libgdx通過鼠標點擊繪製矩形

Question

我正在嘗試使用libgdx或更好的OpenGL。因爲我的演講，我不得不面對Java。

我想繪製一個背景，我可以用鼠標點擊鼠標並在鼠標位置（當我點擊時）繪製一個新的矩形。所以「舊」矩形必須留在那裏。

這是我到目前爲止的代碼：

package com.ru.tgra.lab1; 


import com.badlogic.gdx.ApplicationAdapter; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.graphics.GL20; 

import java.nio.FloatBuffer; 

import com.badlogic.gdx.utils.BufferUtils; 

public class Lab1Game extends ApplicationAdapter { 

private FloatBuffer vertexBuffer; 

private FloatBuffer modelMatrix; 
private FloatBuffer projectionMatrix; 

private int renderingProgramID; 
private int vertexShaderID; 
private int fragmentShaderID; 

private int positionLoc; 

private int modelMatrixLoc; 
private int projectionMatrixLoc; 

private int colorLoc; 

private float position_x; 
private float position_y; 
private float size_rect = 100; 

private int screenWidth; 
private int screenHeight; 


@Override 
public void create() { 

    String vertexShaderString; 
    String fragmentShaderString; 

    vertexShaderString = Gdx.files.internal("shaders/simple2D.vert").readString(); 
    fragmentShaderString = Gdx.files.internal("shaders/simple2D.frag").readString(); 

    vertexShaderID = Gdx.gl.glCreateShader(GL20.GL_VERTEX_SHADER); 
    fragmentShaderID = Gdx.gl.glCreateShader(GL20.GL_FRAGMENT_SHADER); 

    Gdx.gl.glShaderSource(vertexShaderID, vertexShaderString); 
    Gdx.gl.glShaderSource(fragmentShaderID, fragmentShaderString); 

    Gdx.gl.glCompileShader(vertexShaderID); 
    Gdx.gl.glCompileShader(fragmentShaderID); 

    renderingProgramID = Gdx.gl.glCreateProgram(); 

    Gdx.gl.glAttachShader(renderingProgramID, vertexShaderID); 
    Gdx.gl.glAttachShader(renderingProgramID, fragmentShaderID); 

    Gdx.gl.glLinkProgram(renderingProgramID); 

    positionLoc    = Gdx.gl.glGetAttribLocation(renderingProgramID, "a_position"); 
    Gdx.gl.glEnableVertexAttribArray(positionLoc); 

    modelMatrixLoc   = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_modelMatrix"); 
    projectionMatrixLoc = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_projectionMatrix"); 

    colorLoc    = Gdx.gl.glGetUniformLocation(renderingProgramID, "u_color"); 

    Gdx.gl.glUseProgram(renderingProgramID); 

    float[] pm = new float[16]; 

    pm[0] = 2.0f/Gdx.graphics.getWidth(); pm[4] = 0.0f; pm[8] = 0.0f; pm[12] = -1.0f; 
    pm[1] = 0.0f; pm[5] = 2.0f/Gdx.graphics.getHeight(); pm[9] = 0.0f; pm[13] = -1.0f; 
    pm[2] = 0.0f; pm[6] = 0.0f; pm[10] = 1.0f; pm[14] = 0.0f; 
    pm[3] = 0.0f; pm[7] = 0.0f; pm[11] = 0.0f; pm[15] = 1.0f; 

    projectionMatrix = BufferUtils.newFloatBuffer(16); 
    projectionMatrix.put(pm); 
    projectionMatrix.rewind(); 
    Gdx.gl.glUniformMatrix4fv(projectionMatrixLoc, 1, false, projectionMatrix); 


    float[] mm = new float[16]; 

    mm[0] = 1.0f; mm[4] = 0.0f; mm[8] = 0.0f; mm[12] = 0.0f; 
    mm[1] = 0.0f; mm[5] = 1.0f; mm[9] = 0.0f; mm[13] = 0.0f; 
    mm[2] = 0.0f; mm[6] = 0.0f; mm[10] = 1.0f; mm[14] = 0.0f; 
    mm[3] = 0.0f; mm[7] = 0.0f; mm[11] = 0.0f; mm[15] = 1.0f; 

    modelMatrix = BufferUtils.newFloatBuffer(16); 
    modelMatrix.put(mm); 
    modelMatrix.rewind(); 

