Bài 6: How to handle events ~ Programming Tutorial

Bài 6: How to handle events

8/25/2015 08:41:00 SA

Trong bài học này sẽ trình bày các vấn đề về sử lý sự kiện cho các đối tượng.
Nội dung:
I. Tổng quan xử lý sự kiện mức cao và mức thấp:

II. Các kỹ thuật xử lý sự kiện
1/ Onclick in XML: sử dụng xml để gọi hàm tính tổng
2/ Inline anonymous listener
3/ Activity is listener
4/ Activity in variable
5/ Explicit listener class
III. Xử lý sự kiện cho: check boxes , radio button, radio groups, spinners, seek bars
1/ Check boxs, radio buttons
2/ Radio groups
3/ Spinners
4/ Seek bars
VI. Xử lý key và touch
1/ Xử lý sự kiện key
2/ Xử lý sự kiện touch
------------------------------------------
I. Tổng quan xử lý sự kiện mức cao và mức thấp:

II. Các kỹ thuật xử lý sự kiện:
1/ Onclick in XML: sử dụng xml để gọi hàm tính tổng

Outline:

- Code xml:

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

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

android:id="@+id/LinearLayout1"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/so_a"

android:textSize="20sp"/>

<EditText

android:id="@+id/editText_so_a"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:inputType="number">

</EditText>

<TextView

android:id="@+id/textView2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="20sp"

android:text="@string/so_b" />

<EditText

android:id="@+id/editText_so_b"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:inputType="number"/>

<TextView

android:id="@+id/textView3"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:textSize="20sp"

android:text="@string/tong" />

<TextView

android:id="@+id/textView_ketqua"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="" />

<Button

android:id="@+id/btn_tong"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:onClick="btn_tong"

android:layout_gravity="center"

android:text="@string/tinh_tong" />

</LinearLayout>

-Chú ý sử dụng xml:

- Mã nguồn java:

public class MainActivity extends Activity {

EditText eText_a, eText_b;
TextView textView_kq;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

eText_a = (EditText) findViewById(R.id.editText_so_a);
eText_b = (EditText) findViewById(R.id.editText_so_b);
textView_kq = (TextView) findViewById(R.id.textView_ketqua);

}

public void btn_tong(View v) {//trùng tên hàm trong xml

int a = Integer.parseInt( eText_a.getText() + "");

int b = Integer.parseInt( eText_b.getText() + "");

textView_kq.setText(a + b + "");

}

//…………

}

Link download bài 6_1:
https://drive.google.com/file/d/0B8tAQ0_sJKCSeGl0cGptcV81MFE/view?usp=sharing

2/ Inline anonymous listener: Với cách này mỗi button chúng ta sẽ viết một hàm setOnClickListener.

Mã code java:

public class MainActivity extends Activity {

Button btn_tong;

EditText eText_a, eText_b;

TextView textView_kq;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

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

eText_a = (EditText) findViewById(R.id.editText_so_a);

eText_b = (EditText) findViewById(R.id.editText_so_b);

textView_kq = (TextView) findViewById(R.id.textView_ketqua);

btn_tong.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

int a = Integer.parseInt(eText_a.getText() + "");

int b = Integer.parseInt(eText_b.getText() + "");

textView_kq.setText(a + b + "");

}

});

}

//......

}

Link download bài 6_2:
https://drive.google.com/file/d/0B8tAQ0_sJKCSMEYwblpYSmF1cEk/view?usp=sharing

3/ Activity is listener:
Trong cách viết sự kiện này thì Activity sẽ implements OnClickListener
Bước 1: import the interface for the listener
import android.view.View.OnClickListener;
Bước 2a: implement the interface for listener
public class MainActivity extends Activity implements OnClickListener {

Bước 2b: Override lại hàm onClick
@Override

public void onClick(View v) {

switch(v.getId()) {

case R.id.btn_tong:

//xử lý ở đây..

break;

//.....

