FastCampusAndroid

Study and Organize about Android in FastCampus

Need to study

App Fundamental Link
Activity Life Cycle Link
Support Library Link
Static nested class Link

Week1

This week is not working in Android. See Java Lecture

Week2

Basic Widget

Radio Group Listener

public class BasicWidget implements RadioGroup.OnCheckedChangeListener {
    @Override
    public void onCheckedChanged(RadioGroup group, @IdRes int checkedId) {
        if(group.getId() == R.id.radioRgbGroup){
            switch (checkedId){
                case R.id.radioRed:
                    Toast.makeText(this, "RED.", Toast.LENGTH_SHORT).show();
                    break;
                case R.id.radioBlue:
                    Toast.makeText(this, "BLE.", Toast.LENGTH_SHORT).show();
                    break;
                case R.id.radioGreen:
                    Toast.makeText(this, "GREEN.", Toast.LENGTH_SHORT).show();
                    break;
            }
        }
    }
}

Seek Bar

public class BasicWidget implements CompoundButton.OnCheckedChangeListener {
    @Override
    public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
        // seek bar에 변경사항이 있을때마다 호출한다
        seekCount.setText(progress + ""); // setText에 숫자값만 단독으로 들어가면 앱이 다운된다. (int + "")
    }

    @Override
    public void onStartTrackingTouch(SeekBar seekBar) {
    }

    @Override
    public void onStopTrackingTouch(SeekBar seekBar) {

    }
}

Toggle Button

public class BasicWidget implements CompoundButton.OnCheckedChangeListener {
    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        switch (buttonView.getId()){
            case R.id.toggleButton:
                if(isChecked){
                    Toast.makeText(this, "켜졌습니다.", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(this, "꺼졌습니다.", Toast.LENGTH_SHORT).show();
                }
        }
    }
}

-. Basic Layout

GridLayout
LinearLayout
RelativeLayout
ConstraintLayout

-. Intent Filter

Run Activity

If you want to run activity stand alone, You have to add this code in intent-filter in Manifest file

        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" /> 
        </intent-filter>

-. Intent Basic

Send SMS / MMS

Intent it = new Intent(Intent.ACTION_VIEW);
it.putExtra("sms_body", "The SMS text");
it.setType("vnd.android-dir/mms-sms");
startActivity(it);

More example is here...

-. Adapter

-. RecyclerView

Week3

-. Tip

Transaction

That is a Process which handle a data at time. For example if we handle a data which needs process A,B,C and during the processes, if we encounter errors in process B. It goes back before Process A execution. For detail, we already know CRUD, but Read doesn't need Trasaction.
XML, HTML, TXT Files

That type of files are not compiled, So it doesn't have Magic Number, Only things to do in that file is declare the structure
Depedency Injection

Below code is Dependency Injection, But sometimes it's bothersome. So, some tools helps you do this easy. Dagger and Butter Knife is that type of tools. and Actually after Kotlin and Android 3.0 helps you naturally.
```
  this.editName = (EditText) findViewById(R.id.property_inputText_name);
  this.editEmail = (EditText) findViewById(R.id.property_inputText_email);
  this.editPassword = (EditText) findViewById(R.id.property_inputText_pw);
```

Null Handling(If statement vs Try Catch)

Most of case, it's better to use if statement for null handling, because sometimes try catch statement makes system slow

      // Better
      Bundle bundle = getIntent().getExtras();
      if (bundle == null) {
          return;
      }

      // Not recommended
      Bundle bundle = getIntent().getExtras();
      try {
          bundle.getString(/*key*/);           
      } catch (NullPointerException e){
          
      }

Decide which function you use

Look this code. When we get the value from Bundle, We use this code

      Bundle bundle = getIntent().getExtras();
      if (bundle == null) {
          return;
      }
      /* Bundle이 Null이면 getString()이라는 함수가 없다. */
      String value = bundle.getString("key");

But we know another function

      getIntent().getStringExtra("key");

So, second code is look like easier to use. but sometimes we need first code. If we need so many values which is brought from values. In second code case, despite of bundle is null, they run all of getStringExtra() but first code, they don't need to every run by checking bundle is null

