判断网络是否可用

一

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

    <TextView
        android:id="@+id/view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="按钮"/>
</LinearLayout>

二

package com.example.day14;

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

/**
 * Created by 。。。。 on 2018/9/14.
 */

public class NeetworkUtils {
    public static boolean isNetworkAvailable(Context context) {
        boolean available = false;
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo networkInfo = manager.getActiveNetworkInfo();


        if (networkInfo != null) {
            available = networkInfo.isAvailable();
        }
        return available;

    }
}

三

package com.example.day14;

import android.app.Application;
import android.graphics.Bitmap;
import android.os.Environment;

import com.nostra13.universalimageloader.cache.disc.DiskCache;
import com.nostra13.universalimageloader.cache.disc.impl.ext.LruDiskCache;
import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.cache.memory.impl.LruMemoryCache;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.display.BitmapDisplayer;
import com.nostra13.universalimageloader.core.display.CircleBitmapDisplayer;

import java.io.File;
import java.io.IOException;

/**
 * Created by 。。。。 on 2018/9/14.
 */

public class BaseApplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();

        File cacheDir = null;
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File rootSD = Environment.getExternalStorageDirectory();
            cacheDir = new File(rootSD, "imgs");
            if (!cacheDir.exists()) {
                cacheDir.mkdirs();
            }
        }

        DiskCache diskCache = null;
        try {
            diskCache = new LruDiskCache(cacheDir, new Md5FileNameGenerator(), 50 * 1024 * 1024);
        } catch (IOException e) {
            e.printStackTrace();
        }

        BitmapDisplayer displayer = new CircleBitmapDisplayer();

        DisplayImageOptions options = new DisplayImageOptions.Builder()
                .bitmapConfig(Bitmap.Config.RGB_565)
                .cacheOnDisk(true)
                .cacheInMemory(true)
                .displayer(displayer)
                .build();

        ImageLoaderConfiguration configuration = new ImageLoaderConfiguration.Builder(this)
                .diskCache(diskCache)
                .memoryCache(new LruMemoryCache(12 * 1024 * 1024))
                .defaultDisplayImageOptions(options)
                .build();
        ImageLoader.getInstance().init(configuration);
    }
}

四

package com.example.day14;

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

public class MainActivity extends AppCompatActivity {
    private int i=1;
    private TextView view;
    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        view = findViewById(R.id.view);
        button = findViewById(R.id.btn);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                boolean b = NeetworkUtils.isNetworkAvailable(getApplicationContext());
                if (b) {
                    view.setText("网络正常");
                } else {
                    view.setText("网络不可用");
                }
            }
        });
    }
}