}

}
Bước 3: Set the listeners
btn_tinhtong.setOnClickListener(this);

Mã nguồn java:

public class MainActivity extends Activity implements OnClickListener{

Button btn_tinhtong;

EditText eText_a, eText_b;

TextView textView_kq;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

btn_tinhtong = (Button) findViewById(R.id.btn_tong);

btn_tinhtong.setOnClickListener(this);

eText_a = (EditText) findViewById(R.id.editText_so_a);

eText_b = (EditText) findViewById(R.id.editText_so_b);

textView_kq = (TextView) findViewById(R.id.textView_ketqua);

}

@Override

public void onClick(View v) {

switch(v.getId()) {

case R.id.btn_tong:

int a = Integer.parseInt( eText_a.getText() + "");

int b = Integer.parseInt( eText_b.getText() + "");

textView_kq.setText(a + b + "");

break;

//.....

}

//.............

}

Link download bài 6_3:
https://drive.google.com/file/d/0B8tAQ0_sJKCSSTNPNW9KYUpMaTg/view?usp=sharing

4/ Activity in variable: Tương tự như cách 3 Activity Is listener, nhưng khác ở chỗ thay vì implement interface OnClickListener cho Activity thì nó lại được lưu trữ vào một biến có kiểu Listener trong Activity. Làm cách này thì ta có thể chia sẻ chung một biến sự kiện cho các control (cho nhiều button) khác nhau.
Mã nguồn java:

public class MainActivity extends Activity {

Button btn_tong;

EditText eText_a, eText_b;

TextView textView_kq;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

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

eText_a = (EditText) findViewById(R.id.editText_so_a);

eText_b = (EditText) findViewById(R.id.editText_so_b);

textView_kq = (TextView) findViewById(R.id.textView_ketqua);

btn_tong.setOnClickListener(myClickListener);

}

OnClickListener myClickListener = new OnClickListener() {

@Override

public void onClick(View v) {

if (v == btn_tong) {

int a = Integer.parseInt(eText_a.getText() + "");

int b = Integer.parseInt(eText_b.getText() + "");

textView_kq.setText(a + b + "");

}

};

//.....

}

Link download bài 6_4:
https://drive.google.com/file/d/0B8tAQ0_sJKCScUs3REtrRFlKZDg/view?usp=sharing

5/ Explicit listener class: Trường hợp này ta tách riêng một class đóng vai trò là class sự kiện riêng. Khi nào lượng coding trong ứng dụng khổng lồ và phức tạp thì ta nên tách class sự kiện riêng để dễ quản lý.
Lưu ý: Lớp sử lý sự kiện riêng này private class MyEvent implements OnClickListener cũng nằm trong lớp MainActivity gọi lớp lồng lớp.
Mã java:

public class MainActivity extends Activity {

Button btn_tong;

EditText eText_a, eText_b;

TextView textView_kq;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

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

btn_tong.setOnClickListener(new MyEvent());

eText_a = (EditText) findViewById(R.id.editText_so_a);

eText_b = (EditText) findViewById(R.id.editText_so_b);

textView_kq = (TextView) findViewById(R.id.textView_ketqua);

}

private class MyEvent implements OnClickListener {

@Override

public void onClick(View v) {

if (v.getId() == R.id.btn_tong) {

int a = Integer.parseInt(eText_a.getText() + "");

int b = Integer.parseInt(eText_b.getText() + "");

textView_kq.setText(a + b + "");

}

//.....

}

Link download bài 6_5:
https://drive.google.com/file/d/0B8tAQ0_sJKCSWURCZFVQUENCTEE/view?usp=sharing

III. Xử lý sự kiện cho: check boxes , radio button, radio groups, spinners, seek bars
1/ Check box: xử lý sự kiện check box
Bước 1: import android.widget.CompoundButton;

Bước 2a: public class MainActivity extends Activity implements OnCheckedChangeListener {

Bước 2b: Override lại hàm onCheckedChanged

@Override

public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

switch(buttonView.getId()) {

case R.id.CheckBox_music:

if (isChecked) {

Log.i("Checkbox", "true");

} else {

Log.i("Checkbox", "false");

}

break;

//...

}

Bước 3: Set the listeners
checkbox_music.setOnCheckedChangeListener(this);

2/ Radio groups:

3/ Spinners:

4/ Seek bars:
----------------------
Ví dụ 6: Xây dựng dụng như sau, khi bấm vào button nào thì TextView bên dưới sẽ đổi màu theo.

Outline:

Mã XML:

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

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

android:id="@+id/LinearLayout1"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context="com.exampleevenlistener.MainActivity" >

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content" >

<Button

android:id="@+id/btn_red"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Red"

android:textColor="#FF0000" />

<Button

android:id="@+id/btn_green"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Green"

android:textColor="#00FF00" />

<Button

android:id="@+id/btn_blue"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Blue"

android:textColor="#0000FF" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" >

<Button

android:id="@+id/btn_random"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Random"

android:textColor="#FF0000" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<RadioGroup

android:id="@+id/radioGroupColor"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<RadioButton

android:id="@+id/rd_red"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:checked="true"

android:text="Red" />

<RadioButton

android:id="@+id/rd_green"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Green" />

<RadioButton

android:id="@+id/rd_blue"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Blue" />

</RadioGroup>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical" >

<TextView

android:id="@+id/textViewColor"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="#FF0000" />

</LinearLayout>

Mã java: MainActivity.java

//...

public class MainActivity extends Activity implements OnClickListener, OnCheckedChangeListener {

private Button btnRed;

private Button btnGreen;

private Button btnBlue;

private Button btnRandom;

private TextView tvColoring;

private RadioGroup rdColor;

private RadioButton rdbRed;

private RadioButton rdbGreen;

private RadioButton rdbBlue;

private final static int[] mColorChoices = {Color.RED, Color.GREEN, Color.BLUE };

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

//get references to the widgets

btnRed = (Button) findViewById(R.id.btn_red);

btnGreen = (Button) findViewById(R.id.btn_green);

btnBlue = (Button) findViewById(R.id.btn_blue);

btnRandom = (Button) findViewById(R.id.btn_random);

rdbRed = (RadioButton) findViewById(R.id.rd_red);

rdbGreen = (RadioButton) findViewById(R.id.rd_green);

rdbBlue = (RadioButton) findViewById(R.id.rd_blue);

rdColor = (RadioGroup) findViewById(R.id.radioGroupColor);

tvColoring = (TextView) findViewById(R.id.textViewColor);

//set the listeners

btnRed.setOnClickListener(this);

btnGreen.setOnClickListener(this);

btnBlue.setOnClickListener(this);

btnRandom.setOnClickListener(this);

rdColor.setOnCheckedChangeListener(this);

tvColoring.setOnClickListener(this);

}

//Event handler for the button

@Override

public void onClick(View v) {

switch(v.getId()) {

case R.id.btn_red:

changeColor(Color.RED);

break;

case R.id.btn_green:

changeColor(Color.GREEN);

break;

case R.id.btn_blue:

changeColor(Color.BLUE);

break;

case R.id.btn_random:

Random random = new Random();

int numRandom = random.nextInt(mColorChoices.length);

changeColor(mColorChoices[numRandom]);

Log.i("EventListener: ", numRandom + "");

break;

case R.id.textViewColor:

changeColor(Color.WHITE);

break;

}

public void changeColor(int color) {

tvColoring.setBackgroundColor(color);

}

//Event handler for the RadioGroup

@Override

public void onCheckedChanged(RadioGroup group, int checkedId) {

Log.i("Radio button blue change", "checked");

switch(checkedId) {

case R.id.rd_red:

changeColor(Color.RED);

break;

case R.id.rd_green:

changeColor(Color.GREEN);

break;

case R.id.rd_blue:

changeColor(Color.BLUE);

break;

}

//….

}

Link download ví dụ này:
https://drive.google.com/file/d/0B8tAQ0_sJKCSOGtacVAzS1FwM3M/view?usp=sharing

Ví dụ 7: Thiết kế giao diện thông tin cá nhân như hình dưới

Outline:

Mã XML:

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

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

android:id="@+id/LinearLayout1"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context="com.eventlistener.MainActivity" >

<TextView

android:id="@+id/textView1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="#1F45FC"

android:gravity="center"

android:text="Thông tin cá nhân"

android:textColor="#FFFFFF"

android:textSize="25sp" />

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content" >

<TextView

android:id="@+id/textView2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Họ tên:"

android:textSize="20sp" />

<EditText

android:id="@+id/editText_name"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="4"

android:ems="10" >

</EditText>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" >

<TextView

android:id="@+id/textView3"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="#00BFFF"

android:gravity="center"

android:text="Giới tính"

android:textSize="20sp" />

<RadioGroup

android:id="@+id/radioGroup_sex"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<RadioButton

android:id="@+id/radio_sexmale"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:checked="true"

android:text="Nam" />

<RadioButton

android:id="@+id/radio_sexfemale"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Nữ" />