    Gdx.gl.glUniformMatrix4fv(modelMatrixLoc, 1, false, modelMatrix); 

    //COLOR IS SET HERE 
    Gdx.gl.glUniform4f(colorLoc, 0.7f, 0.2f, 0, 1); 


    //VERTEX ARRAY IS FILLED HERE 
    float[] array = {-50.0f, -50.0f, 
        -50.0f, 50.0f, 
        50.0f, -50.0f, 
        50.0f, 50.0f}; 

    vertexBuffer = BufferUtils.newFloatBuffer(8); 
    vertexBuffer.put(array); 
    vertexBuffer.rewind(); 

    position_x = 300; 
    position_y = 300; 

    screenWidth = Gdx.graphics.getWidth(); 
    screenHeight = Gdx.graphics.getHeight(); 

    size_rect = size_rect/2; 
} 

private void update() 
{ 
    if(Gdx.input.justTouched()) 
    { 
     position_x = Gdx.input.getX(); 
     position_y = screenHeight - Gdx.input.getY(); 

     vertexBuffer.put(0, position_x - size_rect); 
     vertexBuffer.put(1, position_y - size_rect); 
     vertexBuffer.put(2, position_x - size_rect); 
     vertexBuffer.put(3, position_y + size_rect); 
     vertexBuffer.put(4, position_x + size_rect); 
     vertexBuffer.put(5, position_y - size_rect); 
     vertexBuffer.put(6, position_x + size_rect); 
     vertexBuffer.put(7, position_y + size_rect); 


    } 

    Gdx.gl.glVertexAttribPointer(positionLoc, 2, GL20.GL_FLOAT, false, 0, vertexBuffer); 
    Gdx.gl.glDrawArrays(GL20.GL_TRIANGLE_STRIP, 0, 4); 

} 

@Override 
public void render() { 

    Gdx.gl.glClearColor(0.7f, 1f, 1f, 1f); 
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); 

    update(); 
} 
} 

不幸的是我不知道如何「拯救」的矩形（或座標）動態..

是否有人有一個很好的提示我或者你如何做到這一點的簡短代碼示例？

Answer 1

只需存儲一個變量，該變量存儲最新矩形頂點的起始索引，另一個變量用於存放矩形數。

private int m_numRectangles; 
private int m_nextRectIndex; 

//initialize both above variables to 0 

//... 

if(Gdx.input.justTouched()) 
{ 
    m_nextRectIndex = m_numRectangles * 8; 
    m_numRectangles++; 

    //save a copy of the old rectangles 
    vertexBuffer.rewind(); 
    Float[] oldRects = new Float[ vertexBuffer.remaining() ]; 
    vertexBuffer.get(oldRects); 

    //allocate more memory for old + one more rectangle 
    vertexBuffer = BufferUtils.newFloatBuffer(m_numRectangles * 8); 

    //copy back the old rectangles 
    vertexBuffer.put(oldbuffer); 
    vectexBuffer.rewind(); 

    position_x = Gdx.input.getX(); 
    position_y = screenHeight - Gdx.input.getY(); 

    vertexBuffer.put(m_nextRectIndex + 0, position_x - size_rect); 
    vertexBuffer.put(m_nextRectIndex + 1, position_y - size_rect); 
    vertexBuffer.put(m_nextRectIndex + 2, position_x - size_rect); 
    vertexBuffer.put(m_nextRectIndex + 3, position_y + size_rect); 
    vertexBuffer.put(m_nextRectIndex + 4, position_x + size_rect); 
    vertexBuffer.put(m_nextRectIndex + 5, position_y - size_rect); 
    vertexBuffer.put(m_nextRectIndex + 6, position_x + size_rect); 
    vertexBuffer.put(m_nextRectIndex + 7, position_y + size_rect); 

} 
Gdx.gl.glVertexAttribPointer(positionLoc, 2, GL20.GL_FLOAT, false, 0, vertexBuffer); 
for(int i=0; i<m_numRectangles * 4; i+=4) 
{ 
    Gdx.gl.glDrawArrays(GL20.GL_TRIANGLE_STRIP, i, 4); 
}