bat-dau-hoc-android-voi-viec-tao-app-todolist-p2

I. Button thêm task mới và AlertDialog

1. Vẽ button thêm task mới

Trước tiên các bạn tạo file res/menu/tasks_fragment.xml với nội dung như sau:

<span class="php"><span class="hljs-meta">&lt;?</span>xml version=<span class="hljs-string">"1.0"</span> encoding=<span class="hljs-string">"utf-8"</span><span class="hljs-meta">?&gt;</span></span>
<span class="hljs-tag">&lt;<span class="hljs-name">menu</span> <span class="hljs-attr">xmlns:android</span>=<span class="hljs-string">"http://schemas.android.com/apk/res/android"</span>
    <span class="hljs-attr">xmlns:app</span>=<span class="hljs-string">"http://schemas.android.com/apk/res-auto"</span>&gt;</span>

    <span class="hljs-tag">&lt;<span class="hljs-name">item</span>
        <span class="hljs-attr">android:title</span>=<span class="hljs-string">"@string/action_add_task"</span>
        <span class="hljs-attr">android:icon</span>=<span class="hljs-string">"@android:drawable/ic_menu_add"</span>
        <span class="hljs-attr">android:id</span>=<span class="hljs-string">"@+id/action_add_task"</span>
        <span class="hljs-attr">app:showAsAction</span>=<span class="hljs-string">"always"</span> /&gt;</span>

<span class="hljs-tag">&lt;/<span class="hljs-name">menu</span>&gt;</span>

<?xml version="1.0" encoding="utf-8"?>

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

xmlns:app="http://schemas.android.com/apk/res-auto">

<item

android:title="@string/action_add_task"

android:icon="@android:drawable/ic_menu_add"

android:id="@+id/action_add_task"

app:showAsAction="always" />

</menu>

2. Hiển thị AlertDialog khi người dùng click vào + button

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">boolean</span> <span class="hljs-title">onOptionsItemSelected</span><span class="hljs-params">(MenuItem item)</span> </span>{
        <span class="hljs-keyword">int</span> id = item.getItemId();
        <span class="hljs-keyword">switch</span> (id){
            <span class="hljs-keyword">case</span> R.id.action_add_task:
                AlertDialog.Builder builder = <span class="hljs-keyword">new</span> AlertDialog.Builder(getActivity());
                builder.setTitle(<span class="hljs-string">"Add a task"</span>);
                <span class="hljs-keyword">final</span> EditText inputField = <span class="hljs-keyword">new</span> EditText(getActivity());
                builder.setView(inputField);
                builder.setPositiveButton(<span class="hljs-string">"Add"</span>, <span class="hljs-keyword">new</span> DialogInterface.OnClickListener() {
                    <span class="hljs-meta">@Override</span>
                    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onClick</span><span class="hljs-params">(DialogInterface dialogInterface, <span class="hljs-keyword">int</span> i)</span> </span>{
                         Toast.makeText(getActivity(), inputField.getText(), Toast.LENGTH_SHORT).show();
                    }
                });
                builder.setNegativeButton(<span class="hljs-string">"Cancel"</span>, <span class="hljs-keyword">null</span>);
                builder.create().show();
                <span class="hljs-keyword">return</span> <span class="hljs-keyword">true</span>;
        }
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">super</span>.onOptionsItemSelected(item);
    }

@Override

public boolean onOptionsItemSelected(MenuItem item) {

int id = item.getItemId();

switch (id){

case R.id.action_add_task:

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

builder.setTitle("Add a task");

final EditText inputField = new EditText(getActivity());

builder.setView(inputField);

builder.setPositiveButton("Add", new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface dialogInterface, int i) {

Toast.makeText(getActivity(), inputField.getText(), Toast.LENGTH_SHORT).show();

}

});

builder.setNegativeButton("Cancel", null);

builder.create().show();

return true;

}

return super.onOptionsItemSelected(item);

}

Khi click vào + button ta sẽ thấy AlertDialog sau hiển thị

II. Lưu trữ và nhận dữ liệu từ Database

1. Tạo database

1.1 Tạo package data như ảnh dưới đây

1.2 Tạo file TaskConTract trong package data

Contract trong file này giúp app có khả năng làm việc với các URIs, tên cột trong bảng, intent actions, và các features của content provider.

<span class="hljs-keyword">package</span> sonyama.todolist.data;

<span class="hljs-keyword">import</span> android.provider.BaseColumns;

<span class="hljs-comment">/**
 * Created by sonyama on 1/11/16.
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TaskConTract</span> </span>{

    <span class="hljs-comment">//Each of xxxEntry corresponds to a table in the database</span>
    <span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TaskEntry</span> <span class="hljs-keyword">implements</span> <span class="hljs-title">BaseColumns</span> </span>{
        <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> String TABLE_NAME = <span class="hljs-string">"tasks"</span>;
        <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> String COLUMN_TASK = <span class="hljs-string">"task"</span>;
    }
}

package sonyama.todolist.data;

import android.provider.BaseColumns;

/**

* Created by sonyama on 1/11/16.

