这是一个关于RenderScript如何使用 Struct 的文章，是学习RenderScript 一个必须要掌握的基础知识点。
大纲
- 如何定义Struct
- 如何得到指针长度并循环为指针赋值
- 整体DEMO代码
如何定义Struct
RenderScript 里面定义结构有两种定义方法，参考如下：
1.
typedef struct tempArray { float2 position ; float size ;} Array_T ; Array_T *myArray;
2.
//定义一个struct
typedef struct __attribute__((packed, aligned(4))) tempArray { int temp ;} Array_T ;Array_T *myArray ;
RenderScript 定义Struct 成功后，会自动生成一个java文件，如上面的tempArray名称的结构，会生产这个文件:ScriptField_tempArray,代码如下：
/* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* * This file is auto-generated. DO NOT MODIFY! * The source Renderscript file: /home/terry/workspace/RenderScriptsArray/src/com/xuzhi/renderScriptArray/array.rs */ package com.xuzhi.renderScriptArray; import android.renderscript.*; import android.content.res.Resources; /** * @hide */ public class ScriptField_tempArray extends android.renderscript.Script.FieldBase { static public class Item { public static final int sizeof = 4; int temp; Item() { } } private Item mItemArray[]; private FieldPacker mIOBuffer; public static Element createElement(RenderScript rs) { Element.Builder eb = new Element.Builder(rs); eb.add(Element.I32(rs), "temp"); return eb.create(); } public ScriptField_tempArray(RenderScript rs, int count) { mItemArray = null; mIOBuffer = null; mElement = createElement(rs); init(rs, count); } public ScriptField_tempArray(RenderScript rs, int count, int usages) { mItemArray = null; mIOBuffer = null; mElement = createElement(rs); init(rs, count, usages); } private void copyToArrayLocal(Item i, FieldPacker fp) { fp.addI32(i.temp); } private void copyToArray(Item i, int index) { if (mIOBuffer == null) mIOBuffer = new FieldPacker(Item.sizeof * getType().getX() /* count */); mIOBuffer.reset(index * Item.sizeof); copyToArrayLocal(i, mIOBuffer); } public synchronized void set(Item i, int index, boolean copyNow) { if (mItemArray == null) mItemArray = new Item[getType().getX() /* count */]; mItemArray[index] = i; if (copyNow) { copyToArray(i, index); FieldPacker fp = new FieldPacker(Item.sizeof); copyToArrayLocal(i, fp); mAllocation.setFromFieldPacker(index, fp); } } public synchronized Item get( int index) { if (mItemArray == null) return null; return mItemArray[index]; } public synchronized void set_temp( int index, int v, boolean copyNow) { if (mIOBuffer == null) mIOBuffer = new FieldPacker(Item.sizeof * getType().getX() /* count */); if (mItemArray == null) mItemArray = new Item[getType().getX() /* count */]; if (mItemArray[index] == null) mItemArray[index] = new Item(); mItemArray[index].temp = v; if (copyNow) { mIOBuffer.reset(index * Item.sizeof); mIOBuffer.addI32(v); FieldPacker fp = new FieldPacker(4); fp.addI32(v); mAllocation.setFromFieldPacker(index, 0, fp); } } public synchronized int get_temp( int index) { if (mItemArray == null) return 0; return mItemArray[index].temp; } public synchronized void copyAll() { for ( int ct = 0; ct < mItemArray.length; ct++) copyToArray(mItemArray[ct], ct); mAllocation.setFromFieldPacker(0, mIOBuffer); } public synchronized void resize( int newSize) { if (mItemArray != null) { int oldSize = mItemArray.length; int copySize = Math.min(oldSize, newSize); if (newSize == oldSize) return; Item ni[] = new Item[newSize]; System.arraycopy(mItemArray, 0, ni, 0, copySize); mItemArray = ni; } mAllocation.resize(newSize); if (mIOBuffer != null) mIOBuffer = new FieldPacker(Item.sizeof * getType().getX() /* count */); } }
