如何檢查Android網絡連接狀態

openkk 12年前發布 | 68K 次閱讀 Android Android開發移動開發

在發送任何HTTP請求前最好檢查下網絡連接狀態，這樣可以避免異常。這個教程將會介紹怎樣在你的應用中檢測網絡連接狀態。

創建新的項目

1.在Eclipse IDE中創建一個新的項目并把填入必須的信息。 File->New->Android Project

2.創建新項目后的第一步是要在AndroidManifest.xml文件中添加必要的權限。

為了訪問網絡我們需要 INTERNET 權限
為了檢查網絡狀態我們需要 ACCESS_NETWORK_STATE 權限

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.detectinternetconnection"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".AndroidDetectInternetConnectionActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

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

    <!-- Network State Permissions -->
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

</manifest>

3.創建一個新的類，名為ConnectionDetector.java，并輸入以下代碼。

ConnectionDetector.java

package com.example.detectinternetconnection;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

public class ConnectionDetector {

    private Context _context;

    public ConnectionDetector(Context context){
        this._context = context;
    }

    public boolean isConnectingToInternet(){
        ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE);
          if (connectivity != null)
          {
              NetworkInfo[] info = connectivity.getAllNetworkInfo();
              if (info != null)
                  for (int i = 0; i < info.length; i++)
                      if (info[i].getState() == NetworkInfo.State.CONNECTED)
                      {
                          return true;
                      }

          }
          return false;
    }
}

4.當你需要在你的應用中檢查網絡狀態時調用isConnectingToInternet()函數，它會返回true或false。

ConnectionDetector cd = new ConnectionDetector(getApplicationContext());

Boolean isInternetPresent = cd.isConnectingToInternet(); // true or false

5.在這個教程中為了測試我僅僅簡單的放置了一個按鈕。只要按下這個按鈕就會彈出一個 alert dialog 顯示網絡連接狀態。

6.打開 res/layout 目錄下的 main.xml 并創建一個按鈕。

main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Detect Internet Status" />

    <Button android:id="@+id/btn_check"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="Check Internet Status"
        android:layout_centerInParent="true"/>

</RelativeLayout>

7.最后打開你的 MainActivity 文件并粘貼下面的代碼。在下面的代碼中我用一個 alert dialog 來顯示預期的狀態信息。

package com.example.detectinternetconnection;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class AndroidDetectInternetConnectionActivity extends Activity {

    // flag for Internet connection status
    Boolean isInternetPresent = false;

    // Connection detector class
    ConnectionDetector cd;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button btnStatus = (Button) findViewById(R.id.btn_check);

        // creating connection detector class instance
        cd = new ConnectionDetector(getApplicationContext());

        /**
         * Check Internet status button click event
         * */
        btnStatus.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                // get Internet status
                isInternetPresent = cd.isConnectingToInternet();

                // check for Internet status
                if (isInternetPresent) {
                    // Internet Connection is Present
                    // make HTTP requests
                    showAlertDialog(AndroidDetectInternetConnectionActivity.this, "Internet Connection",
                            "You have internet connection", true);
                } else {
                    // Internet connection is not present
                    // Ask user to connect to Internet
                    showAlertDialog(AndroidDetectInternetConnectionActivity.this, "No Internet Connection",
                            "You don't have internet connection.", false);
                }
            }

        });

    }

    /**
     * Function to display simple Alert Dialog
     * @param context - application context
     * @param title - alert dialog title
     * @param message - alert message
     * @param status - success/failure (used to set icon)
     * */
    public void showAlertDialog(Context context, String title, String message, Boolean status) {
        AlertDialog alertDialog = new AlertDialog.Builder(context).create();

        // Setting Dialog Title
        alertDialog.setTitle(title);

        // Setting Dialog Message
        alertDialog.setMessage(message);

        // Setting alert dialog icon
        alertDialog.setIcon((status) ? R.drawable.success : R.drawable.fail);

        // Setting OK Button
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }
}

運行并測試下你的程序吧！你將會得到類似下面的結果。