Android——检查网络是否已经链接

<RelativeLayout 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: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.example.testnet.MainActivity" > <TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<Button
android:id="@+id/testNetwrkBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/textView1"
android:layout_centerHorizontal="true"
android:layout_marginTop="31dp"
android:text="@string/btn_testNet" />
</RelativeLayout>

package com.example.testnet;import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
import android.widget.Toast;public class Btn1Listener implements OnClickListener {
private Context context;
private TextView tv1;
private ConnectivityManager cm;
public Btn1Listener(Context context) {
this.context = context;
} @Override
public void onClick(View v) {
//把上下文对象转型为Activity
Activity c = ((Activity) context);
//获取文本控件
tv1 = (TextView) c.findViewById(R.id.textView1);
// tv1.setBackgroundColor(0);
try{
//获取网络。。。。
cm = (ConnectivityManager) c.getSystemService(c.CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();
if(info == null){
//提示没有网络
tv1.setText(R.string.text_Net1);
tv1.setBackgroundResource(R.color.red);
}else{
tv1.setText(R.string.text_Net0);
tv1.setBackgroundResource(R.color.green);
//不需要提示，继续执行相关的代码
}
}catch(RuntimeException e){
//用户没授权的时候给出提示（由于不知道怎么提示用户授权，只能用Toast了，怪我小白）
Toast.makeText(c, "没有权限，请授权", Toast.LENGTH_SHORT).show();
}
}}

package com.example.testnet;import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;public class MainActivity extends Activity {
private Button btn1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = (Button) findViewById(R.id.testNetwrkBtn);
btn1.setOnClickListener(new Btn1Listener(this));
} @Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
} @Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.testnet"
android:versionCode="1"
android:versionName="1.0" >
<!-- 授予局域网权限 -->
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<!-- 授予互联网权限 -->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-sdk
android:minSdkVersion="17"
android:targetSdkVersion="20" /> <application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
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></manifest>