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实现将普通AndroidStudio4.1.2项目增加对c++函数调用的支持

发布时间：2021-06-16 15:45:57编辑：雪饮阅读（）

 如果知道自己的android studio项目会用到c++/c时候则会在建立Android studio项目的时候直接选择c++的模板。

但是有时候项目写着写着才发现需要c++的支持。
这里以我这个项目要依赖ffmpeg这个c写的轮子为例。
在app/build.gradle:
plugins {
    id 'com.android.application'
}
 
android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"
 
    defaultConfig {
        applicationId "com.example.penguinvideoedit"
        minSdkVersion 28
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
 
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-std=c++11"
            }
            ndk{
                abiFilters "arm64-v8a"
            }
        }
        sourceSets{
            main{
                jniLibs.srcDirs=['libs']
            }
        }
    }
 
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "src/main/cpp/CMakeLists.txt"
            version "3.10.2"
        }
    }
   compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    ndkVersion '17.2.4988734'
}
 
dependencies {
 
    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
    implementation 'com.github.bumptech.glide:glide:4.0.0'
}
这里指定了c++标准，我这里用c++11
ndk的abi过滤，这里我只编译了ffmpeg的arm64-v8a。所以就只指定这一个
定义jni的库路径为app/libs
定义了cmake版本以及cmake编译脚本路径为src/main/cpp/CMakeLists.txt。
然后在要使用到c++的地方，引入一个c++程序路径为app\src\main\cpp\native-lib(相对于cmake脚本的路径)，以及声明一个本地函数，该本地函数由c++提供，并将这个来自c++的函数结果输出到日志中。
如app\src\main\java\com\example\penguinvideoedit\MainActivity3.java:
package com.example.penguinvideoedit;
 
import android.app.Activity;
import android.content.Intent;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;
 
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
 
import java.io.File;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.Timer;
import java.util.TimerTask;
 
public class MainActivity3 extends AppCompatActivity {
   static {
        System.loadLibrary("native-lib");
    }
    public native String stringFromJNI();
    private final static int requestCode_to_video_select_list=1;
    private SurfaceView sv;
    private SurfaceHolder holder;
    MediaPlayer mediaPlayer;
    String selectVideo_AbsolutePath=null;
    Boolean ispause=false;
    private Button bt_pause,bt_stop,bt_play;
    private LinearLayout video_control_buttons,seekbar_linearLayout,time_zone;
    private SeekBar seekbar;
    Timer timer;
    TextView seekbar_linearLayout_t1,seekbar_linearLayout_t2;
    EditText s_editTextNumber_h,s_editTextNumber_m,s_editTextNumber_s,s_editTextNumber_ss;
    EditText e_editTextNumber_h,e_editTextNumber_m,e_editTextNumber_s,e_editTextNumber_ss;
    int VideoDuration;
   boolean videoTimeGetOver=false;
    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            String CurrentPlayTime = (String) msg.obj;
            seekbar_linearLayout_t1.setText(CurrentPlayTime);
            super.handleMessage(msg);
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        sv = (SurfaceView) this.findViewById(R.id.sv);
        bt_pause=this.findViewById(R.id.bt_pause);
        bt_stop=this.findViewById(R.id.bt_stop);
        bt_play=this.findViewById(R.id.bt_play);
        seekbar_linearLayout_t1=this.findViewById(R.id.seekbar_linearLayout_t1);
        seekbar_linearLayout_t2=this.findViewById(R.id.seekbar_linearLayout_t2);
        bt_pause=this.findViewById(R.id.bt_pause);
        time_zone=this.findViewById(R.id.time_zone);
        video_control_buttons=this.findViewById(R.id.video_control_buttons);
        seekbar_linearLayout=this.findViewById(R.id.seekbar_linearLayout);
        seekbar=this.findViewById(R.id.seekbar);
        seekbar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
               // txt_cur.setText("当前进度值:" + progress + " / 100 ");
            }
            //进度条拖拽开始
            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
               // Toast.makeText(mContext, "触碰SeekBar", Toast.LENGTH_SHORT).show();
            }
            //进度跳拖拽结束
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                int Position= seekbar.getProgress();
                if(mediaPlayer!=null){
                    mediaPlayer.seekTo(Position);
                }
 