*/

public class TaskConTract {

//Each of xxxEntry corresponds to a table in the database

public class TaskEntry implements BaseColumns {

public static final String TABLE_NAME = "tasks";

public static final String COLUMN_TASK = "task";

}

1.3 Tạo TaskDBHelper

Và sử dụng nó để tạo database theo yêu cầu.

<span class="hljs-keyword">package</span> sonyama.todolist.data;

<span class="hljs-keyword">import</span> android.content.Context;
<span class="hljs-keyword">import</span> android.database.sqlite.SQLiteDatabase;
<span class="hljs-keyword">import</span> android.database.sqlite.SQLiteOpenHelper;

<span class="hljs-comment">/**
 * Created by sonyama on 1/11/16.
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TaskDBHelper</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">SQLiteOpenHelper</span> </span>{
    <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> String DATABASE_NAME = <span class="hljs-string">"tasks.db"</span>;
    <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">final</span> <span class="hljs-keyword">int</span> DATABASE_VERSION = <span class="hljs-number">1</span>;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">TaskDBHelper</span><span class="hljs-params">(Context context)</span> </span>{
        <span class="hljs-keyword">super</span>(context, DATABASE_NAME, <span class="hljs-keyword">null</span>, DATABASE_VERSION);
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onCreate</span><span class="hljs-params">(SQLiteDatabase db)</span> </span>{
        <span class="hljs-keyword">final</span> String SQL_CREATE_TASKS_TABLE =
                <span class="hljs-string">"CREATE TABLE "</span> + TaskConTract.TaskEntry.TABLE_NAME + <span class="hljs-string">" ("</span> +
                        TaskConTract.TaskEntry._ID + <span class="hljs-string">" INTEGER PRIMARY KEY,"</span> +
                        TaskConTract.TaskEntry.COLUMN_TASK + <span class="hljs-string">" TEXT NOT NULL"</span> +
                        <span class="hljs-string">" );"</span>;
        db.execSQL(SQL_CREATE_TASKS_TABLE);
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onUpgrade</span><span class="hljs-params">(SQLiteDatabase db, <span class="hljs-keyword">int</span> oldVersion, <span class="hljs-keyword">int</span> newVersion)</span> </span>{
        db.execSQL(<span class="hljs-string">"DROP TABLE IF EXISTS "</span> + TaskConTract.TaskEntry.TABLE_NAME);
        onCreate(db);
    }
}

package sonyama.todolist.data;

import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

/**

* Created by sonyama on 1/11/16.

*/

public class TaskDBHelper extends SQLiteOpenHelper {

public static final String DATABASE_NAME = "tasks.db";

private static final int DATABASE_VERSION = 1;

public TaskDBHelper(Context context) {

super(context, DATABASE_NAME, null, DATABASE_VERSION);

}

@Override

public void onCreate(SQLiteDatabase db) {

final String SQL_CREATE_TASKS_TABLE =

"CREATE TABLE " + TaskConTract.TaskEntry.TABLE_NAME + " (" +

TaskConTract.TaskEntry._ID + " INTEGER PRIMARY KEY," +

TaskConTract.TaskEntry.COLUMN_TASK + " TEXT NOT NULL" +

" );";

db.execSQL(SQL_CREATE_TASKS_TABLE);

}

@Override

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

db.execSQL("DROP TABLE IF EXISTS " + TaskConTract.TaskEntry.TABLE_NAME);

onCreate(db);

}

2. Đọc ghi dữ liệu vào database

2.1 Ghi dữ liệu

Chúng ta sẽ chỉnh sửa code ở MainActivityFragment.java sao cho khi click vào nút + ta có thể nhập tên task muốn làm và lưu vào một bản ghi trong database.