  //better
  Bundle bundle = getIntent().getExtras();
  if (bundle == null) {
      return;
  }
  String value1 = bundle.getString("key1");
  String value2 = bundle.getString("key2");
  String value3 = bundle.getString("key3");
  String value4 = bundle.getString("key4");

  //Not recommended
  String value1= getIntent().getStringExtra("key1");
  String value2= getIntent().getStringExtra("key2");
  String value3= getIntent().getStringExtra("key3");
  String value4= getIntent().getStringExtra("key4");

Get Result from Next Activity using Intent

Present Activitysource code

Next Activity source code

Present Activity

Using startActivityForResult(), not Using startActivity()

  Intent intent = new Intent( /* Context */, /* Next Activity */)
  intent.putExtra("myKey", inputText.getText().toString());
  startActivityForResult(intent, /* Request Code */);

Using Activity Life Cycle, onActivityResult() called when it appears again.

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data/*결과값이 담겨 온다*/) {
     super.onActivityResult(requestCode, resultCode, data);
 
     if (resultCode == RESULT_OK /* this is same as Request Code */) {
         switch (requestCode) {
             case BTN_RESULT :
                 int result = data.getIntExtra(/* key */, /* Default Value */);
                 break;
             case BTN_START:
                 break;
         }
     }
 }

Next Activity

Intent without Context, because they don't need to use System Resource

  Intent intent = new Intent();
  intent.putExtra(/* key */, result);
  setResult(RESULT_OK, intent);
  finish();

-. Properties

source code

Actually each Activity can create each Preference but nowadays It's common to use only one perference file in the application. we called that SharedPreference

// Save Preference
public void savePreference(String key, String value) {
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putString(key, value);
    editor.commit();
}

//Load Preference
public void loadPreference() {
    String name = sharedPreferences.getString("name", "[none]");
    String email = sharedPreferences.getString("email", "[none]");
    String password = sharedPreferences.getString("password", "");

    this.editName.setText(name);
    this.editEmail.setText(email);
    this.editPassword.setText(password);

}

//Remove Preference
private void removePreference(String key){
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.remove(key);
    editor.commit();
}

//Remove All Preference
private void removeAllPreferences(){
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.clear();
    editor.commit();
}

-. WebView

source code

If you want to use WebView, You need resource permission. It's different form Runtime Permission

Note : You need to add this code to manifest file to obtain permission.
 <uses-permission android:name="android.permission.INTERNET" />

/* Dependency Injection */
webView = (WebView) findViewById(R.id.webview);

/* Create Client */
webView.setWebViewClient(new WebViewClient());
webView.setWebChromeClient(new WebChromeClient());

/* JavaScript Enable */
webView.getSettings().setJavaScriptEnabled(true);

-. Runtime Permission

Using Contacts Permission source code

Manifest File

Add below code

<uses-permission android:name="android.permission.CAMERA"/>

Present Activity

If the version is corresponded, check permission. and then if don't have permission, request permission to User If have permission execution.

/* Version Compatibilty Check statement */
// Bring present android version and do if version is above the Mashmallow
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M){ // After Mashmallow version, Write Initial is ok
  String permissions[] = {Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.CAMERA};
  boolean hasPermissions = PermissionUtil.hasPermissionsAndRequestIfNot(this, permissions, REQ_PERMISSION);
  if(hasPermissions){
    init();
  }
} else {
  init();
}

PermissionUtil Class

PermissionUtil.hasPermissionAndRequestIfNot() method needs annotation @TargetApi(/* Version */) It means that function can execute above That Android Version

public class PermissionUtil {
    @RequiresApi(api = Build.VERSION_CODES.M)
    public static boolean hasPermissionsAndRequestIfNot(Activity activity, String[] permissions, int requestCode) {
        Context context = activity.getBaseContext();

        for (String permission : permissions) {
            if(context.checkSelfPermission(permission) != PackageManager.PERMISSION_GRANTED){
                activity.requestPermissions(permissions, requestCode);
                return false;
            }
        }
        return true;
    }
}

again Present Activity

You need to override onRequestPermissionsResult() in the activity, This is same as Intent For result, After activity.requestPErmission(permission, requestCode) is called, The code which is overrided executes.

