TextView tv ;
    Button bt;

setContentView(R.layout.activity_main);
... findViewById( R.id.textView );
//...............
@string/textText
//...............
@drawble/icon123 //<- file icon123.png tuye res/drawble hast

android:id="@+id/button"

package com.example.ali.myapplication2;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    TextView tv ;
    Button bt;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt = findViewById( R.id.button );
        bt.setOnClickListener( this );
        tv = findViewById( R.id.textView );
    }

    @Override
    public void onClick(View view) {
        tv.setText("dsdsdsd");
    }
}

Intent intent = new Intent(MainActivity.this, SecondActivity.class);
startActivityForResult(intent);

Bundle extras = getIntent().getExtras()
if( extras.containsKey("test") )
{
	extras.getString("phone");
}

--	//startActivity(intetnt);
++	startActivityForResult(intetnt,SUCCES_CODE);

setResult(50);
finish();

Intent intent = new Intent();
intent.putExtra("DATA","SALAM1");  
setResult(50,intent);
finish();

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        
        return super.onCreateOptionsMenu(menu);
    }

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

onOptionsItemSelected

    public boolean onOptionsItemSelected(MenuItem item) {
        if( item.getItemId() == R.id.alakiToast ){
            Toast.makeText(this, "alaki!", Toast.LENGTH_LONG).show();
        }else
        {
            Toast.makeText(this, "vaghei!", Toast.LENGTH_LONG).show();
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        menu.add("item1");
		SubMent item2 = menu.addSubmenu("item2");
		item2.add("sub item2");
        return super.onCreateOptionsMenu(menu);
    }

		//global
		EditText et ;
		//main
        et = findViewById(R.id.etTest);
        et.setOnFocusChangeListener(this);
        TextWatcher textWatcher = new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                tv.setText(  charSequence );
            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        };
        et.addTextChangedListener(textWatcher);
		
		
		
	@Override
    public void onFocusChange(View view, boolean b) {
        String s = "Hii";
        if (view.getId() == R.id.etTest){
            s = "Byyy";
        }
        if (b) s="sick";
        Toast.makeText(this, s  , Toast.LENGTH_SHORT).show();
    }

 String s = et.getText().toString();
 et.setText(TEXT);

<include layout="@layout/NAME_FILE_XML" 
	android:id="@+id/id_layout"/>

Intent intent = new Intent( Intent.ACTION_VIEW );
intent.SetData( Uri.parse("sms:+1234456") );
startActivity(intent);

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

if(item.getItemId() == android.R.id.home)
{
	finish();
}

	iv.animate().alpha(0f).setDuration(2000);

	iv.animate().translationYBy(50).setDuration(2000);
	//------
	iv.animate().translationY(50).setDuration(2000);

	iv.animate().rotation(90f).setDuration(2000);
	iv.animate().rotationBy(90f).setDuration(2000);

ImageView iv = findbyid(...)
iv.SetImageResource(R.drawable.axname);

	LinearLayout L = findViewById(R.id.LID);
	L.getChildCount(); // <-- tedad farzand
	L.getChildAt( i ); // <--  farzand i'om

	VideView vv = findById(R.id.videview);
	vv.setVideoPath( "android.resource://"  + getPackageName() + R.raw.videofilename );
	vv.start();

	VideView vv = findById(R.id.videview);
	vv.setVideoPath( "android.resource://"  + getPackageName() + R.raw.videofilename );
	
	MediaController c = new MediController(this);
	
	c.setAmchorView(vv);
	vv.SetMediaController( c );	
	
	vv.start();

	MediaPlayer mp = MediaPlayer.create( this, R.raw.audiofile );
	mp.start();
	mp.pause();
	mp.isPlayeing();
	mp.getDuration(); //<- modat zamane ahang 

	AudioManager audioManager;
	audioManager = getSystemService(Context.AUDIO_SERVICE);
	int maxVolume = audioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
	int curVolume = audioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
	
	audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, NUMBER , 0); // <-set deviice volume
	

	SeekBar sb  = findById(...);
	sb.setProgress(10);
	sb.setMax(100);
	
	sb.setOnSeekBarChangeListener(this);
	sb.setOnSeekBarChangeListener( new  SeekBar.OnSeekBarChangeListener(){
		@Override
		public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
			// change volume
			//progress <- adade seek bar
			
			// audioManager da r bala tashrih shode
			audioManager.setStreamVolume(AudioManager.STREAM_MUSIC, progress, 0); 
		}

		@Override
		public void onStartTrackingTouch(SeekBar seekBar) {}
		@Override
		public void onStopTrackingTouch(SeekBar seekBar) {}
	});

