第3章（第24讲） 示例24

分类：C#、Android、百度地图应用； 日期：2016-02-04

一、简介

百度地图SDK为广大开发者开放了OpenGL绘制接口，帮助开发者在地图上实现更灵活的样式绘制，丰富地图使用效果体验。

二、运行截图

简介：介绍如何使用OpenGL在地图上实现自定义绘制。

详述：

（1）利用OpenGL绘制基本折线；

（2）利用OpenGL在地图上进行纹理绘制；

本示例运行截图如下：

三、设计步骤

1、添加demo24_opengl.在layout文件夹下添加该文件，然后将代码改为下面的内容：

<??><RelativeLayout ="http://schemas.android.com/apk/res/android"  android:layout_width="fill_parent"  android:layout_height="fill_parent"  android:orientation="vertical" > <com.baidu.mapapi.map.TextureMapView   android:id="@+id/bmapView"   android:layout_width="match_parent"   android:layout_height="fill_parent" /></RelativeLayout>

2、添加Demo24OpenGL.cs文件

在SrcSdkDemos文件夹下添加该文件，然后将代码改为下面的内容：

using Android.App;using Android.OS;using Com.Baidu.Mapapi.Map;using Com.Baidu.Mapapi.Model;using Android.Graphics;using Android.Util;using System.Collections.Generic;using Javax.Microedition.Khronos.Opengles;using Java.Nio;using Android.Opengl;namespace BdMapV371Demos.SrcSdkDemos{  /// <summary>  /// 此demo用来展示如何在地图绘制的每帧中再额外绘制一些用户自己的内容  /// </summary>  [Activity(Label = "@string/demo_name_opengl")]  public class Demo24OpenGL : Activity, BaiduMap.IOnMapDrawFrameCallback  {    // 地图相关    private TextureMapView mMapView;    private BaiduMap mBaiduMap;    private Bitmap bitmap;    private LatLng latlng1 = new LatLng(39.97923, 116.357428);    private LatLng latlng2 = new LatLng(39.94923, 116.397428);    private LatLng latlng3 = new LatLng(39.96923, 116.437428);    private IList<LatLng> latLngPolygon;    private float[] vertexs;    private FloatBuffer vertexBuffer;    private int textureId = -1;    private readonly string LTAG = "Demo24OpenGL";    protected override void OnCreate(Bundle savedInstanceState)    {      base.OnCreate(savedInstanceState);      SetContentView(Resource.Layout.demo24_opengl);      mMapView = FindViewById<TextureMapView>(Resource.Id.bmapView);      mBaiduMap = mMapView.Map;      latLngPolygon = new List<LatLng>()      {        latlng1,latlng2,latlng3      };      mBaiduMap.SetOnMapDrawFrameCallback(this);      bitmap = BitmapFactory.DecodeResource(Resources,        Resource.Drawable.ground_overlay);    }    protected override void OnPause()    {      mMapView.OnPause();      base.OnPause();    }    protected override void OnResume()    {      mMapView.OnResume();      textureId = -1;      base.OnResume();    }    protected override void OnDestroy()    {      mMapView.OnDestroy();      base.OnDestroy();    }    public void OnMapDrawFrame(IGL10 gl, MapStatus drawingMapStatus)    {      if (mBaiduMap.Projection != null)      {        calPolylinePoint(drawingMapStatus);        drawPolyline(gl, Color.Argb(255, 255, 0, 0), vertexBuffer, 10, 3,            drawingMapStatus);        drawTexture(gl, bitmap, drawingMapStatus);      }    }    public void calPolylinePoint(MapStatus mspStatus)    {      PointF[] polyPoints = new PointF[latLngPolygon.Count];      vertexs = new float[3 * latLngPolygon.Count];      int i = 0;      foreach (LatLng xy in latLngPolygon)      {        polyPoints[i] = mBaiduMap.Projection.ToOpenGLLocation(xy, mspStatus);        vertexs[i * 3] = polyPoints[i].X;        vertexs[i * 3 + 1] = polyPoints[i].Y;        vertexs[i * 3 + 2] = 0.0f;        i++;      }      for (int j = 0; j < vertexs.Length; j++)      {        Log.Debug(LTAG, "vertexs[" + j + "]: " + vertexs[j]);      }      vertexBuffer = makeFloatBuffer(vertexs);    }    private FloatBuffer makeFloatBuffer(float[] fs)    {      ByteBuffer bb = ByteBuffer.AllocateDirect(fs.Length * 4);      bb.Order(ByteOrder.NativeOrder());      FloatBuffer fb = bb.AsFloatBuffer();      