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
  super.onRequestPermissionsResult(requestCode, permissions, grantResults);
  if(requestCode == REQ_PERMISSION){
      // User accept give permission
      if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
          run();
      // User deny give permission
      } else {
          cancle();
      }
  }
}

-. Implicit Intent

source code

reference

This is the code for Pick and Returning Image

class Activity {
  @Override
      public void onClick(View v) {
          Intent intent = null;
          switch (v.getId()) {
              case R.id.camera_btn_gallery :
                  intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                  startActivityForResult(Intent.createChooser(intent, "Select Photo"), 100); // for returnning Image
                  break;
              case R.id.camera_btn_camera :
                  break;
          }
      }
      
      @Override
      protected void onActivityResult(int requestCode, int resultCode, Intent data) {
          super.onActivityResult(requestCode, resultCode, data);
          if (resultCode == RESULT_OK) {
              switch (requestCode) {
                  case 100:
                      Uri imageUri = data.getData();
                      imageView.setImageURI(imageUri);
                      break;
      
              }
          }
      }
}

-. Manifest File

more detail

provider

Declares a content provider component.

-. Content URI

Content URIs have the syntax more detail

content://authority/path/id

-. Content Provider

Get Contact Example

First add permission to Manifest File

<!-- 전화번호부 권한 -->
<uses-permission android:name="android.permission.READ_CONTACTS" />

And version and permission check. If doesn't have permission, ask user to allow to get permission in this app.

@Override
protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_recycler_again);
 
     if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
         String[] permissions = {Manifest.permission.READ_CONTACTS};
         PermissionUtil.hasPermissionsAndRequestIfNot(this, permissions, 100);
     } else {
         init();
     }
 }
 
 @Override
 public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
     super.onRequestPermissionsResult(requestCode, permissions, grantResults);
 
     if (requestCode == 100) {
         if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
             init();
         } else {
             Toast.makeText(this, "권한을 승인하셔야만 사용할 수 있습니다.", Toast.LENGTH_SHORT).show();
         }
     }
 }

If you want to get Contacts you have to use Content Resolover,

List<Contact> contactList = new ArrayList<>();
ContentResolver contentResolver = context.getContentResolver();

// Table Address
Uri phoneUri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI;

// Column name from table
String proj[] = {ContactsContract.CommonDataKinds.Phone.CONTACT_ID
        , ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME
        , ContactsContract.CommonDataKinds.Phone.NUMBER};

// Bring data using Content resolver
Cursor cursor = contentResolver.query(phoneUri, proj, null, null, null);

// Check data is existed in cursor
if (cursor != null) {
    while (cursor.moveToNext()) {
        int index = cursor.getColumnIndex(proj[0]);
        String id = cursor.getString(index);

        index = cursor.getColumnIndex(proj[1]);
        String name = cursor.getString(index);

        index = cursor.getColumnIndex(proj[2]);
        String tel = cursor.getString(index);

        contactList.add(new Contact(id, name, tel));
    }
}
// Note : Should be closed
cursor.close();

Non-blocking, Blocking, Channel, Stream, Database.. that type should be closed after task. because Even if memory allocation is released, it couldn't be closed.
Alarm, Calendar and more Content URI is here
See Static nested class

-. FileProvider and Camera

FileProvider is a special subclass of ContentProvider that facilitates secure sharing of files associated with an app by creating a content:// Uri for a file instead of a file:/// Uri.

Why have to use FileProvider in Camera Action.

Becuase when under the Lollipop Version. Photo file can be obtained from result Intent. See below

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    imageUri = data.getData();
}

But above the Lollipop Version, returned Intent which was sent as Camera Capture Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); is null. So the way to get Uri is store Global Variable as File. and obtain Uri from File

Uri fileURI;        // Global Variable

public void takePhoto(){
    // Create File
    fileURI = Uri.fromFile(tempFile);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
        imageUri = data.getData(); // Return URI
    } else {
        imageUri = fileUri;
    }imageUri = data.getData();
}

As the version updated, It is impossible obtaining URI from URI.fromFile() method after Marshmallow version, because of security issue the way of obtaining URI is using File Provider

FileProvider.getURiForFile(Context, Authority, File);

Note : File Provider is belong to support package.

