android - 如何放大 ImageView 而不会稍微跳转到其他地方？ (安卓)-6ren

android - 如何放大 ImageView 而不会稍微跳转到其他地方？ (安卓)

转载作者：行者123 更新时间：2023-12-02 21:06:55

我正在尝试创建一个应用程序，用户可以在其中拖动和缩放 ImageView。但我在使用以下代码时遇到了问题。

当scaleFactor不为1并且第二根手指放下时，它会稍微平移到其他地方。我不知道这个翻译是从哪里来的...

这是完整的类:

package me.miutaltbati.ramaview;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;

import static android.view.MotionEvent.INVALID_POINTER_ID;

public class RamaView extends ImageView {
    private Context context;
    private Matrix matrix = new Matrix();
    private Matrix translateMatrix = new Matrix();
    private Matrix scaleMatrix = new Matrix();

    // Properties coming from outside:
    private int drawableLayoutId;
    private int width;
    private int height;

    private static float MIN_ZOOM = 0.33333F;
    private static float MAX_ZOOM = 5F;

    private PointF mLastTouch = new PointF(0, 0);
    private PointF mLastFocus = new PointF(0, 0);
    private PointF mLastPivot = new PointF(0, 0);
    private float mPosX = 0F;
    private float mPosY = 0F;

    public float scaleFactor = 1F;
    private int mActivePointerId = INVALID_POINTER_ID;

    private Paint paint;
    private Bitmap bitmapLayout;

    private OnFactorChangedListener mListener;
    private ScaleGestureDetector mScaleDetector;

    public RamaView(Context context) {
        super(context);
        initializeInConstructor(context);
    }

    public RamaView(Context context, @android.support.annotation.Nullable AttributeSet attrs) {
        super(context, attrs);
        initializeInConstructor(context);
    }

    public RamaView(Context context, @android.support.annotation.Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initializeInConstructor(context);
    }

    public void initializeInConstructor(Context context) {
        this.context = context;
        paint = new Paint();
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        mScaleDetector.setQuickScaleEnabled(false);

        setScaleType(ScaleType.MATRIX);
    }

    public Bitmap decodeSampledBitmap() {
        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inMutable = true;
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(getResources(), drawableLayoutId, options);

        // Calculate inSampleSize
        options.inSampleSize = Util.calculateInSampleSize(options, width, height); // e.g.: 4, 8

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeResource(getResources(), drawableLayoutId, options);
    }

    public void setDrawable(int drawableId) {
        drawableLayoutId = drawableId;
    }

    public void setSize(int width, int height) {
        this.width = width;
        this.height = height;

        bitmapLayout = decodeSampledBitmap();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mScaleDetector.onTouchEvent(event);

        int action = event.getActionMasked();

        switch (action) {
            case MotionEvent.ACTION_DOWN: {
                int pointerIndex = event.getActionIndex();
                float x = event.getX(pointerIndex);
                float y = event.getY(pointerIndex);

                // Remember where we started (for dragging)
                mLastTouch = new PointF(x, y);

                // Save the ID of this pointer (for dragging)
                mActivePointerId = event.getPointerId(0);
            }

            case MotionEvent.ACTION_POINTER_DOWN: {
                if (event.getPointerCount() == 2) {
                    mLastFocus = new PointF(mScaleDetector.getFocusX(), mScaleDetector.getFocusY());
                }
            }

            case MotionEvent.ACTION_MOVE: {
                // Find the index of the active pointer and fetch its position
                int pointerIndex = event.findPointerIndex(mActivePointerId);

                float x = event.getX(pointerIndex);
                float y = event.getY(pointerIndex);

                // Calculate the distance moved
                float dx = 0;
                float dy = 0;

                if (event.getPointerCount() == 1) {
                    // Calculate the distance moved
                    dx = x - mLastTouch.x;
                    dy = y - mLastTouch.y;

                    matrix.setScale(scaleFactor, scaleFactor, mLastPivot.x, mLastPivot.y);

