高是"+getHeight());
    			Log.i("Alex", "scrolly是"+scrollX+"  distX是"+distX+"  origi宽是"+originalImage.getWidth()+"  自宽是"+getWidth());
    			//distY为正值，正值向下滑
    			//scrollY一直是0或负值
    			//getHeight是自高
    			if (Math.abs(scrollY+distY) <= originalImage.getHeight() - getHeight() && Math.abs(scrollX+distX) <= originalImage.getWidth() - getWidth()) {
    				adaptedImage = Bitmap.createBitmap(originalImage, (int)distX+scrollX, (int) distY+scrollY, getWidth(), getHeight());
    
    				invalidate();
    			}
    		}
    
    	}
    
    	public void setoriginalImage(Bitmap bmp) {
    		this.originalImage = bmp;
    		adaptedImage = Bitmap.createBitmap(bmp);
    		invalidate();
    	}
    
    
    }

调用方法

1，先抓到对象

ScrollableImageView image = (ScrollableImageView) findViewById(R.id.window);

2、设置显示内容

image .setoriginalImage(一个bitmap对象);

3、确定移动距离

window.handleScroll(10f,20f);//横纵都移动，一般放在ontouchListener中执行