Autority name should be same as android:authorities in Manifest File

Note : you have to add <provider> tag in Manifest File

In result, you have to add this code.

public void takePhoto(){
    // Create File
    
     /* Under Marshmallow Version doesn't need File Provider during access URI*/
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
        fileURI = Uri.fromFile(tempFile);
    } else { /* You have to access Using File Privider */
        // File Provider need Authority
        // Authority should be set in manifest file using <provider> tag for run below code
        String authority = BuildConfig.APPLICATION_ID + ".provider"; // get app ID from Gradle
        fileURI = FileProvider.getUriForFile((activity.getBaseContext()), authority, tempFile);
    }
}

So, this is all code about Using Camera

note :

add file_paht.xml file in xml folder in res folder

  <?xml version="1.0" encoding="utf-8"?>
  <path>
      <!--실제 경로와 추상경로가 있다. 실제 매핑되어 있는 것은 ...-->
      <!--path = /Exteranal Strage/CameraPath이 된다. 갤러리 폴더가 하나 생성되어 있다.-->
      <!--name = cotnent:// 로 시작하는 uri 주소체계의 suffix가 된다.-->
      <external-path name="CameraName" path="CameraPath" />
  </path>

add Permission in manifest file

  <!-- 카메라 권한 -->
  <uses-permission android:name="android.permission.CAMERA" />
  <!-- Exteranl Storage Write Permission -->
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

add add Provider in manifest file

note : android:authorities get its name from gradle.

note : android:resource="@xml/file_path" should be match real xml file.

  <provider
      android:name="android.support.v4.content.FileProvider"
      android:authorities="${applicationId}.provider"
      android:exported="false"
      android:grantUriPermissions="true">
      <meta-data
          android:name="android.support.FILE_PROVIDER_PATHS"
          android:resource="@xml/file_path" />
  </provider>

Main Activity(Camera Capture)

@Override
public void onClick(View v) {
    this.fileUri = DeviceUtil.Camera.takePhoto(this, "CameraPath", Const.Device.REQ_CODE_CAMERA);
}

/* Above the Lollipop version, Capture Camera Intent be returned as null(Intent is empty)
 * That's why FileURI set to be global variable and call Image using this variable */
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == Const.Device.REQ_CODE_CAMERA) {
        if (resultCode == RESULT_OK) {
            Uri imageUri = null;
            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
                imageUri = data.getData(); // Return URI
            } else {
                imageUri = fileUri;
            }
            imageView.setImageURI(imageUri);
        }
    }
}

Camera Util (File provider and Start Activity)

public static class Camera{
    public static Uri takePhoto(Activity activity, String xmlExternalPath/* Folder Name */ , int requestCode) {
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);

        /* Under Lollipop Version Doesn't need Convert File to URI*/
        /* Just send Intent and In onActivityResult, You can get simply File's URI using Intent.getData(); */
        if(Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP){
            activity.startActivityForResult(intent, requestCode);
            return null;
        }

        Uri fileURI = null;
        File tempFile = null;

        try {
            /* Create temp file for saving photo */
            tempFile = DeviceUtil.createFileForCamera(xmlExternalPath); //TODO : Need to change File Util
        } catch (IOException e) {
            e.printStackTrace();
        }

        if (tempFile == null) {
            Log.e(TAG, "Created File is null for Camera(Photo Capture)");
            return null;
        }

        /* Under Marshmallow Version doesn't need File Provider during access URI*/
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            fileURI = Uri.fromFile(tempFile);
        } else { /* You have to access Using File Privider */
            // File Provider need Authority
            // Authority should be set in manifest file using <provider> tag for run below code
            String authority = BuildConfig.APPLICATION_ID + ".provider"; // get app ID from Gradle
            fileURI = FileProvider.getUriForFile((activity.getBaseContext()), authority, tempFile);
        }

        intent.putExtra(MediaStore.EXTRA_OUTPUT, fileURI);
        activity.startActivityForResult(intent, requestCode); // NOTE : Context doesn't have startActivityForResult() method.

        return fileURI;
    }
}

// 파일생성에 관한 함수를 만들고 Exception에 담는다.
private static File createFileForCamera(String xmlExternalPath) throws IOException {
    // 임시 파일명 생성
    String tempFilename = "TEMP_" + System.currentTimeMillis();
    // 임시파일 저장용 디렉토리 생성
    // 익스터널 스토리지의 루트 경로(실제 시스템의 루트가 아님)
    // XML에서 설정했던 그 경로에 대한 권한을 얻는 것이다.
    File tempDir = new File(Environment.getExternalStorageDirectory() +"/" + xmlExternalPath + "/"); // path라는 것을 알려주기 위해 /로 랩한다
    if(!tempDir.exists()){
        tempDir.mkdir(); // 없으면 모두 생성
    }

