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我已经在我的自定义视图上实现了缩放，它在画布上绘制了一个网格，但是如果我同时将两个手指放在屏幕上，缩放将不起作用。我必须先放一个，然后再放另一个。

我按照Adam Powell 的这篇博客文章来实现缩放，并制作了这个自定义视图：

public class ZoomView extends View{

    private float width;    
    private float height;   

    Paint lineColor; 
    Paint bgColor;

    private float mScaleFactor;
    private ScaleGestureDetector scaleDetector;

    public CanvasView(Context context) {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);

        lineColor = new Paint();
        lineColor.setColor(getResources().getColor(R.color.white));
        bgColor = new Paint();
        bgColor.setColor(getResources().getColor(R.color.black));

        mScaleFactor = 1;
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh){
        width = w/9;
        height = h/9;
        super.onSizeChanged(w,h,oldw,oldh);
    }

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

        canvas.save();
        canvas.scale(mScaleFactor, mScaleFactor);     //for zooming

        for(int i=0; i <= 9; i++){
            canvas.drawLine(0,i*height, 9*width,i*height,lineColor);
            canvas.drawLine(i*width, 0, i*width, 9*height, lineColor);
        }

        canvas.restore();
    }

    @Override 
    public boolean onTouchEvent(MotionEvent ev){

        mScaleDetector.onTouchEvent(ev);
        return true;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
        setMeasuredDimension(800, 1000);
    }

    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, 5.0f));

            invalidate();
            return true;
        }
    }   
}

那么为什么缩放会这样呢？任何帮助将不胜感激。谢谢！

4

1 回答 1

1

This may look like a silly question, but does the multi touch behavior work on other apps (Maps for example) at this device? I've tested your code (with minor changes, see below) on an LG Optimus Black, Android 4.0.3, and it worked, both fingers simultaneously.

package com.example.teste;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;

public class ZoomView extends View {

private float width;
private float height;

Paint lineColor;
Paint bgColor;

private float mScaleFactor;
private ScaleGestureDetector mScaleDetector;

public ZoomView(Context context) {
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);

    lineColor = new Paint();
    lineColor.setColor(getResources().getColor(R.color.ics_blue_bright));
    bgColor = new Paint();
    bgColor.setColor(getResources().getColor(R.color.black));

    mScaleFactor = 1;
    mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    width = w / 9;
    height = h / 9;
    super.onSizeChanged(w, h, oldw, oldh);
}

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

    canvas.save();
    canvas.scale(mScaleFactor, mScaleFactor); // for zooming

    for (int i = 0; i <= 9; i++) {
        canvas.drawLine(0, i * height, 9 * width, i * height, lineColor);
        canvas.drawLine(i * width, 0, i * width, 9 * height, lineColor);
    }

    canvas.restore();
}

@Override
public boolean onTouchEvent(MotionEvent ev) {

    mScaleDetector.onTouchEvent(ev);
    return true;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    setMeasuredDimension(800, 1000);
}

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, 5.0f));

        invalidate();
        return true;
    }
}
}
于 2013-05-29T23:00:05.397 回答