Android如何利用svg实现可缩放的地图控件
作者：solo_99
这篇文章主要给大家介绍了关于Android如何利用svg实现可缩放的地图控件的相关资料,文中通过实例代码介绍的非常详细,对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下
序言
闲来无事写了个地图控件，基于SVG。可以缩放，可拖动，可点击。SVG具有体积小，不失真的优点。而且由于保存的是路径信息，可以做到复杂图形的点击判断功能。还是很香的。
效果
实现
原理，SVG 意为可缩放矢量图形（Scalable Vector Graphics）。 SVG 使用 XML 格式定义图像。在xml中定义了路径，只需要将路径解析保存到path中。再绘制出来就行了。
svg地图的获取
使用如下地址
String url="https://pixelmap.amcharts.com/";
下载需要的地图
下载以后的地图内容是这样的。
这种xml格式需要转换为Android支持的格式，很简单。new一个Vector Asset
控件实现
svg解析
转换以后的svg图片也只有125kb。而且怎么放大也不会失真。svg真香。
转换为android的svg格式以后。其中每个path保存的就是每个省的地图数据，而其中的pathData就是具体的路径。
svg解析是放在单独的线程中进行的，避免造成UI卡顿，其原理就是解析XML文件。最后通过Android官方的。PathParser 将svg的路径数据解析成对应的path。
Path path = PathParser.createPathFromPathData(pathData);
还有一点就是定义了一个 MapItem用来保存下一级对象的路径，是否被点击等信息。其中的绘制功能，和判断是否被点击也是由该类完成。
class MapItem {
Path path;
private final Region region;
private boolean isSelected = false;
private final RectF rectF;
private final int index;
public boolean onTouch(float x, float y) {
if (region.contains((int) x, (int) y)) {
isSelected = true;
return true;
}
isSelected = false;
return false;
}
public MapItem(Path path, int index) {
this.path = path;
rectF = new RectF();
path.computeBounds(rectF, true);
region = new Region();
region.setPath(path, new Region(new Rect((int) rectF.left
, (int) rectF.top, (int) rectF.right, (int) rectF.bottom)));
this.index = index;
}
protected void onDraw(Canvas canvas, Paint paint) {
paint.reset();
paint.setColor(isSelected ? Color.YELLOW : Color.GRAY);
paint.setStyle(Paint.Style.FILL);
canvas.drawPath(path, paint);
paint.setStyle(Paint.Style.STROKE);
paint.setColor(Color.RED);
canvas.drawPath(path, paint);
paint.setColor(Color.GRAY);
paint.setColor(Color.BLUE);
// canvas.drawText(index+"",rectF.centerX(),rectF.centerY(),paint);
}
}缩放
关于缩放使用的是系统自带的GestureDetector和ScaleGestureDetector，其中GestureDetector用来实现拖动，滑动，ScaleGestureDetector用来实现双指缩放。具体用法可以自行百度。我讲一下其中需要注意的点。在SVG刚解析出来的时候需要，解析出其中的android:width
去掉其中的dp。比如上图的1920dp去掉以后就是1920 。这个就行svg中路径的绘制坐标系中的宽度。通过它和我们控件的宽度就行缩放就可以将svg图片完整的显示在控件里面。
上面的vectorWidth 就是记录的svg中的初始宽度，在onDraw中就行计算。其中的viewScale代表的就是将svg完整展示到view中的需要的缩放比，这个值初始化以后是不会改变的。
用户手指缩放改变的是变量userScale。 用户拖动改变的是offsetX,offsetY 手指缩放的中心点用变量focusX和focusY
这些变量最后都会作用到一个matrix中。再绘制之前调用
canvas.setMatrix(matrix);
就可以实现图形的缩放，拖动。
而invertMatrix是matrix的逆矩阵。用于将手势的坐标映射为svg中的坐标。所有手势操作之前都需要调用以下代码进行坐标转换。
invertMatrix.mapPoints(points);
还有一点需要注意。用户滚动和滑动都需要对距离和速度进行缩放。
源码
一共只有319行，直接粘贴过来了。
package com.trs.app.learnview.view;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Region;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import android.widget.Scroller;
import androidx.annotation.Nullable;
import androidx.core.graphics.PathParser;
import com.trs.app.learnview.R;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
/**
* Created by zhuguohui
* Date: 2021/12/28
* Time: 10:56
* Desc:
*/
public class MapView extends View {
private List<MapItem> list = new ArrayList<>();
private Paint paint;
private int vectorWidth = -1;
private Matrix matrix = new Matrix();
private Matrix invertMatrix = new Matrix();
private float viewScale = -1f;
private float userScale = 1.0f;
private boolean initFinish = false;