    //실제 임시파일을 생성
    File tempFile = File.createTempFile(
            tempFilename,// 파일네임
            ".jpg",     // suffix
            tempDir     // 디렉토리
    );
    return tempFile;
}

Google Map and GPS in ViewPager

-. Const

You can manage all Constant Value Using Class. This is example

public class Const {
    // Grouping(namespace)
    public static class Camera {
        public static final int REQ_CAMERA = 100;
    }        
    public static class Intent {
        public static final int REQ_CODE = 101;
    }
}

Week4

-. Thread Clock Example

-. Thread Communication

This Example is multiple counter(text view). Change 4 Text View at the same time using each Thread

Main Activity

/* Error Counter */
ErrorCounter errorCounter = new ErrorCounter(textViews[0]);
new Thread(errorCounter).start();

/* Way 1 - RunOnUiThread */
RunOnUiThreadCounter runOnUiThreadCounter = new RunOnUiThreadCounter(this, textViews[1]);
new Thread(runOnUiThreadCounter).start();

/* Way 2 - Handler */
HandlerCounter handlerCounter = new HandlerCounter(this);
new Thread(handlerCounter).start();

ErrorCounter

If you try to change UI widget directly in sub thread, you encounter below error message. Android prevent Sub Thread set UI Widget directly, It is because of sync issue.

  CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

public class ErrorCounter implements Runnable {

    private TextView textView;
    int count = 0;

    public ErrorCounter(TextView textView) {
        this.textView = textView;
    }

    @Override
    public void run() {
        for(int i=0; i<10; i++) {
            try {
                Thread.sleep(500);
            } catch (Exception e){

            }
            this.textView.setText(count+"");  // This code occurs error
            count ++;
        }
    }
}

RunOnUiThread

Below code may work, but issue is still here. sometimes count until 10, sometimes count until 9. because It can't be synced between setText() and count. RunOnUiThread throw their own code to main thread. so, sub thread doesn't have that code.

this.activity.runOnUiThread(new Runnable() { // 코드로 가면 이렇게 객체를 생성하지 않고 함수를 직접 넘겨주면 된다.
    @Override
    public void run() {
        textView.setText(count+""); // 여기는 메인스레드에서 동작한다. 코드를 넘겨준다.
                                    // 메인 스레드에 붙이기 때문에.. Sub 스레드와 타이밍이 어긋난다.
                                    // 9번째 왔을때 이 코드를 메인 스레드에 던져 놓고
                                    // count++ 실행되고 이 코드가 실행하면 10이 찍히고
                                    // count++가 실행되기 전에 이코드가 실행되면 9가 찍힌다.
    }
});

Handler

Using Handler and Looper

// Handler 클래스를 전달 받아서.. 서브 thread로 부터 메세지를 전달받을 Handler를 생성한다... 메세지 통신
public class HandlerCounter extends  Handler implements Runnable{

    public static final int SET_COUNT = 99;
    private Activity activity;
    private int count = 0;

    public HandlerCounter(Activity activity) {
        this.activity = activity;
    }

    @Override
    public void run() {
        for(int i=0; i < 10; i ++) {
            try {
                Thread.sleep(500);
            } catch (Exception e) {
                e.printStackTrace();
            }

            // 핸들러를 통해 메세지를 날릴때 Msg를 생성해서 날릴 수 있따.
            // 메세직 객체가 그렇게 설계가 되어 있다. arg1, arg2 두개의 argument를 날려줄 수 있다.
            Message msg = new Message();
            msg.what = SET_COUNT;
            msg.arg1 = count;
            // msg.arg1 = integer;
            // msg.arg2 = integer;
            // msg.setData();       // send Instance
            sendMessage(msg);
            /* Empty Message */
            // sendEmptyMessage(SET_COUNT);

            count++;
        }
    }

    // 서브 thread에서 메세지를 전달하면 handleMessage 함수가 동작한다.
    @Override
    public void handleMessage(Message msg) {
        // 메세지가 정해져 있따.
        // msg.arg1;
        // msg.arg2;

