java - 如何创建一个 super 类，我可以调用它来处理我的下载

Question

我真的在为我的 Dropbox API 苦苦挣扎。
我想把它放在我可以从其他类调用的父类(super class)中。
令我困惑的是我不知道如何正确设置它。
我创建了该类并宣布它为父类(super class)。
我已经获得了所有 API 信息，但我需要能够从不同的 Activity 中选择文件夹名称和文件名。
即:我有一个名为启动器的部分，该部分有 7 个下载选项；然后我有另一个名为 anima 的具有 3 个下载的 Activity，我想使用相同的 API，只需更改目录和路径即可。
另外，我将如何从另一个 Activity 中调用它？

public class HarropDropBoxApi extends Activity {

    public static String APP_TYPE = "I want to name this from other classes??";
    public static String APK_NAME = "I want to name this depending on the item in my list view in other classes ";
    public static String path = Environment.getExternalStorageDirectory().getAbsolutePath() + APP_TYPE;
    public static File Dir = new File(path);
    AndroidAuthSession session = buildSession();


    static DropboxAPI<AndroidAuthSession> dropboxAPI;
    private final String APP_KEY = "my-app-key";
    private final String APP_ACCESS = "my-access-key";
    private final String TOKEN = "my-token";
    private DropboxAPI.UploadRequest request;

    public HarropDropBoxApi() {


    }

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

        Dir.mkdir();

        dropboxAPI = new DropboxAPI<AndroidAuthSession>(session);
        //below was how i was calling the api for a single App Type and Apk name
        //DownloadFromDropboxFromPath(path + "downloadFileFromDropbox", "CastingApps/AllCast.apk");

        /// This line ive changed to match my strings above to be called from other classes/activities will this work?
        // Also this line is where the file is downloaded to and from so does this line get called from here or from my activities??
        DownloadFromDropboxFromPath(path + "downloadFileFromDropbox", APP_TYPE + APK_NAME );

    }

    private AndroidAuthSession buildSession() {
        AppKeyPair appKeyPair = new AppKeyPair(APP_KEY, APP_ACCESS);
        AndroidAuthSession session = new AndroidAuthSession(appKeyPair);
        session.setOAuth2AccessToken(TOKEN);
        return session;
    }

    public static String DropboxDownloadPathFrom = "";
    public static String DropboxDownloadPathTo = "";

    private void DownloadFromDropboxFromPath(String downloadPathTo, final String downloadPathFrom) {
        DropboxDownloadPathTo = downloadPathTo;
        DropboxDownloadPathFrom = downloadPathFrom;

        runOnUiThread(new Runnable() {
            @Override
            public void run() {

                Toast.makeText(getApplicationContext(), "Downloading  Please wait ...", Toast.LENGTH_LONG).show();
                Thread th = new Thread(new Runnable() {
                    public void run() {
                        final File file = new File(DropboxDownloadPathTo + DropboxDownloadPathFrom.substring(DropboxDownloadPathFrom.lastIndexOf('.')));
                        if (file.exists()) file.delete();


                        try {
                            FileOutputStream outputStream = new FileOutputStream(file);
                            HarropDropBoxApi.dropboxAPI.getFile(DropboxDownloadPathFrom, null, outputStream, null);
                            getMain().runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    Toast.makeText(getApplicationContext(), "File successfully downloaded.", Toast.LENGTH_SHORT).show();





                                    Intent promptInstall = new Intent(Intent.ACTION_VIEW).setDataAndType(Uri.fromFile(file),
                                            "application/vnd.android.package-archive");
                                    promptInstall.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                                    startActivity(promptInstall);

                                }
                            });
                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                    }
                });
                th.start();
            }
        });
    }


    public HarropDropBoxApi getMain() {
        return this;
    }
}

Answer 1

因为我没有使用 Dropbox API，所以我没有测试就把它放在一起，但逻辑对我来说似乎不错。

首先，使用AsyncTask，而不是低级Thread 进行后台操作。这里需要注意的是:

