深入解析Android AsyncTask下载功能源码实现

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资源摘要信息:"Android应用源码之AsyncTask_Download1)_源码.zip" 知识点说明: 1. Android应用开发基础: Android应用开发是基于Java编程语言的,使用Android SDK进行应用的编写、测试、调试和发布。了解Android的四大组件(Activity, Service, Broadcast Receiver, Content Provider)是进行Android开发的基础。 2. AsyncTask类: AsyncTask是一个抽象类,用于简化后台线程(线程池)与UI线程之间的通信。它是Android早期版本中常用的异步处理机制,允许开发者在后台执行耗时操作(如网络请求、文件IO等),而不需要直接操作线程和Handler。AsyncTask提供了一套简单的模板方法来执行操作,包括onPreExecute()(准备执行时调用),doInBackground(Params...)(后台执行耗时操作),onPostExecute(Result)(后台任务完成后调用)等。 3. 网络请求与下载: 在Android应用中,网络请求是经常需要的功能。AsyncTask常被用于在后台线程执行网络请求,并将结果更新到UI线程。对于Android 9(API 28)之前的版本,可以使用如HttpURLConnection或者第三方库如Volley、Retrofit来执行网络请求。Android 9及以上版本推荐使用HttpsURLConnection或okhttp3库,因为从Android 9开始,默认对明文HTTP流量进行了限制。 4. 源码分析与调试: 分析源码是开发者提升编程技能的重要手段。通过对源码的阅读和调试,开发者可以理解程序的执行流程和逻辑。源码中包含的注释和文档说明也有助于理解程序的设计思想。在Android Studio等开发环境中,使用断点调试可以逐步观察程序的运行状态,了解变量的变化和方法的调用情况。 5. 文件压缩与解压缩: "Android应用源码之AsyncTask_Download1)_源码.zip" 表示这是一个压缩包文件,其中包含了源码文件。在Android开发中,文件压缩与解压缩是一个常见的操作,尤其是在需要分发应用或者共享项目时。开发者需要熟悉使用zip、rar等文件压缩工具和格式,以便于打包和分发项目文件。 在本资源中,由于只提供了标题和文件名,并没有具体的代码内容,因此无法进一步分析具体的实现细节。但上述知识点总结了AsyncTask在Android开发中的应用背景、网络请求的基础知识、源码分析的重要性以及文件压缩与解压缩的基本概念,为理解Android应用源码和开发过程中的关键技术提供了基础。

01-01 08:11:27.038 E/StrictMode( 2641): Tried to access the API:ViewConfiguration which needs to have proper configuration from a non-UI Context:com.android.camera.app.CameraApp@32d9eff The API:ViewConfiguration needs a proper configuration. Use UI contexts such as an activity or a context created via createWindowContext(Display, int, Bundle) or createConfigurationContext(Configuration) with a proper configuration. 01-01 08:11:27.038 E/StrictMode( 2641): java.lang.IllegalAccessException: Tried to access the API:ViewConfiguration which needs to have proper configuration from a non-UI Context:com.android.camera.app.CameraApp@32d9eff 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.StrictMode.assertConfigurationContext(StrictMode.java:2296) 01-01 08:11:27.038 E/StrictMode( 2641): at android.view.ViewConfiguration.get(ViewConfiguration.java:521) 01-01 08:11:27.038 E/StrictMode( 2641): at android.view.View.<init>(View.java:5321) 01-01 08:11:27.038 E/StrictMode( 2641): at android.widget.ImageView.<init>(ImageView.java:181) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.PhotoItem.getView(PhotoItem.java:127) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.CameraFilmstripDataAdapter.getView(CameraFilmstripDataAdapter.java:151) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.widget.FilmstripView.buildViewItemAt(FilmstripView.java:850) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.widget.FilmstripView.reload(FilmstripView.java:1827) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.widget.FilmstripView.access$1300(FilmstripView.java:58) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.widget.FilmstripView$3.onFilmstripItemLoaded(FilmstripView.java:1567) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.CameraFilmstripDataAdapter.replaceItemList(CameraFilmstripDataAdapter.java:276) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.CameraFilmstripDataAdapter.access$700(CameraFilmstripDataAdapter.java:39) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.CameraFilmstripDataAdapter$QueryTask.onPostExecute(CameraFilmstripDataAdapter.java:447) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.camera.data.CameraFilmstripDataAdapter$QueryTask.onPostExecute(CameraFilmstripDataAdapter.java:379) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.AsyncTask.finish(AsyncTask.java:771) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.AsyncTask.access$900(AsyncTask.java:199) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:788) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.Handler.dispatchMessage(Handler.java:106) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.Looper.loopOnce(Looper.java:201) 01-01 08:11:27.038 E/StrictMode( 2641): at android.os.Looper.loop(Looper.java:288) 01-01 08:11:27.038 E/StrictMode( 2641): at android.app.ActivityThread.main(ActivityThread.java:7870) 01-01 08:11:27.038 E/StrictMode( 2641): at java.lang.reflect.Method.invoke(Native Method) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548) 01-01 08:11:27.038 E/StrictMode( 2641): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)

