Vòng đời của Activity trong Android

public class MainActivity extends AppCompatActivity {

    private static final String STATE = "Trang thai";

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

        Log.e(STATE, "onCreate");
    }

    @Override
    protected void onPause() {
        super.onPause();

        Log.e(STATE, "onPause");
    }

    @Override
    protected void onResume() {
        super.onResume();

        Log.e(STATE, "onResume");
    }

    @Override
    protected void onStop() {
        super.onStop();

        Log.e(STATE, "onStop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        Log.e(STATE, "onDestroy");
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

        Log.e(STATE, "onRestoreInstanceState");
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

        Log.e(STATE, "onSaveInstanceState");
    }
}
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<?xml version="1.0" encoding="utf-8"?>

<LinearLayout

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

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

    android:id="@+id/activity_main"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin">



    <EditText

        android:id="@+id/et_first_number"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:inputType="number"/>



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="+"/>



    <EditText

        android:id="@+id/et_second_number"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:inputType="number"/>



    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="="/>



    <TextView

        android:id="@+id/tv_result"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"/>



    <Button

        android:id="@+id/btn_tinh_tong"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Tinh tong"/>



</LinearLayout>
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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.howkteam.activitylifecycle">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".SavedInstanceActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>

</manifest>
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package com.howkteam.activitylifecycle;



import android.os.Bundle;

import android.support.annotation.Nullable;

import android.support.v7.app.AppCompatActivity;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;



public class SavedInstanceActivity extends AppCompatActivity implements View.OnClickListener {



    private EditText etFirstNumber;

    private EditText etSecondNumber;

    private TextView tvResult;

    private Button btnTinhTong;



    private int firstNumber;

    private int secondNumber;

    private int result;



    @Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        etFirstNumber = (EditText) findViewById(R.id.et_first_number);

        etSecondNumber = (EditText) findViewById(R.id.et_second_number);

        tvResult = (TextView) findViewById(R.id.tv_result);

        btnTinhTong = (Button) findViewById(R.id.btn_tinh_tong);

        btnTinhTong.setOnClickListener(this);

    }



    @Override

    public void onClick(View view) {

        if (view == btnTinhTong) {

            if (etFirstNumber.getText().toString().isEmpty() || etSecondNumber.getText().toString().isEmpty()) {

                Toast.makeText(this, "Vui long nhap so", Toast.LENGTH_SHORT).show();

            } else {

                firstNumber = Integer.parseInt(etFirstNumber.getText().toString());

                secondNumber = Integer.parseInt(etSecondNumber.getText().toString());



                result = firstNumber + secondNumber;



                tvResult.setText(String.valueOf(result));

            }

        }

    }

}
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package com.howkteam.activitylifecycle;



import android.os.Bundle;

import android.support.annotation.Nullable;

import android.support.v7.app.AppCompatActivity;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;



public class SavedInstanceActivity extends AppCompatActivity implements View.OnClickListener {



    private EditText etFirstNumber;

    private EditText etSecondNumber;

    private TextView tvResult;

    private Button btnTinhTong;



    private int firstNumber;

    private int secondNumber;

    private int result;



    @Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        etFirstNumber = (EditText) findViewById(R.id.et_first_number);

        etSecondNumber = (EditText) findViewById(R.id.et_second_number);

        tvResult = (TextView) findViewById(R.id.tv_result);

        if (savedInstanceState != null) {

            etFirstNumber.setText(String.valueOf(savedInstanceState.getInt("SO_THU_NHAT")));

            etSecondNumber.setText(String.valueOf(savedInstanceState.getInt("SO_THU_HAI")));

            tvResult.setText(String.valueOf(savedInstanceState.getInt("KET_QUA")));

        }



        btnTinhTong = (Button) findViewById(R.id.btn_tinh_tong);

        btnTinhTong.setOnClickListener(this);

    }



    @Override

    protected void onSaveInstanceState(Bundle outState) {

        if (!tvResult.getText().toString().isEmpty()) {

            outState.putInt("SO_THU_NHAT", Integer.parseInt(etFirstNumber.getText().toString()));

            outState.putInt("SO_THU_HAI", Integer.parseInt(etSecondNumber.getText().toString()));

            outState.putInt("KET_QUA", Integer.parseInt(tvResult.getText().toString()));

        }

    }



    @Override

    public void onClick(View view) {

        if (view == btnTinhTong) {

            if (etFirstNumber.getText().toString().isEmpty() || etSecondNumber.getText().toString().isEmpty()) {

                Toast.makeText(this, "Vui long nhap so", Toast.LENGTH_SHORT).show();

            } else {

                firstNumber = Integer.parseInt(etFirstNumber.getText().toString());

                secondNumber = Integer.parseInt(etSecondNumber.getText().toString());



                result = firstNumber + secondNumber;



                tvResult.setText(String.valueOf(result));

            }

        }

    }

}
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package com.howkteam.fragmentexample;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

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