파드레의 요모조모

kotlin은 이전에 특별히 바인딩이라는 것을 하지않아도 자동으로 되었었는데 2020년 초부터 binding을 해야하는 것으로 바뀌었고 강좌들은 이전 것과 이후 것이 혼재되어 헷갈리게 되어 있다.

view binding만 보면...

build.gradle ( module) 파일에

plugins {
      id 'com.android.application'
      id 'kotlin-android'
      id 'kotlin-android-extensions'
}

android {
...
    buildFeatures {
          viewBinding =true
    }
}

를 추가하고 왼쪽 위에 sync now를 눌러 싱크를 맞춘다.

그리고,  

<LinearLayout
        ...
        tools:viewBindingIgnore="true" >
    ...
</LinearLayout>

위의 내용을 activity_main등의 레이아웃 파일에 넣으면 바인딩이 되지않으니 넣지말라!!

==========activity_main.xml====================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity">
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello world"
android:id="@+id/myBtn"/>
</LinearLayout>

=============== MainActivity.kt============

import android.app.Activity
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.jstudio.coroutin.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {
   private lateinit var binding:ActivityMainBinding

   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      binding = ActivityMainBinding.inflate(layoutInflater)
      setContentView(binding.root)

      binding.myBtn.text = "button works"
   }
}

package com.jproject.mysturdy;

import androidx.appcompat.app.AppCompatActivity;

import android.app.LauncherActivity;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.util.SparseBooleanArray;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import java.lang.reflect.Array;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    ArrayList<String> Items = new ArrayList<String>();
    ArrayAdapter<String> Adapter;
    ListView list;

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

        Items.add("Frist");
        Items.add("Second");
        Items.add("Third");
        Items.add("Fourth");
        Items.add("Fifth");

        Adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, Items);

        list = (ListView) findViewById(R.id.list);
        list.setAdapter(Adapter);
        list.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
    }

    public void mOnclick(View v) {
        EditText ed = (EditText)findViewById(R.id.newitem);
        int pos;
        String text;
        SparseBooleanArray sb;

        switch(v.getId()){
            case R.id.add:
                text = ed.getText().toString();
                if (text.length() != 0){
                    Items.add(text);
                    ed.setText("");
                    Adapter.notifyDataSetChanged();
                }
                break;
                case R.id.change:
                    sb = list.getCheckedItemPositions();
                    text = ed.getText().toString();
                    pos = list.getCheckedItemPosition();
                    if (sb.size() != 0){
                        for (int i = list.getCount()-1;i>=0;i--){
                            if(sb.get(i)){
                                Items.remove(i);
                                Items.add(i,text);
                            }
                        }

                        list.clearChoices();
                        ed.setText("");
                        Adapter.notifyDataSetChanged();
                    }
                    break;

            case R.id.delete:

                pos = list.getCheckedItemPosition();
                sb = list.getCheckedItemPositions();

                if (sb.size() != 0){
                    for (int i = list.getCount()-1;i>=0;i--){
                        if(sb.get(i)){
                            Items.remove(i);
                        }
                    }

                    list.clearChoices();
                    Adapter.notifyDataSetChanged();
                }
                break;
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/newitem"
        android:layout_width="wrap_content"
        android:layout_height="120px"
        />
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/add"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="add"
            android:onClick="mOnclick"
            />
        <Button
            android:id="@+id/change"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="change"
            android:onClick="mOnclick"
        />
        <Button
            android:id="@+id/delete"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="delete"
            android:onClick="mOnclick"
            />
    </LinearLayout>
    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="500px"
        />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/newitem"
        android:layout_width="wrap_content"
        android:layout_height="120px"
        />
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:id="@+id/add"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="add"
            android:onClick="mOnclick"
            />
        <Button
            android:id="@+id/change"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="change"
            android:onClick="mOnclick"
        />
        <Button
            android:id="@+id/delete"
            android:layout_width="8px"
            android:layout_weight="3"
            android:layout_height="wrap_content"
            android:text="delete"
            android:onClick="mOnclick"
            />
    </LinearLayout>
    <ListView
        android:id="@+id/list"
        android:layout_width="match_parent"
        android:layout_height="500px"
        />
</LinearLayout>

package com.jproject.mysturdy;

import androidx.appcompat.app.AppCompatActivity;

import android.app.LauncherActivity;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.view.View;
import android.widget.Adapter;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import java.lang.reflect.Array;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    String[] arGeneral = {"김유신","이순신","강감찬","을지문덕"};
    ArrayList<String> Items = new ArrayList<String>();
    ArrayAdapter<String> Adapter;
    ListView list;

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

        Items.add("Frist");
        Items.add("Second");
        Items.add("Third");

        Adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_single_choice, Items);

        list = (ListView) findViewById(R.id.list);
        list.setAdapter(Adapter);
        list.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
    }

    public void mOnclick(View v) {
        EditText ed = (EditText)findViewById(R.id.newitem);
        int pos;
        String text;
        switch(v.getId()){
            case R.id.add:
                text = ed.getText().toString();
                if (text.length() != 0){
                    Items.add(text);
                    ed.setText("");
                    Adapter.notifyDataSetChanged();
                }
                break;
                case R.id.change:
                    text = ed.getText().toString();
                    pos = list.getCheckedItemPosition();
                    if (text.length() != 0|pos != ListView.INVALID_POSITION){
                        Items.remove(pos);
                        Items.add(pos,text);
                        ed.setText("");
                        Adapter.notifyDataSetChanged();
                    }
                    break;

            case R.id.delete:

                pos = list.getCheckedItemPosition();
                if (pos != ListView.INVALID_POSITION){
                    Items.remove(pos);
                    list.clearChoices();
                    Adapter.notifyDataSetChanged();
                }
                break;
        }
    }
}

안드로이드에서는  보안과 관련된 중요한 사항에 사용자의 허가를 받아야 하는데, 허가가 필요한 사항응 반드시 manifest에 명시해야하는데 빨간색과 같이 표시하면 된다.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.snazzyapp">

    <uses-permission android:name="android.permission.INTERNET"/>
    <!-- other permissions go here -->

    <application ...>
        ...
    </application>
</manifest>

한편 사용자의 허가를 받아야하는 서비스는 아래 표와 같으며 이들 서비스를 사용할 때는 위의 manifest에 반드시 명시해야하며 한번 허가받으면 다시 받을 필요가 없으나 사용자는 언제든 허가를 취소할 수 있다. 그리고, 권한이 없을 때는 사용자에게 권한을 요청해야만 한다.

String input="5.2", output;

Double ans = 0;

ans=Double.parseDouble(input);

//if input is not String type, it throws NumberFormatException error

//만일 input이 String Type이 아니면 NumberFormatExecption error를 발생시킨다.

//if input is null, it throws NullpointException error

//만일 input이 Null이면 NullpointException error를 발생시킨다.

함수는 Double형을 반환한다.

output=Double.toString(ans*2);

//ans*2의 값을 ASCII의 형태의 문자열로 반환한다.

Toast.makeText(MainActivity.this, output, Toast.LENGTH_SHORT).show();

//안드로이드에서 간단한 문자열(output)로 화면에 표시

10.4