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">boolean</span> <span class="hljs-title">onOptionsItemSelected</span><span class="hljs-params">(MenuItem item)</span> </span>{
        <span class="hljs-keyword">int</span> id = item.getItemId();
        <span class="hljs-keyword">switch</span> (id){
            <span class="hljs-keyword">case</span> R.id.action_add_task:
                AlertDialog.Builder builder = <span class="hljs-keyword">new</span> AlertDialog.Builder(getActivity());
                builder.setTitle(<span class="hljs-string">"Add a task"</span>);
                builder.setMessage(<span class="hljs-string">"What do you want to do"</span>);
                <span class="hljs-keyword">final</span> EditText inputField = <span class="hljs-keyword">new</span> EditText(getActivity());
                builder.setView(inputField);
                builder.setPositiveButton(<span class="hljs-string">"Add"</span>, <span class="hljs-keyword">new</span> DialogInterface.OnClickListener() {
                    <span class="hljs-meta">@Override</span>
                    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onClick</span><span class="hljs-params">(DialogInterface dialogInterface, <span class="hljs-keyword">int</span> i)</span> </span>{
                        <span class="hljs-comment">//Get user input</span>
                        String inputTask = inputField.getText().toString();

                        <span class="hljs-comment">//Get DBHelper to write to database</span>
                        TaskDBHelper helper = <span class="hljs-keyword">new</span> TaskDBHelper(getActivity());
                        SQLiteDatabase db = helper.getWritableDatabase();

                        <span class="hljs-comment">//Put in the values within a ContentValues</span>
                        ContentValues values = <span class="hljs-keyword">new</span> ContentValues();
                        values.clear();
                        values.put(TaskConTract.TaskEntry.COLUMN_TASK, inputTask);

                        <span class="hljs-comment">//Insert the values into the Table for Tasks</span>
                        db.insertWithOnConflict(
                                TaskConTract.TaskEntry.TABLE_NAME,
                                <span class="hljs-keyword">null</span>,
                                values,
                                SQLiteDatabase.CONFLICT_IGNORE
                        );

                        <span class="hljs-comment">//Query database again to get updated data</span>
                        Cursor cursor = db.query(TaskConTract.TaskEntry.TABLE_NAME,
                                <span class="hljs-keyword">new</span> String[]{TaskConTract.TaskEntry._ID, TaskConTract.TaskEntry.COLUMN_TASK},
                                <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>);

                        <span class="hljs-comment">//Swap old data with new data for display</span>
                        mTaskAdapter.swapCursor(cursor);

                    }
                });
                builder.setNegativeButton(<span class="hljs-string">"Cancel"</span>, <span class="hljs-keyword">null</span>);
                builder.create().show();
                <span class="hljs-keyword">return</span> <span class="hljs-keyword">true</span>;
        }
        <span class="hljs-keyword">return</span> <span class="hljs-keyword">super</span>.onOptionsItemSelected(item);
    }

@Override

int id = item.getItemId();

switch (id){

case R.id.action_add_task:

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

builder.setTitle("Add a task");

builder.setMessage("What do you want to do");

final EditText inputField = new EditText(getActivity());

builder.setView(inputField);

builder.setPositiveButton("Add", new DialogInterface.OnClickListener() {

@Override

//Get user input

String inputTask = inputField.getText().toString();

//Get DBHelper to write to database

TaskDBHelper helper = new TaskDBHelper(getActivity());

SQLiteDatabase db = helper.getWritableDatabase();

//Put in the values within a ContentValues

ContentValues values = new ContentValues();

values.clear();

values.put(TaskConTract.TaskEntry.COLUMN_TASK, inputTask);

//Insert the values into the Table for Tasks

db.insertWithOnConflict(

TaskConTract.TaskEntry.TABLE_NAME,

null,

values,

SQLiteDatabase.CONFLICT_IGNORE

);

//Query database again to get updated data

Cursor cursor = db.query(TaskConTract.TaskEntry.TABLE_NAME,

new String[]{TaskConTract.TaskEntry._ID, TaskConTract.TaskEntry.COLUMN_TASK},

null, null, null, null, null);

//Swap old data with new data for display

mTaskAdapter.swapCursor(cursor);

}

});

builder.setNegativeButton("Cancel", null);

builder.create().show();

return true;

}

return super.onOptionsItemSelected(item);

}

2.2 Xoá dữ liệu

Tạo file TaskAdapter.java với nội dung như sau:

<span class="hljs-keyword">package</span> sonyama.todolist;

<span class="hljs-keyword">import</span> ...

<span class="hljs-keyword">import</span> sonyama.todolist.data.TaskConTract;
<span class="hljs-keyword">import</span> sonyama.todolist.data.TaskDBHelper;

<span class="hljs-comment">/**
 * Created by sonyama on 1/12/16.
 */</span>
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">TaskAdapter</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">CursorAdapter</span> </span>{

    <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> Context context;
    TaskDBHelper helper;

    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-title">TaskAdapter</span> <span class="hljs-params">(Context context, Cursor cursor)</span> </span>{
        <span class="hljs-keyword">super</span>(context, cursor, <span class="hljs-number">0</span>);
        <span class="hljs-keyword">this</span>.context = context;
        helper = <span class="hljs-keyword">new</span> TaskDBHelper(context);
    }