private int bgColor;
private GestureDetector gestureDetector;
private int offsetX, offsetY;
private Scroller scroller;
private float[] points;
private float[] pointsFocusBefore;
private float focusX, focusY;
private ScaleGestureDetector scaleGestureDetector;
private boolean showDebugInfo = false;
private static final int MAX_SCROLL = 10000;
private static final int MIN_SCROLL = -10000;
private int mapId = R.raw.ic_african;
public MapView(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
init();
}
private void init() {
bgColor = Color.parseColor("#f5f5f5");
paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.GRAY);
scroller = new Scroller(getContext());
gestureDetector = new GestureDetector(getContext(), onGestureListener);
scaleGestureDetector = new ScaleGestureDetector(getContext(), scaleGestureListener);
}
private ScaleGestureDetector.OnScaleGestureListener scaleGestureListener = new ScaleGestureDetector.OnScaleGestureListener() {
float lastScaleFactor;
boolean mapPoint = false;
@Override
public boolean onScale(ScaleGestureDetector detector) {
float scaleFactor = detector.getScaleFactor();
float[] points = new float[]{detector.getFocusX(), detector.getFocusY()};
pointsFocusBefore = new float[]{detector.getFocusX(), detector.getFocusY()};
if (mapPoint) {
mapPoint = false;
invertMatrix.mapPoints(points);
focusX = points[0];
focusY = points[1];
}
float change = scaleFactor - lastScaleFactor;
lastScaleFactor = scaleFactor;
userScale += change;
postInvalidate();
return false;
}
@Override
public boolean onScaleBegin(ScaleGestureDetector detector) {
lastScaleFactor = 1.0f;
mapPoint = true;
return true;
}
@Override
public void onScaleEnd(ScaleGestureDetector detector) {
}
};
private GestureDetector.OnGestureListener onGestureListener = new GestureDetector.OnGestureListener() {
@Override
public boolean onDown(MotionEvent e) {
return true;
}
@Override
public void onShowPress(MotionEvent e) {
}
@Override
public boolean onSingleTapUp(MotionEvent event) {
boolean result = false;
float x = event.getX();
float y = event.getY();
points = new float[]{x, y};
invertMatrix.mapPoints(points);
for (MapItem item : list) {
if (item.onTouch(points[0], points[1])) {
result = true;
}
}
postInvalidate();
return result;
}
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
offsetX += -distanceX / userScale;
offsetY += -distanceY / userScale;
postInvalidate();
return true;
}
@Override
public void onLongPress(MotionEvent e) {
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
scroller.fling(offsetX, offsetY, (int) ((int) velocityX / userScale), (int) ((int) velocityY / userScale), MIN_SCROLL,
MAX_SCROLL, MIN_SCROLL, MAX_SCROLL);
postInvalidate();
return true;
}
};
@Override
public boolean onTouchEvent(MotionEvent event) {
gestureDetector.onTouchEvent(event);
scaleGestureDetector.onTouchEvent(event);
return true;
}
public void setMapId(int mapId) {
this.mapId = mapId;
userScale=1.0f;
offsetY=0;
offsetX=0;
focusX=0;
focusY=0;
new Thread(new DecodeRunnable()).start();
}
private class DecodeRunnable implements Runnable {
@Override
public void run() {
//Dom 解析 SVG文件
InputStream inputStream = getContext().getResources().openRawResource(mapId);
