JNI DETECTED ERROR IN APPLICATION: jarray was NULL
项目中用到了opengles去展示三维点云数据，个人比较生疏，所以打算学一学。根据官方的示例先画了一个三角形，后面在画方形的时候怎么都不成功，报错:JNI DETECTED ERROR IN APPLICATION: jarray was NULL。可是对比别人的代码和自己的代码，根本看不出有什么区别，从别人的博客中看到以下内容:
在Java中当我们要对数据进行更底层的操作时，一般是操作数据的字节（byte）形式，这时经常会用到
ByteBuffer这样一个类。ByteBuffer提供了两种静态实例方式：
public static ByteBuffer allocate(int capacity)
public static ByteBuffer allocateDirect(int capacity)
为什么要提供两种方式呢？这与Java的内存使用机制有关。第一种分配方式产生的内存开销是在JVM中的，
而另外一种的分配方式产生的开销在JVM之外，以就是系统级的内存分配。当Java程序接收到外部传来的数据时，
首先是被系统内存所获取，然后在由系统内存复制复制到JVM内存中供Java程序使用。所以在另外一种分配方式
中，能够省去复制这一步操作，效率上会有所提高。可是系统级内存的分配比起JVM内存的分配要耗时得多，所以
并非不论什么时候allocateDirect的操作效率都是最高的前面在写三角形之前已经了解到了，opengles是不能直接使用java jvm分配的内存的，要将数组转换到系统内存才能使用，
我的示例里面因为用了这个所以一直报数组是空的
改成这样，方形就绘制出来了。
三角形和方形源码
public class Triangle {
private FloatBuffer vertextBuffer;
//number of coordinates per vertex in this array
//每个顶点的坐标包括x,y,z 三个
static final int COORDS_PER_VERTEXT = 3;
//顺时针的顺序
static float triangleCoords[] = { // in counterclockwise order:
0.0f, 0.622008459f, 0.0f, // top
-0.5f, -0.311004243f, 0.0f, // bottom left
0.5f, -0.311004243f, 0.0f // bottom right
};
// Set color with red, green, blue and alpha (opacity) values
float color[] = {0.63671875f, 0.76953125f, 0.22265625f, 1.0f};
//1.为顶点在native层分配缓冲区内存，然后将顶点坐标放进缓冲区
//2.绘制需要顶点着色器和片段着色器
//绘制形状需要一个顶点着色程序和一个片段着色程序
private final String vertexShaderCode =
"attribute vec4 vPosition;" +
"void main() {" +
" gl_Position = vPosition;" +
"}";
private final String fragmentShaderCode =
"precision mediump float;" +
"uniform vec4 vColor;" +
"void main() {" +
" gl_FragColor = vColor;" +
"}";
private final int mProgram;
private int positionHandle;
private int colorHandle;
//顶点数
private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEXT;
//每个顶点占的字节数
private final int vertexStride = COORDS_PER_VERTEXT * 4;
public Triangle() {
// 初始化顶点字节的缓冲区
//需要在native 层分配内存
ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
// 使用设备硬件的本机字节顺序
bb.order(ByteOrder.nativeOrder());
// 创建float缓冲区
vertextBuffer = bb.asFloatBuffer();
//将顶点坐标放进float缓冲区
vertextBuffer.put(triangleCoords);
// 设置缓冲区以读取第一个坐标
vertextBuffer.position(0);
int vertextShader = GlRender_1.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = GlRender_1.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
// create empty OpenGL ES Program
mProgram = GLES20.glCreateProgram();
//将顶点着色器添加到项目
GLES20.glAttachShader(mProgram, vertextShader);
GLES20.glAttachShader(mProgram, fragmentShader);
// creates OpenGL ES program executables
GLES20.glLinkProgram(mProgram);
}
public void draw() {
// Add program to OpenGL ES environment
GLES20.glUseProgram(mProgram);
// get handle to vertex shader's vPosition member
positionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
// Enable a handle to the triangle vertices
GLES20.glEnableVertexAttribArray(positionHandle);
// Prepare the triangle coordinate data
GLES20.glVertexAttribPointer(positionHandle,
vertexCount,
GLES20.GL_FLOAT,
false,
vertexStride,
vertextBuffer);
// get handle to fragment shader's vColor member
colorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
// Set color for drawing the triangle
GLES20.glUniform4fv(colorHandle, 1, color, 0);
// Draw the triangle
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount);
// Disable vertex array
GLES20.glDisableVertexAttribArray(positionHandle);
}
}public class Square {
//1.顶点坐标缓冲区
private FloatBuffer vertextBuffer;
//2.绘制顺序缓冲区
private ShortBuffer drawListBuffer;
//每个顶点包含坐标个数
static final int COORDS_PER_VERTEXT = 3;
static float squareCoords[] = {
-0.5f, 0.5f, 0.0f, // top left
-0.5f, -0.5f, 0.0f, // bottom left
0.5f, -0.5f, 0.0f, // bottom right
0.5f, 0.5f, 0.0f}; // top right
static short drawOrder[] = {0, 1, 2, 0, 2, 3};
private final int vertexCount = squareCoords.length / COORDS_PER_VERTEXT;
private final int vertextStride = COORDS_PER_VERTEXT * 4;
private final int mProgram;
//绘制形状需要一个顶点着色程序和一个片段着色程序
private final String vertexShaderCode =
"attribute vec4 vPosition;" +
"void main() {" +
" gl_Position = vPosition;" +
"}";
private final String fragmentShaderCode =
"precision mediump float;" +
"uniform vec4 vColor;" +
"void main() {" +
" gl_FragColor = vColor;" +
"}";
// Set color with red, green, blue and alpha (opacity) values
float color[] = {0.63671875f, 0.76953125f, 0.22265625f, 1.0f};
private int positionHandle;
private int colorHandle;
public Square() {
//1.在native 层分配内存 float 占4个字节
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4);
//字节顺序
bb.order(ByteOrder.nativeOrder());
vertextBuffer = bb.asFloatBuffer();
vertextBuffer.put(squareCoords);
vertextBuffer.position(0);
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2);
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
int vertexShader = GlRender_1.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
int fragmentShader = GlRender_1.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
mProgram = GLES20.glCreateProgram();
GLES20.glAttachShader(mProgram, vertexShader);
GLES20.glAttachShader(mProgram, fragmentShader);
GLES20.glLinkProgram(mProgram);
}
public void draw() {
GLES20.glUseProgram(mProgram);
//顶点
positionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
GLES20.glEnableVertexAttribArray(positionHandle);
GLES20.glVertexAttribPointer(positionHandle, COORDS_PER_VERTEXT, GLES20.GL_FLOAT,
false, vertextStride, vertextBuffer);
//颜色
colorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
GLES20.glUniform4fv(colorHandle, 1, color, 0);
/**索引法绘制矩形*/
Log.i("test", "draw: "+drawListBuffer.toString());
Log.i("test", "draw: "+ Arrays.toString(drawOrder));
GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer);
//Disable vertex array
GLES20.glDisableVertexAttribArray(positionHandle);
}
}
说明:博客的所有内容均为自己探索实现的，受自身知识点的限制很多地方不一定正确的