fb.Put(fs);      fb.Position(0);      return fb;    }    private void drawPolyline(IGL10 gl, int color, FloatBuffer lineVertexBuffer,        float lineWidth, int pointSize, MapStatus drawingMapStatus)    {      gl.GlEnable(GL10.GlBlend);      gl.GlEnableClientState(GL10.GlVertexArray);      gl.GlBlendFunc(GL10.GlSrcAlpha, GL10.GlOneMinusSrcAlpha);      float colorA = Color.GetAlphaComponent(color) / 255f;      float colorR = Color.GetRedComponent(color) / 255f;      float colorG = Color.GetGreenComponent(color) / 255f;      float colorB = Color.GetBlueComponent(color) / 255f;      gl.GlVertexPointer(3, GL10.GlFloat, 0, lineVertexBuffer);      gl.GlColor4f(colorR, colorG, colorB, colorA);      gl.GlLineWidth(lineWidth);      gl.GlDrawArrays(GL10.GlLineStrip, 0, pointSize);      gl.GlDisable(GL10.GlBlend);      gl.GlDisableClientState(GL10.GlVertexArray);    }    /// <summary>    /// 使用opengl坐标绘制    /// </summary>    /// <param name="gl"></param>    /// <param name="bitmap"></param>    /// <param name="drawingMapStatus"></param>    public void drawTexture(IGL10 gl, Bitmap bitmap, MapStatus drawingMapStatus)    {      PointF p1 = mBaiduMap.Projection.ToOpenGLLocation(latlng2,          drawingMapStatus);      PointF p2 = mBaiduMap.Projection.ToOpenGLLocation(latlng3,          drawingMapStatus);      ByteBuffer byteBuffer = ByteBuffer.AllocateDirect(4 * 3 * 4);      byteBuffer.Order(ByteOrder.NativeOrder());      FloatBuffer vertices = byteBuffer.AsFloatBuffer();      vertices.Put(new float[] { p1.X, p1.Y, 0.0f, p2.X, p1.Y, 0.0f, p1.X,        p2.Y, 0.0f, p2.X, p2.Y, 0.0f });      ByteBuffer indicesBuffer = ByteBuffer.AllocateDirect(6 * 2);      indicesBuffer.Order(ByteOrder.NativeOrder());      ShortBuffer indices = indicesBuffer.AsShortBuffer();      indices.Put(new short[] { 0, 1, 2, 1, 2, 3 });      ByteBuffer textureBuffer = ByteBuffer.AllocateDirect(4 * 2 * 4);      textureBuffer.Order(ByteOrder.NativeOrder());      FloatBuffer texture = textureBuffer.AsFloatBuffer();      texture.Put(new float[] { 0, 1f, 1f, 1f, 0f, 0f, 1f, 0f });      indices.Position(0);      vertices.Position(0);      texture.Position(0);      // 生成纹理      if (textureId == -1)      {        int[] textureIds = new int[1];        gl.GlGenTextures(1, textureIds, 0);        textureId = textureIds[0];        Log.Debug(LTAG, "textureId: " + textureId);        gl.GlBindTexture(GL10.GlTexture2d, textureId);        GLUtils.TexImage2D(GL10.GlTexture2d, 0, bitmap, 0);        gl.GlTexParameterf(GL10.GlTexture2d, GL10.GlTextureMinFilter, GL10.GlNearest);        gl.GlTexParameterf(GL10.GlTexture2d, GL10.GlTextureMagFilter, GL10.GlNearest);        gl.GlBindTexture(GL10.GlTexture2d, 0);      }      gl.GlEnable(GL10.GlTexture2d);      gl.GlEnableClientState(GL10.GlVertexArray);      gl.GlEnableClientState(GL10.GlTextureCoordArray);      gl.GlEnable(GL10.GlBlend);      gl.GlBlendFunc(GL10.GlSrcAlpha, GL10.GlOneMinusSrcAlpha);      gl.GlColor4f(1.0f, 1.0f, 1.0f, 1.0f);      // 绑定纹理ID      gl.GlBindTexture(GL10.GlTexture2d, textureId);      gl.GlVertexPointer(3, GL10.GlFloat, 0, vertices);      gl.GlTexCoordPointer(2, GL10.GlFloat, 0, texture);      gl.GlDrawElements(GL10.GlTriangleStrip, 6, GL10.GlUnsignedShort, indices);      gl.GlDisable(GL10.GlTexture2d);      gl.GlDisableClientState(GL10.GlVertexArray);      gl.GlDisableClientState(GL10.GlTextureCoordArray);      gl.GlDisable(GL10.GlBlend);    }  }}

3、修改MainActivity.cs文件

在MainActivity.cs文件的demos字段定义中，去掉【示例24】下面的注释。

运行观察效果。

原标题：第3章（第24讲） 示例24

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