android应用学习--14.读取framebuffer

一.android下读取framebuffer的内容
1. 读取
读取framebuffer跟linux下读取区别不大,只不过linux下是/dev/fb0, android下是/dev/graphics/fb0.

int capture()
{
    int fd = 0;
    FILE *out_file;

    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;

    long int screensize = 0;
    struct fb_bitfield red;
    struct fb_bitfield green;
    struct fb_bitfield blue;

    if ((out_file = fopen("/sdcard/123.raw", "w+")) == NULL)
        LOGME("open file error\n");

    fd = open("/dev/graphics/fb0", O_RDWR);

    ioctl(fd, FBIOGET_FSCREENINFO, &finfo);
    ioctl(fd, FBIOGET_VSCREENINFO, &vinfo);

    int xres = vinfo.xres;
    int yres = vinfo.yres;
    int bits_per_pixel = vinfo.bits_per_pixel;
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
    char * fb_mem = (char *)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    fwrite(fb_mem, screensize, 1, out_file);
    munmap(fb_mem, screensize);
    close(fd);
    return 0;

}

2. 区别
a. 跟linux差别最大的是权限设置
工程的AndroidManifest.xml如下:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""
      package="com.capture"
      android:versionCode="1"
      android:versionName="1.0"
      >
    <uses-sdk android:minSdkVersion="14" />
    <application android:label="@string/app_name"
                 android:debuggable="true">
        <activity android:name="com.capture.Capture"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.ACCESS_SURFACE_FLINGER"/>
<uses-permission android:name="android.permission.READ_FRAME_BUFFER"/>
</manifest>

b. 还需要关键的一步
修改了AndroidManifest.xml之后,还是会在open("/dev/graphics/fb0", O_RDWR); 时报错
再加上这一步就ok了.

adb shell chmod 777 /dev/graphics/fb0

二.附录
1. 在xml中加上READ_FRAME_BUFFER报错的解决方法

在AndroidManifest.xml中加入如下:
<uses-permission android:name="android.permission.READ_FRAME_BUFFER" />
会报错: Permission is only granted to system app
解决方法:
Window -> Preferences -> Android -> Lint Error Checking.
In the list find an entry with ID = ProtectedPermission. Set the Severity to something lower than Error. This way you can still compile the project using Eclipse.

参考文章:


完整的代码下载:
( cu上的代码怎么会是在csdn?
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