                    // Remember this touch position for the next move event
                    mLastTouch = new PointF(x, y);
                } else if (event.getPointerCount() == 2) {
                    // Calculate the distance moved
                    dx = mScaleDetector.getFocusX() - mLastFocus.x;
                    dy = mScaleDetector.getFocusY() - mLastFocus.y;

                    matrix.setScale(scaleFactor, scaleFactor, -mPosX + mScaleDetector.getFocusX(), -mPosY + mScaleDetector.getFocusY());

                    mLastPivot = new PointF(-mPosX + mScaleDetector.getFocusX(), -mPosY + mScaleDetector.getFocusY());
                    mLastFocus = new PointF(mScaleDetector.getFocusX(), mScaleDetector.getFocusY());
                }

                mPosX += dx;
                mPosY += dy;

                matrix.postTranslate(mPosX, mPosY);

                break;
            }

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

            case MotionEvent.ACTION_POINTER_UP: {
                final int pointerIndex = event.getActionIndex();
                final int pointerId = event.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;
                    mLastTouch = new PointF(event.getX(newPointerIndex), event.getY(newPointerIndex));
                    mActivePointerId = event.getPointerId(newPointerIndex);
                } else {
                    final int tempPointerIndex = event.findPointerIndex(mActivePointerId);
                    mLastTouch = new PointF(event.getX(tempPointerIndex), event.getY(tempPointerIndex));
                }

                break;
            }
        }

        invalidate();
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.save();

        canvas.setMatrix(matrix);
        canvas.drawColor(Color.BLACK);
        canvas.drawBitmap(bitmapLayout, 0, 0, paint);

        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            scaleFactor *= detector.getScaleFactor();
            scaleFactor = Math.max(MIN_ZOOM, Math.min(scaleFactor, MAX_ZOOM));

            return true;
        }
    }
}

我认为问题出在这一行:

matrix.setScale(scaleFactor, scaleFactor, -mPosX + mScaleDetector.getFocusX(), -mPosY + mScaleDetector.getFocusY());

我尝试了很多方法，但无法让它正常工作。

更新:

以下是初始化 RamaView 实例的方法:

主要 Activity 的 onCreate:

rvRamaView = findViewById(R.id.rvRamaView);

final int[] rvSize = new int[2];
ViewTreeObserver vto = rvRamaView.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
    @Override
    public boolean onPreDraw() {
        rvRamaView.getViewTreeObserver().removeOnPreDrawListener(this);
        rvSize[0] = rvRamaView.getMeasuredWidth();
        rvSize[1] = rvRamaView.getMeasuredHeight();

        rvRamaView.setSize(rvSize[0], rvSize[1]);
        return true;
    }
});

rvRamaView.setDrawable(R.drawable.original_jpg);

最佳答案

最好使用矩阵来累积变化，而不是尝试自己重新计算转换。您可以使用矩阵 post... 和 pre... 方法来完成此操作，并远离重置的 set... 方法矩阵。

这里是 RamaView 类的重写，除了上面提到的矩阵的具体处理之外，它基本上达到了目标。这些 mod 是针对 onTouchEvent() 方法的。该视频是示例应用程序中运行的代码的输出。

RamaView.java

public class RamaView extends ImageView {
    private final Matrix matrix = new Matrix();

    // Properties coming from outside:
    private int drawableLayoutId;
    private int width;
    private int height;

    private static final float MIN_ZOOM = 0.33333F;
    private static final float MAX_ZOOM = 5F;

    private PointF mLastTouch = new PointF(0, 0);
    private PointF mLastFocus = new PointF(0, 0);

    public float scaleFactor = 1F;
    private int mActivePointerId = INVALID_POINTER_ID;

    private Paint paint;
    private Bitmap bitmapLayout;