    <span class="hljs-comment">//The newView method is used to inflate a new view and return it,</span>
    <span class="hljs-comment">//you don't bind any data to the view at this point</span>
    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> View <span class="hljs-title">newView</span><span class="hljs-params">(Context context, Cursor cursor, ViewGroup parent)</span> </span>{
        <span class="hljs-keyword">return</span> LayoutInflater.from(context).inflate(R.layout.list_item_task, parent, <span class="hljs-keyword">false</span>);
    }

    <span class="hljs-meta">@Override</span>
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">bindView</span><span class="hljs-params">(View view, Context context, Cursor cursor)</span> </span>{
        <span class="hljs-comment">//Find Views to populate in inflated template</span>
        TextView textView = (TextView) view.findViewById(R.id.list_item_task_textview);
        Button done_button = (Button) view.findViewById(R.id.list_item_task_done_button);

        <span class="hljs-comment">//Extract properties from cursor</span>
        <span class="hljs-keyword">final</span> String id = cursor.getString(MainActivityFragment.COL_TASK_ID);
        <span class="hljs-keyword">final</span> String task = cursor.getString(MainActivityFragment.COL_TASK_NAME);

        <span class="hljs-comment">//Populate views with extracted properties</span>
        textView.setText(task);
        done_button.setOnClickListener(<span class="hljs-keyword">new</span> View.OnClickListener() {
            <span class="hljs-meta">@Override</span>
            <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">onClick</span><span class="hljs-params">(View v)</span> </span>{
                <span class="hljs-comment">//Create a SQL command for deleting a particular ID.</span>
                String sql = String.format(<span class="hljs-string">"DELETE FROM %s WHERE %s = '%s'"</span>,
                        TaskConTract.TaskEntry.TABLE_NAME,
                        TaskConTract.TaskEntry._ID,
                        id);
                SQLiteDatabase sqlDB = helper.getWritableDatabase();
                <span class="hljs-comment">//Execute the delete command</span>
                sqlDB.execSQL(sql);
                Log.d(<span class="hljs-string">"kakakak"</span>, <span class="hljs-string">"kekekek"</span>);
                notifyDataSetChanged();

                <span class="hljs-comment">//Query database for updated data</span>
                Cursor cursor = sqlDB.query(TaskConTract.TaskEntry.TABLE_NAME,
                        <span class="hljs-keyword">new</span> String[]{TaskConTract.TaskEntry._ID, TaskConTract.TaskEntry.COLUMN_TASK},
                        <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>, <span class="hljs-keyword">null</span>);
                <span class="hljs-comment">//Instance method with TaskAdapter so no need to use adapter.swapCursor()</span>
                swapCursor(cursor);
            }
        });
    }
}

package sonyama.todolist;

import ...

import sonyama.todolist.data.TaskConTract;

import sonyama.todolist.data.TaskDBHelper;

/**

* Created by sonyama on 1/12/16.

*/

public class TaskAdapter extends CursorAdapter {

private static Context context;

TaskDBHelper helper;

public TaskAdapter (Context context, Cursor cursor) {

super(context, cursor, 0);

this.context = context;

helper = new TaskDBHelper(context);

}

//The newView method is used to inflate a new view and return it,

//you don't bind any data to the view at this point

@Override

public View newView(Context context, Cursor cursor, ViewGroup parent) {

return LayoutInflater.from(context).inflate(R.layout.list_item_task, parent, false);

}

@Override

public void bindView(View view, Context context, Cursor cursor) {

//Find Views to populate in inflated template

TextView textView = (TextView) view.findViewById(R.id.list_item_task_textview);

Button done_button = (Button) view.findViewById(R.id.list_item_task_done_button);

//Extract properties from cursor

final String id = cursor.getString(MainActivityFragment.COL_TASK_ID);

final String task = cursor.getString(MainActivityFragment.COL_TASK_NAME);

//Populate views with extracted properties

textView.setText(task);

done_button.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

//Create a SQL command for deleting a particular ID.

String sql = String.format("DELETE FROM %s WHERE %s = '%s'",

TaskConTract.TaskEntry.TABLE_NAME,

TaskConTract.TaskEntry._ID,

id);

SQLiteDatabase sqlDB = helper.getWritableDatabase();

//Execute the delete command

sqlDB.execSQL(sql);

Log.d("kakakak", "kekekek");

notifyDataSetChanged();

//Query database for updated data

Cursor cursor = sqlDB.query(TaskConTract.TaskEntry.TABLE_NAME,

new String[]{TaskConTract.TaskEntry._ID, TaskConTract.TaskEntry.COLUMN_TASK},

//Instance method with TaskAdapter so no need to use adapter.swapCursor()

swapCursor(cursor);

}

});

}

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Bắt đầu Học Android Với Việc Tạo App ToDoList (P2)

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