1. 您提供一个Context 参数(就像一个Activity)，期望您将硬编码的字符串从Java 代码中移出并放入某个资源文件中。
2. 已添加接口(interface)回调，以便您可以将结果返回到执行此任务的位置。如果不调用 setOnDownloadListener，文件将下载，但不会发生任何结果。
3. (附加说明):看起来您可以硬编码一个始终存在的目录；无需指定“下载到”目录。

public class DropboxDownloadTask extends AsyncTask<String, Void, File> {

    public interface OnDropboxDownloadListener {
        void onSuccess(File dropboxFile);
    }

    private static final String APP_KEY = "my-app-key";
    private static final String APP_ACCESS = "my-access-key";
    private static final String TOKEN = "my-token";

    // TODO: See below
    // private final String appKey, appAccess, dropboxToken;

    private final Context context;
    private final AndroidAuthSession session;
    private final DropboxAPI<AndroidAuthSession> dropboxAPI;

    private OnDropboxDownloadListener listener;

    public DropboxDownloadTask(Context c) {
        this.context = c;

        // TODO: Move those strings to a string resource file
        /*
        appKey = c.getResources().getString(R.string.dropbox_app_key);
        appAccess = c.getResources().getString(R.string.dropbox_access_key);
        dropboxToken = c.getResources().getString(R.string.dropbox_token);
        */

        session = buildSession();
        dropboxAPI = new DropboxAPI<AndroidAuthSession>(session);
    }

    public void setOnDownloadListener(OnDropboxDownloadListener listener) {
        this.listener = listener;
    }

    private AndroidAuthSession buildSession() {
        AppKeyPair appKeyPair = new AppKeyPair(APP_KEY, APP_ACCESS);
        AndroidAuthSession session = new AndroidAuthSession(appKeyPair);
        session.setOAuth2AccessToken(TOKEN);
        return session;
    }

    @Override
    protected File doInBackground(String... params) {
        File file;
        if (params.length != 2) {
            throw new IllegalArgumentException("Must give Dropbox to and from paths!");
        }
        String downloadPathTo = params[0];
        String downloadPathFrom = params[1];

        file = new File(downloadPathTo + downloadPathFrom.substring(downloadPathFrom.lastIndexOf('.')));
        if (file.exists()) file.delete();

        try {
            FileOutputStream outputStream = new FileOutputStream(file);
            dropboxAPI.getFile(downloadPathFrom, null, outputStream, null);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

        return file;
    }

    @Override
    protected void onPostExecute(File result) {
        if (this.listener != null) {
            this.listener.onSuccess(result);
        }
    }
}

现在您有了它，您可以从任何地方使用您有 Context 引用并且可以实现 OnDropboxDownloadListener。在您的问题中不清楚为什么要扩展 Activity 类，但如果您要使用 Activity，它可能看起来像这样。

public class MainActivity extends Activity implements DropboxDownloadTask.OnDropboxDownloadListener {

    private DropboxDownloadTask dropboxDownloadTask;

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

        // pass the context 
        dropboxDownloadTask = new DropboxDownloadTask(this);
        // pass the listener 
        dropboxDownloadTask.setOnDownloadListener(this);

        // TODO: Implement 
        downloadFromDropbox("to", "from");

    }

    private void downloadFromDropbox(String downloadPathTo, final String downloadPathFrom) {
        Toast.makeText(getApplicationContext(), "Downloading  Please wait ...", Toast.LENGTH_LONG).show();
        dropboxDownloadTask.execute(downloadPathFrom, downloadPathTo);
    }

    @Override
    public void onSuccess(File dropboxFile) {
        Toast.makeText(getApplicationContext(), "File successfully downloaded.", Toast.LENGTH_SHORT).show();

        Intent promptInstall = new Intent(Intent.ACTION_VIEW)
                .setDataAndType(Uri.fromFile(dropboxFile), "application/vnd.android.package-archive");
        promptInstall.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

        startActivity(promptInstall);
    }
}