<RadioButton

android:id="@+id/radio_sexother"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Khác" />

</RadioGroup>

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" >

<TextView

android:id="@+id/TextView01"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="#00BFFF"

android:gravity="center"

android:text="Sở thích"

android:textSize="20sp" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<CheckBox

android:id="@+id/CheckBox_music"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Nghe Nhạc" />

<CheckBox

android:id="@+id/CheckBox_sport"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Thể thao" />

<CheckBox

android:id="@+id/checkBox_coding"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Lập trình" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical" >

<TextView

android:id="@+id/TextView02"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="#00BFFF"

android:gravity="center"

android:text="Thông tin khác"

android:textSize="20sp" />

</LinearLayout>

<EditText

android:id="@+id/editText_information"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:ems="10"

android:inputType="textMultiLine"

android:maxLines="5"

android:minLines="5" />

<LinearLayout

android:layout_width="match_parent"

android:layout_height="match_parent"

android:gravity="center|bottom"

android:orientation="vertical" >

<Button

android:id="@+id/btn_send"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="Gởi thông tin" />

<TextView

android:id="@+id/textView_bottombar"

android:layout_width="match_parent"

android:layout_height="20dp"

android:background="#1F45FC" />

</LinearLayout>

Mã java:

package com.eventlistener;

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.CheckBox;

import android.widget.CompoundButton;

import android.widget.RadioButton;

import android.widget.Toast;

import android.widget.CompoundButton.OnCheckedChangeListener;

import android.widget.RadioGroup;

public class MainActivity extends Activity implements OnClickListener, OnCheckedChangeListener, android.widget.RadioGroup.OnCheckedChangeListener {

CheckBox checkbox_music, checkbox_sport, checkbox_coding;

RadioButton rdb_sexmale, rdb_sexfemale, rdb_sexother;

RadioGroup radioGroup_sex;

Button btn_send;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

checkbox_music = (CheckBox) findViewById(R.id.CheckBox_music);

checkbox_sport = (CheckBox) findViewById(R.id.CheckBox_sport);

checkbox_coding = (CheckBox) findViewById(R.id.checkBox_coding);

radioGroup_sex = (RadioGroup) findViewById(R.id.radioGroup_sex);

rdb_sexmale = (RadioButton) findViewById(R.id.radio_sexmale);

rdb_sexfemale = (RadioButton) findViewById(R.id.radio_sexfemale);

rdb_sexother = (RadioButton) findViewById(R.id.radio_sexother);

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

radioGroup_sex.setOnCheckedChangeListener(this);

checkbox_music.setOnCheckedChangeListener(this);

checkbox_sport.setOnCheckedChangeListener(this);

checkbox_coding.setOnCheckedChangeListener(this);

btn_send.setOnClickListener(this);

}

@Override

public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

switch(buttonView.getId()) {

case R.id.CheckBox_music:

if (isChecked) {

Log.i("Checkbox", "true");

} else {

Log.i("Checkbox", "false");

}

break;

//...

}

//Handler event button

@Override

public void onClick(View v) {

String result = "";

if (v.getId() == R.id.btn_send) {

if (checkbox_music.isChecked()) {

result += "Music ";

}

if (checkbox_sport.isChecked()) {

result += "Sport ";

}

if (checkbox_coding.isChecked()) {

result += "Coding ";

}

Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG).show();

}

//Event handler for the RadioGroup

@Override

public void onCheckedChanged(RadioGroup group, int checkedId) {

Log.i("Radio button change", "checked");

String radioSelect = "";

switch(checkedId){

case R.id.radio_sexmale:

radioSelect += "Male";

break;

case R.id.radio_sexfemale:

radioSelect += "Female";

break;

case R.id.radio_sexother:

radioSelect += "Other";

break;

}

Toast.makeText(getApplicationContext(), radioSelect, Toast.LENGTH_LONG).show();

}

//...