        // 자바에서는 주로 integer로 주고 받는다,
        // 핸들러간 통신을 할때는 미리 상수로 정의 해 놓는다.

        switch (msg.what) {
            case SET_COUNT:
                int tempCount = msg.arg1;
                ((TextView) activity.findViewById(R.id.multipleCount_tv_3)).setText(tempCount + "");
                break;
        }

    }
}

Interthread

Link

wait(), notify(), syncTocken

-. Paint

public class PaintExample {
    public PaintExample() {
        Paint paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setAntiAlias(true);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setDither(true);
    }
}

Sqlite and ORM

There are two famous ORM. One is Ormlite and the other is GreenDAO. In this lecture, we are going to use ORMLite

Add dependendy

                // package / class / version
compile 'com.j256.ormlite:ormlite-core:5.0'
compile 'com.j256.ormlite:ormlite-android:5.0'

Week 5

Progress Dialog

progressDialog = new ProgressDialog(this);
progressDialog.setTitle("진행중....");
progressDialog.setMessage("진행중 표시되는 메세지 입니다.");
progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);

Async Task

Subthread vs Async Task vs Retrofit

AsyncTask is type of sub thread. It helps do something in background as same as sub thread. But we use Asynctask when task's number is limited or Routine is already fixed unlike sub thread.

Note : It means we can expect when the Thread is ended. For example get data using Network is belong to be in this case, but Chat Server and Client not. because we can't expect when the user ended their Chat server and client

Default AsyncTask

public void test(){
    // First Generic, Second Generic, Third Generic
    new AsyncTask<Void, Void, Void>() {
        @Override
        protected void onPreExecute() {
            // Run Main Thread(Can access UI Thread)
        }

        @Override
        protected Void doInBackground(Void... params) {
            // Run Sub Thread
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            // Run Main Thread(Can access UI Thread)
        }
        
    }.execute();
}

First Generic

the variable from main thread can be passed on First Generic. .excute(/* params */) and ge doInBackground(Void... params) ... means it's array but not fixed size. see String params example.

AsyncTask<String, Void, Void>() ...

    @Override
    protected Void doInBackground(String... params) {
        // Run Sub Thread
        String param1 = params[0];
        String param2 = param[1];
        return null;
        
}.execute("Param1", "Param2", "Param3");

Second Generic

Call publishProgress() in doInBackground() and then onProgressUpdate() method is called over and over again until do in doInBackground()

AsyncTask<Void, Integer, Void>() ...
    @Override
    protected void onProgressUpdate(Integer... values) { /* Second Generic Param */)
        super.onProgressUpdate(values);
        progressDialog.setMessage("진행율 =" + values[0] + "%");
    }
    @Override
    protected Void doInBackground(String... params) {
        publishProgress(int1, int2, ... ); /* Second Generic Param */
    }
}

Third Generic

doInBackground() method's return value passes to onPostExecute() params

@Override
protected Float doInBackground(String... params) { // ... 세개표시가 배열이라는 표시고 몇개가 들어올지 모르는것.
   try {
       for(int i=0; i<10; i++) {
           publishProgress(i*10);  // onProgressUpdate 주기적으로 업데이트 해준다.
           Thread.sleep(100);
       }
   } catch (InterruptedException e) {
       e.printStackTrace();
   }
   return 1000.4f; /* Third Generic */
}

@Override
protected void onPostExecute(Float result) { /* Third Generic */
   setDone();
   postProcess();
}

Remote Data from Network

Network

asfrom30/FastCampusAndroid

FastCampusAndroid

Need to study

Week1

Week2

Basic Widget

-. Basic Layout

-. Intent Filter

-. Intent Basic

-. Adapter

-. RecyclerView

Week3

-. Tip

-. Properties

-. WebView

-. Runtime Permission

-. Implicit Intent

-. Manifest File

-. Content URI

-. Content Provider

-. FileProvider and Camera

Google Map and GPS in ViewPager

-. Const

Week4

-. Thread Clock Example

-. Thread Communication

-. Paint

Sqlite and ORM

Week 5

Progress Dialog

Async Task

Remote Data from Network