2023-07-14 上传

E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #1 Process: com.ncusoft.weatherchina, PID: 32468 java.lang.RuntimeException: An error occurred while executing doInBackground() at android.os.AsyncTask$4.done(AsyncTask.java:415) at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:381) at java.util.concurrent.FutureTask.setException(FutureTask.java:250) at java.util.concurrent.FutureTask.run(FutureTask.java:269) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1137) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:637) at java.lang.Thread.run(Thread.java:1012) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:121) at org.json.JSONTokener.nextValue(JSONTokener.java:98) at org.json.JSONObject.<init>(JSONObject.java:168) at org.json.JSONObject.<init>(JSONObject.java:185) at com.ncusoft.weatherchina.RemoteDataParser.parseJsonToWeather(RemoteDataParser.java:52) at com.ncusoft.weatherchina.RemoteDataParser.parseWeatherData(RemoteDataParser.java:20) at com.ncusoft.weatherchina.MainActivity$weatherTask.doInBackground(MainActivity.java:48) at com.ncusoft.weatherchina.MainActivity$weatherTask.doInBackground(MainActivity.java:36) at android.os.AsyncTask$3.call(AsyncTask.java:394) at java.util.concurrent.FutureTask.run(FutureTask.java:264) at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:305)  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1137)  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:637)  at java.lang.Thread.run(Thread.java:1012)  W/ft.weatherchina: Cleared Reference was only reachable from finalizer (only reported once) W/System: A resource failed to call close.

2023-05-17 上传

inventoryButton.setOnClickListener( new View.OnClickListener() { @Override public void onClick(View v) { if (isFastClick()) { showLoadToast(); goToMainActivity(); loadExcelFile(); } } private boolean isFastClick() { return ButtonOnCilk.isFastViewClick(inventoryButton, getBaseContext()); } private void showLoadToast() { CustomToast.showLoad(HomeActivity.this, getString(R.string.load)); } private void goToMainActivity() { Intent intent = new Intent(getApplicationContext(), MainActivity.class); intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(intent); } private void loadExcelFile() { new AsyncTask<Void, Void, List<String>>() { @Override protected List<String> doInBackground(Void... voids) { return readExcelFile(); } @Override protected void onPostExecute(List<String> data) { showDataInListView(data); } }.execute(); } private void showDataInListView(List<String> data) { listView = findViewById(R.id.rv_list); if (listView != null) { ArrayAdapter<String> adapter = new ArrayAdapter<>(HomeActivity.this, android.R.layout.simple_list_item_1, data); listView.setAdapter(adapter); } } });private List<String> readExcelFile() { List<String> datas = new ArrayList<>(); try { FileInputStream inputStream = new FileInputStream("/sdcard/Template/IC1001.xlsx"); Workbook workbook = WorkbookFactory.create(inputStream); Sheet sheet = workbook.getSheetAt(0); for (Row row : sheet) { for (Cell cell : row) { datas.add(cell.toString()); } } workbook.close(); } catch (IOException | InvalidFormatException e) { e.printStackTrace(); } return datas; }报错

2023-05-24 上传