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(inputStream);
Element rootElement = doc.getDocumentElement();
String strWidth = rootElement.getAttribute("android:width");
vectorWidth = Integer.parseInt(strWidth.replace("dp", ""));
NodeList items = rootElement.getElementsByTagName("path");
list.clear();
for (int i = 1; i < items.getLength(); i++) {
Element element = (Element) items.item(i);
String pathData = element.getAttribute("android:pathData");
@SuppressLint("RestrictedApi")
Path path = PathParser.createPathFromPathData(pathData);
MapItem item = new MapItem(path, i);
list.add(item);
}
initFinish = true;
postInvalidate();
} catch (Exception e) {
e.printStackTrace();
}
}
};
@Override
public void computeScroll() {
if (scroller.computeScrollOffset()) {
offsetX = scroller.getCurrX();
offsetY = scroller.getCurrY();
invalidate();
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.save();
if (vectorWidth != -1 && viewScale == -1) {
int width = getWidth();
viewScale = width * 1.0f / vectorWidth;
}
if (viewScale != -1) {
float scale = viewScale * userScale;
matrix.reset();
matrix.postTranslate(offsetX, offsetY);
matrix.postScale(scale, scale, focusX, focusY);
invertMatrix.reset();
matrix.invert(invertMatrix);
}
canvas.setMatrix(matrix);
canvas.drawColor(bgColor);
if (initFinish) {
for (MapItem item : list) {
item.onDraw(canvas, paint);
}
}
showDebugInfo(canvas);
}
private void showDebugInfo(Canvas canvas) {
if (!showDebugInfo) {
return;
}
if (points != null) {
paint.setColor(Color.GREEN);
paint.setStyle(Paint.Style.FILL);
canvas.drawCircle(points[0], points[1], 20, paint);
}
paint.setColor(Color.BLUE);
paint.setStyle(Paint.Style.FILL);
canvas.drawCircle(focusX, focusY, 20, paint);
if (pointsFocusBefore != null) {
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL);
canvas.drawCircle(pointsFocusBefore[0], pointsFocusBefore[1], 20, paint);
}
}
}
class MapItem {
Path path;
private final Region region;
private boolean isSelected = false;
private final RectF rectF;
private final int index;
public boolean onTouch(float x, float y) {
if (region.contains((int) x, (int) y)) {
isSelected = true;
return true;
}
isSelected = false;
return false;
}
public MapItem(Path path, int index) {
this.path = path;
rectF = new RectF();
path.computeBounds(rectF, true);
region = new Region();
region.setPath(path, new Region(new Rect((int) rectF.left
, (int) rectF.top, (int) rectF.right, (int) rectF.bottom)));
this.index = index;
}
protected void onDraw(Canvas canvas, Paint paint) {
paint.reset();
paint.setColor(isSelected ? Color.YELLOW : Color.GRAY);
paint.setStyle(Paint.Style.FILL);
canvas.drawPath(path, paint);
paint.setStyle(Paint.Style.STROKE);
paint.setColor(Color.RED);
canvas.drawPath(path, paint);
paint.setColor(Color.GRAY);
paint.setColor(Color.BLUE);
// canvas.drawText(index+"",rectF.centerX(),rectF.centerY(),paint);
}
}Demo
最后想看效果的可以下载demo运行。
String url="https://github.com/zhuguohui/MapView";
总结
做技术总是需要厚积薄发，这样工作才能游刃有余。项目中虽然不需要，但是学习的脚步不能停止。提高自己解决问题的广度和深度，才是程序员的核心价值。
到此这篇关于Android如何利用svg实现可缩放的地图控件的文章就介绍到这了,更多相关Android svg实现可缩放地图控件内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！