ProgressDialog pd = new ProgressDialog(this);

pdialog.setCancelable(false);

pdialog.setTitle("progress dialog example");
pdialog.setMessage("please wait ...");

pdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

pdialog.show();

pdialog.dismiss();

pdialog.setProgress(0);
pdialog.getMax()
pdialog.incrementProgressBy(1)

pdialog.setIndeterminate(true);

pdialog.getSecondaryProgress();
pdialog.incrementSecondaryProgressBy(1);

final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("AlertDialog")
		.setMessage("MSG")
		.setCancelable(false)
		.setIcon(android.R.drawable.ic_dialog_info)
		.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
			@Override
			public void onClick(DialogInterface dialogInterface, int i) {
				Toast.makeText(DialogActivity.this, "File Deleted!", Toast.LENGTH_SHORT).show();
			}
		})
		.setNegativeButton("No", null)
		.setNeutralButton("Cancel", null);

builder.setTitle("Question ?")
		.setCancelable(false)
		.setSingleChoiceItems(new String[]{"A", "B", "C", "D"}, -1, new DialogInterface.OnClickListener() {
			@Override
			public void onClick(DialogInterface dialogInterface, int i) {
				Toast.makeText(DialogActivity.this, "i = " + i, Toast.LENGTH_SHORT).show();
			}
		})
		.setPositiveButton("OK", null);

builder.setTitle("")
		.setCancelable(true)
		.setMultiChoiceItems(new String[]{"item0", "item1", "item2", "item3", "item4", "item5"},
				new boolean[]{false, true, false, true, true, false},
				new DialogInterface.OnMultiChoiceClickListener() {
					@Override
					public void onClick(DialogInterface dialogInterface, int i, boolean b) {
						Toast.makeText(DialogActivity.this, "item" + i + " : " + b, Toast.LENGTH_SHORT).show();
					}
				})
		.setPositiveButton("Ok", null);



builder.show();

Dialog dialog = new Dialog(this);
dialog.setContentView(R.layout.play_ground);
dialog.show();

List<String> items;

items = new ArrayList<>();
items.add("Tehran");
items.add("Mashhad");
items.add("Isfahan");
items.add("Shiraz");

ListView listview;
listview = (ListView) findViewById(R.id.listview);


ArrayAdapter<String> adapter;
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);

listview.setAdapter(adapter);

listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
	@Override
	public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
		Toast.makeText(SimpleListActivity.this, items.get(i), Toast.LENGTH_SHORT).show();
	}
});

items.add("new item");
adapter.notifyDataSetChanged();
//------------------------------------
items.remove(items.size()-1);
adapter.notifyDataSetChanged();

public class MyContacts {
    private String name;

    public MyContacts(String name){
        setName(name);
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Hi: " + name;
    }
}

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        LayoutInflater lif = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = lif.inflate(R.layout.listviewdesgin,parent,false);
        ImageView I = v.findViewById(R.id.imageView2);
        I.setImageResource(R.drawable.an);
        return v;
    }

new Handler().postDelayed(new Runnable(){

	@override
	public void run(){
		//process
	}

} , 10000L );

new Timer().scheduleAtFixedRate(new TimerTask() {
	@Override
	public void run() {
		//process
	}
}, /*Delay:*/ 0,  /*duration:*/ 200);

Toast toast = Toast.makeText(this, "Test Color For Toast", Toast.LENGTH_LONG);
toast.getView().setBackgroundColor(0x7ff44436);
toast.show();

this.context = context;
this.toast = new Toast(context);
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
this.view = inflater.inflate(R.layout.colored_toast_layout, null);
toast.setView(view);

simpleSpinner = (Spinner) findViewById(R.id.simple_spinner);
simpleItems = getResources().getStringArray(R.array.tours);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, simpleItems);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
simpleSpinner.setAdapter(adapter);

package org.faradars.firstproject;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;


public class CountrySpinnerAdapter extends BaseAdapter {

    private Context context;
    private int[] flags;
    private String[] names;
    private LayoutInflater inflater;
    public CountrySpinnerAdapter(Context context, int[] countryFlagIds, String[] countryNames){
        this.context = context;
        this.flags = countryFlagIds;
        this.names = countryNames;
        inflater = LayoutInflater.from(context);
    }


    @Override
    public int getCount() {
        return flags.length;
    }

    @Override
    public Object getItem(int i) {
        return names[i];
    }

    @Override
    public long getItemId(int i) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup viewGroup) {
        ViewHolder holder;
        if(convertView == null){
            convertView = inflater.inflate(R.layout.custom_spinner_item, viewGroup, false);
            holder = new ViewHolder();
            holder.country_flag = (ImageView) convertView.findViewById(R.id.country_flag);
            holder.country_name = (TextView) convertView.findViewById(R.id.country_name);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.fill(position);
        return convertView;
    }


    public class ViewHolder{
        public ImageView country_flag;
        public TextView country_name;

        public void fill(int position){
            country_flag.setImageResource(flags[position]);
            country_name.setText(names[position]);
        }
    }
}

private void initCustomSpinner() {
	customSpinner = (Spinner) findViewById(R.id.custom_spinner);
	final CountrySpinnerAdapter adapter = new CountrySpinnerAdapter(this, countryFlags, countryNames);
	customSpinner.setAdapter(adapter);
	customSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
		@Override
		public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
			Toast.makeText(SpinnerActivity.this,
					(String) adapterView.getSelectedItem(),
					Toast.LENGTH_SHORT).show();
		}

		@Override
		public void onNothingSelected(AdapterView<?> adapterView) {

		}
	});
}