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Android手势滑动实现ImageView缩放图片大小

时间:2021-05-28 15:41     来源/作者:Android教程网

本文推出了两种Android手势实现ImageView缩放图片大小的方法,分享给大家供大家参考,具体内容如下

方法一:

将以下代码写到MulitPointTouchListener.java中,然后对你相应的图片进行OnTouchListener。
例如:imageView.setOnTouchListener(new MulitPointTouchListener ());

在xml中要将ImageView的缩放格式改成Matrix

例如:android:scaleType="matrix"

这样就可以实现图片的缩放了

下面是MulitPointTouchListener.java代码:

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public class MulitPointTouchListener implements OnTouchListener {
  private static final String TAG = "Touch";
  // These matrices will be used to move and zoom image
  Matrix matrix = new Matrix();
  Matrix savedMatrix = new 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 start = new PointF();
  PointF mid = new PointF();
  float oldDist = 1f;
 
  @Override
  public boolean onTouch(View v, MotionEvent event) {
 
    ImageView view = (ImageView) v;
    // Log.e("view_width",
    // view.getImageMatrix()..toString()+"*"+v.getWidth());
    // Dump touch event to log
    dumpEvent(event);
 
    // Handle touch events here...
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN:
 
      matrix.set(view.getImageMatrix());
      savedMatrix.set(matrix);
      start.set(event.getX(), event.getY());
      //Log.d(TAG, "mode=DRAG");
      mode = DRAG;
 
       
      //Log.d(TAG, "mode=NONE");
      break;
    case MotionEvent.ACTION_POINTER_DOWN:
      oldDist = spacing(event);
      //Log.d(TAG, "oldDist=" + oldDist);
      if (oldDist > 10f) {
        savedMatrix.set(matrix);
        midPoint(mid, event);
        mode = ZOOM;
        //Log.d(TAG, "mode=ZOOM");
      }
      break;
    case MotionEvent.ACTION_UP:
    case MotionEvent.ACTION_POINTER_UP:
      mode = NONE;
      //Log.e("view.getWidth", view.getWidth() + "");
      //Log.e("view.getHeight", view.getHeight() + "");
 
      break;
    case MotionEvent.ACTION_MOVE:
      if (mode == DRAG) {
        // ...
        matrix.set(savedMatrix);
        matrix.postTranslate(event.getX() - start.x, event.getY()
            - start.y);
      } else if (mode == ZOOM) {
        float newDist = spacing(event);
        //Log.d(TAG, "newDist=" + newDist);
        if (newDist > 10f) {
          matrix.set(savedMatrix);
          float scale = newDist / oldDist;
          matrix.postScale(scale, scale, mid.x, mid.y);
        }
      }
      break;
    }
 
    view.setImageMatrix(matrix);
    return true; // indicate event was handled
  }
 
  private void dumpEvent(MotionEvent event) {
    String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE",
        "POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
    StringBuilder sb = new StringBuilder();
    int action = event.getAction();
    int actionCode = action & MotionEvent.ACTION_MASK;
    sb.append("event ACTION_").append(names[actionCode]);
    if (actionCode == MotionEvent.ACTION_POINTER_DOWN
        || actionCode == MotionEvent.ACTION_POINTER_UP) {
      sb.append("(pid ").append(
          action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
      sb.append(")");
    }
    sb.append("[");
    for (int i = 0; i < event.getPointerCount(); i++) {
      sb.append("#").append(i);
      sb.append("(pid ").append(event.getPointerId(i));
      sb.append(")=").append((int) event.getX(i));
      sb.append(",").append((int) event.getY(i));
      if (i + 1 < event.getPointerCount())
        sb.append(";");
    }
    sb.append("]");
    //Log.d(TAG, sb.toString());
  }
 
   
  private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
  }
 
   
  private void midPoint(PointF point, MotionEvent event) {
    float x = event.getX(0) + event.getX(1);
    float y = event.getY(0) + event.getY(1);
    point.set(x / 2, y / 2);
  }
}

方法二:自定义一个ImageView,例如TouchImageView:

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import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.ImageView;
 
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.d("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();
 }
}

然后在我们的Activity中就可以直接使用了:

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public class TouchImageViewActivity extends Activity {
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  TouchImageView img = (TouchImageView) findViewById(R.id.snoop);
  img.setImageResource(R.drawable.snoopy);
  img.setMaxZoom(4f);
 }
}

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

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