}

Link download ví dụ này:

VI. Xử lý key và touch
1/ Xử lý sự kiện key:

2/ Xử lý sự kiện touch:

Bài tập:
1. Xây dựng ứng dụng máy tính cá nhân

Outline:

Mã XML:

<LinearLayout 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:orientation="vertical"

android:padding="5dp" >

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="vertical"

android:layout_marginBottom="5dp">

<EditText

android:id="@+id/editText_input"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:editable="false"

android:ems="10"

android:gravity="right" >

</EditText>

<EditText

android:id="@+id/editText_result"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:editable="false"

android:ems="10"

android:gravity="right" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<Button

android:id="@+id/btn_xoa"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="C" />

<Button

android:id="@+id/btn_del"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="2"

android:text="Del" />

<Button

android:id="@+id/btn_cong"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="+" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<Button

android:id="@+id/btn_7"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="7" />

<Button

android:id="@+id/btn_8"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="8" />

<Button

android:id="@+id/btn_9"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="9" />

<Button

android:id="@+id/btn_tru"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="-" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<Button

android:id="@+id/btn_4"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="4" />

<Button

android:id="@+id/btn_5"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="5" />

<Button

android:id="@+id/btn_6"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="6" />

<Button

android:id="@+id/btn_nhan"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="*" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:orientation="horizontal" >

<Button

android:id="@+id/btn_1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="1" />

<Button

android:id="@+id/btn_2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="2" />

<Button

android:id="@+id/btn_3"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="3" />

<Button

android:id="@+id/btn_chia"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="/" />

</LinearLayout>

<LinearLayout

android:layout_width="match_parent"

android:layout_height="wrap_content" >

<Button

android:id="@+id/btn_0"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="2"

android:text="0" />

<Button

android:id="@+id/btn_cham"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="." />

<Button

android:id="@+id/btn_tinh"

android:layout_width="0dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="=" />

</LinearLayout>

Mã java: xem link bên dưới

Hàm tính giá trị biểu thức với chuỗi string biểu thức truyền vào:

public static double Tinh(final String str) {
    return new Object() {
        int pos = -1, ch;

        void nextChar() {
            ch = (++pos < str.length()) ? str.charAt(pos) : -1;
        }

        boolean eat(int charToEat) {
            while (ch == ' ') nextChar();
            if (ch == charToEat) {
                nextChar();
                return true;
            }
            return false;
        }

        double parse() {
            nextChar();
            double x = parseExpression();
            if (pos < str.length()) throw new RuntimeException("Unexpected: " + (char)ch);
            return x;
        }

        // Grammar:
        // expression = term | expression `+` term | expression `-` term
        // term = factor | term `*` factor | term `/` factor
        // factor = `+` factor | `-` factor | `(` expression `)`
        //        | number | functionName factor | factor `^` factor

        double parseExpression() {
            double x = parseTerm();
            for (;;) {
                if      (eat('+')) x += parseTerm(); // addition
                else if (eat('-')) x -= parseTerm(); // subtraction
                else return x;
            }
        }

        double parseTerm() {
            double x = parseFactor();
            for (;;) {
                if      (eat('*')) x *= parseFactor(); // multiplication
                else if (eat('/')) x /= parseFactor(); // division
                else return x;
            }
        }

        double parseFactor() {
            if (eat('+')) return parseFactor(); // unary plus
            if (eat('-')) return -parseFactor(); // unary minus

            double x;
            int startPos = this.pos;
            if (eat('(')) { // parentheses
                x = parseExpression();
                eat(')');
            } else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers
                while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
                x = Double.parseDouble(str.substring(startPos, this.pos));
            } else if (ch >= 'a' && ch <= 'z') { // functions
                while (ch >= 'a' && ch <= 'z') nextChar();
                String func = str.substring(startPos, this.pos);
                x = parseFactor();
                if (func.equals("sqrt")) x = Math.sqrt(x);
                else if (func.equals("sin")) x = Math.sin(Math.toRadians(x));
                else if (func.equals("cos")) x = Math.cos(Math.toRadians(x));
                else if (func.equals("tan")) x = Math.tan(Math.toRadians(x));
                else throw new RuntimeException("Unknown function: " + func);
            } else {
                throw new RuntimeException("Unexpected: " + (char)ch);
            }

            if (eat('^')) x = Math.pow(x, parseFactor()); // exponentiation

            return x;
        }
    }.parse();
}

Link download bài máy tính:
https://drive.google.com/file/d/0B8tAQ0_sJKCSbnZ2MkxYYktOcGs/view?usp=sharing

Chuyên mục Android

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Bài 6: How to handle events

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