    //    private OnFactorChangedListener mListener;
    private ScaleGestureDetector mScaleDetector;

    public RamaView(Context context) {
        super(context);
        initializeInConstructor(context);
    }

    public RamaView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        initializeInConstructor(context);
    }

    public RamaView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initializeInConstructor(context);
    }

    public void initializeInConstructor(Context context) {
        paint = new Paint();
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        mScaleDetector.setQuickScaleEnabled(false);

        setScaleType(ScaleType.MATRIX);
    }

    public Bitmap decodeSampledBitmap() {
        // First decode with inJustDecodeBounds=true to check dimensions
        final BitmapFactory.Options options = new BitmapFactory.Options();
        options.inMutable = true;
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeResource(getResources(), drawableLayoutId, options);

        options.inSampleSize = Util.calculateInSampleSize(options, width, height); // e.g.: 4, 8

        // Decode bitmap with inSampleSize set
        options.inJustDecodeBounds = false;
        return BitmapFactory.decodeResource(getResources(), drawableLayoutId, options);
    }

    public void setDrawable(int drawableId) {
        drawableLayoutId = drawableId;
    }

    public void setSize(int width, int height) {
        this.width = width;
        this.height = height;

        bitmapLayout = decodeSampledBitmap();
    }

    private float mLastScaleFactor = 1.0f;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        mScaleDetector.onTouchEvent(event);

        int action = event.getActionMasked();

        switch (action) {
            case MotionEvent.ACTION_DOWN: {
                int pointerIndex = event.getActionIndex();
                float x = event.getX(pointerIndex);
                float y = event.getY(pointerIndex);

                // Remember where we started (for dragging)
                mLastTouch = new PointF(x, y);

                // Save the ID of this pointer (for dragging)
                mActivePointerId = event.getPointerId(0);
            }

            case MotionEvent.ACTION_POINTER_DOWN: {
                if (event.getPointerCount() == 2) {
                    mLastFocus = new PointF(mScaleDetector.getFocusX(), mScaleDetector.getFocusY());
                }
            }

            case MotionEvent.ACTION_MOVE: {
                // Find the index of the active pointer and fetch its position
                int pointerIndex = event.findPointerIndex(mActivePointerId);

                float x = event.getX(pointerIndex);
                float y = event.getY(pointerIndex);

                // Calculate the distance moved
                float dx = 0;
                float dy = 0;

                if (event.getPointerCount() == 1) {
                    // Calculate the distance moved
                    dx = x - mLastTouch.x;
                    dy = y - mLastTouch.y;

                    // Remember this touch position for the next move event
                    mLastTouch = new PointF(x, y);
                } else if (event.getPointerCount() == 2) {
                    // Calculate the distance moved
                    float focusX = mScaleDetector.getFocusX();
                    float focusY = mScaleDetector.getFocusY();
                    dx = focusX - mLastFocus.x;
                    dy = focusY - mLastFocus.y;

                    // Since we are accumating translation/scaling, we are just adding to
                    // the previous scale.
                    matrix.postScale(scaleFactor/mLastScaleFactor, scaleFactor/mLastScaleFactor, focusX, focusY);
                    mLastScaleFactor = scaleFactor;

                    mLastFocus = new PointF(focusX, focusY);
                }

                // Translation is cumulative.
                matrix.postTranslate(dx, dy);

                break;
            }

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

            case MotionEvent.ACTION_POINTER_UP: {
                final int pointerIndex = event.getActionIndex();
                final int pointerId = event.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;
                    mLastTouch = new PointF(event.getX(newPointerIndex), event.getY(newPointerIndex));
                    mActivePointerId = event.getPointerId(newPointerIndex);
                } else {
                    final int tempPointerIndex = event.findPointerIndex(mActivePointerId);
                    mLastTouch = new PointF(event.getX(tempPointerIndex), event.getY(tempPointerIndex));
                }

                break;
            }
        }

        invalidate();
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.save();

        canvas.setMatrix(matrix);
        canvas.drawColor(Color.BLACK);
        canvas.drawBitmap(bitmapLayout, 0, 0, paint);

        canvas.restore();
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            scaleFactor *= detector.getScaleFactor();
            scaleFactor = Math.max(MIN_ZOOM, Math.min(scaleFactor, MAX_ZOOM));

            return true;
        }
    }
}

关于android - 如何放大 ImageView 而不会稍微跳转到其他地方？ (安卓)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/58667202/

