public class AsyncTaskTwoActivity extends AppCompatActivity {

private TextView info; private ProgressBar progressBar; private @SuppressLint(“StaticFieldLeak”) AsyncTask<String, Integer, File> asyncTask;

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

info = findViewById(R.id.info);
progressBar = findViewById(R.id.progress);

findViewById(R.id.download).setOnClickListener(new View.OnClickListener() {
  @Override public void onClick(View v) {
    download();
  }
});

}

@SuppressLint(“StaticFieldLeak”) private void download() { asyncTask = new AsyncTask<String, Integer, File>() { //子執行緒下載 @Override protected File doInBackground(String… strings) { Log.i(“TEST”, “doInBackground”); try { URL url = new URL(strings[0]); HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); int responseCode = urlConnection.getResponseCode(); if (responseCode == 200) { //將流轉換成String //一邊讀流一邊寫 //File file = saveFile(urlConnection.getInputStream());

        File file = new File(getCacheDir(), "downloadfile.apk");
        FileOutputStream fos = new FileOutputStream(file);
        InputStream is = urlConnection.getInputStream();

        final int totalCount = urlConnection.getContentLength();
        byte[] buf = new byte[10240];
        int count = 0;
        for (int i = is.read(buf); i != -1; i = is.read(buf)) {
          //寫資料到檔案
          fos.write(buf, 0, i);

          //釋出進度
          count = count + i;


          //當前進度 檔案總大小                   666666
          publishProgress(count, totalCount);
        }

        //關閉流
        fos.flush();
        fos.close();

        return file;
      }
    } catch (MalformedURLException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return null;
  }

  //進度更新了 主執行緒
  @Override protected void onProgressUpdate(Integer... values) {
    info.setText(values[0] + "  /  " + values[1]);
    //progressBar.setProgress((int)((100f / values[1]) * values[0]));
    progressBar.setProgress((int) ((values[0] * 1.0f / values[1]) * 100));
  }

  @Override protected void onPreExecute() {
    //先於onPostExecute呼叫
    Log.i("TEST", "onPreExecute");
  }

  //主執行緒接收
  @Override protected void onPostExecute(File file) {
    String filePath = file.getAbsolutePath();
    Log.i("TEST", "onPostExecute: " + file.getAbsolutePath());
    Toast.makeText(AsyncTaskTwoActivity.this, "下載完成：" + file.getAbsolutePath(),
        Toast.LENGTH_SHORT).show();
  }
}.execute(apkUrl);
 

}

private File saveFile(InputStream is) throws IOException { //getCacheDir() 應用快取目錄 ; 檔名 File file = new File(getCacheDir(), “downloadfile.apk”); //把檔案 和 輸出流 關聯起來 FileOutputStream fos = new FileOutputStream(file);

byte[] buf = new byte[10240];
for (int i = is.read(buf); i != -1; i = is.read(buf)) {
  //寫資料到檔案
  fos.write(buf, 0, i);
}

//關閉流
fos.flush();
fos.close();

return file;

}

@Override protected void onDestroy() { super.onDestroy(); asyncTask.cancel(true); } }