Asynctask Sederhana

Asyntask Sederhana

            Dibawah ini merupakan contoh program android yang mengimplementasikan AsyncTask dan ProgressBar pada android. User akan memilih sebuah file dari media penyimpanan, kemudian file tersebut akan dikirimkan ke AsyncTask untuk di baca (pembacaan file dilakukan pada background thread). Pada saat file sedang dibaca, AsyncTask akan mengirimkan kemajuan dari pembacaan file ke UI thread dan menampilkannya melalui ProgressBar. Setelah file selesai di baca atau proses pembacaan file di batalkan, secara otomatis progressbar akan menghilang, kemudian hasil dari operasi akan ditampilkan melalui TextView (lama operasi dan status operasi yang terjadi di background). Berikut adalah source code dari file HelloWorldActivity.java:

package com.example.helloworld;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;

import java.io.BufferedInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.net.URISyntaxException;

import android.content.Context;

import android.content.Intent;

import android.database.Cursor;

import android.net.Uri;

import android.os.AsyncTask;

import android.support.v4.app.Fragment;

import android.view.LayoutInflater;

import android.view.ViewGroup;

import android.widget.ProgressBar;

import android.widget.TextView;

import com.example.asyntask.R;

public class HelloWorldActivity extends ActionBarActivity {

       private static final int REQ_CODE = 0;

       private ReadTask tasker;

       @Override

       protected void onCreate(Bundle savedInstanceState) {

              super.onCreate(savedInstanceState);

              setContentView(R.layout.activity_hello_world);

              if (savedInstanceState == null) {

                     getSupportFragmentManager().beginTransaction()

                                  .add(R.id.container, new PlaceholderFragment()).commit();

              }

       }

       public void cancelButton(View v) {

              // check is there any task that can be aborted

              if (tasker.getStatus() == AsyncTask.Status.RUNNING

                           || tasker.getStatus() == AsyncTask.Status.PENDING) {

                     // abort the task

                     tasker.cancel(true);

              }

       }

       /** AsyncTask class used for reading a file <Params, Progress, Result> */

       private class ReadTask extends AsyncTask<String, Integer, String> {

              // private String data;

              private String time;

              private int progressStatus;

              ProgressBar bar;

              TextView barPercent;

              Button openButton;

              Button cancelButton;

              TextView tv1;

              TextView tv2;

              @Override

              protected void onPreExecute() {

                     super.onPreExecute();

                     // initial the Views

                     bar = (ProgressBar) findViewById(R.id.progressbar);

                     barPercent = (TextView) findViewById(R.id.barPercent);

                     openButton = (Button) findViewById(R.id.openButton);

                     cancelButton = (Button) findViewById(R.id.cancelButton);

                     tv1 = (TextView) findViewById(R.id.textView1);

                     tv1.setText("Elapsed: ");

                     tv2 = (TextView) findViewById(R.id.textView2);

                     tv2.setText("Status: ");

                     // disable openButton

                     openButton.setEnabled(false);

                     // show the Views

                     bar.setVisibility(View.VISIBLE);

                     barPercent.setVisibility(View.VISIBLE);

                     cancelButton.setVisibility(View.VISIBLE);

                     progressStatus = 0;

                     bar.setProgress(progressStatus);

                     barPercent.setText("Reading... 0%");

              }

              @Override

              protected String doInBackground(String... params) {

                     // TODO Auto-generated method stub

                     File file = new File(params[0]);

                     int length = (int) file.length();

                     int i = 0;

                     InputStream in = null;

                     byte[] buffer = new byte[8192];

                     try {

                           in = new BufferedInputStream(new FileInputStream(file));

                           long start = System.currentTimeMillis();

                           while ((i = in.read(buffer)) != -1) {

                                  // temp[j++] = (byte) i;

                                  progressStatus += i;

                                  // update the progressbar

                                  publishProgress((int) ((progressStatus / (float) length) * 100));

                                  // Escape early if cancel() is called

                                  if (isCancelled())

                                         break;

                           }

                           // data = byteToString(temp).toString();

                           time = ((System.currentTimeMillis() - start) + "ms").toString();

                     } catch (FileNotFoundException ex) {

                           ex.printStackTrace();

                           time = ex.getMessage();

                     } catch (IOException ex) {

                            // TODO Auto-generated catch block

                           ex.printStackTrace();

                           time = ex.getMessage();

                     } finally {

                           if (in != null) {

                                  try {

                                         in.close();

                                  } catch (IOException e) {

                                         // TODO Auto-generated catch block

                                         e.printStackTrace();

                                         time = e.getMessage();

                                  }

                           }

                     }

                     return time;

              }

              @Override

              protected void onProgressUpdate(Integer... progress) {

                     super.onProgressUpdate(progress);

                     // bar.incrementProgressBy(progress[0]);

                     bar.setProgress(progress[0]);

                     barPercent.setText("Reading... " + progress[0] + "%");

              }

              @Override

              protected void onCancelled() {

                     super.onCancelled();

                     results("-", "Cancelled");

              }

              @Override

              protected void onPostExecute(String result) {

                     super.onPostExecute(result);

                     results(result, "Finished");

              }

              void results(String e, String s) {

                     // clean up the Tasker

                     tasker = null;

                     // enable the openButton

                     openButton.setEnabled(true);