文章推荐： sms - 如何在 SMPP 中正确表示消息类别

文章推荐： haskell - Let .. in 语句在 IO 中不起作用？

文章推荐： parsing - 将解析树转换为 AST

文章推荐： haskell - 类型类 - 简要说明

c# - 从同一个可视化 C# 项目创建两个(稍微)不同的可执行文件
我有一个可视化 C# 项目，我想从中编译两个可执行文件:Full.exe 和 Limited.exe。 Limited.exe 只是隐藏了几个 UI 控件。我正在考虑添加另一对解决方案配置(Debu
ios - (稍微)使用 objective-c 的高级线性代数
我和我的伙伴正计划将我们拥有的 python 应用程序移植到 iOS。我们使用 numpy 的 SVD、范数和 pinv功能，我不知道如何转换为 iOS。我查看了 Accelerate文档，没有看到任
java - Random.nextInt(int) [稍微] 有偏差
即，它永远不会使用某些特定的 upperBound 参数连续生成超过 16 个偶数: Random random = new Random(); int c = 0; int max = 17; in
c++ - 将 double 值舍入为(稍微)较低精度的好方法是什么？
我的问题是我必须使用第三方函数/算法，它采用 double 数组作为输入，但显然对输入数据中的非常小的变化很敏感.但是对于我的应用程序，我必须为(几乎)相同的输入获得相同的结果!特别是我有两个测试输入
c++ - "mouse_event"函数 - 将光标发送到(稍微)错误的坐标
mouse_event 函数将光标发送到稍有错误的坐标(偏离 1-20 像素)。它“关闭”的程度取决于我不太清楚的模式。这是我的代码 int x, y; int repeats = 1000; in
math - 为什么简化的数学方程比在 Julia-Lang 中有更多运算的等价方程运行得(稍微)慢？
在 C++ 类(class)中，我学到了避免重复计算、使用更多加法而不是更多乘法、避免幂等技巧来提高性能。然而，当我尝试让他们用 Julia-Lang 优化代码时，我对相反的结果感到惊讶。例如，这里
php - 在这种(稍微)复杂的 MySQL 数据库情况下，如何删除重复行？
好的。请耐心听我说，我不擅长解释事情。我有一个通过网站上的表格收集的联系信息数据库。显然，人们不小心(或故意，但修复是一个不同的问题)多次按下“提交”，因此该数据库中有很多重复的行。因此，tabl
Python+C 比纯 C 快(稍微)快
我一直在用各种语言和实现实现相同的代码(在 Blackjack 中发牌而不爆牌的方法的数量)。我注意到的一个奇怪之处是，Python 在 C 中调用分区函数的实现实际上比用 C 编写的整个程序快一点。
python - 使用 Pandas 的具有(稍微)不稳定时区的 Python 日期时间的字符串格式
我在使用 Pandas 解析数据的时间戳时遇到问题。我尝试解析的日期时间格式示例类似于 2012-05-02 01:00:00-05:00。从 Pandas 文档中，我被驱动到相关的 Python
c++ - 尝试(稍微)概括 C++ 模板。关联容器 key :Value Inversion
下面函数模板的目标是取任意unordered_map并产生一个新的unordered_map与 key_type和 mapped_type倒。下面的函数适用于 std::unorderd_map .我

行者123

个人简介

我是一名优秀的程序员,十分优秀！

作者热门文章

滴滴打车优惠券免费领取

全站热门文章

首页

博学

6Ren·AI

商城

android - 如何放大 ImageView 而不会稍微跳转到其他地方？ (安卓)