JNI DETECTED ERROR IN APPLICATION: jarray was NULL

項目中用到了opengles去展示三維點雲數據，個人比較生疏，所以打算學一學。根據官方的示例先畫了一個三角形，後面在畫方形的時候怎麼都不成功，報錯:JNI DETECTED ERROR IN APPLICATION: jarray was NULL。可是對比別人的代碼和自己的代碼，根本看不出有什麼區別，從別人的博客中看到以下內容:

在Java中當我們要對數據進行更底層的操作時，一般是操作數據的字節（byte）形式，這時經常會用到
ByteBuffer這樣一個類。ByteBuffer提供了兩種靜態實例方式：
    public static ByteBuffer allocate(int capacity)  
    public static ByteBuffer allocateDirect(int capacity)  
爲什麼要提供兩種方式呢？這與Java的內存使用機制有關。第一種分配方式產生的內存開銷是在JVM中的，
而另外一種的分配方式產生的開銷在JVM之外，以就是系統級的內存分配。當Java程序接收到外部傳來的數據時，
首先是被系統內存所獲取，然後在由系統內存複製複製到JVM內存中供Java程序使用。所以在另外一種分配方式
中，能夠省去複製這一步操作，效率上會有所提高。可是系統級內存的分配比起JVM內存的分配要耗時得多，所以
並非不論什麼時候allocateDirect的操作效率都是最高的

前面在寫三角形之前已經瞭解到了，opengles是不能直接使用java jvm分配的內存的，要將數組轉換到系統內存才能使用，

我的示例裏面因爲用了這個所以一直報數組是空的

改成這樣，方形就繪製出來了。

三角形和方形源碼

public class Triangle {
    private FloatBuffer vertextBuffer;

    //number of coordinates per vertex in this array
    //每個頂點的座標包括x,y,z 三個
    static final int COORDS_PER_VERTEXT = 3;

    //順時針的順序
    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.爲頂點在native層分配緩衝區內存，然後將頂點座標放進緩衝區

    //2.繪製需要頂點着色器和片段着色器

    //繪製形狀需要一個頂點着色程序和一個片段着色程序
    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;

    //頂點數
    private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEXT;

    //每個頂點佔的字節數
    private final int vertexStride = COORDS_PER_VERTEXT * 4;

    public Triangle() {
        // 初始化頂點字節的緩衝區
        //需要在native 層分配內存
        ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
        // 使用設備硬件的本機字節順序
        bb.order(ByteOrder.nativeOrder());
        // 創建float緩衝區
        vertextBuffer = bb.asFloatBuffer();
        //將頂點座標放進float緩衝區
        vertextBuffer.put(triangleCoords);
        // 設置緩衝區以讀取第一個座標
        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();

        //將頂點着色器添加到項目
        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.頂點座標緩衝區
    private FloatBuffer vertextBuffer;
    //2.繪製順序緩衝區
    private ShortBuffer drawListBuffer;

    //每個頂點包含座標個數
    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;

    //繪製形狀需要一個頂點着色程序和一個片段着色程序
    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 層分配內存 float 佔4個字節
        ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4);
        //字節順序
        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);
        //頂點
        positionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        GLES20.glEnableVertexAttribArray(positionHandle);
        GLES20.glVertexAttribPointer(positionHandle, COORDS_PER_VERTEXT, GLES20.GL_FLOAT,
                false, vertextStride, vertextBuffer);
        //顏色
        colorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
        GLES20.glUniform4fv(colorHandle, 1, color, 0);
        /**索引法繪製矩形*/
        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);
    }


}

 

說明:博客的所有內容均爲自己探索實現的，受自身知識點的限制很多地方不一定正確的