Introduction

Wrapandroid and CLE project gives a choice to write android gui applications with multiple languages, such as python, lua, or c++. This article continues to talk about writing programming using c++. For gui applications, list view control is the most commonly used control, which is to present information to users to perform some action. For list view, to speed up scroll speed, a view holder is often used. We can find many materials talking about it in java. But how to write holder using c++?

Android gui object is wrapped with a cle object. For each cle object, cle presents functions “MallocPrivateBuf” and “GetPrivateBuf” to malloc it private buf, which can be used to contain objects pointers. The buffer will be freed with object automatically. Like this:

struct Holder{

void *Object1;

void *Object2;

…

}*holder;

holder = (struct Holder *)SRPInterface -> MallocPrivateBuf(…);

and then get the holder,

holder = (struct Holder *)SRPInterface -> GetPrivateBuf(…);

Begin programming

Using eclipse and NDK to development application. How to install them, please refer to other related articles. Android version should be above 2.2. Wrapandroid has updated to version 0.9.0, please download from http://code.google.com/p/wrapandroid-for-multilanguage. CLE has update to version r7, website is http://www.code.google.com/p/cle-for-android.

Steps :

a. Open eclipse, create a new android project named “listviewholder”

b. cle may be installed from network when application started, in this case, the following permission should be added:

<uses-permission android:name="android.permission.INTERNET" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

c. Copy java library starcore_android_r7.jar and wrapandroid.jar to project directory, and add them into project:

d. edit ListviewholderActivity.java，changed as follow，loading native share library.

import com.srplab.wrapandroid.*;

public class ListviewholderActivity extends WrapAndroidActivity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

//setContentView(R.layout.main);

StarActivity._Call("DoFile","","/data/data/"+getPackageName()+"/lib/libCode.so");

}

d. cle may also be included in the project, in this case, you should copy share libraries of cle to the directory of the project:

And change download flag to false

public class ListviewholderActivity extends WrapAndroidActivity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

DownloadFromNetFlag = false;

super.onCreate(savedInstanceState);

//setContentView(R.layout.main);

StarActivity._Call("DoFile","","/data/data/"+getPackageName()+"/lib/libCode.so");

}

e. edit listview layout：vlist2.xml.

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:orientation="horizontal"

android:layout_width="fill_parent"

android:layout_height="fill_parent">

<ImageView android:id="@+id/img"