                     // close the Views

                     bar.setVisibility(View.GONE);

                     barPercent.setVisibility(View.GONE);

                     cancelButton.setVisibility(View.GONE);

                     // update the TextView1 and TextView2

                     tv1.setText("Elapsed: " + e);

                     tv2.setText("Status: " + s);

              }

       }

       boolean gotStatus() {

              if (tasker == null || tasker.getStatus() == AsyncTask.Status.PENDING

                           || tasker.getStatus() == AsyncTask.Status.FINISHED) {

                     // initial the Tasker

                     tasker = new ReadTask();

                     return true;

              }

              if (tasker.getStatus() == AsyncTask.Status.RUNNING) {

                     return false;

              }

              return false;

       }

       /** called when button "Open a File" clicked */

       public void openFile(View v) {

              if (gotStatus()) {

                     Intent intent = new Intent(Intent.ACTION_GET_CONTENT);

                     intent.setType("*/*");

                     intent.addCategory(Intent.CATEGORY_OPENABLE);

                     try {

                           startActivityForResult(

                                         Intent.createChooser(intent, "Select a file"), REQ_CODE);

                     } catch (android.content.ActivityNotFoundException ex) {

                           Toast.makeText(getBaseContext(), "You a need a File Manager",

                                         Toast.LENGTH_LONG).show();

                           ex.printStackTrace();

                     }

              } else {

                     Toast.makeText(HelloWorldActivity.this, "Task is still Running",

                                  Toast.LENGTH_LONG).show();

              }

       }

       @Override

       protected void onActivityResult(int reqCode, int resultCode, Intent data) {

              switch (reqCode) {

              case REQ_CODE:

                     if (resultCode == RESULT_OK) {

                           // get Uri data from intent

                           Uri uri = data.getData();

                           String path = null;

                           try {

                                  // convert Uri to file path (String)

                                  path = getPath(getBaseContext(), uri);

                                  // send the task to the AsyncTask

                                  tasker.execute(path);

                           } catch (URISyntaxException e) {

                                  // TODO Auto-generated catch block

                                  e.printStackTrace();

                           }

                     }

              }

       }

       private static String getPath(Context context, Uri uri)

                     throws URISyntaxException {

              if ("content".equalsIgnoreCase(uri.getScheme())) {

                     String[] projection = { "_data" };

                     Cursor cursor = null;

                     try {

                           cursor = context.getContentResolver().query(uri, projection,

                                         null, null, null);

                           int column_index = cursor.getColumnIndexOrThrow("_data");

                           if (cursor.moveToFirst()) {

                                  return cursor.getString(column_index);

                           }

                     } catch (Exception e) {

                           e.printStackTrace();

                     }

              } else if ("file".equalsIgnoreCase(uri.getScheme())) {

                     return uri.getPath();

              }

              return null;

       }

       @Override

       public boolean onCreateOptionsMenu(Menu menu) {

              // Inflate the menu; this adds items to the action bar if it is present.

              getMenuInflater().inflate(R.menu.hello_world, menu);

              return true;

       }

       @Override

       public boolean onOptionsItemSelected(MenuItem item) {

              int id = item.getItemId();

              if (id == R.id.action_settings) {

                     return true;

              }

              return super.onOptionsItemSelected(item);

       }

       public static class PlaceholderFragment extends Fragment {

              public PlaceholderFragment() {

              }

              @Override

              public View onCreateView(LayoutInflater inflater, ViewGroup container,

                           Bundle savedInstanceState) {

                     View rootView = inflater.inflate(R.layout.fragment_main, container,

                                  false);

                     return rootView;

              }

       }

}

Kemudian pada file activity_hello_world.xml ubah source code menjadi seperti berikut:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/container"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context="com.example.helloworld.HelloWorldActivity"

    tools:ignore="MergeRootFrame" />

Kemudian buat file fragment_main.xml, contoh source code adalah sebagai berikut:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.me.asynctaskprogressbarsample.MainActivity$PlaceholderFragment" >

    <Button

        android:id="@+id/openButton"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignParentTop="true"

        android:onClick="openFile"

        android:text="Open a File" />

    <LinearLayout

        android:id="@+id/linear"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_below="@id/openButton"

        android:orientation="vertical" >

        <TextView

            android:id="@+id/textView1"

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:layout_marginTop="10dp"

            android:text="Elapsed: " />

        <TextView

            android:id="@+id/textView2"

            android:layout_width="match_parent"

            android:layout_height="wrap_content"

            android:layout_marginTop="10dp"

            android:text="Status: " />

    </LinearLayout>

    <ProgressBar

        android:id="@+id/progressbar"

        style="@android:style/Widget.ProgressBar.Horizontal"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@id/linear"

        android:layout_below="@id/linear"

        android:visibility="invisible" />

    <TextView

        android:id="@+id/barPercent"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignLeft="@id/linear"

        android:layout_below="@id/progressbar"

        android:visibility="invisible" />

    <Button

        android:id="@+id/cancelButton"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@id/barPercent"

        android:layout_centerHorizontal="true"

        android:onClick="cancelButton"

        android:text="Cancel"

        android:visibility="invisible" />

</RelativeLayout>

Setelah selesai semuanya maka ini adalah beberapa screenshot dari aplikasi ini:

setelah klik open a file, maka akan muncul document yang akan dipilih