android NDK 交叉编译

android中间件开发,本来利用NDK就直接生成了一个SO文件,然后直接打包到APK里,即可运行,但是由于一般真机是不带有root权限的,即使SSH可以解决root权限,当到了java层,root权限又失效了。经常碰到operation not permitted 或 permission delied 之类的错误,但目前还有一个可以运行在真机上的C编译器,因为手机的资源毕竟是很有限的,可喜的是android-NDK给我们提供了这个交叉编译环境,只是生成SO文件的时候,把里面的细节全部省掉了。不过还是保留了许多中间过程的开发HTML文档。下面说说具体的实现过程:

1,下载NDK,并配合NDK环境变量为NDK的安装路径

2,根据NDK里docs文档里的standalone-toolchain.html来抽取交叉编译的环境。

3,配置SYSROOT环境变量:  SYSROOT=$NDK/platforms/android-8/arch-arm //android-8是你的android开发版本所定
4,然后运行命令:

     $NDK/build/tools/make-standalone-toolchain.sh --platform=android-5 --install-dir=/tmp/my-android-toolchain

     /tmp/my-android-toolchain是你交叉编译环境的复制路径。最好别放在tmp目录里,因为重启机子就立即消失了。这个新生成的文件 夹即是你的交叉编译环境

5,配置PAHT和CC环境变量:

    export PATH=/tmp/my-android-toolchain/bin:$PATH
    export CC=arm-linux-androideabi-gcc
    如果需要长久有效,在/etc/profile里加上PATH=/..../bin:$PATH

                                                            export PATH

   其他的类似处理。

6,把你要需要编译的C文件放在以上生成的编译环境的bin目录下,例如:/tmp/my-android-toolchain/bin,进入这个目录里,输入命令: $CC -o  hello hello.c (这相当于我们平时的gcc命令,只是这里需要引用arm里的库,而不是X86里的库)

hello.c:

 #include<string.h>

 #include<stdio.h>
 int main()

 {

printf("hello,toolchain!/n");

return 0;

 }

 

即生成了可在手机arm里运行的可执行文件hello

7,把这个可执行文件hello放到手机里的/data/目录下,方法有很多,这里介绍两种:

    一、把这个文件放在电脑的某个目录下,然后进入DOS的这个目录下,运行如下命令:adb push hello /data/

    二、放在SDCARD目录下,然后执行cp /sdcard/hello /data/也可以

8,进入/data/目录下,运行这个hello文件,例如“./hello”,即可以在adb shell里看到打印结果: hello,toolchain!

# NDK Camera [![Build Status](https://travis-ci.org/luncliff/NdkCamera.svg?branch=master)](https://travis-ci.org/luncliff/NdkCamera) > If there is an issue with this library, please mail to luncliff@gmail.com Simplified [Android Camera 2 API](https://www.youtube.com/watch?v=Bi4QjMfSOE0). Available for both Java/JNI. - API level: 24+ - NDK ### Reference - Personal Template Project: https://github.com/luncliff/Muffin - [API Reference](https://developer.android.com/ndk/reference/group/camera) - [Android Camera Overview](https://source.android.com/devices/camera) - Camera HAL3: https://source.android.com/devices/camera/camera3 - HAL Subsystem: https://source.android.com/devices/camera/camera3_requests_hal - Multi-Camera Support: https://source.android.com/devices/camera/multi-camera - Version Support: https://source.android.com/devices/camera/versioning - Android Media - https://source.android.com/devices/media/framework-hardening ## How to ### Build For **Windows** environment, latest [Android Studio](https://developer.android.com/studio/) is recommended. For **Linux/MacOS**, [Gradle 4.10.2](https://gradle.org/) will be enough. ```console $ git clone https://github.com/luncliff/NdkCamera $ cd ./NdkCamera $ gradle assemble # Build: libndk_camera.so & NdkCamera.aar ``` ### Test Connect your device and run the test with Gradle. Please reference the [test codes](./android/test/ndcam/). ```console $ gradle connectedAndroidTest # Run test ``` ### Use The following code shows working with `SurfaceView` class. ```java package dev.example; // ... import dev.ndcam.*; // Expect we already have a camera permission public class SurfaceDisplay implements SurfaceHolder.Callback { SurfaceView surfaceView; Surface surface; ndcam.Device camera; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // ... // Load/Init library ndcam.CameraModel.Init(); surfaceView = findViewById(R.id.surfaceView); SurfaceHolder holder = surfaceView.getHolder(); holder.setFixedSize(1920, 1080); holder.setFormat(ImageFormat.YUV_420_888); holder.addCallback(this); } @Override public void surfaceCreated(SurfaceHolder surfaceHolder) { // Get all devices in array form for(ndcam.Device device : ndcam.CameraModel.GetDevices()) if(device.facing() == CameraCharacteristics.LENS_FACING_BACK) camera = device; } @Override public void surfaceChanged(SurfaceHolder surfaceHolder, int format, int width, int height) { // Make a repeating caputre request with surface surface = surfaceHolder.getSurface(); camera.repeat(surface); } @Override public void surfaceDestroyed(SurfaceHolder surfaceHolder) { // No more capture if(camera != null) camera.stopRepeat(); } } ```
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