生成的代码是提供给你做内存分配和操作类似数组的功能。
如何得到指针长度并循环为指针赋值
RenderScript 有两个函数是专门用来获取指针长度的：
rsGetAllocation： 返回一个己经分配过地址的指针
rsAllocationGetDimX ：获取返回指针的长度
通过将这两个函数做组合使用可以返回指针长度,代码如下：
const int size = rsAllocationGetDimX(rsGetAllocation(myArray)) ;
取得了长度即可以为指针内部变量赋值，代码如下：
for(int i=0 ; i<size;i++){ array->temp=i ; //循环赋值 rsDebug("current value is ====>", array->temp) ; //打印当前值 //指向下个指针 array++ ; }
整体DEMO代码
本DEMO没有任何界面 ，只是演示如何使用struct并打印出指针下标原素的值，如此简单， 涉及的rs文件代码如下：
#pragma version(1) #pragma rs java_package_name(com.xuzhi.renderScriptArray) #include "rs_graphics.rsh" static int initialized = 0 ; //定义一个struct typedef struct __attribute__((packed, aligned(4))) tempArray { int temp ;} Array_T ;Array_T *myArray ; static void initArray(){ Array_T *array=myArray ; //得到struct长度 //1.返回一个己经分配过地址的指针 //2.获取返回指针的长度 const int size = rsAllocationGetDimX(rsGetAllocation(myArray)) ; for(int i=0 ; i<size;i++){ array->temp=i ; //循环赋值 rsDebug("current value is ====>", array->temp) ; //打印当前值 //指向下个指针 array++ ; } } int root(){ rsgClearColor(0.0f, 1.0f, 0.0f, 1.0f) ; if(initialized==0){ initArray() ; initialized=1 ; } return 16 ; }
java 代码如下：
package com.xuzhi.renderScriptArray; import android.app.Activity; import android.content.Context; import android.content.res.Resources; import android.os.Bundle; import android.renderscript.Allocation; import android.renderscript.RSSurfaceView; import android.renderscript.RenderScriptGL; public class RenderScriptsArrayActivity extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView( new renderScriptView( this)); } public class renderScriptRS { private ScriptC_array mScript; private ScriptField_tempArray array; RenderScriptGL mRS; public renderScriptRS(RenderScriptGL rs,Resources resource) { // TODO Auto-generated constructor stub mRS=rs; // 初始化struct 并为其指定有多少个下标 array= new ScriptField_tempArray(mRS, 10,Allocation.USAGE_SCRIPT|Allocation.USAGE_GRAPHICS_VERTEX); // 实始化CcriptC mScript= new ScriptC_array(mRS, resource, R.raw.array); // 绑定struct mScript.bind_myArray(array); // 绑定脚本 mRS.bindRootScript(mScript); } } public class renderScriptView extends RSSurfaceView { private RenderScriptGL mRS; private renderScriptRS mRender; public renderScriptView(Context context) { super(context); // TODO Auto-generated constructor stub } @Override protected void onAttachedToWindow() { super.onAttachedToWindow(); android.util.Log.e("rs", "onAttachedToWindow"); if (mRS == null) { RenderScriptGL.SurfaceConfig sc = new RenderScriptGL.SurfaceConfig(); mRS = createRenderScriptGL(sc); mRender = new renderScriptRS(mRS, getResources()); } } @Override protected void onDetachedFromWindow() { super.onDetachedFromWindow(); if (mRS != null) { mRS = null; destroyRenderScriptGL(); } } } }
都加了注释了，最主要的四段代码标注了红色，要注意。
运行结果：
03-09 15:47:50.492: D/RenderScript(2298): current value is ====> 0 0x0 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 1 0x1 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 2 0x2 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 3 0x3 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 4 0x4 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 5 0x5 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 6 0x6 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 7 0x7 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 8 0x8 03-09 15:47:50.507: D/RenderScript(2298): current value is ====> 9 0x9