flutter - 使用 Flutter Downloader 插件,下载应用关闭后
问题描述
**我使用 Flutter Downloader Package 完成下载一些文件后,我的应用程序会自动关闭并断开与 android studio 的连接。任何人都可以帮助我找到解决方案。
final status = await Permission.storage.request();
if (status.isGranted) {
await downloadPDF();
}
downloadPDF() async {
final externalDir = await getExternalStorageDirectory();
taskId = await FlutterDownloader.enqueue(
url: pdfURL,
savedDir: externalDir.path,
fileName: "Flamingo Order Details",
showNotification: true,
openFileFromNotification: true,
);
}
这是我的控制台错误:
I/flutter (15913): Fatal: could not find callback
F/libc (15913): Fatal signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0 in tid 15956 (1.raster), pid 15913 (le.order_system)
*** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
Build fingerprint: 'motorola/chef/chef_sprout:10/QPTS30.61-18-16-8/03acd:user/release-keys'
Revision: 'pvt'
ABI: 'arm64'
Timestamp: 2021-04-23 16:39:38+0530
pid: 15913, tid: 15956, name: 1.raster >>> com.example.order_system <<<
uid: 10870
signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0x0
Cause: null pointer dereference
x0 000000741e5a6478 x1 00000074841cfa00 x2 0000000000000001 x3 0000000000000000
x4 0000000000000000 x5 00000000ffffffff x6 00000000ffffffff x7 0000000b96c6a75c
x8 0000000080000081 x9 658adf78f7e836ee x10 0000000000000000 x11 0000000000000000
x12 0000000000000001 x13 000000747b19fe80 x14 0000007489a0a280 x15 0000000000000000
x16 000000747b19b050 x17 0000007515c9787c x18 000000741d05e000 x19 000000741e5a6478
x20 00000074841cfa00 x21 0000000000000001 x22 0000000000000000 x23 00000074843db380
x24 000000741e5a7020 x25 000000741e5a7020 x26 0000000000000000 x27 0000000000000001
x28 0000000000000043 x29 000000741e5a6450
sp 000000741e5a6420 lr 000000747b013f84 pc 000000747b01c378
backtrace:
#00 pc 00000000001d8378 /vendor/lib64/egl/libGLESv2_adreno.so (BuildId: 22cc95e0051ae85072c405eeeeeb312d)
#01 pc 00000000001cff80 /vendor/lib64/egl/libGLESv2_adreno.so (BuildId: 22cc95e0051ae85072c405eeeeeb312d)
#02 pc 00000000000207b0 /system/lib64/libEGL.so (android::eglSwapBuffersWithDamageKHRImpl(void*, void*, int*, int)+316) (BuildId: 248ba7f2d80e7bb9952a20e1c3493c86)
#03 pc 000000000001d0a8 /system/lib64/libEGL.so (eglSwapBuffers+80) (BuildId: 248ba7f2d80e7bb9952a20e1c3493c86)
#04 pc 00000000012ec528 /data/app/com.example.order_system-8XYsushVsEZPOltQ3k8npA==/lib/arm64/libflutter.so (BuildId: e14966237eb013b063fed6484195268f7398b594)
Lost connection to device.
解决方案
也许为时已晚,但它可能会帮助其他人。最近我遇到了这个错误,我解决了它。您的 UI 在 Main 隔离中呈现,您的下载事件来自后台隔离。因为回调中的代码是在后台isolate运行的,所以你必须处理两个isolate之间的通信。通常,需要进行通信以在主 UI 中显示下载进度。实现以下代码来处理通信:
import 'dart:isolate';
import 'dart:ui'; // You need to import these 2 libraries besides another libraries to work with this code
ReceivePort _port = ReceivePort();
@override
void initState() {
super.initState();
IsolateNameServer.registerPortWithName(_port.sendPort, 'downloader_send_port');
_port.listen((dynamic data) {
String id = data[0];
DownloadTaskStatus status = data[1];
int progress = data[2];
setState((){ });
});
FlutterDownloader.registerCallback(downloadCallback);
}
@override
void dispose() {
IsolateNameServer.removePortNameMapping('downloader_send_port');
super.dispose();
}
static void downloadCallback(String id, DownloadTaskStatus status, int progress) {
final SendPort send = IsolateNameServer.lookupPortByName('downloader_send_port')!;
send.send([id, status, progress]);
}
void _download(String url) async {
final status = await Permission.storage.request();
if(status.isGranted) {
final externalDir = await getExternalStorageDirectory();
final id = await FlutterDownloader.enqueue(
url: url,
savedDir: externalDir!.path,
showNotification: true,
openFileFromNotification: true,
);
} else {
print('Permission Denied');
}
}
在您的按钮中调用 _download(url) 函数,您就可以开始了。
注意:我在我的应用程序中使用了可靠的 null 安全性,因此我在这行代码中使用了 null 感知运算符:
final SendPort send = IsolateNameServer.lookupPortByName('downloader_send_port')!;
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