            }
        });
        Intent intent = getIntent();
        selectVideo_AbsolutePath = intent.getStringExtra("selectVideo_AbsolutePath");
        holder = sv.getHolder();
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        holder.addCallback(new MyHolderCallback());
        s_editTextNumber_h=this.findViewById(R.id.s_editTextNumber_h);
        s_editTextNumber_m=this.findViewById(R.id.s_editTextNumber_m);
        s_editTextNumber_s=this.findViewById(R.id.s_editTextNumber_s);
        s_editTextNumber_ss=this.findViewById(R.id.s_editTextNumber_ss);
 
        e_editTextNumber_h=this.findViewById(R.id.e_editTextNumber_h);
        e_editTextNumber_m=this.findViewById(R.id.e_editTextNumber_m);
        e_editTextNumber_s=this.findViewById(R.id.e_editTextNumber_s);
        e_editTextNumber_ss=this.findViewById(R.id.e_editTextNumber_ss);
 
 
        s_editTextNumber_h.setText(intent.getStringExtra("s_editTextNumber_h"));
        s_editTextNumber_m.setText(intent.getStringExtra("s_editTextNumber_m"));
        s_editTextNumber_s.setText(intent.getStringExtra("s_editTextNumber_s"));
        s_editTextNumber_ss.setText(intent.getStringExtra("s_editTextNumber_ss"));
 
        e_editTextNumber_h.setText(intent.getStringExtra("e_editTextNumber_h"));
        e_editTextNumber_m.setText(intent.getStringExtra("e_editTextNumber_m"));
        e_editTextNumber_s.setText(intent.getStringExtra("e_editTextNumber_s"));
        e_editTextNumber_ss.setText(intent.getStringExtra("e_editTextNumber_ss"));
 
    }
    @Override
    public void onBackPressed() {
        if(mediaPlayer!=null){
            mediaPlayer.stop();
            mediaPlayer.release();
        }
        finish();
    }
    public void videoInit() throws IOException {
 
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setDataSource(selectVideo_AbsolutePath);
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mediaPlayer.setDisplay(holder);
        mediaPlayer.prepare();
    }
    public void play(View view) throws Exception {
        mediaPlayer.release();
       videoInit();
        // 播放视频之前必须要初始化 视频的播放器
        //mediaPlayer.prepare();
        play(selectVideo_AbsolutePath,0);
        bt_pause.setVisibility(View.VISIBLE);
        bt_pause.setText("暂停");
        ispause=false;
        bt_play.setVisibility(View.GONE);
        bt_stop.setVisibility(View.VISIBLE);
    }
 
    private class MyHolderCallback implements SurfaceHolder.Callback {
        public void surfaceCreated(SurfaceHolder holder) {
            //System.out.println("holder 被创建 ");
            // 当视频播放最小化之后 下一次 必须在holder被创建后 再去播放视频
            /*
            if (position > 0) {
                String path = et_path.getText().toString().trim();
                try {
                    // 重新设置显示的holder
                    MainActivity.this.holder = holder;
                    play(path, position);
                } catch (Exception e) {
                    Toast.makeText(getApplicationContext(), "播放出现一次", Toast.LENGTH_SHORT).show();
                    e.printStackTrace();
                }
            }
            */
            if(selectVideo_AbsolutePath!=null){
                try {
                    video_control_buttons.setVisibility(View.VISIBLE);
                    bt_pause.setText("暂停");
                    videoInit();
                    //显示进度条
                    VideoDuration=mediaPlayer.getDuration();
                    videoTimeGetOver=true;
                    seekbar_linearLayout.setVisibility(View.VISIBLE);
                    seekbar.setMax(VideoDuration);
                    //设置进度条左右时间样式
                    String end_time_style=formatDateTime(VideoDuration);
                    System.out.println("毫秒:"+VideoDuration);
                    System.out.println("end_time_style:"+end_time_style);
                    seekbar_linearLayout_t1.setText("00:00:00.00");
                    seekbar_linearLayout_t2.setText(end_time_style);
                    play(selectVideo_AbsolutePath,0);
 
                    //显示时间区间编辑区域
                    time_zone.setVisibility(View.VISIBLE);
 
                    timer = new Timer();//时间监听器
                    timer.schedule(new TimerTask() {
                        @Override
                        public void run() {
                            try{
                                if(mediaPlayer!=null){
                                    if(mediaPlayer.isPlaying()){
                                        String current_time_style=formatDateTime(mediaPlayer.getCurrentPosition());
                                        //updateCurrentPlayTimeUi(current_time_style);
                                        seekbar.setProgress(mediaPlayer.getCurrentPosition());
                                        Message msg = new Message();
                                        msg.obj = current_time_style;
                                        handler.sendMessage(msg);
                                    }
                                }
                            }
                            catch(IllegalStateException e){
                                e.printStackTrace();
                            }
                        }
                    },0,500);
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
           }
 
        }
 
        @Override
        public void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {
            //实现SurfaceHolder.Callback接口，则surfaceChanged不实现不行，实际上这个方法可以根据情况编写一些逻辑
            //这里暂时用不上
           // System.out.println("holder 改变:format"+format+"width:"+width+"height:"+height);
        }
        public void surfaceDestroyed(SurfaceHolder holder) {
            //一般如按home键最小化后会触发这个方法
            //System.out.println("holder 被销毁 ");
            // 记录最小化之后播放器播放的位置
            /*
            if (mediaPlayer != null && mediaPlayer.isPlaying()) {
                position = mediaPlayer.getCurrentPosition();
                mediaPlayer.stop();
                mediaPlayer.release();
                mediaPlayer = null;
            }
            */
 
        }
 
    }
 
    public static String formatDateTime(long milliseconds) {
        StringBuilder sb = new StringBuilder();
        long hours = (long)Math.floor(milliseconds/1000/3600);
        long minutes =(long)Math.floor((milliseconds-hours*3600*1000)/1000/60);
        long seconds =(long)Math.floor((milliseconds-hours*3600*1000-minutes*60*1000)/1000);
        long ms =milliseconds-hours*3600*1000-minutes*60*1000-seconds*1000;
        DecimalFormat format = new DecimalFormat("00");
        sb.append(format.format(hours)).append(":").append(format.format(minutes)).append(":").append(format.format(seconds)).append(":").append(format.format(ms));
        return sb.toString();
    }
    public void pause(View view) {
        bt_play.setVisibility(View.GONE);
        bt_stop.setVisibility(View.VISIBLE);
        if (mediaPlayer != null && mediaPlayer.isPlaying()) {
            mediaPlayer.pause();
            bt_pause.setText("播放");
            ispause=true;
        }
        else if (mediaPlayer != null && ispause==true) {
            mediaPlayer.start();
            bt_pause.setText("暂停");
            ispause = false;
        }
    }
    public void stop(View view) {
        if(mediaPlayer!=null){
            mediaPlayer.stop();
            mediaPlayer.release();
            bt_pause.setVisibility(View.GONE);
            bt_stop.setVisibility(View.GONE);
            bt_play.setVisibility(View.VISIBLE);
        }
    }
    private void play(String path, int position) throws Exception {
        File file = new File(path);
        if (file.exists()) {
            mediaPlayer.start();
            mediaPlayer.seekTo(position);
            //播放完成
            mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                public void onCompletion(MediaPlayer mp) {
                    // TODO Auto-generated method stub
                    mediaPlayer.release();
                    mediaPlayer = null;
                    String CurrentPlayTime= formatDateTime(VideoDuration);
                    seekbar_linearLayout_t1.setText(CurrentPlayTime);
                }
            });
            // 当播放出现错误的时候的回调方法
            mediaPlayer.setOnErrorListener(new MediaPlayer.OnErrorListener() {
                public boolean onError(MediaPlayer mp, int what, int extra) {
                    mp.release();
                    mediaPlayer = null;
                    return false;
                }
            });
        } else {
            Toast.makeText(this, "文件不存在", Toast.LENGTH_SHORT).show();
            return;
        }
 
    }
    public void video_cut(View view) {
        int s_editTextNumber_h_v=Integer.parseInt(s_editTextNumber_h.getText().toString());
        int s_editTextNumber_m_v=Integer.parseInt(s_editTextNumber_m.getText().toString());
        int s_editTextNumber_s_v=Integer.parseInt(s_editTextNumber_s.getText().toString());
        int s_editTextNumber_ss_v=Integer.parseInt(s_editTextNumber_ss.getText().toString());
 
        int e_editTextNumber_h_v=Integer.parseInt(e_editTextNumber_h.getText().toString());
        int e_editTextNumber_m_v=Integer.parseInt(e_editTextNumber_m.getText().toString());
        int e_editTextNumber_s_v=Integer.parseInt(e_editTextNumber_s.getText().toString());
        int e_editTextNumber_ss_v=Integer.parseInt(e_editTextNumber_ss.getText().toString());
 
        int s_time=s_editTextNumber_h_v*3600000+s_editTextNumber_m_v*60000+s_editTextNumber_s_v*1000+s_editTextNumber_ss_v;
        int e_time=e_editTextNumber_h_v*3600000+e_editTextNumber_m_v*60000+e_editTextNumber_s_v*1000+e_editTextNumber_ss_v;
 
        if(videoTimeGetOver==false){
            Toast.makeText(this, "视频暂未载入完成", Toast.LENGTH_SHORT).show();
            return;
        }
        else if(s_time>=VideoDuration){
 
            Toast.makeText(this, "开始时间不得大于等于视频总时长", Toast.LENGTH_SHORT).show();
            return;
        }
        else if(s_time>=e_time){
            Log.i("MainActivity3","s_time:"+s_time+",e_time:"+e_time+",e_editTextNumber_m_v:"+e_editTextNumber_m_v);
            Toast.makeText(this, "开始时间不得大于等于结束时间", Toast.LENGTH_SHORT).show();
            return;
        }
        else if(e_time>VideoDuration){
            Log.i("MainActivity3","e_time:"+e_time+",VideoDuration:"+VideoDuration);
            Toast.makeText(this, "结束时间不得大于视频总时长", Toast.LENGTH_SHORT).show();
            return;
        }
        Log.i("MainActivity3","来自c++:"+stringFromJNI());
        //ffmpeg -i blmsyb.mp4 -ss 00:00:01.10 -t 00:00:03.50 -c copy blmsyb2.mp4
    }
    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==requestCode_to_video_select_list){
            if(resultCode == Activity.RESULT_OK){
                selectVideo_AbsolutePath = data.getData().getPath();
            }
        }
    }
}
在app中建立include目录用来存放ffmpeg编译出来的头文件.h
 
D:\penguinVideoEdit\app\include>tree /F
卷 软件 的文件夹 PATH 列表
卷序列号为 0592-36B3
D:.
├─libavcodec
│      ac3_parser.h
│      adts_parser.h
│      avcodec.h
│      avdct.h
│      avfft.h
│      bsf.h
│      codec.h
│      codec_desc.h
│      codec_id.h
│      codec_par.h
│      d3d11va.h
│      dirac.h
│      dv_profile.h
│      dxva2.h
│      jni.h
│      mediacodec.h
│      packet.h
│      qsv.h
│      vaapi.h
│      vdpau.h
│      version.h
│      videotoolbox.h
│      vorbis_parser.h
│      xvmc.h
│
├─libavfilter
│      avfilter.h
│      buffersink.h
│      buffersrc.h
│      version.h
│
├─libavformat
│      avformat.h
│      avio.h
│      version.h
…………………………………….
然后建立app/libs目录用来存放ffmpeg编译出来的动态链接库：
D:\penguinVideoEdit\app\libs>tree /F
卷 软件 的文件夹 PATH 列表
卷序列号为 0592-36B3
D:.
└─arm64-v8a
        libavcodec.so
        libavfilter.so
        libavformat.so
        libavutil.so
        libswresample.so
        libswscale.so
然后建立cmake编译脚本于app\src\main\cpp\ CMakeLists.txt:
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
 
# Sets the minimum version of CMake required to build the native library.
 
cmake_minimum_required(VERSION 3.10.2)
 
# Declares and names the project.
 
project("penguinvideoedit")
 
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
#添加頭文件路徑(括號中的include是相對於本文件路徑)
include_directories(../../../include)
 
add_library( # Sets the name of the library.
             native-lib
             # Sets the library as a shared library.
             SHARED
             # Provides a relative path to your source file(s).
            native-lib.cpp
        )
 
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
 
find_library( # Sets the name of the path variable.
              log-lib
 
              # Specifies the name of the NDK library that
              # you want CMake to locate.
              log )
 
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
 
target_link_libraries( # Specifies the target library.
                       native-lib
                       android
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )
这里project指定Androidstudio项目中包名的最后一级名称。
include_directories添加头文件路径（相对于cmake脚本路径）。
target_link_libraries中的android看情况，一般都是会用到的。
然后创建一个给前面java程序用的c++程序native-lib.cpp于app\src\main\cpp中：
#include <jni.h>
#include <string>

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_penguinvideoedit_MainActivity3_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}
这里函数的格式是将包名一直到最后那个java程序文件的类名的”.”连字符替换为”_”连字符的格式。
然后运行在如魅族16T中

可以看到成功调用了c++的程序。