安卓图片缩放（Pinch to Zoom）技术

Question

我有一个单独的图片 ImageView 布局。

import android.app.Activity;
import android.os.Bundle;

public class americanfootball extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.americanfootball);
    }

}

如何在图像上启用简单的捏合缩放？

- sidhant

---

请查看此库 https://github.com/sephiroth74/ImageViewZoom - 测试中有如何使用src。 - Athul Harikumar

Answer 1

您需要使用自定义ImageView来完成此操作。可以使用以下内容：

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class PinchImageView extends View {

private static final int INVALID_POINTER_ID = -1;

private Drawable mImage;
private float mPosX;
private float mPosY;

private float mLastTouchX;
private float mLastTouchY;
private int mActivePointerId = INVALID_POINTER_ID;

private ScaleGestureDetector mScaleDetector;
private float mScaleFactor = 1.f;

public PinchImageView(Context context) {
    this(context, null, 0);
mImage=act.getResources().getDrawable(context.getResources().getIdentifier("imag­ename", "drawable", "packagename"));

    mImage.setBounds(0, 0, mImage.getIntrinsicWidth(), mImage.getIntrinsicHeight());
}

public PinchImageView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public PinchImageView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    // Let the ScaleGestureDetector inspect all events.
    mScaleDetector.onTouchEvent(ev);

    final int action = ev.getAction();
    switch (action & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_DOWN: {
        final float x = ev.getX();
        final float y = ev.getY();

        mLastTouchX = x;
        mLastTouchY = y;
        mActivePointerId = ev.getPointerId(0);
        break;
    }

    case MotionEvent.ACTION_MOVE: {
        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
        final float x = ev.getX(pointerIndex);
        final float y = ev.getY(pointerIndex);

        // Only move if the ScaleGestureDetector isn't processing a gesture.
        if (!mScaleDetector.isInProgress()) {
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            mPosX += dx;
            mPosY += dy;

            invalidate();
        }

        mLastTouchX = x;
        mLastTouchY = y;

        break;
    }

    case MotionEvent.ACTION_UP: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_CANCEL: {
        mActivePointerId = INVALID_POINTER_ID;
        break;
    }

    case MotionEvent.ACTION_POINTER_UP: {
        final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) 
                >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
        final int pointerId = ev.getPointerId(pointerIndex);
        if (pointerId == mActivePointerId) {
            // This was our active pointer going up. Choose a new
            // active pointer and adjust accordingly.
            final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
            mLastTouchX = ev.getX(newPointerIndex);
            mLastTouchY = ev.getY(newPointerIndex);
            mActivePointerId = ev.getPointerId(newPointerIndex);
        }
        break;
    }
    }

    return true;
}

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    canvas.save();
    Log.d("DEBUG", "X: "+mPosX+" Y: "+mPosY);
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor);
    mImage.draw(canvas);
    canvas.restore();
}

private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();

        // Don't let the object get too small or too large.
        mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));

        invalidate();
        return true;
    }
}

}

- Asanka Senavirathna

Answer 2

不要创建自定义ImageView，试试这个开源库：https://github.com/martinwithaar/PinchToZoom

它不扩展ImageView类，因此您可能还可以使用其他ImageView实现。此外，它具有一些非常流畅的动画，我个人认为。

- whitebrow

Answer 3

你可以看到下面的链接：

https://androidcookbook.com/Recipe.seam?recipeId=2273

注意：

这是我曾经找到的最好的缩放（和移动）示例！

1. 在XML文件中的ImageView中添加android:scaleType="matrix"。

例如：

<ImageView android:layout_width="wrap_content" android:layout_height="wrap_content"  app:srcCompat="@drawable/menu2" android:id="@+id/imageView7"android:scaleType="matrix"
    />

2. 复制代码并将其粘贴到您的活动中。

请记得将下面的代码更改为您自己的图片。 “ImageView view =（ImageView）findViewById（R.id.imageView）;”

- kuo chang