Xử lý bất đồng bộ trong lập trình Android cơ bản

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.howkteam.asyncexample.MainActivity">

    <TextView
        android:id="@+id/tv_ip"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</RelativeLayout>
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package com.howkteam.asyncexample;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class MainActivity extends AppCompatActivity {

    TextView tvIP;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tvIP = (TextView) findViewById(R.id.tv_ip);

        testNetwork();
    }

    private void testNetwork() {
        try {
            StringBuilder sb;
            // Website này sẽ cho biết địa chỉ IP của bạn.
            URL url = new URL("http://icanhazip.com/");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                sb = new StringBuilder();
                String line;
                while ((line = br.readLine()) != null) {
                    sb.append(line).append("\n");
                }

                tvIP.setText(sb.toString());
                Log.e("Dia chi IP ", sb.toString());

                br.close();

            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.howkteam.asyncexample">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <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.asyncexample;

import android.os.AsyncTask;

public class AsyncTaskNetwork extends AsyncTask<String, Void, Boolean> {
    
}
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package com.howkteam.asyncexample;

import android.os.AsyncTask;

public class AsyncTaskNetwork extends AsyncTask<String, Void, Boolean> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Boolean doInBackground(String... strings) {
        return null;
    }

    @Override
    protected void onPostExecute(Boolean aBoolean) {
        super.onPostExecute(aBoolean);
    }
}
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package com.howkteam.asyncexample;

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class AsyncTaskNetwork extends AsyncTask<String, Void, String> {

    ProgressDialog progressDialog;
    Context context;
    TextView textView;

    public AsyncTaskNetwork(Context context, TextView textView) {
        this.context = context;
        this.textView = textView;
    }

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

        // Hiển thị Dialog khi bắt đầu xử lý.
        progressDialog = new ProgressDialog(context);
        progressDialog.setTitle("HowKteam");
        progressDialog.setMessage("Dang xu ly...");
        progressDialog.show();
    }

    @Override
    protected String doInBackground(String... strings) {
        try {
            StringBuilder sb;
            // Website này sẽ cho biết địa chỉ IP của bạn.
            URL url = new URL(strings[0]);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                sb = new StringBuilder();
                String line;
                while ((line = br.readLine()) != null) {
                    sb.append(line).append("\n");
                }

                Log.e("Dia chi IP ", sb.toString());
                br.close();
                return sb.toString();
            }

        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }

        return null;
    }

    @Override
    protected void onPostExecute(String aString) {
        super.onPostExecute(aString);
        // Hủy dialog đi.
        progressDialog.dismiss();
        // Hiển thị IP lên TextView.
        textView.setText(aString);
    }
}
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package com.howkteam.asyncexample;

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

public class MainActivity extends AppCompatActivity {

    TextView tvIP;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tvIP = (TextView) findViewById(R.id.tv_ip);

        new AsyncTaskNetwork(this, tvIP).execute("http://icanhazip.com/");
    }
}
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