判断网络 并选择加载图片的方式

主界面：

public class MainActivity extends AppCompatActivity {    Broad broad;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        IntentFilter filter = new IntentFilter();        filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);        broad = new Broad();        registerReceiver(broad,filter);    }    public void TextView(View view){        String[] string = {"最佳效果", "较省流量", "极省流量"};        int mode = MyApplication.getAppContext().getSharedPreferences(Utils.SP_NAME, Context.MODE_PRIVATE).getInt(Utils.PICTURE_LOAD_MODE_KEY, 0);        AlertDialog.Builder builder = new AlertDialog.Builder(this);        builder.setTitle("非wifi网络流量");        builder.setSingleChoiceItems(string, mode, new DialogInterface.OnClickListener() {            @Override            public void onClick(DialogInterface dialog, int which) {                MyApplication.getAppContext().getSharedPreferences(Utils.SP_NAME,Context.MODE_PRIVATE).edit().putInt(Utils.PICTURE_LOAD_MODE_KEY,which).commit();                dialog.dismiss();            }        });        builder.setNegativeButton("取消", null);        builder.create().show()    }    public void Button(View view){        Toast.makeText(MainActivity.this, Utils.getInstance().getBASE_URL(), Toast.LENGTH_SHORT).show();    }    public class Broad extends BroadcastReceiver{        @Override        public void onReceive(Context context, Intent intent) {            if(ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction())){                boolean wang = true;                ConnectivityManager manager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);                NetworkInfo networkInfo = manager.getActiveNetworkInfo();                if(networkInfo != null && networkInfo.isConnected()){                    if (ConnectivityManager.TYPE_WIFI == networkInfo.getType()) {                        Toast.makeText(MainActivity.this, "wifi可用，下载吧", Toast.LENGTH_SHORT).show();                        wang = false;                    } else if (ConnectivityManager.TYPE_MOBILE == networkInfo.getType()) {                      Toast.makeText(MainActivity.this, "现在是移动网络，当心", Toast.LENGTH_SHORT).show();                        wang = true;                        //获得现在的网络状态 是移动网络，去改变我们的访问接口                    } else {                   Toast.makeText(MainActivity.this, "网络不可用，请检查网络", Toast.LENGTH_SHORT).show();                    }                }else {                    Toast.makeText(MainActivity.this, "网络不可用，请检查网络", Toast.LENGTH_SHORT).show();                }                Utils.getInstance().changeNetState(wang);            }        }    }    @Override    protected void onDestroy() {        super.onDestroy();        //解注册        unregisterReceiver(broad);    }}

Utils类：

public class Utils {    private static final String DATU = "http://www.big.picture";    private static final String ZHONGTU = "http://www.small.picture";    private static final String XIAOTU = "http://www.no.picture";    private String BASE_URL=DATU;    private static Utils utils;    private boolean wang = true;    public static final String SP_NAME = "SP_NAME";    public static final String PICTURE_LOAD_MODE_KEY = "PICTURE_LOAD_MODE_KEY";    private Utils(){    }    public static Utils getInstance() {        if (utils == null) {            synchronized (Utils.class) {                if (utils == null) {                    utils = new Utils();                }            }        }        return utils;    }    public String getBASE_URL(){        if(wang){            int mode = MyApplication.getAppContext().getSharedPreferences(SP_NAME, Context.MODE_PRIVATE).getInt(PICTURE_LOAD_MODE_KEY, 0);            switch (mode){                case 0:{                    BASE_URL = DATU;                }                break;                case 1:{                    BASE_URL = ZHONGTU;                }                break;                case 2:{                    BASE_URL = XIAOTU;                }                break;            }        }else {            BASE_URL = DATU;        }        return BASE_URL;    }    public void changeNetState(boolean wang) {        this.wang = wang;    }}

MyApplication类：

public class MyApplication extends Application {    private static MyApplication myApplication;    @Override    public void onCreate() {        super.onCreate();        myApplication = this;    }    public static Context getAppContext(){        return myApplication;    }} 
<!--上网权限 和 获取网络状态的权限--><uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />