1、创建c++工程

通过 file -> new -> new project，创建一个新的c++工程。

创建c++工程

2、配置ndk路径

在 local.properties 文件中配置自己的ndk路径

sdk.dir=D\:\\ProgramFiles\\sdk
ndk.dir=D\:\\ProgramFiles\\sdk\\ndk

3、下载giflib源码，并拷贝到工程中

（1）giflib在源码的 external/giflib 目录下：giflib
（2）将源码文件拷贝到 main/cpp/giflib/ 目录下：

main/cpp/giflib/ 目录

4、修改 CMakeLists.txt

拷贝完源码后，会提示头文件错误，修改CMakeLists.txt配置，执行 Build -> Refresh Linked C++ Project 。

cmake_minimum_required(VERSION 3.18.1)

project("gifdemo")

file(GLOB_RECURSE GIF_LIB ${CMAKE_SOURCE_DIR}/giflib/*.*)

add_library(
        gifdemo
        SHARED
        ${GIF_LIB} # 添加giflib
        native-lib.cpp)

find_library(
        log-lib
        log)

target_link_libraries(
        gifdemo
        jnigraphics # 增加依赖
        ${log-lib})

5、定义 GifHandler 处理gif

public class GifHandler {
    static {
        System.loadLibrary("gifdemo");
    }

    private long gifFileInfo;

    private GifHandler(long gifFileInfo) {
        this.gifFileInfo = gifFileInfo;
    }

    // 生成GifHandler
    public static GifHandler load(String path) {
        long gifFileInfo = openGifFile(path);
        return new GifHandler(gifFileInfo);
    }

    // 获取宽
    public int getWidth() {
        return getWidth(gifFileInfo);
    }

    // 获取高
    public int getHeight() {
        return getHeight(gifFileInfo);
    }

    // 将gif当前帧绘制到bitmap上
    public int updateFrame(Bitmap bitmap) {
        return updateFrame(gifFileInfo, bitmap);
    }

    /**
     * 打开gif文件
     *
     * @param path gif路径
     * @return native层GifFileType的指针
     */
    public static native long openGifFile(String path);

    /**
     * @param gifFileInfo native层GifFileType的指针
     * @return gif文件的高
     */
    public static native int getHeight(long gifFileInfo);

    /**
     * @param gifFileInfo native层GifFileType的指针
     * @return gif文件的宽
     */
    public static native int getWidth(long gifFileInfo);

    /**
     * @param gifFileInfo native层GifFileType的指针
     * @param bitmap      用于显示gif的bitmap
     * @return gif当前帧的展示时长
     */
    public static native int updateFrame(long gifFileInfo, Bitmap bitmap);
}

6、编写 native 代码

#include <jni.h>
#include <string>
#include <malloc.h>
#include <android/bitmap.h>
#include <string.h>

// 引入gif库
extern "C" {
#include "giflib/gif_lib.h"
}

// 存储gif的播放进度
struct GifPlayInfo {
    int current_frame;
    int total_frame;
};

extern "C"
JNIEXPORT jlong JNICALL
Java_com_example_gifdemo_GifHandler_openGifFile(JNIEnv *env, jclass clazz, jstring jpath) {
    const char *path = env->GetStringUTFChars(jpath, 0); // 将java字符串转换成c字符串
    int error;// 打开是成功还是失败；0成功，1失败
    GifFileType *gifFileType = DGifOpenFileName(path, &error);
    DGifSlurp(gifFileType);// 将gif读入内核

    // 创建GifPlayInfo对象
    GifPlayInfo *gifPlayInfo = static_cast<GifPlayInfo *>(malloc(sizeof(GifPlayInfo)));
    memset(gifPlayInfo, 0, sizeof(GifPlayInfo)); // 清空
    // 设置总帧数和当前播放帧
    gifPlayInfo->total_frame = gifFileType->ImageCount;
    gifPlayInfo->current_frame = 0;
    gifFileType->UserData = gifPlayInfo; // 类似于view的setTag

    // 释放字符串
    env->ReleaseStringUTFChars(jpath, path);
    return reinterpret_cast<jlong>(gifFileType); // 将指针返回
}

extern "C"
JNIEXPORT jint JNICALL
Java_com_example_gifdemo_GifHandler_getHeight(JNIEnv *env, jclass clazz, jlong gif_file_info) {
    GifFileType *gifFileType = reinterpret_cast<GifFileType *>(gif_file_info);
    return gifFileType->SHeight;
}

extern "C"
JNIEXPORT jint JNICALL
Java_com_example_gifdemo_GifHandler_getWidth(JNIEnv *env, jclass clazz, jlong gif_file_info) {
    GifFileType *gifFileType = reinterpret_cast<GifFileType *>(gif_file_info);
    return gifFileType->SWidth;
}

// 将argb转换成abgr
int32_t argb2Abgr(int alpha, GifByteType red, GifByteType green, GifByteType blue) {
    return ((alpha & 0xff) << 24) | ((blue & 0xff) << 16) | ((green) << 8) | (red);
}

// 计算展示时长
int delay(ExtensionBlock *ext) {
    return (10 * ((ext)->Bytes[2] << 8 | (ext)->Bytes[1]));
}

// 绘制当前帧
int myDrawFrame(GifFileType *gif, AndroidBitmapInfo *info, int *pixels, int frame_no) {
    SavedImage *savedImage = &(gif->SavedImages[frame_no]); // 获取当前帧
    GifImageDesc *frameInfo = &(savedImage->ImageDesc); // 当前帧的描述文件
    ColorMapObject *colorMap; // 当前帧的颜色列表
    if (frameInfo->ColorMap) {
        colorMap = frameInfo->ColorMap;
    } else {
        //没有的话就获取全局的颜色列表
        colorMap = gif->SColorMap;
    }
    ExtensionBlock *ext;
    //遍历当前帧的扩展块，找到具有GRAPHICS_EXT_FUNC_CODE标志位的，这个扩展快存放着对该帧图片的处置方法，是不处理还是其他
    for (int i = 0; i < savedImage->ExtensionBlockCount; ++i) {
        if (savedImage->ExtensionBlocks[i].Function == GRAPHICS_EXT_FUNC_CODE) {
            ext = &(savedImage->ExtensionBlocks[i]);
            break;
        }
    }

    int loc; // 当前位置
    GifColorType *color; // 当前像素的颜色
    int *px = pixels; // 二维指针
    int *line; // 行
    px = (int *) ((char *) px + info->stride * frameInfo->Top); // 计算像素，对每一个像素进行颜色填充

    for (int y = frameInfo->Top; y < frameInfo->Top + frameInfo->Height; ++y) {
        line = px; // 更新行数
        for (int x = frameInfo->Left; x < frameInfo->Left + frameInfo->Width; ++x) {
            loc = (y - frameInfo->Top) * frameInfo->Width + (x - frameInfo->Left);
            //判断处置方法，拿到当前帧loc位置的字节，看是否等于扩展块中索引为3的字节，并且数值为1
            if (savedImage->RasterBits[loc] == ext->Bytes[3] && ext->Bytes[0]) {
                continue;
            }
            color = &colorMap->Colors[savedImage->RasterBits[loc]];
            line[x] = argb2Abgr(255, color->Red, color->Green, color->Blue);
        }
        px = (int *) ((char *) px + info->stride);
    }
    return delay(ext);
}

extern "C"
JNIEXPORT jint JNICALL
Java_com_example_gifdemo_GifHandler_updateFrame(JNIEnv *env, jclass clazz, jlong gif_file_info,
                                                jobject bitmap) {
    // 获取到gif数据
    GifFileType *gifFileType = reinterpret_cast<GifFileType *>(gif_file_info);
    GifPlayInfo *gifPlayInfo = static_cast<GifPlayInfo *>(gifFileType->UserData);
    AndroidBitmapInfo info;// 获取bitmap信息
    AndroidBitmap_getInfo(env, bitmap, &info);
    void *srcBuf;// 解析bitmap，并将像素信息保存到srcBuf中
    AndroidBitmap_lockPixels(env, bitmap, &srcBuf);
    int delay = myDrawFrame(gifFileType, &info, (int *) srcBuf,
                            gifPlayInfo->current_frame); // 绘制gif
    AndroidBitmap_unlockPixels(env, bitmap); // 释放锁定
    gifPlayInfo->current_frame++;// 更新播放进度
    if (gifPlayInfo->current_frame >= gifPlayInfo->total_frame - 1) {
        gifPlayInfo->current_frame = 0;
    }
    return delay;
}

7、MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private ActivityMainBinding binding;
    private GifHandler mGifHandler;
    private Bitmap mBitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        // 申请权限
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
            initData();
        } else {
            ActivityCompat.requestPermissions(this,
                    new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE,
                            Manifest.permission.READ_EXTERNAL_STORAGE},
                    1);
        }
    }

    private void initData() {
        // /storage/emulated/0/Android/data/com.example.gifdemo/cache/test.gif
        String path = getExternalCacheDir().getPath() + "/test.gif";
        Log.v("AAAAA", path);
        if (!new File(path).exists()) {
            Toast.makeText(this, "gif路径无效，请重试", Toast.LENGTH_SHORT).show();
            return;
        }
        mGifHandler = GifHandler.load(path);
        mBitmap = Bitmap.createBitmap(mGifHandler.getWidth(), mGifHandler.getHeight(), Bitmap.Config.ARGB_8888);
        binding.sampleText.setOnClickListener(this);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == 1 && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            initData();
        } else {
            Toast.makeText(this, "请授予读写权限", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onClick(View view) {
        if (view.getId() == R.id.sample_text) {
            int delay = mGifHandler.updateFrame(mBitmap);
            binding.iv.setImageBitmap(mBitmap);
            mHandler.removeMessages(1);
            mHandler.sendEmptyMessageDelayed(1, delay);
        }
    }

    private final Handler mHandler = new Handler(Looper.getMainLooper()) {
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            if (msg.what == 1) {
                int delay = mGifHandler.updateFrame(mBitmap);
                binding.iv.setImageBitmap(mBitmap);
                mHandler.removeMessages(1);
                mHandler.sendEmptyMessageDelayed(1, delay);
            }
        }
    };
}

8、加载效果

demo演示.gif

9、demo地址

https://github.com/Timey729/GifDemo