Question

我是Android开发的初学者。我正在尝试学习多线程并与Internet一起工作，因此我通过使用AsyncTask通过后台线程从链接下载PDF文件来做到这一点。我对最好的解决方法感到困惑。

我是否在URI类的onCreate或doInBackground方法中创建AsyncTask和其他必要的连接对象？

要仅下载一个PDF文件，我需要调用哪种对象？

我已经检查了文档，但我不太了解。我很感谢外行的解释，甚至可能是伪代码。

这是我到目前为止的代码：

public class MainActivity extends AppCompatActivity {
    Button downloadPDF;
    DownloadingClass downPDF;
    private static final String TAG = "omar.asynctaskdemo;";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        String urlExample = "https://doc.lagout.org/programmation/Actionscript%20-%20Flash%20-%20Flex%20-%20Air/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29.pdf");

        downloadPDF = findViewById(R.id.download_pdf);
        downPDF = new DownloadingClass();

        downloadPDF.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                downPDF.execute();
            }
        });
    }

    private class DownloadingClass extends AsyncTask<String, Integer, Void>{
        @Override
        protected Void doInBackground(String... strings) {
            return null;
        }
    }
}

Answer 1

AsyncTask只是在后台线程中运行您的代码。下载pdf文件就像其他任何文件一样。

您将需要使用$("div#myId").dropzone({ url: "/stores/sell_upload/", maxFiles: 4, acceptedFiles: "image/*", addRemoveLinks: true, renameFile: function(file) { let newName = file.name.replace("." + file.name.split(".").pop(), "") + "-" + new Date().getTime() + "." + file.name.split(".").pop(); return newName; }, removedfile: function(file) { $.ajax({ type: "POST", url: "/stores/sell_upload/", data: { name: file.name, action: "delete" } }); var _ref; return (_ref = file.previewElement) != null ? _ref.parentNode.removeChild(file.previewElement) : void 0; } });，创建一个String constr = (@"Data source=(localdb)\MSSQLLocalDB; initial catalog=DataHRD; integrated security=true;"); // Create a new SqlConnectionStringBuilder and // initialize it with a few name/value pairs. SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder(constr); // Now that the connection string has been parsed, // you can work with individual items. builder["Data Source"] = @"C:\Users\SONY\Desktop\asda\asd\MainMenu\DataHRD.mdf" // or anything else builder.Password = "new@1Password"; builder.AsynchronousProcessing = true; // You can refer to connection keys using strings, // as well. When you use this technique (the default // Item property in Visual Basic, or the indexer in C#), // you can specify any synonym for the connection string key // name. builder["Server"] = "."; builder["Connect Timeout"] = 1000; builder["Trusted_Connection"] = true;并编写HttpUrlConnection。请参阅this

让上述代码在AsyncTask类的FileOutputStream中执行，并更好地在构造函数中传递url并在inputstream方法内进行所有操作。因为您不想阻止UI线程。

使用AsyncTask下载单个文件

1 个答案: